arXiv subjects

Preeti Kharb

Publications and source records attributed to Preeti Kharb.

At least 19 recordsLinked to original sources

arXiv2026

Chandra X-ray imaging and IC/CMB model for the inner jet of PKS 0637-752

We present the X-ray surface brightness maps of the jet from the quasar PKS 0637-752, using two epochs of archival Chandra observations (1999 and 2017). We present, for the first time, a model of the faint inner jet extending from 3.4 to 7 arcsec from the core, interpreting its X-ray emission as inverse Compton scattering of cosmic microwave background photons by the synchrotron-emitting relativistic electrons. The inner jet contrasts with the bright outer part of the jet, dominated by several discrete knots for which upper limits to the Fermi gamma-ray flux rule out the inverse Compton mechanism. It is the first detailed inverse Compton model published for this inner jet. We examine three physically motivated scenarios, distinguished by the high-energy cutoff of the electron distribution, that can account for the observed radio, millimeter/submillimeter, and X-ray emission while remaining consistent with optical and gamma-ray upper limits. We also report for the first time X-rays from the radio lobe at the end of the receding jet.

astro-ph.HE↗

arXiv2026

A Rare Gamma-ray Flaring episode of the Narrow-Line Seyfert 1 Galaxy 1H 0323+342

Gamma-ray-emitting narrow-line Seyfert 1 ($\gamma$-NLSy1) galaxies represent an enigmatic class of active galactic nuclei (AGNs) bridging populations of radio-quiet and radio-loud AGNs. Here we report the multi-wavelength investigation of a rare $\gamma$-ray flaring episode of an NLSy1 galaxy, 1H 0323+342 ($z=0.063$), using data from Fermi-Large Area Telescope, Swift, and Nuclear Spectroscopic Telescopic Array. The source exhibited a significant enhancement in $\gamma$-ray flux along with rapid variability on $\sim$sub-hour timescales in both $\gamma$-ray and hard X-ray wavelengths, hinting that the energy dissipation is happening from a compact region close to the central supermassive black-hole. The time-resolved X-ray spectral study revealed a transition between a jet-dominated and a mixed jet+corona emission state. Reproducing the broadband spectral energy distribution with a one-zone leptonic model suggested that the high-energy emission is mainly produced by external Compton scattering of the accretion disc and broad line region photons. The inferred jet power reaches values of the order of $10^{46}$ erg s$^{-1}$ comparable to those of powerful flat-spectrum radio quasars, suggesting that even low black-hole mass systems can occasionally produce powerful $\gamma$-ray outbursts.

astro-ph.HE↗

arXiv2026

VLTI-GRAVITY observations of blazars

Parsec-scale jets of blazars have so far been spatially resolved only in millimeter and submillimeter wavelengths, where very long baseline interferometry can be used to obtain milliarcsecond-scale images of the jets. We have attempted to spatially resolve the near-infrared emission in jet-dominated blazars for the first time. We used the VLTI-GRAVITY instrument to obtain milliarcsecond-scale near-infrared interferometric observations of a flaring blazar Ton 599. Additionally, we observed four non-flaring blazars using the GRAVITY-wide mode, where a nearby bright star is used as a fringe tracker. We modeled the squared visibilities of Ton 599 and found that they are incompatible with a single unresolved point source unless there is a significant amount of additional unknown coherence loss in the instrument. With the present data, we cannot distinguish between a model with an unresolved point source and extended emission or coherence loss and a model with a single Gaussian component. This suggests that we are seeing the unresolved or only partially resolved jet-base in near-infrared wavelengths. The wide-field mode of GRAVITY was challenging for the additional relatively faint targets, resulting in either non-detections or poor-quality data that could not be modeled. Our observations demonstrate that it is possible to detect the compact jet emission in blazars with near-infrared interferometry, suggesting that with the improved GRAVITY+ instrument it will be possible to spatially resolve and image the near-infrared emission of blazar jets.

