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DOE OSTI2022

Galaxy pairs in the Sloan Digital Sky Survey – XV. Properties of ionized outflows

ABSTRACT Powerful outflows are thought to play a critical role in galaxy evolution and black hole growth. We present the first large-scale systematic study of ionized outflows in paired galaxies and post-mergers compared to a robust control sample of isolated galaxies. We isolate the impact of the merger environment to determine if outflow properties depend on merger stage. Our sample contains ∼4000 paired galaxies and ∼250 post-mergers in the local universe (0.02 ≤ z ≤ 0.2) from the Sloan Digital Sky Survey Data Release 7 (SDSS DR 7) matched in stellar mass, redshift, local density of galaxies, and [O iii] λ5007 luminosity to a control sample of isolated galaxies. By fitting the [O iii] λ5007 line, we find ionized outflows in ∼15 per cent of our entire sample. Outflows are much rarer in star-forming galaxies compared to active galactic nuclei (AGNs), and outflow incidence and velocity increase with [O iii] λ5007 luminosity. Outflow incidence is significantly elevated in the optical + mid-infrared selected AGN compared to purely optical AGN; over 60 per cent show outflows at the highest luminosities ($L_{\mathrm{[OIII]~\lambda 5007}}\, \gtrsim$ 1042 erg s−1), suggesting mid-infrared AGN selection favours galaxies with powerful outflows, at least for higher [O iii] λ5007 luminosities. However, we find no statistically significant difference in outflow incidence, velocity, and luminosity in mergers compared to isolated galaxies, and there is no dependence on merger stage. Therefore, while interactions are predicted to drive gas inflows and subsequently trigger nuclear star formation and accretion activity, when the power source of the outflow is controlled for, the merging environment has no further impact on the large-scale ionized outflows as traced by [O iii] λ5007.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2024

Automating galaxy morphology classification using k -nearest neighbours and non-parametric statistics

ABSTRACT Morphology is a fundamental property of any galaxy population. It is a major indicator of the physical processes that drive galaxy evolution and in turn the evolution of the entire Universe. Historically, galaxy images were visually classified by trained experts. However, in the era of big data, more efficient techniques are required. In this work, we present a k-nearest neighbours based approach that utilizes non-parametric morphological quantities to classify galaxy morphology in Sloan Digital Sky Survey images. Most previous studies used only a handful of morphological parameters to identify galaxy types. In contrast, we explore 1023 morphological spaces (defined by up to 10 non-parametric statistics) to find the best combination of morphological parameters. Additionally, while most previous studies broadly classified galaxies into early types and late types or ellipticals, spirals, and irregular galaxies, we classify galaxies into 11 morphological types with an average accuracy of ${\sim} 80\!-\!90 \, {{\rm per\, cent}}$ per T-type. Our method is simple, easy to implement, and is robust to varying sizes and compositions of the training and test samples. Preliminary results on the performance of our technique on deeper images from the Hyper Suprime-Cam Subaru Strategic Survey reveal that an extension of our method to modern surveys with better imaging capabilities might be possible.

Mukundan, Kavya↗
DOE OSTI2023

Ageing and quenching through the Ageing Diagram – II. Physical characterization of galaxies

The connection between quenching mechanisms, which rapidly turn star-forming systems into quiescent, and the properties of the galaxy population remains difficult to discern. In this work we investigate the physical properties of MaNGA and SAMI galaxies at different stages of their star formation history. Specifically, we compare galaxies with signatures of recent quenching (Quenched) – Hα in absorption and low D n (4000) – with the rest of the low star-forming and active population (Retired and Ageing, respectively). The analysis is performed in terms of characteristics such as the total stellar mass, half-light radius, velocity-to-dispersion ratio, metallicity, and environment. We find that the Ageing population comprises a heterogeneous mixture of galaxies, preferentially late-type systems, with diverse physical properties. Retired galaxies, formerly Ageing or Quenched systems, are dominated by early-type high-mass galaxies found both at low and dense environments. Most importantly, we find that recently quenched galaxies are consistent with a population of compact low-mass satellite systems, with higher metallicities than their Ageing analogues. We argue that this is compatible with being quenched after undergoing a star-burst phase induced by environmental processes (e.g. ram pressure). However, we also detect a non-negligible fraction of field central galaxies likely quenched by internal processes. This study highlights that, in order to constrain the mechanisms driving galaxy evolution, it is crucial to distinguish between old (Retired) and recently quenched galaxies, thus requiring at least two estimates of the specific star formation rate over different time-scales.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Understanding the role of morphology and environment in the dynamical evolution of isolated galaxy triplets

