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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Faint and Fading Tails: The Fate of Stripped H i Gas in Virgo Cluster Galaxies

Although many galaxies in the Virgo cluster are known to have lost significant amounts of H i gas, only about a dozen features are known where the H i extends significantly outside its parent galaxy. Previous numerical simulations have predicted that H i removed by ram pressure stripping should have column densities far in excess of the sensitivity limits of observational surveys. We construct a simple model to try and quantify how many streams we might expect to detect. This accounts for the expected random orientation of the streams in position and velocity space as well as the expected stream length and mass of stripped H i. Using archival data from the Arecibo Galaxy Environment Survey, we search for any streams that might previously have been missed in earlier analyses. We report the confident detection of 10 streams as well as 16 other less-certain detections. We show that these well match our analytic predictions for which galaxies should be actively losing gas; however, the mass of the streams is typically far below the amount of missing H i in their parent galaxies, implying that a phase change and/or dispersal renders the gas undetectable. By estimating the orbital timescales, we estimate that dissolution rates of 1–10 M {sub ⊙} yr{sup −1} are able to explain both the presence of a few long, massive streams and the greater number of shorter, less-massive features.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

Star formation in CALIFA survey perturbed galaxies – II. Star-formation histories and oxygen abundances

ABSTRACT Galaxy evolution is generally affected by tidal interactions. First, in this series, we reported several effects that suggest that tidal interactions contribute to the regulation of star formation (SF). To confirm this, we now compare stellar mass assembly histories and SF look-back time annular profiles between CALIFA survey tidally and non-tidally perturbed galaxies. We pair their respective star-forming regions at the closest stellar mass surface densities to reduce the influence of stellar mass. The assembly histories and annular profiles show statistically significant differences so that higher star-formation rates characterize regions in tidally perturbed galaxies. These regions underwent a more intense (re)activation of SF in the last 1 Gyr. Varying shapes of the annular profiles also reflect fluctuations between suppression and (re)activation of SF. Since gas-phase abundances used to be lower in more actively than in less actively star-forming galaxies, we further explore the plausible presence of metal-poor gas inflows able to dilute such abundances. The resolved relations of oxygen (O) abundance with stellar mass density and with total gas fraction show slightly lower O abundances for regions in tidally perturbed galaxies. The single distributions of O abundances statistically validate this. Moreover, from a metallicity model based on stellar feedback, the mass rate differentials (inflows−outflows) show statistically valid higher values for regions in tidally perturbed galaxies. These differentials, and the metal fractions from the population synthesis, suggest dominant gas inflows in these galaxies. This dominance and the differences in SF through time confirm the previously reported effects of tidal interactions on SF.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

Structural decomposition of merger-free galaxies hosting luminous AGNs

ABSTRACT Active galactic nucleus (AGN) growth in disc-dominated, merger-free galaxies is poorly understood, largely due to the difficulty in disentangling the AGN emission from that of the host galaxy. By carefully separating this emission, we examine the differences between AGNs in galaxies hosting a (possibly) merger-grown, classical bulge, and AGNs in secularly grown, truly bulgeless disc galaxies. We use galfit to obtain robust, accurate morphologies of 100 disc-dominated galaxies imaged with the Hubble Space Telescope. Adopting an inclusive definition of classical bulges, we detect a classical bulge component in $53.3 \pm 0.5$ per cent of the galaxies. These bulges were not visible in Sloan Digital Sky Survey photometry, however these galaxies are still unambiguously disc-dominated, with an average bulge-to-total luminosity ratio of $0.1 \pm 0.1$. We find some correlation between bulge mass and black hole mass for disc-dominated galaxies, though this correlation is significantly weaker in comparison to the relation for bulge-dominated or elliptical galaxies. Furthermore, a significant fraction ($\gtrsim 90$ per cent) of our black holes are overly massive when compared to the relationship for elliptical galaxies. We find a weak correlation between total stellar mass and black hole mass for the disc-dominated galaxies, hinting that the stochasticity of black hole–galaxy co-evolution may be higher in disc-dominated than bulge-dominated systems.