astro-ph.GA↗

arXiv2026

AGN Fueling and Radio Jet Evolution in the Galaxy Group NGC 5044 revealed by VLBA HI Absorption and Proper-Motion Radio Observations

The role of cooling gas in triggering active galactic nucleus (AGN) feedback in the centers of galaxy groups and clusters remains a key open question. NGC 5044, the X-ray brightest galaxy group, hosts the largest known reservoir of molecular gas among cool-core groups and exhibits multiple AGN outbursts, making it an ideal system to study AGN feeding. We present new multi-frequency Very Long Baseline Array (VLBA) observations of NGC 5044 at 1.4 GHz, 4.9 GHz, and 8.4 GHz, combining continuum imaging with HI spectroscopy. At 1.4 GHz, we recovered the previously known symmetric northeast-southwest jets extending for 5.5 pc each, along with evidence for previously undetected, more extended faint emission aligned with the older, kpc-scale outbursts. Comparison of 4.9 GHz and 8.4 GHz data from 2020 and 2024 reveals clear outward proper motion of jet components, yielding an average expansion speed of $(0.10\pm0.02)\,c$ and implying a dynamical age of $\sim$180 yr for the ejection of the parsec-scale jet components. The jet width profile suggests a transition from parabolic to conical collimation at a few $\times 10^{4}$ Schwarzschild radii. We detect a narrow, redshifted HI absorption line at $+264\,\mathrm{km\,s^{-1}}$ against the VLBA core, tracing a compact, cold atomic cloud within $\sim$10-20 pc of the AGN. The close velocity correspondence with previously detected CO and HI absorption features in ALMA and MeerKAT data, respectively, demonstrates that cold atomic and molecular gas coexists in infalling clouds at parsec scales. Overall, these results provide an unprecedented high angular resolution view of AGN cycling, jet growth, and feeding in a galaxy group environment.

astro-ph.GA↗

arXiv2026

Survey of compact sources for pulsars and exotic objects -- I. Overview and initial discoveries

Targeted searches for pulsars based on their counterparts in radio images have resulted in the discovery of interesting pulsars including the first ever discovered millisecond pulsar (MSP). Here, we report the first results from our image-based survey of compact sources for pulsars and exotic objects (SCOPE). SCOPE utilizes interferometric as well as time-domain observations to search for radio pulsations as well as characterize the sources in the image-domain to identify their true nature. In the first stage of the SCOPE survey, we have used the Giant Metrewave Radio Telescope (GMRT) and the Green Bank Telescope (GBT) to follow up a sample of 31 compact and steep-spectrum sources. We provide an overview of the survey, the sample selection, the search procedures, and present discoveries of two MSPs -- PSR J1840+1102 and PSR J1827-0849. PSR J1840+1102 is a 1.6 ms pulsar at the edge of the Scutum-Centaurus arm, while PSR J1827-0849 is the radio counterpart of a gamma-ray pulsar that was earlier thought to be radio-quiet, and both the sources have very steep radio spectra. Using the interferometric data, we also provide a morphological classification of all the sources, model and characterize their spectra and identify the resolved, extragalactic sources in our sample. We discuss these results in the context of future image-based pulsar surveys.

astro-ph.HE↗

arXiv2026

The Quasar Feedback Survey: Revealing the importance of sensitive radio imaging for AGN identification deeper into the radio-quiet regime

