LOFAR VLBI Observations of Coma a - Nearby Laboratory of Massive Galaxy and Black Hole Formation

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Coma A (3C277.3) is one of few luminous low-redshift radio sources where jet-galaxy interactions deflect the jet and induce star formation - a nearby laboratory of massive galaxy formation. We present the first LOFAR VLBI radio image of Coma A and compare it with VLT/MUSE optical images and Chandra X-ray maps. Remarkable features of the radio emission are clumpiness, multiple filaments and the relation of the radio to the optical and X-ray morphologies. The optical continuum image shows a swarm of galaxies apparently merging with Coma A, similar to high-redshift radio protoclusters. Three optical clumps are probable remnants of a merging galaxy, fragmented by collision with the jet. We suggest that magnetic turbulence in Coma A-type radio-emitting clumps, could trigger radio jets in quiescent black holes and that positive feedback from radio jets could contribute to the structure of the high-redshift cosmic web. A prediction of such a scenario is that the morphologies of high-redshift extended radio sources are oriented preferentially along cosmic web filaments, with important implications for how the first supermassive black holes formed. Physical sciences/Astronomy and planetary science/Astronomy and astrophysics/Early universe Physical sciences/Astronomy and planetary science/Astronomy and astrophysics/Galaxies and clusters Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 1. MAIN It has long been known that radio jets can induce star formation in their host galaxies 1 , 2 , 3 , 4 , particularly at high redshifts, z > 2 5,6 . Although the “positive feedback” mechanism by which jets create stars is not fully understood, it involves the interaction of radio jets with the interstellar medium of the host galaxy. The high-speed plasma from the jet shocks the ambient gas, compressing it and increasing its density. This leads to the formation of dense clouds of gas and dust, which are the sites of star formation. A radio jet can also clear out the surrounding material, creating channels that allow gas and dust to flow towards the centre of the galaxy, where they collapse and form stars 7 . Observationally, several nearby and high-redshift systems provide strong evidence that such jet-induced triggering occurs. At higher redshift, luminous radio galaxies show aligned UV/optical continuum and line emission that has long been interpreted as at least partly due to jet-induced star formation 5 . Recent JWST observations of TN J1338–1942 at z≃4.1 directly resolve extreme, spatially extended star formation associated with radiative shocks along the jet axis 6 . Taken together, these observations and simulations support a scenario in which relativistic jets can locally trigger or enhance star formation in dense gas, even while contributing to the longer-term regulation and quenching of star formation on galactic scales 7 , 8 . 9 . Studying such jet-induced star formation is fundamental for understanding the birth of galaxies in the early Universe and the simultaneous growth and co-evolution of nuclear supermassive black holes 10 , 11 , 12 . Radio jets launched by massive black holes could play a crucial role in regulating accretion onto the black holes and the growth of the central bulges of their host galaxies. The luminous high-redshift radio galaxies and quasars with redshifts, z > 2 in which jet-induced star formation is frequently observed are among the most massive galaxies known and often found at the cores of forming galaxy clusters. Although jet-induced star formation occurs less often at redshifts z < 1, the higher linear resolution and effective sensitivity achievable at low redshifts provide unique diagnostics for studying this intriguing and potentially fundamental phenomenon. Coma A (3C277.3), a radio galaxy with redshift, z = 0.086, is a prime nearby laboratory of jet-induced star formation 12 . It is associated with an elliptical galaxy at the centre of a cluster and has a double-lobed radio structure with a size of ~ 90 kpc (~ 45”). A morphological association of its extended radio source with optical emission was first reported in 1980 12,13,14 . These observations demonstrated that the Coma A jet triggers the formation of stars in the surrounding ISM and that the jet is deflected by Hα-emitting gas knots. There have been several subsequent studies of Coma A. These include the detection with Chandra of aligned X-Ray-radio emission, attributed to large-scale shocks produced in the galaxy's ionised gas halo by the outward-moving radio jets 15 , 16 and X-ray synchrotron emission from the nucleus and compact components. There is also evidence from HST imaging 17 and optical spectroscopy 18 that Coma A is undergoing a merger with one or more gas-rich neighbours fuelling the black hole and feeding the AGN activity responsible for the radio jets. Extended HI absorption against both radio lobes of Coma A, at up to ~ 30 kpc from the nucleus has been detected using the Westerbork Synthesis Radio Telescope 19, 20 . Recent landmark deep optical imaging-spectroscopic observations of Coma A with the VLT/MUSE IFS imaging spectrograph at sub-arcsecond resolution 21 provided detailed information about the ionisation state, metallicity, kinematics and velocity-dispersion throughout the galaxy, the associated ionized gas nebula and the radio source and a VLA polarisation study has inferred the presence of a Faraday screen associated with the ionised gas 22 . Full exploitation of the MUSE optical data requires comparison with the most detailed high-resolution radio observations of Coma A. The International LOFAR Telescope (ILT) is uniquely suited to imaging extended steep-spectrum nonthermal emission at low radio frequencies, sub-arc second resolution and high sensitivity. Here we present new sub-arcsecond images of Coma A at ~ 144 MHz with the ILT (LOFAR VLBI) and compare them with the VLT MUSE optical and Chandra X-ray images. Together, these sub-arcsecond images provide the most detailed view yet of radio-jet induced star formation and jet-gas interactions in a gas-rich radio galaxy that is in the process of merging with a swarm of fainter galaxies. We discuss the implications of these results for the influence of massive black holes and nuclear activity on galaxy formation at high redshifts. 2. RESULTS 2.1 Images 2.1.1 LOFAR VLBI Radio Images Figures 1 and 2 show the new ILT 0.4"-resolution radio image of Coma A. Three different contrast levels are displayed to accentuate the visibility of important radio features. Figure 2 has been filtered to accentuate the compact features and radio clumps, by smoothing to a resolution of ~ 3" and subtracting this smoothed image from the original image. Note the clumpy faint northern jet, the large-scale radio filaments, the jet-aligned nuclear core, the inner jet and 3 southern radio clumps at the location of the jet deflection 12 ,13, 14 . 2.1.2. Comparison With MUSE/VLT Optical Images The VLT MUSE IFS observations have been described and discussed in detail 21 , where it is suggested that Coma A is unique case in the local Universe, for which the expanding outflow from a galaxy of stellar mass ~ 10 11.5 M ☉ triggers star formation throughout the radio source. The new grey-scale representations and in the optical overlays shown in Figs. 3 and 4 provide the most revealing demonstration so far of interactions between an extended radio source and its host galaxy. The MUSE optical continuum image in Fig. 3 shows that the massive galaxy host is embedded in a swarm of fainter galaxies. The greyscale representation of Fig. 4 shows the ionised gas distribution in more detail than previously published. The Hα filaments at the outer boundary of the radio source are moving with a line-of-sight velocity of ~ 200 km/s outwards from the nucleus ( ~ + 200 km/s northwards, ~-200 km/s southwards) 21 . Because of their proximity to the radio lobe boundaries, the velocities of the gas filaments are also likely to be the velocities at which the radio lobes are advancing into the circumgalactic medium. The fact that the typical outflow velocities in the nuclear kiloparsec-scale narrow line region of active galaxies are also a few hundred kilometres per second, is consistent with the advance speed of the lobe boundary not having varied substantially during its history. Assuming a uniform advance-speed of ~ 200 km/s, and neglecting projection effects, the radio source boundary would take ~2x10 8 y to traverse the ~ 45 kpc distance from the nucleus to the present edge. 2.1.3. Comparison with Chandra X-Ray Images The Chandra image 16 and its overlay on the LOFAR radio image are shown in Fig. 5 . A huge halo of hot gas envelops the system and several compact features in the radio image also emit X-rays. The X-ray hot gas (T~10 8 K) is oriented along the radio source and has a total mass of ~ 10 11 M ⊙ out to a radius of 40 kpc. Note that the southern X-ray hotspot (xHS) is oriented along the undeflected jet direction. A faint X-ray filamentary shell emanating from the nucleus appears to stretch along the southern boundary of the northern radio lobe. 2.1.4. Parameters of prominent compact features. Approximate parameters of important compact features indicated in the figures are tabulated in Table 1 , measured from the VLT/MUSE data-set 21 . Table 1 Parameters of radio knots ( Fig. 1 – 2 ) and Hα gas clumps ( Fig. 4 ). Gas Clumps + Radio knots R.A. (J2000) (deg) Dec. (J2000) (deg) Velocity (km/s) Vel. 1 Disp. (km/s) Ionisation OIII]5007/ Hα6563 Remarks (v = 0 corresponds to z = 0.08566) 21 gN 193.55011 27.62602 -10 225 1.2 Nuclear gas, extended by ~ 1.5" in E-W direction rN 193.55011 27.60609 -10 330 1.2 Radio nuclear core. Extended by ~ 2" in PA ~ 22 deg., along jet gC12 193.55105 27.62468 -20 220 6.7 Jet deflecting gas clump. Extended by ~ 2.5", located ~ 1" west of the radio rK1 and rK2. S-shaped wisps connecting to southern and northern filaments rK1 193.55088 27.62454 -80 330 5.8 Bright radio knots associated with jet deflection rK2 193.55078 27.62393 -80 380 1.7 gC3 193.55449 27.62576 -215 60 0.8 S-shaped wisps connecting to southern and northern filaments gC4 193.55380 27.62571 -190 55 0.6 gHN 193.54713 27.63087 + 10 90 2.6 Velocity differs by ~ 140 km/s from adjacent large-scale filament rHN 193.54766 27.63120 -30 120 1.0 gHS 193.55177 27.62222 -190 170 1.5 1 Velocity dispersion within large-scale filamentary structure is typically < ~ 150 km/s. 2.2 Inferences about Coma A from the Images 2.2.1. Overall structure – Jet and lobe deflection. The figures illustrate the power of multispectral morphology, combined with high angular resolution as a diagnostic tool for probing galaxy evolution. The radio nuclear core (rN), the radio jet, the southern radio knots at the location of the jet deflection (rK1, rK2), the wide radio lobes and the compact "hot spot" at the outer edge of the northern radio lobe (rHN) detected previously 12 ,13, 14 are all prominently visible. 