Fahey, Matthew J.↗
DOE OSTI2024

An Excess of AGNs Triggered by Galaxy Mergers in MaNGA Galaxies of Stellar Mass $\sim10^{11}$$M_{\odot}$

To facilitate new studies of galaxy merger driven fueling of active galactic nuclei (AGNs), we present a catalog of 387 AGNs that we have identified in the final population of over $10,000$$z<0.15$ galaxies observed by the SDSS-IV integral field spectroscopy survey Mapping Nearby Galaxies at Apache Point Observatory (MaNGA). We selected the AGNs via mid-infrared WISE colors, Swift/BAT ultra hard X-ray detections, NVSS and FIRST radio observations, and broad emission lines in SDSS spectra. By combining the MaNGA AGN catalog with a new SDSS catalog of galaxy mergers that were identified based on a suite of hydrodynamical simulations of merging galaxies, we study the link between galaxy mergers and nuclear activity for AGNs above a limiting bolometric luminosity of $10^{44.4}$ erg s$^{-1}$. We find an excess of AGNs in mergers, relative to non-mergers, for galaxies with stellar mass $\sim10^{11}$$M_{\odot}$, where the AGN excess is somewhat stronger in major mergers than in minor mergers. Further, when we combine minor and major mergers and sort by merger stage, we find that the highest AGN excess occurs in post-coalescence mergers in the highest mass galaxies. However, we find no evidence of a correlation between galaxy mergers and AGN luminosity or accretion rate. In summary, while galaxy mergers overall do appear to trigger or enhance AGN activity more than non-mergers, they do not seem to induce higher levels of accretion or higher luminosities. We provide the MaNGA AGN Catalog and the MaNGA Galaxy Merger Catalog for the community here.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

A Multiwavelength Study of Active Galactic Nuclei in Post-merger Remnants

Here, we investigate the role of galaxy mergers in triggering active galactic nuclei (AGN) in the nearby universe. Our analysis is based on a sample of 79 post-merger remnant galaxies with deep X-ray observations from Chandra/XMM-Newton capable of detecting a low-luminosity AGN of ≥10 40.5 erg s -1 . This sample is derived from a visually classified, volume-limited sample of 807 post-mergers identified in the Sloan Digital Sky Survey Data Release 14 with log M * /M ⊙ ≥ 10.5 and 0.02 ≤ z ≤ 0.06. We find that the X-ray AGN fraction in this sample is 55.7% ± 5.6% compared to 23.6% ± 2.8% for a mass- and redshift-matched noninteracting control sample. The multiwavelength AGN fraction (identified as an AGN in one of X-ray, IR, radio or optical diagnostics) for post-mergers is 76.6% ± 4.8% compared to 39.1% ± 3.2% for controls. Thus post-mergers exhibit a high overall AGN fraction with an excess between 2 and 4 depending on the AGN diagnostics used. In addition, we find most optical, IR, and radio AGN are also identified as X-ray AGN while a large fraction of X-ray AGN are not identified in any other diagnostic. This highlights the importance of deep X-ray imaging to identify AGN. We find that the X-ray AGN fraction of post-mergers is independent of the stellar mass above log M * /M ⊙ ≥ 10.5 unlike the trend seen in control galaxies. Overall, our results show that post-merger galaxies are a good tracer of the merger–AGN connection and strongly support the theoretical expectations that mergers trigger AGN.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

Multiphase outflows in post-starburst E+A galaxies – I. General sample properties and the prevalence of obscured starbursts