We present new sub-arcsecond ($\sim$0.3-1 arcsec; $\sim$1--3\,kpc) VLA imaging at 1.4\,GHz and 6\,GHz of 29 optically-selected, [O~{\sc iii}] luminous ($L_{\rm [O III]}$ > 10$^{42.1}$\,erg\,s$^{-1}$), $z<0.2$ quasars drawn from the expanded Quasar Feedback Survey (QFeedS; with $L_\mathrm{1.4\,GHz} = 10^{22.6}$--10$^{26.3}$\,W\,Hz$^{-1}$). These 29 new objects occupy the low end of the radio-power distribution ($L_\mathrm{1.4\,GHz}$=$10^{22.63}$--10$^{23.45}$\,W\,Hz$^{-1}$) in the QFeedS sample and are nominally `radio quiet'. Despite this, we find widespread evidence of AGN-driven synchrotron activity. Nearly $\sim 31\,$per\,cent exhibit resolved radio structures on $\sim$0.1--20\,kpc scales consistent with compact jets or wind-driven outflows, and $\sim 90\,$per\,cent display steep spectra ($\alpha \lesssim -1$) indicative of optically thin synchrotron emission. Combining morphology, spectral index and brightness-temperature diagnostics, at least $\sim38\,$per\,cent of the sample show clear AGN signatures that cannot be explained by star formation alone. These constitute the first results from the expanded QFeedS (now 71 quasars spanning $\approx 4$ dex in radio power) and demonstrate that compact, low-power jets and AGN shocks are common deep inside the radio-quiet regime. A thorough understanding of feedback processes from quasars, deep into the `radio-quiet' regime, will be obtained by connecting these high resolution radio observations with multi-wavelength observations.

astro-ph.GA↗

arXiv2025

Two Epochs of VLBI Observations of 8 KISSR Seyfert & LINER Galaxies: Suggestions of Fast and Filamentary Outflows

We present here the results from a second epoch of phase-referenced VLBA observations of 8 Seyfert and LINER galaxies from the KISSR sample. These sources were chosen based on the presence of double peaks or asymmetries in their emission lines as observed in SDSS spectra. Parsec-scale radio emission is detected in 7 of the 8 sources in the second epoch. Jet-like features appear to persist over a $\sim4-9$ year timeline in these `radio-quiet' AGN. A few sources like KISSR1494, however, show significantly different structures after a 9 year interval. KISSR102, which was previously suggested to be a binary black hole candidate based on the presence of two compact cores, shows the tentative signatures of superluminal jet motion ($1.05\pm0.45$c). Tentative superluminal motion in a jet knot has been reported in another source, KISSR872 ($1.65\pm0.57$c). We present 1.5 GHz images from the VLA A-array of 4 sources. These images reveal core-lobe or core-halo structures. The alignment of the VLBI jet direction with the kpc-scale spectral index gradient, as well as the mismatch between the star formation rate derived from the radio and H$\alpha$ line emission, support the suggestion that the kpc-scale emission is AGN-jet-related. The jets in KISSR sources appear to lose collimation over spatial scales between 200 parsec and 1 kpc. Overall, the characteristics of the KISSR jets are reminiscent of similar properties observed in VLBI monitoring studies of `radio-loud' AGN jets even as subtle differences related to the compactness and brightness of jet features remain.

astro-ph.GA↗

arXiv2025

A Deep Chandra View of Abell 2597: Bubbles, Shocks, Cold Fueling, and a Plasma Depletion Layer

To examine how AGN feedback shapes the intracluster medium (ICM) and fuels black hole accretion in the cool-core galaxy cluster Abell 2597, we present deep ($\sim$600 ks) Chandra X-ray observations complemented by archival GMRT radio and SINFONI near-infrared data. Radio-mode AGN activity has inflated seven X-ray cavities and driven one to three potential weak shocks ($M \sim 1.05-1.14$) extending to $\sim 150$ kpc, suggesting recurrent outbursts occurring on $\sim 10^7$ year timescales. We also detect a narrow, $\sim$57 kpc X-ray surface brightness deficit-a potential plasma depletion layer-likely shaped by residual sloshing motions that amplified magnetic fields and/or displaced gas within the cluster core. Although the AGN injects $\sim 10^{44}$ erg s$^{-1}$ of energy, comparable to the cluster's cooling luminosity, radiative cooling persists at $\sim$15 M$_{\odot} $yr$^{-1}$, replenishing the billion solar mass cold gas reservoir at the heart of the brightest cluster galaxy. Sustaining this level of activity requires a continuous fuel supply, yet the estimated Bondi accretion power ($\sim 2 \times 10^{43}$ erg s$^{-1}$) falls an order of magnitude short of the observed cavity power, suggesting that "hot" gas fueling is insufficient. Instead, archival ALMA observations continue to support a chaotic cold accretion scenario, where turbulence-driven condensation fuels the AGN at rates exceeding Bondi accretion, sustaining a self-regulated feedback cycle that repeatedly shapes the core of Abell 2597.