The environments where galaxies reside affects their evolutionary histories. Galaxy triplets (systems composed of three physically bound galaxies) are one of simplest groups of galaxies, and are therefore excellent laboratories to study evolutionary mechanisms where effects of the environment are minimal. We present a statistical study of the dynamical properties of isolated galaxy triplets as a function of their local and large-scale environments. To explore the connection of the dynamical evolution on the systems with the evolution of the galaxies composing the triplets, we consider observational properties such as morphology and star formation rate (SFR). We used the SDSS-based catalogue of Isolated Triplets (SIT), which contains 315 triplets. We classified each triplet according to galaxy morphologies and defined a parameter Q trip to quantify the total local tidal strengths in the systems. To quantify the dynamical stage of the system we used the parameters of harmonic radius R H , velocity dispersion σvr, crossing time H 0 t c , and virial mass M vir . Triplets composed of three early-type galaxies present the smallest R H , indicating that they are in general more compact than triplets with one or more late-type galaxies. Among triplets with low values of R H and H 0 t c , SIT triplets with Q trip < –2 are relaxed systems that are more dynamically evolved, while triplets with Q trip > –2 show compact configurations due to interactions within the system, such as ongoing mergers. We found that there is no dominant galaxy in triplets in terms of properties of stellar populations such as global colour and SFR. Moreover, the global SFR in isolated triplets composed of two or more early-type galaxies increases with the stellar mass ratio of the galaxies with respect to the central galaxy, therefore the system is globally ‘rejuvenated’.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Completeness of the NASA/IPAC Extragalactic Database (NED) Local Volume Sample

We introduce the NASA/IPAC Extragalactic Database (NED) Local Volume Sample (NED-LVS), a subset of ~1.9 million objects with distances out to 1000 Mpc. We use UV and IR fluxes available in NED from all-sky surveys to derive physical properties, and estimate the completeness relative to the expected local luminosity density. The completeness relative to near-IR luminosities (which traces a galaxy's stellar mass) is roughly 100% at D < 30 Mpc and remains moderate (70%) out to 300 Mpc. For brighter galaxies (≳L * ), NED-LVS is ~100% complete out to ~400 Mpc. When compared to other local Universe samples (GLADE and HECATE), all three are ~100% complete below 30 Mpc. At distances beyond ~80 Mpc, NED-LVS is more complete than both GLADE and HECATE by ~10%–20%. NED-LVS is the underlying sample for the NED gravitational-wave follow-up service (NED-GWF), which provides prioritized lists of host candidates for GW events within minutes of alerts issued by the LIGO–Virgo–KAGRA collaboration. We test the prioritization of galaxies in the volume of GW170817 by three physical properties, where we find that both stellar mass and inverse specific star formation rate place the correct host galaxy in the top 10. In addition, NED-LVS can be used for a wide variety of other astrophysical studies: galaxy evolution, star formation, large-scale structure, galaxy environments, and more. The data in NED are updated regularly, and NED-LVS will be updated concurrently. Consequently, NED-LVS will continue to provide an increasingly complete sample of galaxies for a multitude of astrophysical research areas for years to come.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

The Open Cluster Chemical Abundances and Mapping Survey. V. Chemical Abundances of CTIO/Hydra Clusters Using The Cannon

Open clusters are key chemical and age tracers of Milky Way evolution. While open clusters provide significant constraints on galaxy evolution, their use has been limited due to discrepancies in measuring abundances from different studies. We analyze medium-resolution ( R ~ 19,000) Cerro Tololo Inter-American Observatory/Hydra spectra of giant stars in 58 open clusters using The Cannon to determine [Fe/H], [Mg/Fe], [Si/Fe], [Al/Fe], and [O/Fe]. This work adds an additional 55 primarily southern hemisphere open clusters calibrated to the Sloan Digital Sky Survey/Apache Point Observatory Galactic Evolution Experiment DR16 metallicity system. This uniform analysis is compared to previous studies [Fe/H] measurements for 23 clusters and we present spectroscopic metallicities for the first time for 35 open clusters.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2022

