arXiv subjects

Daniel Stern

Publications and source records attributed to Daniel Stern.

At least 55 records · Page 3Linked to original sources

arXiv2025

BASS. XLIX. Characterization of highly luminous and obscured AGNs: local X-ray and [NeV]$λ$3426 emission in comparison with the high-redshift Universe

We present a detailed analysis of the most luminous and obscured Active Galactic Nuclei (AGNs) detected in the ultra-hard X-ray band (14-195 keV) by Swift/BAT. Our sample comprises 21 X-ray luminous (log $L_X/{\rm erg\,s^{-1}}>44.6$, 2-10 keV) AGNs at $z<0.6$, optically classified as Seyfert 1.9-2. Using NuSTAR, XMM-Newton, Suzaku, and Chandra, we constrain AGN properties such as absorption column density $N_H$, photon index $Γ$, intrinsic $L_X$, covering factor, and iron K$α$ equivalent width. For sources with black hole mass estimates (12/20), we find a weak correlation between $Γ$ and Eddington ratio ($λ_{Edd}$). Of these, six ($50\pm13\%$) lie in the $N_H$-$λ_{Edd}$ "forbidden region'' and exhibit a combined higher prevalence of $N_H$ variability and outflow signatures, suggesting a transitional phase where AGN feedback may be clearing the obscuring material. For the 13/21 sources with multi-epoch X-ray spectra, $82^{+6}_{-16}\%$ exhibit variability in either 2-10 keV flux ($73^{+9}_{-16}\%$) or line-of-sight $N_H$ ($33^{+15}_{-10}\%$). For the 20/21 sources with available near-UV/optical spectroscopy, we detect [NeV]$λ$3426 in 17 ($85^{+5}_{-11}\%$), confirming its reliability to probe AGN emission even in heavily obscured systems. When normalized to the same [OIII]$λ$5007 peak flux as $z = 2$-$9$ narrow-line AGNs identified with JWST, our sample exhibits significantly stronger [NeV]$λ$3426 emission, suggesting that high-redshift obscured AGNs may be intrinsically weaker in [NeV]$λ$3426 or that [NeV]$λ$3426 is more challenging to detect in those environments. The sources presented here serve as a benchmark for high-redshift analogs, showing the potential of [NeV]$λ$3426 to reveal obscured AGNs and the need for future missions to expand X-ray studies into the high-redshift Universe.

astro-ph.GA↗

arXiv2025

Gas-Poor Hosts and Gas-Rich Companions of $z\approx$3.5 Radio Active Galactic Nuclei: ALMA Insights into Jet Triggering and Feedback

Cold gaseous systems play important roles in galaxy evolution by possibly providing fuel to ignite active galactic nuclei (AGN) activity and star-formation. In this work, we analyze [CII]$158\rm μm$ and continuum observations from ALMA for a sample of four radio AGN at $z \approx 3.5$, focusing on eight associated companion cloud systems discovered within projected distances of tens of kiloparsecs or less. The spatial distribution of these companions indicates that the majority of cold gas is not located at the AGN position, i.e., not in their host galaxies. With the assistance of [CII] at $0.2"$ resolution, we further confirm the gas-poor nature of the hosts by re-analyzing archival [CI] (a tracer of H$_{2}$) at $\sim2"$ resolution. Our sample has [CII] luminosities in a range of $2.8\times10^{8}<L_{\rm [CII]}/L_{\odot}<4.2\times10^{9}$. The $L_{\rm [CII]}/L_{\rm IR}$ ratio, $\sim 9.4\times10^{-4}$, is consistent with sources discussed in the literature. Our findings show the gas-poor radio AGN hosts have nearby gas-rich companions. We propose that these companions may be stripped clouds resulting from merger processes, which could be a trigger of radio-loud AGN. They may also be a signature of negative AGN feedback (e.g., shock heating) on these infalling companions and on the host galaxy. In general, our analysis shows that powerful AGN at and before Cosmic Noon are impacting and being impacted by cold gaseous clouds in their circumgalactic or protointracluster media.