ABSTRACT E+A galaxies are believed to be a short phase connecting major merger ultraluminous infrared galaxies (ULIRGs) with red and dead elliptical galaxies. Their optical spectrum suggests a massive starburst that was quenched abruptly, and their bulge-dominated morphologies with tidal tails suggest that they are merger remnants. Active galactic nucleus (AGN)-driven winds are believed to be one of the processes responsible for the sudden quenching of star formation and for the expulsion and/or destruction of the remaining molecular gas. Little is known about AGN-driven winds in this short-lived phase. In this paper, we present the first and unique sample of post-starburst galaxy candidates with AGNs that show indications of ionized outflows in their optical emission lines. Using Infrared Astronomical Satellite–far infrared (IRAS–FIR) observations, we study the star formation in these systems and find that many systems selected to have post-starburst signatures in their optical spectrum are in fact obscured starbursts. Using SDSS spectroscopy, we study the stationary and outflowing ionized gas. We also detect neutral gas outflows in 40 per cent of the sources with mass outflow rates 10–100 times more massive than in the ionized phase. The mean mass outflow rate and kinetic power of the ionized outflows in our sample ($\dot{M}\sim 1\, \mathrm{M_{\odot }\, yr^{-1}}$, $\dot{E}\sim 10^{41}\, \mathrm{erg\, s}^{-1}$) are larger than those derived for active galaxies of similar AGN luminosity and stellar mass. For the neutral outflow ($\dot{M}\sim 10\, \mathrm{M_{\odot }\, yr^{-1}}$, $\dot{E}\sim 10^{42}\, \mathrm{erg\, s}^{-1}$), their mean is smaller than that observed in (U)LIRGs with and without AGN.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Constraining radio mode feedback in galaxy clusters with the cluster radio AGNs properties to z ∼ 1

ABSTRACT We study the properties of the Sydney University Molonglo Sky Survey (SUMSS) 843 MHz radio active galactic nuclei (AGNs) population in galaxy clusters from two large catalogues created using the Dark Energy Survey (DES): ∼11 800 optically selected RM-Y3 and ∼1000 X-ray selected MARD-Y3 clusters. We show that cluster radio loud AGNs are highly concentrated around cluster centres to $z$ ∼ 1. We measure the halo occupation number for cluster radio AGNs above a threshold luminosity, finding that the number of radio AGNs per cluster increases with cluster halo mass as N ∝ M1.2 ± 0.1 (N ∝ M0.68 ± 0.34) for the RM-Y3 (MARD-Y3) sample. Together, these results indicate that radio mode feedback is favoured in more massive galaxy clusters. Using optical counterparts for these sources, we demonstrate weak redshift evolution in the host broad-band colours and the radio luminosity at fixed host galaxy stellar mass. We use the redshift evolution in radio luminosity to break the degeneracy between density and luminosity evolution scenarios in the redshift trend of the radio AGNs luminosity function (LF). The LF exhibits a redshift trend of the form (1 + $z$)γ in density and luminosity, respectively, of γD = 3.0 ± 0.4 and γP = 0.21 ± 0.15 in the RM-Y3 sample, and γD = 2.6 ± 0.7 and γP = 0.31 ± 0.15 in MARD-Y3. We discuss the physical drivers of radio mode feedback in cluster AGNs, and we use the cluster radio galaxy LF to estimate the average radio-mode feedback energy as a function of cluster mass and redshift and compare it to the core (<0.1R500) X-ray radiative losses for clusters at $z$ < 1.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Upper boundaries of active galactic nucleus regions in optical diagnostic diagrams

The distribution of galaxies in optical diagnostic diagrams can provide information about their physical parameters when compared with ionization models under proper assumptions. By using a sample of central emitting regions from the Mapping Nearby Galaxies at Apache Point Observatory survey (MaNGA), we find evidence of the existence of upper boundaries for narrow-line regions (NLRs) of active galactic nuclei (AGNs) in optical Baldwin, Phillips & Terlevich (BPT) diagrams, especially in diagrams involving [Sii]λλ6716, 6731/Hα. Photoionization models can reproduce the boundaries well, as a consequence of the decrease of [Sii]λλ6716, 6731/Hα and [Oiii]λ5007/Hβ ratios at very high metallicity. Whilst the exact location of the upper boundary in the [Sii] BPT diagram depends only weakly on the electron density of the ionized cloud and the secondary nitrogen prescription, its dependence on the shapes of the input spectral energy distributions (SEDs) is much stronger. This allows us to constrain the power-law index of the AGN SED between 1 Ryd and ~100 Ryd to be less than or equal to -1.40 ± 0.05. The coverage of photoionization models in the [Nii] BPT diagram has a stronger dependence on the electron density and the secondary nitrogen prescription. With the density constrained by the [Sii] doublet ratio and the input SED constrained by the [Sii] BPT diagram, we find that the extent of the data in the [Nii] BPT diagram favours those prescriptions with high N/O ratios. Furthermore, although shock-ionized clouds can produce line ratios similar to those from photoionization, the resulting shapes of the upper boundaries, if they exist, would likely be different from those of photoionizing origin.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2024