COMAP Early Science. V. Constraints and Forecasts at z ~ 3

We present the current state of models for the z ~ 3 carbon monoxide (CO) line intensity signal targeted by the CO Mapping Array Project (COMAP) Pathfinder in the context of its early science results. Our fiducial model, relating dark matter halo properties to CO luminosities, informs parameter priors with empirical models of the galaxy–halo connection and previous CO (1–0) observations. The Pathfinder early science data spanning wavenumbers k = 0.051–0.62 Mpc –1 represent the first direct 3D constraint on the clustering component of the CO (1–0) power spectrum. Our 95% upper limit on the redshift-space clustering amplitude A clust ≲ 70 μK 2 greatly improves on the indirect upper limit of 420 μK 2 reported from the CO Power Spectrum Survey (COPSS) measurement at k ~ 1 Mpc –1 . The COMAP limit excludes a subset of models from previous literature and constrains interpretation of the COPSS results, demonstrating the complementary nature of COMAP and interferometric CO surveys. Using line bias expectations from our priors, we also constrain the squared mean line intensity–bias product, ${\left\langle {Tb}\right\rangle }_{2}$ ≲ 50 μK 2 , and the cosmic molecular gas density, ρ H2 < 2.5 × 10 8 M ⊙ Mpc –3 (95% upper limits). Based on early instrument performance and our current CO signal estimates, we forecast that the 5 yr Pathfinder campaign will detect the CO power spectrum with overall signal-to-noise ratio of 9–17. Between then and now, we also expect to detect the CO–galaxy cross-spectrum using overlapping galaxy survey data, enabling enhanced inferences of cosmic star formation and galaxy evolution history.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

Evaluating quenching in cosmological simulations of galaxy formation with spectral covariance in the optical window

ABSTRACT Cosmological hydrodynamical simulations provide valuable insights on galaxy evolution when coupled with observational data. Comparisons with real galaxies are typically performed via scaling relations of the observables. Here, we follow an alternative approach based on the spectral covariance in a model-independent way. We build upon previous work by Sharbaf et al. that studied the covariance of high-quality SDSS (Sloan Digital Sky Survey) continuum-subtracted spectra in a relatively narrow range of velocity dispersion ($\sigma \in [100,150]$ km s$^{-1}$). Here, the same analysis is applied to synthetic data from the eagle and IllustrisTNG100 simulations, to assess the ability of these runs to mimic real galaxies. The real and simulated spectra are consistent regarding spectral covariance, although with subtle differences that can inform the implementation of subgrid physics. Spectral fitting done a posteriori on stacks segregated with respect to latent space reveals that the first principal component (PC1) is predominantly influenced by the stellar age distribution, with an underlying age–metallicity degeneracy. Good agreement is found regarding star formation prescriptions but there is disagreement with active galactic nucleus (AGN) feedback, that also affects the subset of quiescent galaxies. We show a substantial difference in the implementation of the AGN subgrid prescriptions, regarding central black hole seeding, that could lead to the mismatch. Differences are manifest between these two simulations in the star formation histories stacked with respect to latent space. We emphasize that this methodology only relies on the spectral covariance to assess whether simulations provide a true representation of galaxy formation.