astro-ph.GA↗

arXiv2025

BASS XLVIII: [Ne v] λ3427 Emission in Powerful Nearby Active Galactic Nuclei

We investigate the high-ionization, narrow [Ne v] $λ$3427 emission line in a sample of over 340 ultrahard X-ray (14-195 keV) selected Active Galactic Nuclei (AGN) drawn from the BASS project. The analysis includes measurements in individual and stacked spectra, and considers several key AGN properties such as X-ray luminosity, supermassive black hole (SMBH) mass, Eddington ratios, and line-of-sight column density. The [Ne v] $λ$3427 line is robustly detected in ~43% (146/341) of the AGN in our sample, with no significant trends between the detection rate and key AGN/SMBH properties. In particular, the detection rate remains high even at the highest levels of obscuration (>70% for log[N_H/cm^-2] > 23). On the other hand, even some of our highest signal-to-noise spectra (S/N > 50) lack a robust [Ne v] detection. The typical (median) scaling ratios between [Ne v] line emission and (ultra-)hard X-ray emission in our sample are log L[Ne v]/L(14-150 keV) = -3.75 and log L[Ne v]/L(2-10 keV) = -3.36. The scatter on these scaling ratios, of ~0.5 dex, is comparable to, and indeed smaller than, what is found for other commonly used tracers of AGN radiative outputs (e.g., [O III] $λ$5007). Otherwise, we find no significant relations between the (relative) strength of [Ne v] and the basic AGN/SMBH properties under study, in contrast with simple expectations from models of SMBH accretion flows. Our results reaffirm the usability of [Ne v] as an AGN tracer even in highly obscured systems, including dual AGN and high redshift sources.

astro-ph.GA↗

arXiv2025

BASS. XLIV. Morphological preferences of local hard X-ray selected AGN

We present morphological classifications for the hosts of 1189 hard X-ray selected (14-195 keV) active galactic nuclei (AGNs) from the Swift-BAT 105-month catalog as part of the BAT AGN Spectroscopic Survey (BASS). BASS provides a powerful all-sky census of nearby AGN, minimizing obscuration biases and providing a robust dataset for studying AGN-host galaxy connections. Classifications are based on volunteer-based visual inspection on the Zooniverse platform, adapted from Galaxy Zoo DECaLS (GZD). Dual-contrast grz color composite images, generated from public surveys (e.g., NOAO Legacy Survey, Pan-STARRS, SDSS) and dedicated observations enabled key morphological features to be identified. Our analysis reveals that, with respect to a control sample of inactive galaxies matched in redshift and i-band magnitude, BASS AGN hosts show a deficiency of smooth ellipticals (~70%) and disks with prominent arms (~80%), while displaying an excess of mergers or disturbed systems (~400%), and disk galaxies without a spiral structure (~300%). These trends suggest a preference for AGN activity in gas-rich, dynamically disturbed environments or transitional disk systems. We also find a higher bar fraction among AGN hosts than the control sample (~50% vs. ~30%). We further explore the relations between AGN properties (e.g., X-ray luminosity, black hole mass, and Eddington ratio) and host morphology, and find that high-luminosity and high-accretion AGN preferentially reside in smooth or point-like hosts. In parallel, lower-luminosity AGN are more common in disk galaxies. These results underscore the importance of morphological studies in understanding the fueling and feedback mechanisms that drive AGN activity and their role in galaxy evolution. Our dataset provides a valuable benchmark for future multiwavelength surveys (e.g. LSST, Roman, and Euclid) and automated morphological classification efforts.

astro-ph.GA↗

arXiv2025

Discovery of Faint Nebulosity Around a Z Camelopardalis-type Cataclysmic Variable in Antlia: Nova Shell or Ancient Planetary Nebula?

We report our discovery of a faint nebula surrounding a previously little-studied 15th-mag variable star, ASASSN-19ds, in the southern-hemisphere constellation Antlia. Spectra verify that the star is a cataclysmic variable (CV). Using new and archival photometry, we confirm that ASASSN-19ds is an eclipsing binary with an orbital period of 0.139 days (3.34 hr). Moreover, its out-of-eclipse brightness shows a "sawtooth" light curve with an amplitude of $\sim$1~mag and an interval between peaks that varies between about three to nearly five weeks. Its mean absolute magnitude in the Gaia system is $M_G=+6.5$. These combined properties lead to a classification of ASASSN-19ds as a Z Camelopardalis-type CV. We obtained deep narrow-band images of the nebulosity, using modest-sized telescopes and extremely long exposure times. Our imagery reveals a bipolar morphology, with thin arcs at the ends of the major axis, likely indicating an interaction with the interstellar medium. We consider several scenarios for the origin of the nebula, but from the existing information we are unable to distinguish between it being ejecta from an unobserved classical-nova outburst several centuries ago, or an ancient planetary nebula. Future observations should be able to decide between these possibilities. At the star's distance of only $\sim$557 pc, a nova eruption would have been a spectacular naked-eye event.