astro-ph.GA↗

arXiv2025

Probing the Low Radio Frequency Emission in PG Quasars with the uGMRT -- II

We present results from uGMRT 685 MHz observations of 87 QSOs belonging to the Palomar Green (PG) quasar sample with $z<0.5$. Radio emission is detected in all sources except for 3 radio-quiet (RQ) sources, viz., PG 0043+039, PG 1121+422, and PG 1552+085. The radio-loud (RL) $-$ RQ dichotomy persists at 685 MHz with only 1 source, PG 1216+069, changing its classification from RQ to RL. Approximately 1/3 of the detected RQ quasars display AGN-dominated radio emission while the rest may show additional contributions from stellar-related processes. Consistent with this, the RL and RQ quasars occupy distinct tracks on the `fundamental plane' of black hole activity. We find that RL quasars have $\log_{10}(L_{685\,\mathrm{MHz}}/\mathrm{W\,Hz}^{-1}) > 25.5$, while RQ quasars have ${\log_{10}(L_{685\,\mathrm{MHz}}/\mathrm{W\,Hz}^{-1})} <23.5$. Furthermore, the radio sizes display the RQ$-$RL divide as well with RQ sources typically having sizes $\lesssim30$ kpc, with only 16 ($\sim22$%) RQ sources having sizes between 30 and 100 kpc where there is an overlap with RL quasar sizes. A strong correlation exists between 685 MHz radio luminosity and black hole mass which is tightened when accretion rate is considered, highlighting the important role played by the accretion rate and accretion disk structure in jet production. We found no difference in the minimum-energy magnetic field strengths of the radio cores of RL and RQ quasars; however, different assumptions of source volume and volume filling factors may apply. High-resolution X-ray observations and radio-X-ray flux comparisons are needed to independently test the `magnetic flux paradigm'.

astro-ph.GA↗

arXiv2025

What drives kpc-scale outflows in Radio-Quiet AGN? Insights from a Polarimetric Study

We present a review of our findings on the origin, drivers, nature, and impact of kiloparsec-scale radio emission in radio-quiet (RQ) AGN. Using radio polarimetric techniques, we probe the dynamics and magnetic (B-) field geometry of outflows in Seyfert and LINER galaxies. Multi-band data from the Karl G. Jansky Very Large Array (VLA) reveal how low-power jets interact with their environment. These interactions can slow down and disrupt the radio outflows while locally regulating star formation through AGN feedback. Several radio properties correlate strongly with the black hole mass, similar to trends observed in radio-loud (RL) AGN. Although their characteristics differ, RQ systems might not be intrinsically distinct from RL AGN, apart from lower jet powers. Our polarization measurements further suggest a composite model in which a black hole-accretion disk system drives both a collimated jet with a small-pitch-angle helical B-field and a wide-angle wind threaded by a high-pitch-angle helical field.