Sharbaf, Z. (ORCID:0009000450545946)↗
DOE OSTI2025

Tripling the Census of Dwarf AGN Candidates Using DESI Early Data

Using early data from the Dark Energy Spectroscopic Instrument (DESI) survey, we search for active galactic nuclei (AGN) signatures in 410,757 line-emitting galaxies. By employing the BPT emission-line ratio diagnostic diagram, we identify AGNs in 75,928/296,261 (≈25.6%) high-mass ($\mathrm{log}({M}_{\star }/{M}_{\odot })\,\gt$ 9.5) and 2444/114,496 (≈2.1%) dwarf ($\mathrm{log}({M}_{\star }/{M}_{\odot })\,\leqslant$ 9.5) galaxies. Of these AGN candidates, 4181 sources exhibit a broad Hα component, allowing us to estimate their BH masses via virial techniques. This study more than triples the census of dwarf AGNs and doubles the number of intermediate-mass black hole (M BH ≤ 10 6 M ⊙ ) candidates, spanning a broad discovery space in stellar mass (7 $\lt \mathrm{log}({M}_{\star }/{M}_{\odot })\,\lt$ 12) and redshift (0.001 < z < 0.45). The observed AGN fraction in dwarf galaxies (≈2.1%) is nearly four times higher than prior estimates, primarily due to DESI’s smaller fiber size, which enables the detection of lower-luminosity dwarf AGN candidates. We also extend the M BH –M⋆ scaling relation down to ${\rm{log}}({M}_{\star }/{M}_{\odot })\,\approx$ 8.5 and $\mathrm{log}({M}_{\mathrm{BH}}/{M}_{\odot })\,\approx$ 4.4, with our results aligning well with previous low-redshift studies. The large statistical sample of dwarf AGN candidates from current and future DESI releases will be invaluable for enhancing our understanding of galaxy evolution at the low-mass end of the galaxy mass function.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

Revisiting stellar properties of star-forming galaxies with stellar and nebular spectral modelling

Spectral synthesis is a powerful tool for interpreting the physical properties of galaxies by decomposing their spectral energy distributions (SEDs) into the main luminosity contributors (e.g. stellar populations of distinct age and metallicity or ionised gas). However, the impact nebular emission has on the inferred properties of star-forming (SF) galaxies has been largely overlooked over the years, with unknown ramifications to the current understanding of galaxy evolution. The objective of this work is to estimate the relations between stellar properties (e.g. total mass, mean age, and mean metallicity) of SF galaxies by simultaneously fitting the stellar and nebular continua and comparing them to the results derived through the more common purely stellar spectral synthesis approach. The main galaxy sample from SDSS DR7 was analysed with two distinct population synthesis codes: FADO, which estimates self-consistently both the stellar and nebular contributions to the SED, and the original version of STARLIGHT, as representative of purely stellar population synthesis codes. Differences between codes regarding average mass, mean age and mean metallicity values can go as high as ~0.06 dex for the overall population of galaxies and ~0.12 dex for SF galaxies (galaxies with EW(Hα) > 3 Å), with the most prominent difference between both codes in the two populations being in the light-weighted mean stellar age. FADO presents a broader range of mean stellar ages and metallicities for SF galaxies than STARLIGHT, with the latter code preferring metallicity solutions around the solar value (Z ⊙ = 0.02). A closer look into the average light- and mass-weighted star formation histories of intensively SF galaxies (EW(Hα) > 75 Å) reveals that the light contributions of simple stellar populations (SSPs) younger than ≤10 7 (10 9 ) years in STARLIGHT are higher by ~5.41% (9.11%) compared to FADO. Moreover, FADO presents higher light contributions from SSPs with metallicity ≤ Z ⊙ /200 (Z ⊙ /50) of around 8.05% (13.51%) when compared with STARLIGHT. This suggests that STARLIGHT is underestimating the average light-weighted age of intensively SF galaxies by up to ~0.17 dex and overestimating the light-weighted metallicity by up to ~0.13 dex compared to FADO (or vice versa). The comparison between the average stellar properties of passive, SF and intensively SF galaxy samples also reveals that differences between codes increase with increasing EW(Hα) and decreasing total stellar mass. Moreover, comparing SF results from FADO in a purely stellar mode with the previous results qualitatively suggests that differences between codes are primarily due to mathematical and statistical differences and secondarily due to the impact of the nebular continuum modelling approach (or lack thereof). However, it is challenging to adequately quantify the relative role of each factor since they are likely interconnected. This work finds indirect evidence that a purely stellar population synthesis approach negatively impacts the inferred stellar properties (e.g. mean age and mean metallicity) of galaxies with relatively high star formation rates (e.g. dwarf spirals, ‘green peas’, and starburst galaxies). In turn, this can bias interpretations of fundamental relations such as the mass-age or mass-metallicity, which are factors worth bearing in mind in light of future high-resolution spectroscopic surveys at higher redshifts (e.g. MOONS and 4MOST-4HS).