astro-ph.SR↗

arXiv2025

Discovery and characterization of 25 new quasars at 4.6 < z < 6.9 from wide-field multi-band surveys

Luminous quasars at $z>4$ provide key insights into the early Universe. Their rarity necessitates wide-field multi-band surveys to efficiently separate them from the main astrophysical contaminants (i.e., ultracool dwarfs). To expand the sample of high-$z$ quasars, we conducted targeted selections using optical, infrared, and radio surveys, complemented by literature-based quasar candidate catalogs. In this paper, we report the discovery of \nqsos\ new quasars at $4.6 6.5$ quasars we selected, but whose independent discovery has already been published in the literature. Three of the newly discovered quasars are strong radio emitters (L$_{1.4~\rm GHz}$$=0.09-1.0\times$10$^{34}$erg s$^{-1}$ Hz$^{-1}$). Among them, one source at $z=4.71$ exhibits typical blazar-like properties, including a flat radio spectrum, radio-loudness $\sim$1000, and multi-frequency variability. It is also detected by SRG/eROSITA X-ray telescope (f$_{\rm 0.2-2.3keV} \sim 1.3\times10^{-13}$erg s$^{-1}$ cm$^{-2}$). In addition, for seven $6.3 6$ quasars reported in the literature. A $z = 6.3$ quasar exhibits a velocity difference of approximately $9000$ km s$^{-1}$ between the C$\rm IV$ and Mg$\rm II$ emission lines, making it one of the most extreme C$\rm IV$ outflows currently known. Additionally, the sample includes three high-ionization broad absorption line quasars. One of these quasars shows potential evidence of an extremely fast outflow feature, reaching $48000$ km s$^{-1}$.

astro-ph.GA↗

arXiv2025

XMM-Newton Conclusively Identifies an Active Galactic Nucleus in a Green Pea Galaxy

Green Pea galaxies are a class of compact, low-mass, low-metallicity star-forming galaxies in the relatively local universe. They are believed to be analogues of high-redshift galaxies that re-ionised the universe and, indeed, the James Webb Space Telescope (JWST) is now uncovering such populations at record redshifts. Intriguingly, JWST finds evidence suggestive of active galactic nuclei (AGN) in many of these distant galaxies, including the elusive Little Red Dots, that broadly lack any detectable X-ray counterparts. Intuitively, one would expect to detect an AGN in their low-redshift analogues with X-rays, yet no study to date has conclusively identified an X-ray AGN within a Green Pea galaxy. Here we present the deepest X-ray campaign of a Green Pea galaxy performed to date, obtained with the goal of discerning the presence of a (potentially low-luminosity) AGN. The target $-$ SDSS J082247.66 +224144.0 (J0822+2241 hereafter) $-$ was previously found to display a comparable X-ray spectral shape to more local AGN ($Γ$ $\sim$ 2) and a high luminosity ($L_{2-10\,{\rm keV}}$ $\sim$ 10$^{42}$ erg s$^{-1}$). We show that over 6.2 years (rest-frame), the 2$-$10 keV luminosity of J0822+2241 is constant, whereas the soft 0.5$-$2 keV flux has decreased significantly by $\sim$60%. We discuss possible scenarios to explain the X-ray properties of J0822+2241, finding transient low-column density obscuration surrounding an AGN to be the only plausible scenario. J0822+2241 thus provides further evidence that low-luminosity AGN activity could have contributed to the epoch of reionisation, and that local analogues are useful to derive a complete multi-wavelength picture of black hole growth in high redshift low luminosity AGN.