2 .2.2. Clumpiness of the radio and ionised gas emissions - widespread turbulence. The most important insight provided by the new sub-arcsecond LOFAR image (Fig. 2 ) is that the Coma A radio source is highly clumped throughout. Besides the previously known bright knots (rK1, rK2), more than 20 fainter radio clumps are detected within the northern and southern lobes. Some of these clumps are located within the radio jet and others are located in the outer region of the radio lobes. Clumps are present both in the unfiltered and filtered maps and several were faintly visible in the original unpublished survey data maps that motivated these observations. The final total observed data set is many times larger and in general of excellent quality. Despite several iterations with different calibration cycles and different subsets of the data, the clumps remained clearly visible. The ubiquity of the radio clumps indicates that the interaction between the radio source and its dense gaseous surroundings results in widespread shocks throughout the source, with enhanced turbulent magnetic field clumps , where reacceleration of the radio-emitting relativistic particles occur. As seen in the radio emission, the MUSE H α brightness distribution (Fig. 4 ) is also clumpy, indicating that the warm gaseous environment is highly disturbed and shocks resulting from the deceleration of relativistic jets at the clumps can result in magnetic turbulence 23 . The previously known brightest gas clump GC12 is associated with the radio continuum knots rK1, rK2 (Fig. 1 c) at the location where the jet is deflected by ~ 40 deg. 12,13,14 . The velocity dispersion in the large-scale gas structures is typically ~ 100–200 km/s 21 . However, the nucleus, gN, the deflecting southern clump gC12 and the southern gas hot spot all have velocity dispersions that are larger, > 350 km/s 21 , indicating that at these locations the collision of the jet with the gas results in enhanced turbulence and shocks. These would be additional sources for increasing the ionisation of the gas, reaccelerating the radio-emitting relativistic electrons and fragmenting the galaxy comprising clumps gC12, gC3 and gC4. An analysis of the MUSE emission line data 21 found that the deflector clump, gC12 has sub-solar metallicity, Z ~ 0.6 - 0.8 Z S , a stellar age of ~ 3x10 6 y and a low gas density derived from the [SII] line ratios ( n e < 100 cm –3 ). The radio knots appear to be in pressure equilibrium with the associated emission-line gas (~ 10 -9 dyne cm -2 ) 12 although given the complexity and model dependence of the interactions and the resultant radiation, such calculations and inferences are subject to large uncertainties. Assuming that the Hα luminosity originates from stars, the star formation rate, estimated from the Hα luminosity of the 5 brightest clumps is ~ 5.4 × 10 40 erg s – 1 , corresponding to ~ 0.8 M ☉ /y 21 . However, the total Hα luminosity of the source would imply a SFR of ~ 4 M ☉ y – 1 , corresponding to a total stellar mass of ~ 4 X 10 8 M ☉ over a radio source lifetime of ~ 10 8 y 21 . These values are also highly model dependent, given the possible influence of photoionisation and interactions on the observed Hα fluxes. The X-ray clump, XC12 coincides with the warm gas/radio deflector clumps gC12 + rK1+rK2 and is orientated along the direction of the deflected jet. Assuming that the X-rays are thermal, the hot gas clump, xC12, that deflects the jet has a mass of ~ 2×10 8 M ⊙ 16 and dominates the mass of the deflector clump. 2.2.3. Filaments and Shells - signatures of episodic nuclear activity. Several large-scale radio and gas filaments can be seen both within and surrounding the radio lobes (Figs. 1 , 2 , 4 ). These filaments are also clumpy and additional clumps are seen beyond and along the trajectory of the north-western H𝜶 shell. The most prominent filaments are located near the outer edges of the lobes and are likely due to shocks produced by the outward-moving radio lobes impinging on the surrounding gas. This gas is being pushed out into the circumgalactic medium by the radio source with a line-of sight velocity of ~ 200 km/s. The multiple filamentary structure is consistent with a variable episodic history, in which each filament arose from separate enhanced outbursts of nuclear activity. Additional evidence for episodic nuclear variability is the morphology of the southern Hα lobe (Fig. 4 ). Its resemblance to the shape of the wide radio lobe despite its orientation in the direction of the non-deflected jet implies that it is the remnant of a previous radio lobe/ nuclear outburst, that occurred before the deflecting gas clump moved into the jet path. Relativistic particles ejected in such an earlier outburst would have aged sufficiently that their radio radiation is no longer detectable. The radiative lifetime of synchrotron emission is highly model dependent 1 , with a nominal equipartition value of ~ 10 6 − 10 8 y and equipartition magnetic field strength ~ 36 µG 22 , but the likelihood of variability and shock reacceleration within the source also makes these values highly uncertain. 2.2.4. Fragmentation of a merging galaxy by the jet. Intriguingly, the eastern non-radio high-ionization gas clumps gC3 and gC4 (Fig. 4 c) are connected by Hα-emitting gas to both the deflector clump gC12 and the large northern gas filament that marks the outer boundary of the radio source. The radial velocities of gC3 and gC4 differ by ~ 190 km/s from that of gC12 (see Table 1 ). The Hα connection between these clumps implies that the gC3/gC4 clumps and the jet deflector, GC12, are likely to be remnants of a single galaxy of mass ~ few x 10 8 M ☉ , that was fragmented ~ 5 x 10 7 y ago, when it drifted into the path of the jet. This would also explain the dented shape of gC12, the disparate line-of-sight velocities and the anomalously large Hα velocity dispersion of the deflector gas clumps (~ 350 km/s). Relativistic jets can fragment a dwarf galaxy’s gas via shocks, turbulence, and entrainment, producing multiphase structures and shocks that could trigger star formation in both the original galaxy and the breakaway gas clumps 23 . However, the stellar body would remain largely intact due to weak coupling. It has been shown that jet-induced galaxy fragmentation can occur mainly through hydrodynamic and radiative processes rather than direct gravitational effects. Key mechanisms include: (1) Shock compression, where supersonic jet-driven shocks over-pressurise and shatter gas clouds; (2) Turbulent entrainment, in which Kelvin–Helmholtz instabilities at the jet–ISM interface mix and ablate gas; and (3) Ram-pressure stripping and cloud crushing, as jets sweep through or engulf gas-rich dwarf systems 24 . Simulations show that the resulting turbulent, multiphase medium can fragment into dense clumps that may either collapse into stars or be dispersed 25 , 26 . Jet-induced gas fragmentation represents both positive and negative feedback - positive, via the formation of dense, star-forming knots and negative, by expelling or heating gas and reducing the long-term star formation potential. In low-mass systems, the balance between these effects likely depends on jet power and ISM structure 27 , 28 . Over the lifetime of the Coma A radio source a mass comparable to the mass of the line-emitting gas (~ 10 7 -10 8 M 0 ) could have been entrained 29 . 2.2.5. Role of photoionisation. There is a high-ionisation bi-cone oriented along the initial direction of the jet 21 . This is indicative of selective directional photoionisation by the nucleus along the jet direction. The bi-cone includes the jet-deflection gas clump gC12 and the northern and southern hot spots. It also overlaps with the Chandra X-ray hot gas structure (Fig. 5 b) 15 , 16 . In view of the small-scale turbulence, the presence of shocks and nuclear AGN variability, the ionisation of the gas clumps is likely due to a complex combination of several processes. Mechanisms that have been proposed include ionisation due to hot cooling gas 30 , thermal conduction within the intracluster medium 30 , optical synchrotron emission 12 , reconnection diffusion 31 , and fast ionizing shocks 32 , 33 . 2.2.6. Radio jet de-collimation Not only is Coma A a radio source with a collimated jet, but it also has wide double-lobes. It is therefore also an important test-bed of jet deflection and jet de-collimation. Both the collimated narrow southern jet and the de-collimated wide southern radio lobe are deflected by a similar angle (~ 40 deg.) at the location of the bright southern radio/Hα knots. Hence, the southern jet is both deflected by its collision with the gas cloud, and also de-collimated by the collision, thereby creating a wide radio lobe oriented along the deflected jet rather than in the original jet direction. Jet deflection and decollimation could also be caused by variable/episodic nuclear activity. When the jet power is large, the gas clump deflects the jet, preserving its collimation. When the jet power is small, collision with the dwarf galaxy would de-collimate the jet, forming wide lobes. 3. DISCUSSION 3.1. Coma A as laboratory of black holes and galaxy formation. One of the most fascinating issues in modern astrophysics is the crucial role that supermassive black holes (SMBHs) and their associated nuclear activity (AGN/quasars) play in the saga of galaxy formation and evolution. The evidence for such a connection includes: the dramatic rise and fall by more than an order of magnitude in the AGN population density as a function of cosmic time (peaking at z ~ 2), that mimics the rise and fall of cosmic star formation 35 . the existence of SMBHs at z > 6, i.e., less than a billion years after the Big Bang 36 , 37 . the correlation between the mass of supermassive black holes (SMBHs) and the velocity dispersion of stars in the bulge of their host galaxies 38 , 39 . Besides jet deflection, jet de-collimation and jet-induced star formation, several features in the new Coma A images are relevant for understanding this SMBH-galaxy connection. The several clumps in the MUSE continuum map (Fig. 3 ) resemble those seen in HST and JWST images of mergers in forming brightest cluster protogalaxies (proto-BCGs) at high redshift, such as the Spiderweb (MRC 1138 − 262) at z ~ 2.2 5 , the Anthill (4C41.17) at z ~ 3.8 40 and TNJ1338-1942 at z ~ 4.1 41,42 . Star formation and gas ionisation aligned with and induced by the radio source occur beyond the confines of the optical galaxy. The observed radio and ionised gas clumpiness indicates that jet-galaxy interaction results in a turbulent clumpy circumgalactic gas, turbulent magnetic field clumps and gas ionisation through shocks and directional nuclear photoionisation. The likely occurrence of multiple episodic nuclear activity in Coma A supports a “popcorn” model that contributes to unifying extended radio sources, in which the host galaxy nucleus undergoes several episodic “quasar” bursts of nuclear activity during the radio source lifetime, fed by merging and accompanied by variation in jet power. As the source ages and cosmic evolution progresses, the merger “food” becomes exhausted and the nuclear “pops” gradually die out. Evidence for the validity of such a model comes from the known variability of quasars on all observable timescales 43 and the existence of “restarted” and “double-double extended radio source, with morphological features located symmetrically about their host nuclei 38 , 39 ,40 . The larger bending in radio sources at z > 1.5 47,48,49 and their frequent envelopment in giant Lyman alpha gas halos 50 show that jet deflection, as observed in Coma A, is more prevalent at high redshifts, when the circumgalactic and intergalactic gas was denser. The likely fragmentation of a merging galaxy by the Coma A radio jet implies that such processes can contribute to AGN-galaxy feedback during massive galaxy formation. 