CIRCLEZ : Reliable photometric redshifts for active galactic nuclei computed solely using photometry from Legacy Survey Imaging for DESI

Photometric redshifts for galaxies hosting an accreting supermassive black hole in their center, known as active galactic nuclei (AGNs), are notoriously challenging. At present, they are most optimally computed via spectral energy distribution (SED) fittings, assuming that deep photometry for many wavelengths is available. However, for AGNs detected from all-sky surveys, the photometry is limited and provided by a range of instruments and studies. This makes the task of homogenizing the data challenging, presenting a dramatic drawback for the millions of AGNs that wide surveys such as SRG/eROSITA are poised to detect. This work aims to compute reliable photometric redshifts for X-ray-detected AGNs using only one dataset that covers a large area: the tenth data release of the Imaging Legacy Survey (LS10) for DESI. LS10 provides deep grizW1-W4 forced photometry within various apertures over the footprint of the eROSITA-DE survey, which avoids issues related to the cross-calibration of surveys. We present the results from CIRCLEZ, a machine-learning algorithm based on a fully connected neural network. CIRCLEZ is built on a training sample of 14 000 X-ray-detected AGNs and utilizes multi-aperture photometry, mapping the light distribution of the sources. The accuracy (σNMAD) and the fraction of outliers (η) reached in a test sample of 2913 AGNs are equal to 0.067 and 11.6%, respectively. The results are comparable to (or even better than) what was previously obtained for the same field, but with much less effort in this instance. We further tested the stability of the results by computing the photometric redshifts for the sources detected in CSC2 and Chandra-COSMOS Legacy, reaching a comparable accuracy as in eFEDS when limiting the magnitude of the counterparts to the depth of LS10. The method can be applied to fainter samples of AGNs using deeper optical data from future surveys (for example, LSST, Euclid), granting LS10-like information on the light distribution beyond the morphological type. Along with this paper, we have released an updated version of the photometric redshifts (including errors and probability distribution functions) for eROSITA/eFEDS.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2024

The rate of extreme coronal line emitting galaxies in the Sloan Digital Sky Survey and their relation to tidal disruption events

High-ionization iron coronal lines (CLs) are a rare phenomenon observed in galaxy and quasi-stellar object spectra that are thought to be created by high-energy emission from active galactic nuclei and certain types of transients. In cases known as extreme coronal line emitting galaxies (ECLEs), these CLs are strong and fade away on a time-scale of years. The most likely progenitors of these variable CLs are tidal disruption events (TDEs), which produce sufficient high-energy emission to create and sustain the CLs over these time-scales. To test the possible connection between ECLEs and TDEs, we present the most complete variable ECLE rate calculation to date and compare the results to TDE rates from the literature. To achieve this, we search for ECLEs in the Sloan Digital Sky Survey (SDSS). We detect sufficiently strong CLs in 16 galaxies, more than doubling the number previously found in SDSS. Using follow-up spectra from the Dark Energy Spectroscopic Instrument and Gemini Multi-Object Spectrograph, Wide-field Infrared Survey Explorer mid-infrared observations, and Liverpool Telescope optical photometry, we find that none of the nine new ECLEs evolve in a manner consistent with that of the five previously discovered variable ECLEs. Using this sample of five variable ECLEs, we calculate the galaxy-normalized rate of variable ECLEs in SDSS to be $R_\mathrm{G}=3.6~^{+2.6}_{-1.8}~(\mathrm{statistical})~^{+5.1}_{-0.0}~(\mathrm{systematic})\times 10^{-6}~\mathrm{galaxy}^{-1}~\mathrm{yr}^{-1}$. The mass-normalized rate is $R_\mathrm{M}=3.1~^{+2.3}_{-1.5}~(\mathrm{statistical})~^{+4.4}_{-0.0}~(\mathrm{systematic})\times 10^{-17}~\mathrm{M_\odot ^{-1}}~\mathrm{yr}^{-1}$ and the volumetric rate is $R_\mathrm{V}=7~^{+20}_{-5}~(\mathrm{statistical})~^{+10}_{-0.0}~(\mathrm{systematic})\times 10^{-9}~\mathrm{Mpc}^{-3}~\mathrm{yr}^{-1}$. Our rates are one to two orders of magnitude lower than TDE rates from the literature, which suggests that only 10–40 per cent of all TDEs produce variable ECLEs. Additional uncertainties in the rates arising from the structure of the interstellar medium have yet to be included.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Finding Peas in the Early Universe with JWST