astro-ph.GA↗

arXiv2025

Existence of metrics maximizing the first Laplace eigenvalue on closed surfaces

Building on seminal work of Nadirashvili and previous work of the authors, we prove the existence of metrics maximizing the area-normalized first eigenvalue of the Laplacian on every closed nonorientable surface, and give a simple new proof of existence in the orientable case complementing that of [Pet24b], thus resolving the long-standing existence problem for $λ_1$-maximizing metrics on closed surfaces of any topology. Namely, we prove by contradiction that the supremum $Λ_1(M)$ of the normalized first eigenvalue over all metrics on $M$ obeys the strict monotonicity $Λ_1(M\#\mathbb{RP}^2)>Λ_1(M)$ and $Λ_1(M\#\mathbb{T}^2)>Λ_1(M)$ under the attachment of cross-caps and handles, via a substantial refinement of techniques introduced in [KKMS24].

math.DG↗

arXiv2025

Infrared-Selected Active Galactic Nuclei in the Kepler Fields

We utilized the Edelson and Malkan (2012) and Stern et al. (2012) selection techniques and other methods to identify AGN candidates that were monitored during the Kepler prime and K2 missions. Subsequent to those observations, we obtained 125 long-slit optical spectra with the Lick 3-m telescope, 58 spectra with the Palomar 5-m telescope, and three with the Keck 10-m telescope to test these identifications. Of these 186 AGN candidates, 105 were confirmed as Type 1 AGN and 35 as Type 2 AGN, while the remaining 46 were found to have other identifications (e.g., stars and normal galaxies). This indicated an overall reliability of about 75%, while the two main methods had much higher reliability, 87%-96%. The spectra indicated redshifts out to z = 3.4. Then, we examined the AGN sample properties through the Baldwin, Phillips & Terlevich diagram and compared the AGN's spectral energy distributions (SEDs) with those from the literature. We found that our sample yielded the same AGN population as those identified through other methods, such as optical spectroscopy.

astro-ph.GA↗

arXiv2025

Powerful nuclear outflows and circumgalactic medium shocks driven by the most luminous known obscured quasar in the Universe

We report integral field spectroscopy observations with the Near-Infrared Spectrograph on board JWST targeting the 60 kpc environment surrounding the most luminous obscured quasar known at $z=4.6$. We detect ionized gas filaments on 40 kpc scales connecting a network of merging galaxies likely to form a cluster. We find regions of low ionization consistent with large-scale shock excitation surrounding the central dust-obscured quasar, out to distances nearly eight times the effective stellar radius of the quasar host galaxy. In the nuclear region, we find an ionized outflow driven by the quasar with velocities reaching 13,000 km s$^{-1}$, one of the fastest discovered to date with an outflow rate of 2000 M$_\odot$ yr$^{-1}$ and a kinetic luminosity of 6$\times10^{46}$ erg s$^{-1}$ resulting in coupling efficiency between the bolometric luminosity of the quasar and the outflow of 5%. The kinetic luminosity of the outflow is sufficient to power the turbulent motion of the gas on galactic and circumgalactic scales and is likely the primary driver of the radiative shocks on interstellar medium and circumgalactic medium scales. This provides compelling evidence supporting long-standing theoretical predictions that powerful quasar outflows are a main driver in regulating the heating and accretion rate of gas onto massive central cluster galaxies.

astro-ph.GA↗

arXiv2025

Multi-Component Ionized Gas Outflows in a Hot Dust-Obscured Galaxy W2026+0716 with Keck/OSIRIS

We present narrowband-filtered integral field unit (IFU) observations of the Hot Dust-Obscured Galaxy (Hot DOG) WISE J202615.27$+$071624.0 (hereafter W2026$+$0716) at redshift $z=2.570$ using Keck/OSIRIS. Our analysis reveals a multi-component ionized gas outflow structure in this heavily obscured AGN host galaxy. Multi-component Gaussian decomposition of the [O III] and H$α$ emission lines uncovers extremely broad and asymmetric profiles, characteristic of AGN-driven outflows. Kinematic mapping shows spatially distinct structures: the [O III] and H$α$ dominated components (with radii of $1.20 \pm 0.56$ kpc) are separated by a projected offset of $\sim 1.1$ kpc and exhibit divergent velocity regimes. The [O III] outflow reaches a velocity of 3210 $\pm$ 50 km s$^{-1}$, while the H$α$ outflow component attains 2310 $\pm$ 840 km s$^{-1}$. Dynamical modeling supports a biconical outflow structure, with [O III] and H$α$ emissions dominating separate cones and significant dust obscuration of the redshifted outflow. Their comparable momentum outflow rates and energy outflow rates suggest a potential physical connection in their driving mechanisms. Spectral energy distribution (SED) analysis reveals anomalous optical/UV excess, attributed to AGN photon scattering by dust or outflowing material, classifying W2026+0716 as a "Blue Hot DOG". The derived outflow timescale ($\sim10^{5}$ yr) aligns with the evolutionary phase of Blue Hot DOGs, suggesting AGN feedback operates persistently during this transitional stage.