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

The influence of Hickson-like compact group environment on galaxy luminosities

Compact groups of galaxies are devised as extreme environments where interactions may drive galaxy evolution. In this work, we analysed whether the luminosities of galaxies inhabiting compact groups differ from those of galaxies in loose galaxy groups. We computed the luminosity functions of galaxy populations inhabiting a new sample of 1412 Hickson-like compact groups of galaxies identified in the Sloan Digital Sky Survey Data Release 16. We observed a characteristic absolute magnitude for galaxies in compact groups brighter than that observed in the field or loose galaxy systems. We also observed a deficiency of faint galaxies in compact groups in comparison with loose systems. Our analysis showed that the brightening is mainly due to galaxies inhabiting the more massive compact groups. In contrast to what is observed in loose systems, where only the luminosities of Red (and Early) galaxies show a dependency with group mass, luminosities of Red and Blue (also Early and Late) galaxies in compact groups are affected similarly as a function of group virial mass. When using Hubble types, we observed that elliptical galaxies in compact groups are the brightest galaxy population, and groups dominated by an elliptical galaxy also display the brightest luminosities in comparison with those dominated by spiral galaxies. Moreover, we show that the general luminosity trends can be reproduced using a mock catalogue obtained from a semi-analytical model of galaxy formation. These results suggest that the inner extreme environment in compact groups prompts a different evolutionary history for their galaxies.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2024

Repainting the colour–mass diagrams by unearthing the green mountain: dust-rich S0 galaxies in the colour–(galaxy stellar mass) diagram, and the colour–(black hole mass) relations for dust-poor versus dust-rich galaxies

ABSTRACT Lenticular galaxies are notoriously misclassified as elliptical galaxies and, as such, a (disc inclination)-dependent correction for dust is often not applied to the magnitudes of dusty lenticular galaxies. This results in overly red galaxy colours, impacting their distribution in the colour–magnitude diagram. It is revealed how this has led to an underpopulation of the ‘green valley’ by hiding a ‘green mountain’ of massive dust-rich lenticular galaxies – known to be built from gas-rich major mergers – within the ‘red sequence’ of colour–(stellar mass) diagrams. Correcting for dust, a ‘green mountain’ appears at M*,gal ∼ 1011 M⊙, along with signs of an extension to lower masses producing a ‘green range’ or ‘green ridge’ on the green side of the ‘red sequence’ and ‘blue cloud.’ The ‘red sequence’ is shown to be comprised of two components: a red plateau defined by elliptical galaxies with a near-constant colour and by lower-mass dust-poor lenticular galaxies, which are mostly a primordial population but may include faded/transformed spiral galaxies. The presence of the quasi-triangular-shaped galaxy evolution sequence, previously called the ‘Triangal’, is revealed in the galaxy colour–(stellar mass) diagram. It tracks the speciation of galaxies and their associated migration through the diagram. The connection of the ‘Triangal’ to previous galaxy morphology sequences (Fork, Trident, and Comb) is also shown herein. Finally, the colour–(black hole mass) diagram is revisited, revealing how the dust correction generates a blue–green sequence for the spiral and dust-rich lenticular galaxies that is offset from a green–red sequence defined by the dust-poor lenticular and elliptical galaxies.

Graham, Alister W. (ORCID:0000000264969414)↗
DOE OSTI2022

Photometric Redshifts and Galaxy Clusters for DES DR2, DESI DR9, and HSC-SSP PDR3 Data

Photometric redshift (photoz) is a fundamental parameter for multi-wavelength photometric surveys, while galaxy clusters are important cosmological probes and ideal objects for exploring the dense environmental impact on galaxy evolution. We extend our previous work on estimating photoz and detecting galaxy clusters to the latest data releases of the Dark Energy Spectroscopic Instrument (DESI) imaging surveys, Dark Energy Survey (DES) and Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) imaging surveys and make corresponding catalogs publicly available for more extensive scientific applications. The photoz catalogs include accurate measurements of photoz and stellar mass for about 320, 293 and 134 million galaxies with r < 23, i < 24 and i < 25 in DESI DR9, DES DR2 and HSC-SSP PDR3 data, respectively. The photoz accuracy is about 0.017, 0.024 and 0.029 and the general redshift coverage is z < 1, z < 1.2 and z < 1.6, respectively for those three surveys. Furthermore, the uncertainty of the logarithmic stellar mass that is inferred from stellar population synthesis fitting is about 0.2 dex. With the above photoz catalogs, galaxy clusters are detected using a fast cluster-finding algorithm. A total of 532,810, 86,963 and 36,566 galaxy clusters with the number of members larger than 10 is discovered for DESI, DES and HSC-SSP, respectively. Their photoz accuracy is at the level of 0.01. The total mass of our clusters is also estimated by using the calibration relations between the optical richness and the mass measurement from X-ray and radio observations. The photoz and cluster catalogs are available at ScienceDB (https://www.doi.org/10.11922/sciencedb.o00069.00003) and PaperData Repository (https://doi.org/10.12149/101089).