3.2. SMBH-jet triggering at cosmic dawn Although supermassive black holes (SMBHs) are essential ingredients of nuclear activity, the mechanism that triggers and sustains relativistic jets in some SMBHs, but not in others, is still not understood. In most theoretical models of jet-triggering, magnetic fields play a key role. Examples are the Blandford–Znajek process in which jet energy is extracted from a rapidly rotating black hole via strong poloidal magnetic fields 51 and the Blandford-Payne mechanism where magnetic field anchored in the accretion disk shoots material outwards 52 . An intriguing possibility motivated by the observations presented here, is that the widespread radio clumpiness and magnetic turbulence, as observed throughout the Coma A radio source be a trigger that can activate jets in SMBHs? Supporting evidence that radio sources could “wake up” quiescent black holes include: the “sudden” appearance of a transient radio source within the Cygnus A radio source between 1989 and 2015 54 , the excess of X-ray AGN by a factor of > 10 within a 2.5 Mpc field around the Spiderweb radio protocluster at z = 2.2, compared with the Cosmos field at a comparable redshift and stellar mass range 55 . 3.3. Do radio sources influence the formation and/ or maintenance of the cosmic web? Observations at z∼3 provide direct evidence that rapidly growing galaxies and active galactic nuclei (AGN) reside within the filamentary structures of the forming cosmic web. Deep Lyα mapping in the SSA22 proto-cluster reveals > 1 Mpc gas filaments in which many of the most active galaxies and AGN are embedded 56 . Similar large-scale structures have been detected around the massive halo RO-1001 at z = 2.91, where 3 Lyα-emitting filaments converge onto a∼4×10 13 M ⊙ group 57 . ALMA observations further show that nodes of the web at these epochs are exceptionally gas rich, implying that filamentary accretion can efficiently supply fuel for both star formation and rapid SMBH growth 58 . Because radio jets induce star formation along their path, as in Coma A, we suggest that the presence of jets could have influenced the formation and/or evolution of galaxies in the cosmic web. Support for such an idea includes: the alignment of the massive X-ray gas halo in Coma A with the radio jet, the inference that magnetic fields in giant radio sources could occupy more than 10% of today’s cosmic web 60 , the remarkable alignments of 14 companion galaxies along the axis and within the lobes of the 2-Mpc giant DA240 radio source 61 and the prominent Pisces chain of NGC galaxies that closely follows the lobes of the 1.1 Mpc giant radio source 3C31 61,62,63 . (The intriguing Pisces chain of bright galaxies was sketched by William Parsons in 1850 from observations with his 72 inch Leviathan Telescope at Birr Castle, then the largest telescope in the world. This was long before radio sources, such as 3C31 or the cosmic web were ever dreamed of. Coincidentally Birr Castle is also the location of the ILT LOFAR Irish station.) Because of their huge sizes, giant radio sources such as DA 240 and 3C31 are likely to be at least ~ 10 9 y old and have formed in the high-redshift cosmic web. If extended radio jets did contribute to galaxy formation in the high-redshift cosmic web, the orientations of the SMBHs that created them must have remained constant during their radio lifetimes of ~ > 10 8 y. The position angles of high-redshift extended radio sources would then be preferentially aligned along high-z cosmic web filaments, not perpendicular to them, as would be the case if gas from the cosmic web feeds accretion of the SMBHs. This would have profound implications for the origin of the first SMBHs and their host galaxies. Deep small-field high-resolution LOFAR surveys are ideal platforms for checking such predictions, because they will enable studies of the structures of populations of extended radio sources to be made over tens of megaparsecs in narrow spectroscopically-defined high-redshift windows. Although previous searches have been made for radio source alignment effects e.g. 64,65,66,67 , robust studies at high redshifts should be based on spectroscopic redshifts and narrow windows to avoid cosmological proximity effects being masked by chance coincidences. 4. LOOKING FORWARD The ILT sub-arcsecond images of Coma A and their relation to the optical and X-ray images illustrates the power of high-angular resolution imaging of radio emission as a tool for studying galaxy evolution. The combination of multispectral images results in a “whole that is greater than the sum of its parts”. Additional observations of Coma A would result in further insight into the interaction processes involved in the merger-SMBH-AGN-jet- star formation cycle. These include high-resolution imaging of the molecular gas with the JCMT and ALMA to determine its composition and morphological relation to the Hα-emitting warm gas and radio clumps, UV spectroscopic observations to constrain the stellar composition and ages, VLBI radio observations of the nucleus and deflection clumps, high-resolution mapping of the HI absorption. Such studies should be complemented by modern astrophysical simulations of several cases, taking into account the wealth of data on the complex interactions involved now available. Also, additional theoretical studies of the details of how magnetic turbulence can trigger radio jets in SMBHs are needed. Understanding the role of supermassive black holes in the early formation of galaxies is a compelling and fundamental reason for conducting a new intensive multispectral sub-arcsecond campaign to observe a large sample of galaxies that exhibit jet-galaxy interactions. Rich food for such a campaign at z > 2 is the list of known radio protoclusters 5 , and bent clumpy radio sources associated with quasars 43 . These objects are generally surrounded by large Lyα halos and host observable radio jet deflections. At low-redshift additional case studies to study at high resolution with the ILT and other wavebands include: Minkowski’s Object (z = 0.019), 3C293 (z = 0.045), 3C305(z = 0.041), 4C29.30 (z = 0.065) and 3C171 (z = 0.238). Another obvious related project is charting the spatial distributions of galaxies within the lobes of giant radio sources now known, easily carried out by comparing data from the Euclid and LOFAR surveys. 5. METHODS Coma A was observed by the ILT for a total of 43.7 hours in the High Band Antenna mode 68 , of which 39.7 hours was usable. The data were recorded in spectral channels of 12 kHz covering a total bandwidth of ~ 48 MHz between ~ 120 and ~ 168 MHz, with a time resolution of 1 second per integration. The gain and bandpass calibrator sources 3C196 and 3C295 were observed for 10 minutes before and after each exposure. Reduction of the data made use of the complex LOFAR VLBI calibration and imaging procedure developed over the past decade to produce sub-arcsecond HBA images with high dynamic range over several square degrees 69 , 70 , 71 , 72 ,73, 74 . This calibration technique treats large fields as multiple smaller "facets" 72 . The data were first processed using the LOFAR Initial Calibration Pipeline (LINC) 69 . After flagging bad data, calibration solutions for slowly-varying instrumental effects (bandpass, clock offsets and polarization alignment), were derived for all stations from the initial calibrators and a secondary round of flagging was carried out. Next, a sky model of the target field was obtained from the TIFR GMRT Sky Survey (TGSS) 75 and applied in a "phase-only" calibration cycle. The LOFAR-VLBI pipeline 74 was then used to calibrate data from the international stations. Applying corrections for the dispersive delays derived from two bright compact sources located within 15’ of Coma A and carrying out phase and amplitude self-calibration resulted in the 0.4" resolution Coma A image discussed here. Finally, a filtered image, to accentuate the clumps and compact structure visible on the image, was constructed by smoothing the image to a resolution of ~ 3” and subtracting the smoothed map from the original 0.4" resolution image. To construct the optical-radio overlays, the MUSE images were aligned with the ILT radio maps. This was done using the positions of panSTARRS galaxies that were visible in both fields. The MUSE maps needed shifting in declination by + 9.5" for the narrow-band images and + 1.6" for the 5000–7000Å broad-band image. Declarations 5. DATA AVAILABILITY The data are available from the LOFAR archive. Coma A was observed for a total of 43 hours as a dedicated LOFAR project (LC20_004), supplemented by 40 minutes data from the LOFAR Two-Metre Sky Survey 60 . 7. ACKNOWLEDGEMENTS. GKM thanks Dr. E.G.B. Vijverberg for his valuable help. This study made use of the excellent ALADIN astronomical display package . LOFAR is the Low Frequency Array, designed and constructed by ASTRON. It has observing, data processing, and data storage facilities in several countries, which are owned by various par- ties (each with their own funding sources), and which are collectively operated by the ILT foundation under a joint scientific policy. The ILT resources have benefited from the following recent major funding sources: CNRS-INSU, Observatoire de Paris and Université d’Orléans, France; BMBF, MIWF-NRW, MPG, Germany; Sci- ence Foundation Ireland (SFI), Department of Business, Enterprise and Innovation (DBEI), Ireland; NWO, The Netherlands; The Science and Technology Facilities Council, UK; Ministry of Science and Higher Education, Poland; The Istituto Nazionale di Astrofisica (INAF), Italy. This research made use of the Dutch national e-infrastructure with support of the SURF Cooperative (e-infra 180169) and the LOFAR e-infra group. The Jülich LOFAR Long Term Archive and the Ger- man LOFAR network are both coordinated and operated by the Jülich Supercomputing Centre (JSC), and computing resources on the supercomputer JUWELS at JSC were provided by the Gauss Centre for Supercomputing e.V. (grant CHTB00) through the John von Neumann Institute for Computing (NIC). This research made use of the University of Hertfordshire high- performance computing facility and the LOFAR-UK computing fa- cility located at the University of Hertfordshire (https://uhhpc. herts.ac.uk) and supported by STFC [ST/P000096/1], and of the Italian LOFAR IT computing infrastructure supported and operated by INAF, and by the Physics Department of Turin University (un- der an agreement with Consorzio Interuniversitario per la Fisica Spaziale) at the C3S Supercomputing Centre, Italy. We also made use of ASTROPY, a community-developed core Python package for astronomy (Astropy Collaboration et al. 2013) hosted at http://www.astropy.org/, of MATPLOTLIB (Hunter 2007), of APLPY, an open-source astronomical plotting package for Python hosted at http://aplpy.github.com/, and of TOPCAT and STILTS (Taylor 2005). The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. 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(Left) MUSE/VLT 5000 - 7000 Å image of Coma A (resolution 0.5”), dominated by stellar continuum emission. Fig 3b. (Right) The MUSE/VLT “continuum” image (blue) superimposed on the filtered ILT 144 MHz image (red - resolution ~0.4”). A swarm of fainter galaxies appear to be merging with the massive Coma A host.