astro-ph.GA↗

arXiv2025

A Massive Gas Outflow Outside the Line-of-Sight: Imaging Polarimetry of the Blue Excess Hot Dust Obscured Galaxy W0204-0506

(Aims) Hot Dust Obscured Galaxies (Hot DOGs) are a population of hyper-luminous, heavily obscured quasars. Although nuclear obscurations close to Compton-thick are typical, a fraction show blue UV spectral energy distributions consistent with unobscured quasar activity, albeit two orders of magnitude fainter than expected from their mid-IR luminosity. The origin of the UV emission in these Blue excess Hot DOGs (BHDs) has been linked to scattered light from the central engine. Here we study the properties of the UV emission in the BHD WISE J020446.13-050640.8 (W0204-0506). (Methods) We use imaging polarization observations in the $R_{\rm Special}$ band obtained with the FORS2 instrument at VLT. We compare these data with radiative transfer simulations to constrain the characteristics of the scattering material. (Results) We find a spatially integrated polarization fraction of $24.7\pm 0.7$%, confirming the scattered-light nature of the UV emission of W0204-0506. The source is spatially resolved in the observations and we find a gradient in polarization fraction and angle that is aligned with the extended morphology of the source found in HST/WFC3 imaging. A dusty, conical polar outflow starting at the AGN sublimation radius with a half-opening angle $\lesssim 50~\rm deg$ viewed at an inclination $\gtrsim 45~\rm deg$ can reproduce the observed polarization fraction if the dust is graphite-rich. We find that the gas mass and outflow velocity are consistent with the range of values found for [OIII] outflows through spectroscopy in other Hot DOGs, though it is unclear whether the outflow is energetic enough to affect the long-term evolution of the host galaxy. Our study highlights the unique potential for polarization imaging to study dusty quasar outflows, providing complementary constraints to those obtained through traditional spectroscopic studies.

astro-ph.GA↗

arXiv2025

Gaia GraL: Gaia gravitational lens systems IX. Using XGBoost to explore the Gaia Focused Product Release GravLens catalogue

Aims. Quasar strong gravitational lenses are important tools for putting constraints on the dark matter distribution, dark energy contribution, and the Hubble-Lemaitre parameter. We aim to present a new supervised machine learning-based method to identify these lenses in large astrometric surveys. The Gaia Focused Product Release (FPR) GravLens catalogue is designed for the identification of multiply imaged quasars, as it provides astrometry and photometry of all sources in the field of 4.7 million quasars. Methods. Our new approach for automatically identifying four-image lens configurations in large catalogues is based on the eXtreme Gradient Boosting classification algorithm. To train this supervised algorithm, we performed realistic simulations of lenses with four images that account for the statistical distribution of the morphology of the deflecting halos as measured in the EAGLE simulation. We identified the parameters discriminant for the classification and performed two different trainings, namely, with and without distance information. Results. The performances of this method on the simulated data are quite good, with a true positive rate and a true negative rate of about 99.99% and 99.84%, respectively. Our validation of the method on a small set of known quasar lenses demonstrates its efficiency, with 75% of known lenses being correctly identified. We applied our algorithm (both trainings) to more than 0.9 million quadruplets selected from the Gaia FPR GravLens catalogue. We derived a list of 1127 candidates with at least one score larger than 0.75, where each candidate has two scores -- one from the model trained with distance information and one from the model trained without distance information -- and including 201 very good candidates with both high scores.