The Early Release Observations (EROs) of JWST beautifully demonstrate the promise of JWST in characterizing the universe at Cosmic Dawn. We analyze the Near Infrared Spectrograph ERO spectra of three z ~ 8 galaxies to determine their metallicities, gas temperatures, and ionization. These galaxies offer the first opportunity to understand the physical properties of Epoch-of-Reionization galaxies through detailed rest-optical emission-line spectroscopy. We show that these objects have metal abundances $12+\mathrm{log}[{\rm{O}}/{\rm{H}}]\,\approx$ 6.9–8.3, based on both the T e method and on a recent calibration of the R 23 metallicity indicator. Since the spectra are some of the earliest science data from JWST, we compare several line ratios with values expected from robust physics, to validate our measurement procedures. We compare the abundances and emission-line ratios to a nearby sample of Green Pea galaxies—a population of nearby emission-line galaxies whose UV properties resemble Epoch-of-Reionization galaxies, and which often have large Lyman continuum escape fractions. The JWST data show striking further similarities between these high-redshift galaxies and nearby Green Peas. The z ~ 8 galaxies span the metallicity range covered by Green Peas. They also show the compact morphology that is typical of emission-line-dominated galaxies at all redshifts. Based on these similarities with Green Peas, it is likely that these are the first rest-optical spectra of galaxies that are actively driving cosmological reionization.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

The ambiguous AT2022rze: changing-look AGN mimicking a supernova in a merging galaxy system

AT2022rze is a luminous, ambiguous transient located south-east of the geometric centre of its host galaxy at redshift $z = 0.08$. The host appears to be formed by a merging galaxy system. The observed characteristics of AT2022rze are reminiscent of active galactic nuclei (AGNs), tidal disruption events, and superluminous supernovae. The transient reached a peak absolute magnitude of $-$20.2 $\pm$ 0.2 mag, showing a sharp rise (t$_{\mathrm{rise,1/e}} = 27.5 \pm 0.6$ d) followed by a slow decline (t$_{\mathrm{dec,1/e}} = 382.9 \pm 0.6$). Its bumpy light curve and narrow Balmer lines indicate the presence of gas (and dust). Its light curve shows rather red colours, indicating that the transient could be affected by significant host extinction. The spectra reveal coronal lines, indicative of high-energy (X-ray/UV) emission. Archival data reveal no prior activity at this location, disfavouring a steady-state AGN, although an optical spectrum obtained prior to the transient is consistent with an AGN classification of the host. Based on this, we conclude that the transient most likely represents a changing-look AGN at the centre of the smallest component of the merging system.