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-8549771/v1/2bcbcef755d9e27d335ae648.png"},{"id":101439239,"identity":"093eba14-76a2-44d8-90cd-4ddc02b775eb","added_by":"auto","created_at":"2026-01-29 16:42:46","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":318443,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003ea (Left). MUSE/VLT H\u003c/em\u003e𝜶\u003cem\u003e image of Coma A, showing the compact gas clumps and the-line-of sight velocities of the gas shells bounding the radio emission.\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eFig. 4b (Right). MUSE/VLT H\u003c/em\u003e𝜶\u003cem\u003e image (blue, resolution ~0.5”) superimposed on the 144 MHz image (red, resolution ~0.4”). Ionised gas clumps coincide with the nucleus (gN), the jet deflection location (gC12), the northern outer hotspot (gHN) and the southern H𝜶 lobe hotspot (gHS1). gHS1 is located along the direction of the \u003c/em\u003e\u003cem\u003e\u003cstrong\u003eundeflected\u003c/strong\u003e\u003c/em\u003e\u003cem\u003e jet. Large-scale gas filaments surround both radio lobes\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eFig. 4c. Blowup of the MUSE/VLT image of H𝜶 (red) and [NII] (blue), showing more clearly than in Fig. 4a, the gas wisps connecting the complex of gas clumps south of the nucleus. The connection indicates that the clumps gC12, gC3 and gC4 were likely part of a single merging galaxy that drifted into the path of the jet and whose gas was fragmented by the collision.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-8549771/v1/27b1c58aed8ed76c716665bd.png"},{"id":101439235,"identity":"87fceb00-f092-463c-8cd3-8c28cda05720","added_by":"auto","created_at":"2026-01-29 16:42:46","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":398076,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003ea (Left). Adaptively smoothed Chandra 0.4 – 5 keV image\u003c/em\u003e\u003csup\u003e\u003cem\u003e16\u003c/em\u003e\u003c/sup\u003e\u003cem\u003e of the Coma A field. This indicates the hot gas (T ~ 10\u003c/em\u003e\u003csup\u003e\u003cem\u003e8 \u003c/em\u003e\u003c/sup\u003e\u003cem\u003eK) is oriented in the direction of the radio source and that X-ray synchrotron radiation is emitted from the nucleus (xN) and northern hot spot (XHN).\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e\u0026nbsp;Fig. 5b (Right). The Chandra 0.4 – 5 keV smoothed image (blue) superimposed on the filtered ILT 144 MHz image (red).\u003c/em\u003e\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-8549771/v1/b1a232c8b29405d8b1090f75.png"},{"id":101754907,"identity":"8173a8b8-ccba-4c97-b5ba-ca9a18cba024","added_by":"auto","created_at":"2026-02-03 10:47:43","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2992907,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8549771/v1/99f0fea2-b1f9-4439-816f-a8ec088c476d.pdf"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.\nNone","formattedTitle":"\u003cp\u003eLOFAR VLBI Observations of Coma a - Nearby Laboratory of Massive Galaxy and Black Hole Formation\u003c/p\u003e","fulltext":[{"header":"1. MAIN","content":"\u003cp\u003eIt has long been known that radio jets can induce star formation in their host galaxies\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e1\u003c/span\u003e,\u003cspan class=\"CitationRef\"\u003e2\u003c/span\u003e,\u003cspan class=\"CitationRef\"\u003e3\u003c/span\u003e,\u003cspan class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e, particularly at high redshifts, z\u0026thinsp;\u0026gt;\u0026thinsp;2 \u003csup\u003e5,6\u003c/sup\u003e. Although the \u0026ldquo;positive feedback\u0026rdquo; mechanism by which jets create stars is not fully understood, it involves the interaction of radio jets with the interstellar medium of the host galaxy. The high-speed plasma from the jet shocks the ambient gas, compressing it and increasing its density. This leads to the formation of dense clouds of gas and dust, which are the sites of star formation. A radio jet can also clear out the surrounding material, creating channels that allow gas and dust to flow towards the centre of the galaxy, where they collapse and form stars\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eObservationally, several nearby and high-redshift systems provide strong evidence that such jet-induced triggering occurs. At higher redshift, luminous radio galaxies show aligned UV/optical continuum and line emission that has long been interpreted as at least partly due to jet-induced star formation\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e. Recent JWST observations of TN J1338\u0026ndash;1942 at z≃4.1 directly resolve extreme, spatially extended star formation associated with radiative shocks along the jet axis\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e. Taken together, these observations and simulations support a scenario in which relativistic jets can locally trigger or enhance star formation in dense gas, even while contributing to the longer-term regulation and quenching of star formation on galactic scales \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e7\u003c/span\u003e,\u003cspan class=\"CitationRef\"\u003e8\u003c/span\u003e.\u003cspan class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eStudying such jet-induced star formation is fundamental for understanding the birth of galaxies in the early Universe and the simultaneous growth and co-evolution of nuclear supermassive black holes\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e10\u003c/span\u003e,\u003cspan class=\"CitationRef\"\u003e11\u003c/span\u003e,\u003cspan class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e. Radio jets launched by massive black holes could play a crucial role in regulating accretion onto the black holes and the growth of the central bulges of their host galaxies.\u003c/p\u003e\n\u003cp\u003eThe luminous high-redshift radio galaxies and quasars with redshifts, z\u0026thinsp;\u0026gt;\u0026thinsp;2 in which jet-induced star formation is frequently observed are among the most massive galaxies known and often found at the cores of forming galaxy clusters. Although jet-induced star formation occurs less often at redshifts z\u0026thinsp;\u0026lt;\u0026thinsp;1, the higher linear resolution and effective sensitivity achievable at low redshifts provide unique diagnostics for studying this intriguing and potentially fundamental phenomenon.\u003c/p\u003e\n\u003cp\u003eComa A (3C277.3), a radio galaxy with redshift, z\u0026thinsp;=\u0026thinsp;0.086, is a prime nearby laboratory of jet-induced star formation\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e. It is associated with an elliptical galaxy at the centre of a cluster and has a double-lobed radio structure with a size of ~\u0026thinsp;90 kpc (~\u0026thinsp;45\u0026rdquo;). A morphological association of its extended radio source with optical emission was first reported in 1980\u003csup\u003e12,13,14\u003c/sup\u003e. These observations demonstrated that the Coma A jet triggers the formation of stars in the surrounding ISM and that the jet is deflected by H\u0026alpha;-emitting gas knots.\u003c/p\u003e\n\u003cp\u003eThere have been several subsequent studies of Coma A. These include the detection with Chandra of aligned X-Ray-radio emission, attributed to large-scale shocks produced in the galaxy\u0026apos;s ionised gas halo by the outward-moving radio jets\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e15\u003c/span\u003e,\u003cspan class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e and X-ray synchrotron emission from the nucleus and compact components. There is also evidence from HST imaging\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e and optical spectroscopy\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e that Coma A is undergoing a merger with one or more gas-rich neighbours fuelling the black hole and feeding the AGN activity responsible for the radio jets. Extended HI absorption against both radio lobes of Coma A, at up to ~\u0026thinsp;30 kpc from the nucleus has been detected using the Westerbork Synthesis Radio Telescope\u003csup\u003e19,\u003cspan class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eRecent landmark deep optical imaging-spectroscopic observations of Coma A with the VLT/MUSE IFS imaging spectrograph at sub-arcsecond resolution\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e provided detailed information about the ionisation state, metallicity, kinematics and velocity-dispersion throughout the galaxy, the associated ionized gas nebula and the radio source and a VLA polarisation study has inferred the presence of a Faraday screen associated with the ionised gas\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e. Full exploitation of the MUSE optical data requires comparison with the most detailed high-resolution radio observations of Coma A. The International LOFAR Telescope (ILT) is uniquely suited to imaging extended steep-spectrum nonthermal emission at low radio frequencies, sub-arc second resolution and high sensitivity.\u003c/p\u003e\n\u003cp\u003eHere we present new sub-arcsecond images of Coma A at ~\u0026thinsp;144 MHz with the ILT (LOFAR VLBI) and compare them with the VLT MUSE optical and Chandra X-ray images. Together, these sub-arcsecond images provide the most detailed view yet of radio-jet induced star formation and jet-gas interactions in a gas-rich radio galaxy that is in the process of merging with a swarm of fainter galaxies. We discuss the implications of these results for the influence of massive black holes and nuclear activity on galaxy formation at high redshifts.\u003c/p\u003e"},{"header":"2. RESULTS","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\n \u003ch2\u003e2.1 Images\u003c/h2\u003e\n \u003cdiv id=\"Sec4\" class=\"Section3\"\u003e\n \u003ch2\u003e2.1.1 LOFAR VLBI Radio Images\u003c/h2\u003e\n \u003cp\u003eFigures \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e and \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e show the new ILT 0.4\u0026quot;-resolution radio image of Coma A. Three different contrast levels are displayed to accentuate the visibility of important radio features. Figure \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e has been filtered to accentuate the compact features and radio clumps, by smoothing to a resolution of ~\u0026thinsp;3\u0026quot; and subtracting this smoothed image from the original image. Note the clumpy faint northern jet, the large-scale radio filaments, the jet-aligned nuclear core, the inner jet and 3 southern radio clumps at the location of the jet deflection\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e12\u003c/span\u003e,13,\u003cspan class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec5\" class=\"Section3\"\u003e\n \u003ch2\u003e2.1.2. Comparison With MUSE/VLT Optical Images\u003c/h2\u003e\n \u003cp\u003eThe VLT MUSE IFS observations have been described and discussed in detail\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e, where it is suggested that Coma A is unique case in the local Universe, for which the expanding outflow from a galaxy of stellar mass\u0026thinsp;~\u0026thinsp;10\u003csup\u003e11.5\u003c/sup\u003e M\u003csub\u003e☉\u003c/sub\u003e triggers star formation throughout the radio source. The new grey-scale representations and in the optical overlays shown in Figs. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e and \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e provide the most revealing demonstration so far of interactions between an extended radio source and its host galaxy. The MUSE optical continuum image in Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e shows that the massive galaxy host is embedded in a swarm of fainter galaxies.\u003c/p\u003e\n \u003cp\u003eThe greyscale representation of Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e shows the ionised gas distribution in more detail than previously published. The H\u0026alpha; filaments at the outer boundary of the radio source are moving with a line-of-sight velocity of ~\u0026thinsp;200 km/s outwards from the nucleus (\u0026thinsp;~\u0026thinsp;+\u0026thinsp;200 km/s northwards, ~-200 km/s southwards)\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e. Because of their proximity to the radio lobe boundaries, the velocities of the gas filaments are also likely to be the velocities at which the radio lobes are advancing into the circumgalactic medium. The fact that the typical outflow velocities in the nuclear kiloparsec-scale narrow line region of active galaxies are also a few hundred kilometres per second, is consistent with the advance speed of the lobe boundary not having varied substantially during its history. Assuming a uniform advance-speed of ~\u0026thinsp;200 km/s, and neglecting projection effects, the radio source boundary would take ~2x10\u003csup\u003e8\u003c/sup\u003e y to traverse the ~\u0026thinsp;45 kpc distance from the nucleus to the present edge.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec6\" class=\"Section3\"\u003e\n \u003ch2\u003e2.1.3. Comparison with Chandra X-Ray Images\u003c/h2\u003e\n \u003cp\u003eThe Chandra image\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e and its overlay on the LOFAR radio image are shown in Fig. \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e. A huge halo of hot gas envelops the system and several compact features in the radio image also emit X-rays. The X-ray hot gas (T~10\u003csup\u003e8\u003c/sup\u003eK) is oriented along the radio source and has a total mass of ~\u0026thinsp;10\u003csup\u003e11\u003c/sup\u003eM\u003csub\u003e⊙\u003c/sub\u003e out to a radius of 40 kpc. Note that the southern X-ray hotspot (xHS) is oriented along the \u003cstrong\u003eundeflected\u003c/strong\u003e jet direction. A faint X-ray filamentary shell emanating from the nucleus appears to stretch along the southern boundary of the northern radio lobe.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec7\" class=\"Section3\"\u003e\n \u003ch2\u003e2.1.4. Parameters of prominent compact features.\u003c/h2\u003e\n \u003cp\u003eApproximate parameters of important compact features indicated in the figures are tabulated in Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e, measured from the VLT/MUSE data-set\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\u0026nbsp;\u003ctable id=\"Tab1\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003e\u003cstrong\u003eParameters of radio knots (\u003c/strong\u003eFig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e\u003cstrong\u003e) and H\u0026alpha; gas clumps (\u003c/strong\u003eFig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e\u003cstrong\u003e).\u003c/strong\u003e\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eGas Clumps\u003c/p\u003e\n \u003cp\u003e+ Radio knots\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eR.A. (J2000)\u003c/p\u003e\n \u003cp\u003e(deg)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eDec. (J2000)\u003c/p\u003e\n \u003cp\u003e(deg)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eVelocity (km/s)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eVel.\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e Disp.\u003c/p\u003e\n \u003cp\u003e(km/s)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eIonisation\u003c/p\u003e\n \u003cp\u003eOIII]5007/\u003c/p\u003e\n \u003cp\u003eH\u0026alpha;6563\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eRemarks\u003c/p\u003e\n \u003cp\u003e(v\u0026thinsp;=\u0026thinsp;0 corresponds to z\u0026thinsp;=\u0026thinsp;0.08566)\u003csup\u003e21\u003c/sup\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003egN\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e193.55011\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e27.62602\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e225\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNuclear gas, extended by ~\u0026thinsp;1.5\u0026quot; in E-W direction\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003erN\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e193.55011\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e27.60609\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e330\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eRadio nuclear core. Extended by ~\u0026thinsp;2\u0026quot; in PA\u0026thinsp;~\u0026thinsp;22 deg., along jet\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003egC12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e193.55105\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e27.62468\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e220\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e6.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eJet deflecting gas clump. Extended by ~\u0026thinsp;2.5\u0026quot;, located\u0026thinsp;~\u0026thinsp;1\u0026quot; west of the radio rK1 and rK2. S-shaped wisps connecting to southern and northern filaments\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003erK1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e193.55088\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e27.62454\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-80\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e330\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e5.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003eBright radio knots associated with jet deflection\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003erK2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e193.55078\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e27.62393\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-80\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e380\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.7\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003egC3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e193.55449\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e27.62576\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-215\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003eS-shaped wisps connecting to southern and northern filaments\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003egC4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e193.55380\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e27.62571\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-190\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e55\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.6\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003egHN\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e193.54713\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e27.63087\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e+\u0026thinsp;10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e90\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eVelocity differs by ~\u0026thinsp;140 km/s from adjacent large-scale filament\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003erHN\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e193.54766\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e27.63120\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e120\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003egHS\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e193.55177\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e27.62222\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-190\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e170\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cp\u003e\u003csup\u003e1\u003c/sup\u003e Velocity dispersion within large-scale filamentary structure is typically\u0026thinsp;\u0026lt;\u0026thinsp;~\u0026thinsp;150 km/s.\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\n \u003ch2\u003e2.2 Inferences about Coma A from the Images\u003c/h2\u003e\n \u003cdiv id=\"Sec9\" class=\"Section3\"\u003e\n \u003ch2\u003e2.2.1. Overall structure \u0026ndash; Jet and lobe deflection.\u003c/h2\u003e\n \u003cp\u003eThe figures illustrate the power of multispectral morphology, combined with high angular resolution as a diagnostic tool for probing galaxy evolution. The radio nuclear core (rN), the radio jet, the southern radio knots at the location of the jet deflection (rK1, rK2), the wide radio lobes and the compact \u0026quot;hot spot\u0026quot; at the outer edge of the northern radio lobe (rHN) detected previously \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e12\u003c/span\u003e,13,\u003cspan class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e are all prominently visible.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec10\" class=\"Section3\"\u003e\n \u003ch2\u003e2\u003cem\u003e.2.2. Clumpiness of the radio and ionised gas emissions - widespread turbulence.\u003c/em\u003e\u003c/h2\u003e\n \u003cp\u003eThe most important insight provided by the new sub-arcsecond LOFAR image (Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e) is that the Coma A radio source is highly clumped throughout. Besides the previously known bright knots (rK1, rK2), \u003cstrong\u003emore than 20 fainter radio clumps are detected\u003c/strong\u003e within the northern and southern lobes. Some of these clumps are located within the radio jet and others are located in the outer region of the radio lobes. Clumps are present both in the unfiltered and filtered maps and several were faintly visible in the original unpublished survey data maps that motivated these observations. The final total observed data set is many times larger and in general of excellent quality. Despite several iterations with different calibration cycles and different subsets of the data, the clumps remained clearly visible.\u003c/p\u003e\n \u003cp\u003eThe ubiquity of the radio clumps indicates that the interaction between the radio source and its dense gaseous surroundings results in widespread shocks throughout the source, with \u003cstrong\u003eenhanced turbulent magnetic field clumps\u003c/strong\u003e, where reacceleration of the radio-emitting relativistic particles occur. As seen in the radio emission, the MUSE H\u003cem\u003e\u0026alpha;\u003c/em\u003e brightness distribution (Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e) is also clumpy, indicating that the warm gaseous environment is highly disturbed and shocks resulting from the deceleration of relativistic jets at the clumps can result in magnetic turbulence\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e. The previously known brightest gas clump GC12 is associated with the radio continuum knots rK1, rK2 (Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003ec) at the location where the jet is deflected by ~\u0026thinsp;40 deg. \u003csup\u003e12,13,14\u003c/sup\u003e.