astro-ph.GA↗

arXiv2025

A Comprehensive Multiwavelength Study of the OH Megamaser galaxy IRAS 09320+6134

We present a multiwavelength study of the gas distribution, kinematics and excitation of the OH megamaser galaxy IRAS 09320+6134 (UGC 5101) using Gemini Multi-Object Spectrograph Integral Field Unit, Hubble Space Telescope, and Very Large Array observations. The HST ACS F814W i-band and H$\alpha$ + [N II] $\lambda\lambda$ 6548,84 narrow-band images indicate that this galaxy is a late-stage merger. The ionized gas emission in the inner $\sim$ 2 kpc radius, traced by the GMOS data, is consistent with two kinematic components: (i) a rotating disk, observed as a narrow component in the emission-line profiles, with velocity dispersion of $\sigma$ $\leq$ 200 km s$^{-1}$, and (ii) an outflow, traced by a broad component in the emission-line profiles, with $\sigma\geq$ 500 km s$^{-1}$. The disk component is well reproduced by a model of rotation in a plane with similar orientation to that of the large-scale galaxy disk. The outflow component presents bulk velocities of up to -500 km s$^{-1}$ and corresponds to a mass outflow rate of $\dot{M}_o = 0.122 \pm 0.026 M_{\odot}$ yr$^{-1}$. Emission-line ratio diagrams indicate that the gas excitation is mainly due to an active galactic nucleus, likely the driver of the outflow. The VLA radio image reveals a dominant radio core with two-sided emission along the NE-SW direction. The radio core's spectral index and brightness temperature indicate AGN emission, with the extended emission resembling both in morphology and spectral index the emission observed in radio-quiet quasars. Combined with previous similar studies of other OHM galaxies, the present work supports that this phase is linked to the triggering of an AGN, that seems to occur in the final stages of a merger.

astro-ph.GA↗

arXiv2025

Investigating the emission mechanism in the spatially-resolved jet of two z $\approx$ 3 radio-loud quasars

This study focuses on high-redshift, z > 3, quasars where resolved X-ray jets remain underexplored in comparison to nearby sources. Building upon previous work, we identify and confirm extended kpc-scale jets emission in two quasars (J1405+0415, z = 3.215 ; J1610+1811, z = 3.122) through meticulous analysis of Chandra X-ray data. To deepen our understanding, high-resolution radio follow- up observations were conducted to constrain relativistic parameters, providing valuable insights into the enthalpy flux of these high-redshift AGN jets. The investigation specifically aims to test the X-ray emission mechanism in these quasars by exploring the inverse Compton scattering of cosmic microwave background (IC/CMB) photons by synchrotron-emitting electrons. Our novel method uses a prior to make a Bayesian estimate of the unknown angle of the jet to our line of sight, thus breaking the usual degeneracy of the bulk Lorentz factor and the Doppler beaming factor.

astro-ph.HE↗

arXiv2025

Jet-mode feedback in NGC 5972: insights from resolved MUSE, GMRT and VLA observations

NGC 5972, a Voorwerp galaxy, features a helical-shaped extended emission-line region (EELR) with a radius > 10 kpc and a S-shaped radio structure spanning about 470 kpc. We use VLT MUSE, GMRT, and VLA to study the stellar and ionized gas kinematics and how the radio jet influences the gas in the galaxy. Our sensitive radio observations detect the southern jet for the first time, roughly coinciding with the southern EELR. The VLA images show a continuous inner jet connected to the outer E-W lobe, confirming the jet origin of the radio emission. Our kinematic analysis shows spatial correlations between the radio jet and the outflowing gas, supporting the jet-driven feedback mechanism. More interestingly, we observe enhanced velocity dispersion in the perpendicular direction along with a shell-like structure. Our BPT analysis shows that the [O III] emission overlapping with the radio jet is consistent with the shock+precursor model, whereas in the perpendicular region, a pure shock model fits well with the observations, indicating jet-induced shocks. Radio observations indicate episodic AGN activity characterized by surface brightness and spectral index discontinuities. Overall, based on our findings, we propose a jet-driven feedback mechanism as one of the key factors in the formation of the EELR in NGC 5972. Future high-resolution radio observations will be crucial to further investigate the origin of the EELR and quantify the extent to which the jet influences its formation and evolution.

astro-ph.GA↗

arXiv2025

The Quasar Feedback Survey: zooming into the origin of radio emission with e-MERLIN