galaxies: active↗
DOE OSTI2021

The incidence of X-ray selected AGN in nearby galaxies

ABSTRACT We present the identification and analysis of an unbiased sample of active galactic nuclei (AGN) that lie within the local galaxy population. Using the MPA-JHU catalogue (based on SDSS DR8) and 3XMM DR7 we define a parent sample of 25 949 local galaxies (z ≤ 0.33). After confirming that there was strictly no AGN light contaminating stellar mass and star-formation rate calculations, we identified 917 galaxies with central, excess X-ray emission likely originating from an AGN. We analysed their optical emission lines using the BPT diagnostic and confirmed that such techniques are more effective at reliably identifying sources as AGN in higher mass galaxies: rising from 30 per cent agreement in the lowest mass bin to 93 per cent in the highest. We then calculated the growth rates of the black holes powering these AGN in terms of their specific accretion rates (∝LX/M*). Our sample exhibits a wide range of accretion rates, with the majority accreting at rates $\le 0.5\ \mathrm{ per \, cent}$ of their Eddington luminosity. Finally, we used our sample to calculate the incidence of AGN as a function of stellar mass and redshift. After correcting for the varying sensitivity of 3XMM, we split the galaxy sample by stellar mass and redshift and investigated the AGN fraction as a function of X-ray luminosity and specific black hole accretion rate. From this we found the fraction of galaxies hosting AGN above a fixed specific accretion rate limit of 10−3.5 is constant (at $\approx 1\ \mathrm{ per \, cent}$) over stellar masses of 8 < log M*/M⊙ < 12 and increases (from $\approx 1\ \mathrm{ per \, cent}$ to 10 per cent) with redshift.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

The MeerKAT Fornax Survey: II. The rapid removal of H I from dwarf galaxies in the Fornax cluster

We present MeerKAT Fornax Survey atomic hydrogen (H I) observations of the dwarf galaxies located in the central ~2.5 × 4 deg 2 of the Fornax galaxy cluster (R vir ~2°). The H I images presented in this work have a 3σ column density sensitivity between 2.7 and 50 × 10 18 cm –2 over 25 km s –1 for spatial resolution between 4 and 1 kpc. We are able to detect an impressive M HI = 5 × 10 5 M ⊙ 3σ point source with a line width of 50 km s –1 at a distance of 20 Mpc. We detected H I in 17 out of the 304 dwarfs in our field, with 14 out of the 36 late-type dwarfs (LTDs) and three out of the 268 early-type dwarfs (ETDs). The H I-detected LTDs have likely just joined the cluster and are on their first infall as they are located at large clustocentric radii, with comparable MHI and mean stellar surface brightness at fixed luminosity as blue, star-forming LTDs in the field. By contrast, the H I-detected ETDs have likely been in the cluster longer than the LTDs and acquired their H I through a recent merger or accretion from nearby H I. Eight of the H I-detected LTDs host irregular or asymmetric H I emission and disturbed or lopsided stellar emission. There are two clear cases of ram pressure shaping the H I, with the LTDs displaying compressed H I on the side closest to the cluster centre and a one-sided, starless tail pointing away from the cluster centre. The H I-detected dwarfs avoid the most massive potentials (i.e. cluster centre and massive galaxies), consistent with massive galaxies playing an active role in the removal of H I. We created a simple toy model to quantify the timescale of H I stripping in the cluster by reproducing the observed M r' –M HI relation. We find that a M HI = 10 8 M ⊙ dwarf is stripped in ~240 Myr. The model is consistent with our observations, where low-mass LTDs are directly stripped of their H I from a single encounter and more massive LTDs can harbour a disturbed H I morphology due to longer times or multiple encounters being required to fully strip their H I. This is the first time dwarf galaxies with M HI ≲ 1 × 10 6 M ⊙ have been detected and resolved beyond the local group and in a galaxy cluster.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

Kiloparsec-scale AGN outflows and feedback in merger-free galaxies

ABSTRACT Recent observations and simulations have challenged the long-held paradigm that mergers are the dominant mechanism driving the growth of both galaxies and supermassive black holes (SMBH), in favour of non-merger (secular) processes. In this pilot study of merger-free SMBH and galaxy growth, we use Keck Cosmic Web Imager spectral observations to examine four low-redshift (0.043 < z < 0.073) disc-dominated ‘bulgeless’ galaxies hosting luminous active galactic nucleus (AGN), assumed to be merger-free. We detect blueshifted broadened [O iii] emission from outflows in all four sources, which the $\mathrm{[O\, \small {III}]}$/$\rm {H}\beta$ ratios reveal are ionized by the AGN. We calculate outflow rates in the range $0.12{-}0.7~\rm {M}_{\odot }~\rm {yr}^{-1}$, with velocities of $675{-}1710~\rm {km}~\rm {s}^{-1}$, large radial extents of $0.6{-}2.4~\rm {kpc}$, and SMBH accretion rates of $0.02{-}0.07~\rm {M}_{\odot }~\rm {yr}^{-1}$. We find that the outflow rates, kinematics, and energy injection rates are typical of the wider population of low-redshift AGN, and have velocities exceeding the galaxy escape velocity by a factor of ∼30, suggesting that these outflows will have a substantial impact through AGN feedback. Therefore, if both merger-driven and non-merger-driven SMBH growth lead to co-evolution, this suggests that co-evolution is regulated by feedback in both scenarios. Simulations find that bars and spiral arms can drive inflows to galactic centers at rates an order of magnitude larger than the combined SMBH accretion and outflow rates of our four targets. This work therefore provides further evidence that non-merger processes are sufficient to fuel SMBH growth and AGN outflows in disc galaxies.