\u003c/p\u003e\n \u003cp\u003eThe velocity dispersion in the large-scale gas structures is typically\u0026thinsp;~\u0026thinsp;100\u0026ndash;200 km/s\u003csup\u003e21\u003c/sup\u003e. However, the nucleus, gN, the deflecting southern clump gC12 and the southern gas hot spot all have velocity dispersions that are larger, \u0026gt; 350 km/s\u003csup\u003e21\u003c/sup\u003e, indicating that at these locations the collision of the jet with the gas results in enhanced turbulence and shocks. These would be additional sources for increasing the ionisation of the gas, reaccelerating the radio-emitting relativistic electrons and fragmenting the galaxy comprising clumps gC12, gC3 and gC4.\u003c/p\u003e\n \u003cp\u003eAn analysis of the MUSE emission line data\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e found that the deflector clump, gC12 has sub-solar metallicity, Z ~ 0.6 - 0.8 Z\u003csub\u003eS\u003c/sub\u003e, a stellar age of ~ 3x10\u003csup\u003e6\u003c/sup\u003e y and a low gas density derived from the [SII] line ratios (\u003cem\u003en\u003c/em\u003e\u003csub\u003ee\u003c/sub\u003e \u0026lt; 100 cm\u003csup\u003e\u0026ndash;3\u003c/sup\u003e). The radio knots appear to be in pressure equilibrium with the associated emission-line gas (~ 10\u003csup\u003e-9\u003c/sup\u003e dyne cm\u003csup\u003e-2\u003c/sup\u003e)\u003csup\u003e12\u003c/sup\u003e although given the complexity and model dependence of the interactions and the resultant radiation, such calculations and inferences are subject to large uncertainties.\u003c/p\u003e\n \u003cdiv class=\"BlockQuote\"\u003e\n \u003cp\u003eAssuming that the H\u0026alpha; luminosity originates from stars, the star formation rate, estimated from the H\u0026alpha; luminosity of the 5 brightest clumps is ~\u0026thinsp;5.4 \u0026times; 10\u003csup\u003e40\u003c/sup\u003e erg s\u003csup\u003e\u0026ndash;\u003cspan class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e, corresponding to ~\u0026thinsp;0.8 M\u003csub\u003e☉\u003c/sub\u003e/y\u003csup\u003e21\u003c/sup\u003e. However, the total H\u0026alpha; luminosity of the source would imply a SFR of ~\u0026thinsp;4 M\u003csub\u003e☉\u003c/sub\u003e y\u003csup\u003e\u0026ndash;\u003cspan class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e, corresponding to a total stellar mass of ~\u0026thinsp;4 X 10\u003csup\u003e8\u003c/sup\u003e M\u003csub\u003e☉\u003c/sub\u003e over a radio source lifetime of ~\u0026thinsp;10\u003csup\u003e8\u003c/sup\u003e y\u003csup\u003e21\u003c/sup\u003e. These values are also highly model dependent, given the possible influence of photoionisation and interactions on the observed H\u0026alpha; fluxes.\u003c/p\u003e\n \u003c/div\u003e\n \u003cp\u003eThe X-ray clump, XC12 coincides with the warm gas/radio deflector clumps gC12\u0026thinsp;+\u0026thinsp;rK1+rK2 and is orientated along the direction of the deflected jet. Assuming that the X-rays are thermal, the hot gas clump, xC12, that deflects the jet has a mass of ~\u0026thinsp;2\u0026times;10\u003csup\u003e8\u003c/sup\u003e M\u003csub\u003e⊙\u003c/sub\u003e\u003csup\u003e16\u003c/sup\u003e and dominates the mass of the deflector clump.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec11\" class=\"Section3\"\u003e\n \u003ch2\u003e2.2.3. Filaments and Shells - signatures of episodic nuclear activity.\u003c/h2\u003e\n \u003cp\u003eSeveral large-scale radio and gas filaments can be seen both within and surrounding the radio lobes (Figs. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e,\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e,\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e). These filaments are also clumpy and additional clumps are seen beyond and along the trajectory of the north-western H𝜶 shell. The most prominent filaments are located near the outer edges of the lobes and are likely due to shocks produced by the outward-moving radio lobes impinging on the surrounding gas. This gas is being pushed out into the circumgalactic medium by the radio source with a line-of sight velocity of ~\u0026thinsp;200 km/s. The multiple filamentary structure is consistent with a variable episodic history, in which each filament arose from separate enhanced outbursts of nuclear activity.\u003c/p\u003e\n \u003cp\u003eAdditional evidence for episodic nuclear variability is the morphology of the southern H\u0026alpha; lobe (Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e). Its resemblance to the shape of the wide radio lobe despite its orientation in the direction of the non-deflected jet implies that it is the remnant of a previous radio lobe/ nuclear outburst, that occurred before the deflecting gas clump moved into the jet path. Relativistic particles ejected in such an earlier outburst would have aged sufficiently that their radio radiation is no longer detectable. The radiative lifetime of synchrotron emission is highly model dependent \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e, with a nominal equipartition value of ~\u0026thinsp;10\u003csup\u003e6\u003c/sup\u003e \u0026minus;\u0026thinsp;10\u003csup\u003e8\u003c/sup\u003e y and equipartition magnetic field strength\u0026thinsp;~\u0026thinsp;36 \u0026micro;G\u003csup\u003e22\u003c/sup\u003e, but the likelihood of variability and shock reacceleration within the source also makes these values highly uncertain.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec12\" class=\"Section3\"\u003e\n \u003ch2\u003e2.2.4. Fragmentation of a merging galaxy by the jet.\u003c/h2\u003e\n \u003cp\u003eIntriguingly, the eastern non-radio high-ionization gas clumps gC3 and gC4 (Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003ec) are connected by H\u0026alpha;-emitting gas to both the deflector clump gC12 and the large northern gas filament that marks the outer boundary of the radio source. The radial velocities of gC3 and gC4 differ by ~\u0026thinsp;190 km/s from that of gC12 (see Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e). The H\u0026alpha; connection between these clumps implies that the gC3/gC4 clumps and the jet deflector, GC12, are likely to be remnants of a single galaxy of mass\u0026thinsp;~\u0026thinsp;few x 10\u003csup\u003e8\u003c/sup\u003e M\u003csub\u003e☉\u003c/sub\u003e, that was fragmented\u0026thinsp;~\u0026thinsp;5 x 10\u003csup\u003e7\u003c/sup\u003e y ago, when it drifted into the path of the jet. This would also explain the dented shape of gC12, the disparate line-of-sight velocities and the anomalously large H\u0026alpha; velocity dispersion of the deflector gas clumps (~\u0026thinsp;350 km/s).\u003c/p\u003e\n \u003cp\u003eRelativistic jets can fragment a dwarf galaxy\u0026rsquo;s gas via shocks, turbulence, and entrainment,\u003c/p\u003e\n \u003cp\u003eproducing multiphase structures and shocks that could trigger star formation in both the original galaxy and the breakaway gas clumps\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e. However, the stellar body would remain largely intact due to weak coupling. It has been shown that jet-induced galaxy fragmentation can occur mainly through hydrodynamic and radiative processes rather than direct gravitational effects. Key mechanisms include: (1) Shock compression, where supersonic jet-driven shocks over-pressurise and shatter gas clouds; (2) Turbulent entrainment, in which Kelvin\u0026ndash;Helmholtz instabilities at the jet\u0026ndash;ISM interface mix and ablate gas; and (3) Ram-pressure stripping and cloud crushing, as jets sweep through or engulf gas-rich dwarf systems\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e. Simulations show that the resulting turbulent, multiphase medium can fragment into dense clumps that may either collapse into stars or be dispersed\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e25\u003c/span\u003e,\u003cspan class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n \u003cp\u003eJet-induced gas fragmentation represents both positive and negative feedback - positive, via the formation of dense, star-forming knots and negative, by expelling or heating gas and reducing the long-term star formation potential. In low-mass systems, the balance between these effects likely depends on jet power and ISM structure\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e27\u003c/span\u003e,\u003cspan class=\"CitationRef\"\u003e28\u003c/span\u003e\u003c/sup\u003e. Over the lifetime of the Coma A radio source a mass comparable to the mass of the line-emitting gas (~\u0026thinsp;10\u003csup\u003e7\u003c/sup\u003e-10\u003csup\u003e8\u003c/sup\u003e M\u003csub\u003e0\u003c/sub\u003e) could have been entrained\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e29\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec13\" class=\"Section3\"\u003e\n \u003ch2\u003e2.2.5. Role of photoionisation.\u003c/h2\u003e\n \u003cdiv class=\"BlockQuote\"\u003e\n \u003cp\u003eThere is a high-ionisation bi-cone oriented along the initial direction of the jet\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e. This is indicative of selective directional photoionisation by the nucleus along the jet direction. The bi-cone includes the jet-deflection gas clump gC12 and the northern and southern hot spots. It also overlaps with the Chandra X-ray hot gas structure (Fig. \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003eb)\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e15\u003c/span\u003e,\u003cspan class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n \u003cp\u003eIn view of the small-scale turbulence, the presence of shocks and nuclear AGN variability, the ionisation of the gas clumps is likely due to a complex combination of several processes. Mechanisms that have been proposed include ionisation due to hot cooling gas\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e30\u003c/span\u003e\u003c/sup\u003e, thermal conduction within the intracluster medium\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e30\u003c/span\u003e\u003c/sup\u003e, optical synchrotron emission\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e, reconnection diffusion\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e31\u003c/span\u003e\u003c/sup\u003e, and fast ionizing shocks\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e32\u003c/span\u003e,\u003cspan class=\"CitationRef\"\u003e33\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n \u003c/div\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec14\" class=\"Section3\"\u003e\n \u003ch2\u003e2.2.6. Radio jet de-collimation\u003c/h2\u003e\n \u003cp\u003eNot only is Coma A a radio source with a collimated jet, but it also has wide double-lobes. It is therefore also an important test-bed of jet deflection \u003cstrong\u003eand\u003c/strong\u003e jet de-collimation. Both the collimated narrow southern jet and the de-collimated wide southern radio lobe are deflected by a similar angle (~\u0026thinsp;40 deg.) at the location of the bright southern radio/H\u0026alpha; knots. Hence, the southern jet is both deflected by its collision with the gas cloud, and also de-collimated by the collision, thereby creating a wide radio lobe oriented along the deflected jet rather than in the original jet direction.\u003c/p\u003e\n \u003cp\u003eJet deflection and decollimation could also be caused by variable/episodic nuclear activity. When the jet power is large, the gas clump deflects the jet, preserving its collimation. When the jet power is small, collision with the dwarf galaxy would de-collimate the jet, forming wide lobes.