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Clash of Titans: the impact of cluster mergers in the galaxy cluster red sequence

ABSTRACT Merging of galaxy clusters are some of the most energetic events in the Universe, and they provide a unique environment to study galaxy evolution. We use a sample of 84 merging and relaxed SPT galaxy clusters candidates, observed with the Dark Energy Camera in the 0.11 < z < 0.88 redshift range, to build colour–magnitude diagrams to characterize the impact of cluster mergers on the galaxy population. We divided the sample between relaxed and disturbed, and in two redshifts bin at z = 0.55. When comparing the high-z to low-z clusters we find the high-z sample is richer in blue galaxies, independently of the cluster dynamical state. In the high-z bin, we find that disturbed clusters exhibit a larger scatter in the red sequence, with wider distribution and an excess of bluer galaxies compared to relaxed clusters, while in the low-z bin we find a complete agreement between the relaxed and disturbed clusters. Our results support the scenario in which massive cluster halos at z < 0.55 galaxies are quenched as satellites of another structure, i.e. outside the cluster, while at z ≥ 0.55 the quenching is dominated by in situ processes.

Aldás, Franklin (ORCID:0000000290215114)↗
DOE OSTI2026

Hubble Space Telescope Imaging of Three Isolated Faint Dwarf Galaxies beyond the Local Group: Pavo, Corvus A, and Kamino

We present new Hubble Space Telescope (HST) imaging of three recently discovered star-forming dwarf galaxies beyond the Local Group: Pavo, Corvus A, and Kamino. The discovery of Kamino is reported here for the first time. They rank among the most isolated faint dwarf galaxies known; hence they provide unique opportunities to study galaxy evolution at the smallest scales, free from the environmental effects of more massive galaxies. Our HST data reach ∼2–4 magnitudes below the tip of the red giant branch (TRGB) for each dwarf, allowing us to measure their distances, structural properties, and recent star formation histories (SFHs). All three galaxies contain a complex stellar population of young and old stars, and are typical of field galaxies in this mass regime (M V = −10.62 ± 0.08 and $D = 2.16_{-0.07}^{+0.08}$ Mpc for Pavo, M V = −10.91 ± 0.10 and D = 3.34 ± 0.11 Mpc for Corvus A, and M V = −12.02 ± 0.12 and $D = 6.50_{-0.11}^{+0.15}$ Mpc for Kamino). Our HST-derived SFHs reveal differences among the three dwarfs: Pavo and Kamino show relatively steady, continuous star formation, while Corvus A formed ∼60% of its stellar mass by 10 Gyr ago. These results align with theoretical predictions of diverse evolutionary pathways for isolated low-mass galaxies.

Mutlu-Pakdil, Burçin [Dartmouth College, Hanover, ↗
DOE OSTI2023

Black hole and galaxy co-evolution in radio-loud active galactic nuclei at z ~ 0.3–4