We present 6 GHz e-MERLIN observations of 42 $z<0.2$ type 1 and type 2 mostly radio-quiet quasars ($L_{\rm[OIII]}\gtrsim10^{42}$ erg s$^{-1}$; $L_{\rm AGN}\gtrsim10^{45}$ erg s$^{-1}$) from the Quasar Feedback Survey. The nature and origin of radio emission in these types of sources is typically ambiguous based on all-sky, low-resolution surveys. With e-MERLIN, we investigate radio emission on sub-kiloparsec scales ($\sim$10s-100s pc). We find 37/42 quasars are detected, with a diversity of radio morphologies, including compact cores, knots and extended jet-like structures, with sizes of 30-540 pc. Based on morphology and brightness temperature, we classify 76 per cent of the quasars as radio-AGN, compared to the $\sim$57 per cent identified as radio-AGN at the $\sim$1-60 kpc scales probed in prior studies. Combining results from e-MERLIN and the Very Large Array, 86 per cent reveal a radio-AGN. On average, $\sim$60 per cent of the total radio flux is resolved away in the e-MERLIN maps, and is likely dominated by jet-driven lobes and outflow-driven shocks. We find no significant differences in measured radio properties between type 1 and type 2 quasars, and estimate sub-relativistic jet speeds of $\sim$0.2-0.3c and modest jet powers of $P_\mathrm{jet} \approx \times$10$^{43}$ erg s$^{-1}$ for the few targets, where these measurements were possible. These quasars share characteristics with compact radio-selected populations, and the global radio emission likely traces strong interactions between the AGN (jets/outflows) and their host galaxy ISM from 10s parsec to 10s kiloparsec scales.

astro-ph.GA↗

arXiv2024

Demographics of black holes at $<$100 R$_{\rm g}$ scales: accretion flows, jets, and shadows

Using the Event Horizon Telescope (EHT), the gravitationally lensed rings around the supermassive black holes (SMBHs) in Messier 87 (M87) and Sagittarius A* (Sgr A*) have now been successfully imaged at a resolution under 10 gravitational radii (R$_{\rm g}$ $ = \rm{GM/c^2}$). To expand studies beyond M87 and Sgr A*, we have constructed the Event Horizon and Environs (ETHER) sample, a comprehensive database encompassing approximately 3.15 million SMBH mass estimates, $\sim$ 20,000 Very-Long Baseline Interferometry (VLBI) radio flux densities, and $\sim$ 36,000 hard X-ray flux densities. This database is designed to identify and optimize target selection for the EHT and its upgrades on the ground and in space. We have identified a Gold Sample (GS) of nearby low-luminosity Active Galactic Nuclei (AGNs) within it that are ideal for studying jet bases and potentially imaging black hole shadows. We observed 27 of these AGNs using the EHT from 2022 to 2024, providing an opportunity to resolve and image accretion flows and jets at resolutions of $\leq$ 100 R$_{\rm g}$. Only a few SMBHs have sufficiently high enough flux density to be imaged at scales of $\leq$ 50 R$_{\rm g}$ with the present EHT. Among these are M87, Sgr A*, NGC4594 (Sombrero/M104), NGC4261, and NGC4374 (Messier 84/M84). Of these, NGC4261, Sombrero, and M84 have been observed and/or are scheduled for deep imaging with EHT+ALMA from 2023 to 2025. Sombrero, NGC4261, M84, NGC4278, and NGC5232 are clearly detected in our EHT+ALMA observations in 2022, indicating that the 230 GHz flux density from the accretion flows is significantly high. Ongoing imaging of the ETHER GS will enable measurements of black hole mass and spin, help constrain General Relativity, and enrich our understanding of jet launching and accretion inflows across a broad multi-parameter space, including black hole mass, spin, accretion rate, and orientation.

astro-ph.GA↗

arXiv2024

A VLBA-uGMRT search for candidate binary black holes: Study of six X-shaped radio galaxies with double-peaked emission lines