\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e"},{"header":"3. DISCUSSION","content":"\u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003e3.1. Coma A \u003cem\u003eas laboratory of black holes and galaxy formation.\u003c/em\u003e\u003c/h2\u003e \u003cp\u003eOne of the most fascinating issues in modern astrophysics is the crucial role that supermassive black holes (SMBHs) and their associated nuclear activity (AGN/quasars) play in the saga of galaxy formation and evolution. The evidence for such a connection includes:\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003ethe dramatic rise and fall by more than an order of magnitude in the AGN population density as a function of cosmic time (peaking at z\u0026thinsp;~\u0026thinsp;2), that mimics the rise and fall of cosmic star formation\u003csup\u003e\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e35\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003ethe existence of SMBHs at z\u0026thinsp;\u0026gt;\u0026thinsp;6, i.e., less than a billion years after the Big Bang \u003csup\u003e\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e36\u003c/span\u003e,\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e37\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003ethe correlation between the mass of supermassive black holes (SMBHs) and the velocity dispersion of stars in the bulge of their host galaxies\u003csup\u003e\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e38\u003c/span\u003e,\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e39\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003cp\u003eBesides jet deflection, jet de-collimation and jet-induced star formation, several features in the new Coma A images are relevant for understanding this SMBH-galaxy connection.\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003eThe several clumps in the MUSE continuum map (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e) resemble those seen in HST and JWST images of mergers in forming brightest cluster protogalaxies (proto-BCGs) at high redshift, such as the Spiderweb (MRC 1138\u0026thinsp;\u0026minus;\u0026thinsp;262) at z\u0026thinsp;~\u0026thinsp;2.2\u003csup\u003e5\u003c/sup\u003e, the Anthill (4C41.17) at z\u0026thinsp;~\u0026thinsp;3.8\u003csup\u003e40\u003c/sup\u003e and TNJ1338-1942 at z\u0026thinsp;~\u0026thinsp;4.1\u003csup\u003e41,42\u003c/sup\u003e.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eStar formation and gas ionisation aligned with and induced by the radio source occur beyond the confines of the optical galaxy. The observed radio and ionised gas clumpiness indicates that jet-galaxy interaction results in a turbulent clumpy circumgalactic gas, turbulent magnetic field clumps and gas ionisation through shocks and directional nuclear photoionisation.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eThe likely occurrence of multiple episodic nuclear activity in Coma A supports a \u0026ldquo;popcorn\u0026rdquo; model that contributes to unifying extended radio sources, in which the host galaxy nucleus undergoes several episodic \u0026ldquo;quasar\u0026rdquo; bursts of nuclear activity during the radio source lifetime, fed by merging and accompanied by variation in jet power. As the source ages and cosmic evolution progresses, the merger \u0026ldquo;food\u0026rdquo; becomes exhausted and the nuclear \u0026ldquo;pops\u0026rdquo; gradually die out. Evidence for the validity of such a model comes from the known variability of quasars on all observable timescales\u003csup\u003e\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e43\u003c/span\u003e\u003c/sup\u003e and the existence of \u0026ldquo;restarted\u0026rdquo; and \u0026ldquo;double-double extended radio source, with morphological features located symmetrically about their host nuclei\u003csup\u003e\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e38\u003c/span\u003e,\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e39\u003c/span\u003e,40\u003c/sup\u003e.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eThe larger bending in radio sources at z\u0026thinsp;\u0026gt;\u0026thinsp;1.5 \u003csup\u003e47,48,49\u003c/sup\u003e and their frequent envelopment in giant Lyman alpha gas halos\u003csup\u003e\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e50\u003c/span\u003e\u003c/sup\u003e show that jet deflection, as observed in Coma A, is more prevalent at high redshifts, when the circumgalactic and intergalactic gas was denser.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eThe likely fragmentation of a merging galaxy by the Coma A radio jet implies that such processes can contribute to AGN-galaxy feedback during massive galaxy formation.\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec17\" class=\"Section2\"\u003e \u003ch2\u003e3.2. SMBH-jet triggering at cosmic dawn\u003c/h2\u003e \u003cp\u003eAlthough supermassive black holes (SMBHs) are essential ingredients of nuclear activity, the mechanism that triggers and sustains relativistic jets in some SMBHs, but not in others, is still not understood. In most theoretical models of jet-triggering, magnetic fields play a key role. Examples are the Blandford\u0026ndash;Znajek process in which jet energy is extracted from a rapidly rotating black hole via strong poloidal magnetic fields\u003csup\u003e\u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e51\u003c/span\u003e\u003c/sup\u003e and the Blandford-Payne mechanism where magnetic field anchored in the accretion disk shoots material outwards\u003csup\u003e\u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e52\u003c/span\u003e\u003c/sup\u003e. An intriguing possibility motivated by the observations presented here, is that the widespread radio clumpiness and magnetic turbulence, as observed throughout the Coma A radio source be a trigger that can activate jets in SMBHs? Supporting evidence that radio sources could \u0026ldquo;wake up\u0026rdquo; quiescent black holes include:\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003ethe \u0026ldquo;sudden\u0026rdquo; appearance of a transient radio source within the Cygnus A radio source between 1989 and 2015\u003csup\u003e54\u003c/sup\u003e,\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003ethe excess of X-ray AGN by a factor of \u0026gt;\u0026thinsp;10 within a 2.5 Mpc field around the Spiderweb radio protocluster at z\u0026thinsp;=\u0026thinsp;2.2, compared with the Cosmos field at a comparable redshift and stellar mass range\u003csup\u003e55\u003c/sup\u003e.\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec18\" class=\"Section2\"\u003e \u003ch2\u003e3.3. Do radio sources influence the formation and/ or maintenance of the cosmic web?\u003c/h2\u003e \u003cp\u003eObservations at z\u0026sim;3 provide direct evidence that rapidly growing galaxies and active galactic nuclei (AGN) reside within the filamentary structures of the forming cosmic web. Deep Lyα mapping in the SSA22 proto-cluster reveals\u0026thinsp;\u0026gt;\u0026thinsp;1 Mpc gas filaments in which many of the most active galaxies and AGN are embedded\u003csup\u003e\u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e56\u003c/span\u003e\u003c/sup\u003e. Similar large-scale structures have been detected around the massive halo RO-1001 at z\u0026thinsp;=\u0026thinsp;2.91, where 3 Lyα-emitting filaments converge onto a\u0026sim;4\u0026times;10\u003csup\u003e13\u003c/sup\u003e M\u003csub\u003e⊙\u003c/sub\u003e group\u003csup\u003e57\u003c/sup\u003e. ALMA observations further show that nodes of the web at these epochs are exceptionally gas rich, implying that filamentary accretion can efficiently supply fuel for both star formation and rapid SMBH growth\u003csup\u003e\u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eBecause radio jets induce star formation along their path, as in Coma A, we suggest that the presence of jets could have influenced the formation and/or evolution of galaxies in the cosmic web. Support for such an idea includes:\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003ethe alignment of the massive X-ray gas halo in Coma A with the radio jet,\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003ethe inference that magnetic fields in giant radio sources could occupy more than 10% of today\u0026rsquo;s cosmic web\u003csup\u003e60\u003c/sup\u003e,\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003ethe remarkable alignments of 14 companion galaxies along the axis and within the lobes of the 2-Mpc giant DA240 radio source\u003csup\u003e\u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e61\u003c/span\u003e\u003c/sup\u003e and the prominent Pisces chain of NGC galaxies that closely follows the lobes of the 1.1 Mpc giant radio source 3C31\u003csup\u003e61,62,63\u003c/sup\u003e. (The intriguing Pisces chain of bright galaxies was sketched by William Parsons in 1850 from observations with his 72 inch Leviathan Telescope at Birr Castle, then the largest telescope in the world. This was long before radio sources, such as 3C31 or the cosmic web were ever dreamed of. Coincidentally Birr Castle is also the location of the ILT LOFAR Irish station.) Because of their huge sizes, giant radio sources such as DA 240 and 3C31 are likely to be at least\u0026thinsp;~\u0026thinsp;10\u003csup\u003e9\u003c/sup\u003e y old and have formed in the high-redshift cosmic web.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eIf extended radio jets did contribute to galaxy formation in the high-redshift cosmic web, the orientations of the SMBHs that created them must have remained constant during their radio lifetimes of ~\u0026thinsp;\u0026gt;\u0026thinsp;10\u003csup\u003e8\u003c/sup\u003ey. The position angles of high-redshift extended radio sources would then be preferentially aligned \u003cb\u003ealong\u003c/b\u003e high-z cosmic web filaments, \u003cb\u003enot perpendicular\u003c/b\u003e to them, as would be the case if gas from the cosmic web feeds accretion of the SMBHs. This would have profound implications for the origin of the first SMBHs and their host galaxies. Deep small-field high-resolution LOFAR surveys are ideal platforms for checking such predictions, because they will enable studies of the structures of populations of extended radio sources to be made over tens of megaparsecs in narrow spectroscopically-defined high-redshift windows. Although previous searches have been made for radio source alignment effects e.g.\u003csup\u003e64,65,66,67\u003c/sup\u003e, robust studies at high redshifts should be based on spectroscopic redshifts and narrow windows to avoid cosmological proximity effects being masked by chance coincidences.\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"4. LOOKING FORWARD","content":"\u003cp\u003eThe ILT sub-arcsecond images of Coma A and their relation to the optical and X-ray images illustrates the power of high-angular resolution imaging of radio emission as a tool for studying galaxy evolution. The \u003cb\u003ecombination\u003c/b\u003e of multispectral images results in a \u0026ldquo;whole that is greater than the sum of its parts\u0026rdquo;. Additional observations of Coma A would result in further insight into the interaction processes involved in the merger-SMBH-AGN-jet- star formation cycle. These include\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003ehigh-resolution imaging of the molecular gas with the JCMT and ALMA to determine its composition and morphological relation to the Hα-emitting warm gas and radio clumps,\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eUV spectroscopic observations to constrain the stellar composition and ages,\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eVLBI radio observations of the nucleus and deflection clumps,\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003ehigh-resolution mapping of the HI absorption.