The relation between the mass of the supermassive black hole (SMBH) in the center of galaxies and their bulge mass or central velocity dispersion is well known. This suggests a coevolution between the SMBHs and their galaxy hosts. Our aim is to study this relation, specifically, for radio loud galaxies, and as a function of redshift z. We selected a sample of 42 radio galaxies and active galactic nuclei (AGN) with broad emission lines and spectroscopic redshifts between z = 0.3 - 4 by cross-matching the low radio frequency sources from Very Large Array (VLA) FIRST with spectroscopically confirmed galaxies from wide-field surveys, including Sloan Digital Sky Survey (SDSS) DR14 ugriz and Dark Energy Survey (DES) DR2 grzY in the optical, Wield Infrared Survey Explorer (WISE), and the Galaxy And Mass Assembly (GAMA) spectroscopic survey. We characterized the stellar mass (M $\star$ ), star formation, and black hole properties (mass of the central SMBH, Eddington ratio η, and jet power, Q jet ). The relation between SMBH mass, M $\star$ , η, and z is placed into context by comparing them with scaling relations (M BH –M $\star$ , M BH /M $\star$ –z, M BH –Q jet , and Q jet –η) from the literature. On the basis of a multiwavelength spectral energy distribution modeling, our radio sources are broadly consistent with being on the star-forming main sequence. They have sub-Eddington accretion rates, η ≃ 1% on average, as typically found in type I AGN, while higher accretion rates favor more powerful jets to be launched by the central engine. We find overmassive SMBHs in (17 ± 5)% of our radio sources, similarly to previous studies on nearby early-type galaxies. Altogether, an evolutionary scenario in which radio-mode AGN feedback regulates the accretion onto the SMBHs and the stellar mass assembly of the radio sources is discussed, which may explain the observed phenomenology. This pilot study represents a benchmark for future studies using wide-field surveys such as those with Euclid and the Vera Rubin Observatory.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

Star formation characteristics of CNN-identified post-mergers in the Ultraviolet Near Infrared Optical Northern Survey (UNIONS)

ABSTRACT The importance of the post-merger epoch in galaxy evolution has been well documented, but post-mergers are notoriously difficult to identify. While the features induced by mergers can sometimes be distinctive, they are frequently missed by visual inspection. In addition, visual classification efforts are highly inefficient because of the inherent rarity of post-mergers (~1 per cent in the low-redshift Universe), and non-parametric statistical merger selection methods do not account for the diversity of post-mergers or the environments in which they appear. To address these issues, we deploy a convolutional neural network (CNN) that has been trained and evaluated on realistic mock observations of simulated galaxies from the IllustrisTNG simulations, to galaxy images from the Canada France Imaging Survey, which is part of the Ultraviolet Near Infrared Optical Northern Survey. We present the characteristics of the galaxies with the highest CNN-predicted post-merger certainties, as well as a visually confirmed subset of 699 post-mergers. We find that post-mergers with high CNN merger probabilities [p(x) > 0.8] have an average star formation rate that is 0.1 dex higher than a mass- and redshift-matched control sample. The SFR enhancement is even greater in the visually confirmed post-merger sample, a factor of 2 higher than the control sample.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

Hubble Space Telescope Observations within the Sphere of Influence of the Powerful Supermassive Black Hole in PKS 0745-191

We present Space Telescope Imaging Spectrograph observations from the Hubble Space Telescope of the supermassive black hole (SMBH) at the center of PKS 0745-191, a brightest cluster galaxy (BCG) undergoing powerful radio-mode active galactic nucleus (AGN) feedback (P cav ~ 5 × 10 45 erg s -1 ). These high-resolution data offer the first spatially resolved map of gas dynamics within an SMBH's sphere of influence under such powerful feedback. Our results reveal the presence of highly chaotic, nondrotational ionized gas flows on subkiloparsec scales, in contrast to the more coherent flows observed on larger scales. While radio-mode feedback effectively thermalizes hot gas in galaxy clusters on kiloparsec scales, within the core, the hot gas flow may decouple, leading to a reduction in angular momentum and supplying ionized gas through cooling, which could enhance accretion onto the SMBH. This process could, in turn, lead to a self-regulating feedback loop. Compared to other BCGs with weaker radio-mode feedback, where rotation is more stable, intense feedback may lead to more chaotic flows, indicating a stronger coupling between jet activity and gas dynamics. Additionally, we observe a sharp increase in velocity dispersion near the nucleus, consistent with a very massive M BH ~ 1.5 × 10 10 M ⊙ SMBH. The density profile of the ionized gas is also notably flat, paralleling the profiles observed in X-ray gas around galaxies where the Bondi radius is resolved. These results provide valuable insights into the complex mechanisms driving galaxy evolution, highlighting the intricate relationship between SMBH fueling and AGN feedback within the host galaxy.

79 ASTRONOMY AND ASTROPHYSICS↗