astro-ph.GA↗

arXiv2025

BASS XLV: Quantifying AGN Selection Effects in the Chandra COSMOS-Legacy Survey with BASS

Deep extragalactic X-ray surveys, such as the Chandra COSMOS-Legacy field (CCLS), are prone to be biased against active galactic nuclei (AGN) with high column densities due to their lower count rates at a given luminosity. To quantify this selection effect, we forward model nearby ($z\sim0.05$) AGN from the BAT AGN Spectroscopic Survey (BASS) with well-characterized ($\gtrsim$1000 cts) broadband X-ray spectra (0.5-195 keV) to simulate the CCLS absorption distribution. We utilize the BASS low-redshift analogs with similar luminosities to the CCLS ($L_\mathrm{2-10\ keV}^\mathrm{int}\sim10^{42-45}\ \mathrm{erg}\ \mathrm{s}^{-1}$), which are much less affected by obscuration and low-count statistics, as the seed for our simulations, and follow the spectral fitting of the CCLS. Our simulations reveal that Chandra would fail to detect the majority (53.3%; 563/1056) of obscured ($N_\mathrm{H}>10^{22}\ \mathrm{cm}^{-2}$) simulated BASS AGN given the observed redshift and luminosity distribution of the CCLS. Even for detected sources with sufficient counts ($\geq30$) for spectral modeling, the level of obscuration is significantly overestimated. This bias is most extreme for objects whose best fit indicates a high-column density AGN ($N_\mathrm{H}\geq10^{24}\ \mathrm{cm}^{-2}$), since the majority (66.7%; 18/27) of these are actually unobscured sources ($N_\mathrm{H}<10^{22}\ \mathrm{cm}^{-2}$). This implies that previous studies may have significantly overestimated the increase in the obscured fraction with redshift and the fraction of luminous obscured AGN. Our findings highlight the importance of directly considering obscuration biases and forward modeling in X-ray surveys, as well as the need for higher-sensitivity X-ray missions such as the Advanced X-ray Imaging Satellite (AXIS), and the importance of multi-wavelength indicators to estimate obscuration in distant supermassive black holes.

astro-ph.GA↗

arXiv2025

Searching for Low-Redshift Hot Dust-Obscured Galaxies

Hot Dust-Obscured Galaxies (Hot DOGs), discovered by the "W1W2 dropout" selection at high redshifts ($z\sim$ 2-4), are a rare population of hyper-luminous obscured quasars. Their number density is comparable to similarly luminous type 1 quasars in the same redshift range, potentially representing a short, yet critical stage in galaxy evolution. The evolution in their number density towards low redshift, however, remains unclear as their selection function is heavily biased against objects at $z\lesssim2$. We combine data from the WISE and Herschel archives to search for Hot DOGs at $z<0.5$ based on their unique spectral energy distributions. We find 68 candidates, and spectroscopic observations confirm that 3 of them are at $z<0.5$. For those 3 we find their black hole accretion is close to the Eddington limit, with lower bolometric luminosities and black hole masses than those of higher-$z$ Hot DOGs. Compared to high-$z$ systems, these low-$z$ systems are closer to the local relation between host galaxy stellar mass and black hole mass but still lie above it, and we discuss several possible scenarios for it. Finally, we also find the surface number density of $z<$0.5 Hot DOGs is $\rm 2.4 \times 10^{-3}$ deg$^{-2}$, about an order of magnitude lower than high-$z$ Hot DOGs but comparable to hyper-luminous unobscured quasars in the same redshift range. These results further support the idea that Hot DOGs may be a transitional phase of galaxy evolution.