\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003cp\u003eSuch studies should be complemented by modern astrophysical simulations of several cases, taking into account the wealth of data on the complex interactions involved now available. Also, additional theoretical studies of the details of how magnetic turbulence can trigger radio jets in SMBHs are needed.\u003c/p\u003e \u003cp\u003eUnderstanding the role of supermassive black holes in the early formation of galaxies is a compelling and fundamental reason for conducting a new intensive multispectral sub-arcsecond campaign to observe a large sample of galaxies that exhibit jet-galaxy interactions. Rich food for such a campaign at z\u0026thinsp;\u0026gt;\u0026thinsp;2 is the list of known radio protoclusters\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e, and bent clumpy radio sources associated with quasars\u003csup\u003e\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e43\u003c/span\u003e\u003c/sup\u003e. These objects are generally surrounded by large Lyα halos and host observable radio jet deflections. At low-redshift additional case studies to study at high resolution with the ILT and other wavebands include: Minkowski\u0026rsquo;s Object (z\u0026thinsp;=\u0026thinsp;0.019), 3C293 (z\u0026thinsp;=\u0026thinsp;0.045), 3C305(z\u0026thinsp;=\u0026thinsp;0.041), 4C29.30 (z\u0026thinsp;=\u0026thinsp;0.065) and 3C171 (z\u0026thinsp;=\u0026thinsp;0.238). Another obvious related project is charting the spatial distributions of galaxies within the lobes of giant radio sources now known, easily carried out by comparing data from the Euclid and LOFAR surveys.\u003c/p\u003e"},{"header":"5. METHODS","content":"\u003cp\u003eComa A was observed by the ILT for a total of 43.7 hours in the High Band Antenna mode\u003csup\u003e68\u003c/sup\u003e, of which 39.7 hours was usable. The data were recorded in spectral channels of 12 kHz covering a total bandwidth of ~\u0026thinsp;48 MHz between ~\u0026thinsp;120 and ~\u0026thinsp;168 MHz, with a time resolution of 1 second per integration. The gain and bandpass calibrator sources 3C196 and 3C295 were observed for 10 minutes before and after each exposure.\u003c/p\u003e \u003cp\u003eReduction of the data made use of the complex LOFAR VLBI calibration and imaging procedure developed over the past decade to produce sub-arcsecond HBA images with high dynamic range over several square degrees\u003csup\u003e\u003cspan citationid=\"CR69\" class=\"CitationRef\"\u003e69\u003c/span\u003e,\u003cspan citationid=\"CR71\" class=\"CitationRef\"\u003e70\u003c/span\u003e,\u003cspan citationid=\"CR72\" class=\"CitationRef\"\u003e71\u003c/span\u003e,\u003cspan citationid=\"CR73\" class=\"CitationRef\"\u003e72\u003c/span\u003e,73,\u003cspan citationid=\"CR74\" class=\"CitationRef\"\u003e74\u003c/span\u003e\u003c/sup\u003e. This calibration technique treats large fields as multiple smaller \"facets\"\u003csup\u003e72\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThe data were first processed using the LOFAR Initial Calibration Pipeline (LINC)\u003csup\u003e\u003cspan citationid=\"CR69\" class=\"CitationRef\"\u003e69\u003c/span\u003e\u003c/sup\u003e. After flagging bad data, calibration solutions for slowly-varying instrumental effects (bandpass, clock offsets and polarization alignment), were derived for all stations from the initial calibrators and a secondary round of flagging was carried out. Next, a sky model of the target field was obtained from the TIFR GMRT Sky Survey (TGSS)\u003csup\u003e\u003cspan citationid=\"CR75\" class=\"CitationRef\"\u003e75\u003c/span\u003e\u003c/sup\u003e and applied in a \"phase-only\" calibration cycle. The LOFAR-VLBI pipeline\u003csup\u003e\u003cspan citationid=\"CR74\" class=\"CitationRef\"\u003e74\u003c/span\u003e\u003c/sup\u003e was then used to calibrate data from the international stations. Applying corrections for the dispersive delays derived from two bright compact sources located within 15\u0026rsquo; of Coma A and carrying out phase and amplitude self-calibration resulted in the 0.4\" resolution Coma A image discussed here. Finally, a filtered image, to accentuate the clumps and compact structure visible on the image, was constructed by smoothing the image to a resolution of ~\u0026thinsp;3\u0026rdquo; and subtracting the smoothed map from the original 0.4\" resolution image.\u003c/p\u003e \u003cp\u003eTo construct the optical-radio overlays, the MUSE images were aligned with the ILT radio maps. This was done using the positions of panSTARRS galaxies that were visible in both fields. The MUSE maps needed shifting in declination by +\u0026thinsp;9.5\" for the narrow-band images and +\u0026thinsp;1.6\" for the 5000\u0026ndash;7000\u0026Aring; broad-band image.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003e5. DATA AVAILABILITY\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe data are available from the LOFAR archive. Coma A was observed for a total of 43 hours as a dedicated LOFAR project (LC20_004), supplemented by 40 minutes data\u0026nbsp;from\u003cem\u003e\u0026nbsp;\u003c/em\u003ethe LOFAR Two-Metre Sky Survey\u003csup\u003e60\u003c/sup\u003e.\u0026nbsp;\u003c/p\u003e\u003cp\u003e\u003cstrong\u003e7. ACKNOWLEDGEMENTS.\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eGKM thanks Dr. E.G.B. Vijverberg for his valuable help. This study made use of the excellent ALADIN astronomical display package .\u003c/p\u003e\n\u003cp\u003eLOFAR is the Low Frequency Array, designed and constructed by ASTRON. It has observing, data processing, and data storage facilities in several countries, which are owned by various par- ties (each with their own funding sources), and which are collectively operated by the ILT foundation under a joint scientific policy. The ILT resources have benefited from the following recent major funding sources: CNRS-INSU, Observatoire de Paris and Université d\u0026rsquo;Orléans, France; BMBF, MIWF-NRW, MPG, Germany; Sci- ence Foundation Ireland (SFI), Department of Business, Enterprise and Innovation (DBEI), Ireland; NWO, The Netherlands; The Science and Technology Facilities Council, UK; Ministry of Science and Higher Education, Poland; The Istituto Nazionale di Astrofisica (INAF), Italy.\u003c/p\u003e\n\u003cp\u003eThis research made use of the Dutch national e-infrastructure with support of the SURF Cooperative (e-infra 180169) and the LOFAR e-infra group. The Jülich LOFAR Long Term Archive and the Ger- man LOFAR network are both coordinated and operated by the Jülich Supercomputing Centre (JSC), and computing resources on the supercomputer JUWELS at JSC were provided by the Gauss Centre for Supercomputing e.V. (grant CHTB00) through the John von Neumann Institute for Computing (NIC).\u003c/p\u003e\n\u003cp\u003eThis research made use of the University of Hertfordshire high- performance computing facility and the LOFAR-UK computing fa- cility located at the University of Hertfordshire (https://uhhpc. herts.ac.uk) and supported by STFC [ST/P000096/1], and of the Italian LOFAR IT computing infrastructure supported and operated by INAF, and by the Physics Department of Turin University (un- der an agreement with Consorzio Interuniversitario per la Fisica Spaziale) at the C3S Supercomputing Centre, Italy.\u003c/p\u003e\n\u003cp\u003eWe also made use of ASTROPY, a community-developed core Python package for astronomy (Astropy Collaboration et al. 2013) hosted at http://www.astropy.org/, of MATPLOTLIB (Hunter 2007), of APLPY, an open-source astronomical plotting package for Python hosted at http://aplpy.github.com/, and of TOPCAT and STILTS (Taylor 2005).\u003c/p\u003e\n\u003cp\u003eThe National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eMiley, G. 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Second data release\u003c/em\u003e. arXiv:2202.11733.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"nature-portfolio","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"","title":"Nature Portfolio","twitterHandle":"","acdcEnabled":false,"dfaEnabled":false,"editorialSystem":"ejp","reportingPortfolio":"","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-8549771/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8549771/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eBlack hole-created radio jets frequently interact violently with their host galaxies at z \u0026gt; 2, creating stars. Coma A (3C277.3) is one of few luminous low-redshift radio sources where jet-galaxy interactions deflect the jet and induce star formation - a nearby laboratory of massive galaxy formation. We present the first LOFAR VLBI radio image of Coma A and compare it with VLT/MUSE optical images and Chandra X-ray maps. \u0026nbsp;Remarkable features of the radio emission are clumpiness, multiple filaments and the relation of the radio to the optical and X-ray morphologies. The optical continuum image shows a swarm of galaxies apparently merging with Coma A, similar to high-redshift radio protoclusters. \u0026nbsp;Three optical clumps are probable remnants of a merging galaxy, fragmented by collision with the jet. We suggest that magnetic turbulence in Coma A-type radio-emitting clumps, could trigger radio jets in quiescent black holes and that positive feedback from radio jets could contribute to the structure of the high-redshift cosmic web. A prediction of such a scenario is that the morphologies of high-redshift extended radio sources are oriented preferentially along cosmic web filaments, with important implications for how the first supermassive black holes formed.\u003c/p\u003e","manuscriptTitle":"LOFAR VLBI Observations of Coma a - Nearby Laboratory of Massive Galaxy and Black Hole Formation","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-01-29 16:42:41","doi":"10.21203/rs.3.rs-8549771/v1","editorialEvents":[],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"nature-communications","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"NCOMMS","sideBox":"Learn more about [Nature Communications](http://www.nature.com/ncomms/)","snPcode":"","submissionUrl":"https://mts-ncomms.nature.com/","title":"Nature Communications","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"ejp","reportingPortfolio":"Nature Communications","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"93ab21de-4f91-4789-8693-7424e866de2e","owner":[],"postedDate":"January 29th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[{"id":61957530,"name":"Physical sciences/Astronomy and planetary science/Astronomy and astrophysics/Early universe"},{"id":61957531,"name":"Physical sciences/Astronomy and planetary science/Astronomy and astrophysics/Galaxies and clusters"}],"tags":[],"updatedAt":"2026-01-29T16:42:41+00:00","versionOfRecord":[],"versionCreatedAt":"2026-01-29 16:42:41","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8549771","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8549771","identity":"rs-8549771","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}