Identifying methods to discover dual AGN has proven to be challenging. Several indirect tracers have been explored in the literature, including X/S-shaped radio morphologies and double-peaked (DP) emission lines in the optical spectra. However, the detection rates of confirmed dual AGN candidates from the individual methods remain extremely small. We search for binary black holes in a sample of six sources that exhibit both X-shaped radio morphology and DP emission lines using the VLBA. Three out of the six sources show dual VLBA compact components, making them strong candidates for binary black hole sources. In addition, we present deep uGMRT images revealing the exquisite details of the X-shaped wings in three sources. We present a detailed precession modeling analysis of these sources. The BH separations estimated from the simplistic geodetic precession model are incompatible with those estimated from emission line offsets and the VLBA separations. However, precession induced by a noncoplanar secondary black hole is a feasible mechanism for explaining the observed X-shaped radio morphologies and the black hole separations estimated from other methods. The black hole separations estimated from the double-peaked emission lines agree well with the VLBA compact component separations. Future multi-frequency VLBA observations will be critical in ruling out or confirming the binary black hole scenario in the three galaxies with dual component detections.

astro-ph.GA↗

arXiv2024

Analysis of the structural complexity of Crab Nebula observed at radio frequency using a multifractal approach

The Crab Nebula is an astrophysical system that exhibits complex morphological patterns at different observing frequencies. We carry out a systematic investigation of the structural complexity of the nebula using publicly available imaging data at radio frequency. For the analysis, we use the well-known multifractal detrended fluctuation analysis in two dimensions. We find that radio data exhibit long-range correlations, as expected from the underlying physics of the supernova explosion and evolution. The correlations follow a power-law scaling with length scales. The structural complexity is found to be multifractal in nature, as evidenced by the dependence of the generalized Hurst exponent on the order of the moments of the detrended fluctuation function. By repeating the analysis on shuffled data, we further probe the origin of the multifractality in the radio imaging data. For the radio data, we find that the probability density function is close to a Gaussian form. Hence, the multifractal behavior is due to the differing nature of long-range correlations of the large and small detrended fluctuation field values. We investigate the multifractal parameters across different partitions of the radio image and find that the structures across the image are highly heterogeneous, making the Crab Nebula a structurally complex astrophysical system. Our analysis thus provides a fresh perspective on the morphology of the Crab Nebula from a complexity science viewpoint.

nlin.AO↗

arXiv2023

AGN driven outflows in the OH absorber galaxy IRAS 19154+2704

We present a two-dimensional study of the gas distribution, excitation and kinematics of the OH absorber galaxy IRAS 19154+2704 using Gemini GMOS-IFU observations. Its continuum image shows a disturbed morphology indicative of a past or on-going interaction. The ionised gas emission presents two kinematic components: a narrow ($σ\lesssim$300 km s$^{-1}$) component that may be tracing the gas orbiting in the galaxy potential and a broad ($σ\gtrsim$500 km s$^{-1}$) component which is produced by an Active Galactic Nucleus (AGN) driven outflow, with velocities reaching $-$500 km s$^{-1}$ which may exceed the escape velocity of the galaxy. The emission-line ratios and BPT diagrams confirm that the gas excitation in the inner $\sim$2 kpc is mainly due the AGN, while in regions farther away, a contribution from star formation is observed. We estimate a mass outflow rate of $\dot{M}_{\rm out}=4.0\pm2.6$ M$_\odot$ yr$^{-1}$ at a distance of 850 pc from the nucleus. The corresponding outflow kinetic power $\dot{E}_{\rm out} = (2.5\pm1.6)\times10^{42}$ erg s$^{-1}$, is only $3\times10^{-4}$ L$_{\rm bol}$ (the AGN luminosity), but the large mass-outflow rate, if kept for a $\sim$10 Myr AGN lifecycle, will expel $\approx10^8$ M$_\odot$ in ionised gas alone. This is the 6th of a series of papers in which we have investigated the kinematics of ULIRGS, most of which are interacting galaxies showing OH Megamasers. IRAS19154 shows the strongest signatures of an active AGN, supporting an evolutionary scenario: interactions trigger AGN that fully appear in the most advanced stages of the interaction.

astro-ph.GA↗