astro-ph.GA↗

arXiv2025

The Host Galaxy of FRB 20190520B and Its Unique Ionized Gas Distribution

The properties of host galaxies associated with Fast Radio Bursts (FRBs) provide critical information for inferring the progenitors and radiation mechanisms of these bursts. We report on the host galaxy of the repeating FRB 20190520B, a dwarf galaxy at the spectroscopic redshift $z=0.241$ with a stellar mass of $(6.2 \pm 0.8) \times 10^8 \ M_{\odot}$. The emission line ratios suggest that the ionized gas is powered by star formation. The total H$α$-traced star formation rate (SFR) is $0.70 \pm 0.01 \ {M_{\odot} ~ \rm yr^{-1}}$, and the metallicity is $\rm 12+log_{10} ([O/H]) \geq 7.4 \pm 0.1$. The specific star formation rate (sSFR) is $\rm log \ sSFR/yr^{-1} = -9.0 \pm 0.1$, higher than the upper limit of $-9.4$ observed in nearby dwarf galaxies. The dispersion measure contribution from the host galaxy is estimated to be $\rm DM_{host} \approx 950 \pm 220 \ pc \ cm^{-3}$, based on the H$α$ emission. The FRB and the associated persistent radio source are located at the H$α$ emission peak, offset by $\sim 1.4^{\prime\prime}$ (5.5 kpc) in projection from the stellar continuum. At this position, the lower limit of $\rm \log \ sSFR/yr^{-1}$ is $-8.5 \pm 0.1$, more than three times the galaxy's total sSFR. The H$α$ velocity difference between the stellar continuum and the offset gas is $39.6 \pm 0.4$ km s$^{-1}$, which is sufficient to draw conclusions about the nature of the offset.

astro-ph.GA↗

arXiv2025

JWST + ALMA ubiquitously discover companion systems within $\lesssim18\,$kpc around four $z$$\approx$3.5 luminous radio-loud AGN

Mergers play important roles in galaxy evolution at and beyond Cosmic Noon ($z\sim3$). They are found to be a trigger of active galactic nuclei (AGN) activity and a process for growing stellar mass and black hole mass. High-$z$ radio galaxies (HzRGs=type-2 radio-loud AGN) are among the most massive galaxies known, and reside in dense environments on scales of tens of kiloparsecs to Megaparsecs. We present the first search for kpc-scale companions in a sample of four $z\sim3.5$ HzRGs, with many supporting datasets, using matched 0.2" resolution ALMA and JWST/NIRSpec integral field unit data. We discover a total of $\sim12$ companion systems within $\lesssim18\,$kpc across all four HzRG fields using two independent detection methods: peculiar [OIII]$4959,5007$ kinematics offset from the main (systemic) ionized gas component and [CII]$158\rm μm$ emitters. We examine the velocity fields of these companions and find evidence of disk rotation along with more complex motions. We estimate the dynamical masses of these nearby systems to be $M_{\rm dyn}\sim10^{9-11}\,M_{\odot}$, which may indicate a minor merger scenario. Our results indicate that these companions may be the trigger of the powerful radio-loud AGN. We discuss the roles of the discovered companion systems in galaxy evolution for these powerful jetted AGN and indicate that they may impede jet launch and deflect the jet.

astro-ph.GA↗

arXiv2025

The Massive and Distant Clusters of $WISE$ Survey. XII. Exploring X-ray AGN in Dynamically Active Massive Galaxy Clusters at z~1

We present an analysis of the cluster X-ray morphology and active galactic nucleus (AGN) activity in nine $z\sim1$ galaxy clusters from the Massive and Distant Clusters of $WISE$ Survey (MaDCoWS) observed with $Chandra$. Using photon asymmetry ($A_{\text{phot}}$) to quantify X-ray morphologies, we find evidence that the four most dynamically disturbed clusters are likely to be mergers. Employing a luminosity cut of $7.6\times10^{42}$ erg/s to identify AGN in the 0.7-7.0 keV, we show that the majority of these clusters host excess AGN compared to the local field. We use the cumulative number-count ($\log N-\log S$) model to predict AGN incidence in cluster isophotes under this luminosity cut. Our analysis finds evidence (at $> 2σ$) of a positive correlation between AGN surface densities and photon asymmetry, suggesting that a disturbed cluster environment plays a pivotal role in regulating AGN triggering. Studying AGN incidence in cluster X-ray isophotes equivalent in area to $1.0r_{500}$, we find that the AGN space density inversely scales with cluster mass as $\sim M^{-0.5^{+0.18}_{-0.18}}$ at the 3.18$σ$ level. Finally, when we separately explore the cluster mass dependence of excess AGN surface density in disturbed and relaxed clusters, we see tentative evidence that the two morphologically distinct sub-populations exhibit diverging trends, especially near the outskirts, likely due to cluster merger-driven AGN triggering/suppression.

astro-ph.GA↗