Smethurst, R. J. (ORCID:0000000164177196)↗
DOE OSTI2021

The rapid transition from star formation to AGN-dominated rest-frame ultraviolet light at z ≃ 4

ABSTRACT With the advent of deep optical-to-near-infrared extragalactic imaging on the degree scale, samples of high-redshift sources are being selected that contain both bright star-forming (SF) galaxies and faint active galactic nuclei (AGN). In this study, we investigate the transition between SF- and AGN-dominated systems at z ≃ 4 in the rest-frame ultraviolet (UV). We find a rapid transition to AGN-dominated sources brightward of MUV ≃ −23.2. The effect is observed in the rest-frame UV morphology and size–luminosity relation, where extended clumpy systems become point-source-dominated, and also in the available spectra for the sample. These results allow us to derive the rest-frame UV luminosity function (LF) for the SF- and AGN-dominated subsamples. We find the SF-dominated LF is best fit with a double power law, with a lensed Schechter function being unable to explain the existence of extremely luminous SF galaxies at MUV ≃ −23.5. If we identify AGN-dominated sources according to a point-source morphology criterion, we recover the relatively flat faint-end slope of the AGN LF determined in previous studies. If we instead separate the LF according to the current spectroscopic AGN fraction, we find a steeper faint-end slope of α = −1.83 ± 0.11. Using a simple model to predict the rest-frame AGN LF from the z = 4 galaxy LF, we find that the increasing impact of host galaxy light on the measured morphology of faint AGN can explain our observations.

Bowler, R. A. A.↗
DOE OSTI2023

Rotation curves and dynamical masses of MaNGA barred galaxies

In this paper we analyse a sample of 46 barred galaxies of MaNGA. Our goal is to investigate the stellar kinematics of these galaxies and obtain their rotation curves. Additionally, we aim to derive the total stellar and dynamical masses, as well as the maximum rotation velocity, in order to examine their distributions and scaling relations. Using the Pipe3D dataproducts publicly available we obtained the rotation curves, which were fitted considering two components of an axisymmetric Miyamoto–Nagai gravitational potential. We found a wide range of the maximum rotation velocities (117–340 ${\rm km\, s^{-1}}$), with a mean value of 200 ${\rm km\, s^{-1}}$. In addition we found that the total stellar and dynamical masses are in the range of log(M star /M ⊙ ) = 10.1−11.5, with a mean value of log(M star /M ⊙ ) = 10.8, and log(M dyn /M ⊙ ) = 10.4−12.0, with a mean value of log(M dyn /M ⊙ ) = 11.1, respectively. We found a strong correlation between dynamical mass and maximum velocity, between maximum velocity and magnitude, and between stellar mass and maximum velocity. According to these results, barred galaxies exhibit similar behaviour to that of normal spiral galaxies with respect to these relations, as well as in terms of the distribution of their dynamical mass and maximum rotation velocity. However, we found that the distribution of stellar masses of barred galaxies is statistically different from other samples including non-barred galaxies. Finally, analysing the galaxies that show nuclear activity, we find no difference with the rotation curves of normal galaxies.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

The Origin of Star Formation in Early-type Galaxies Inferred from Spatially Resolved Spectroscopy

Abstract We investigate the origin of star formation activity in early-type galaxies with current star formation using spatially resolved spectroscopic data from the Mapping Nearby Galaxies at Apache Point Observatory in the Sloan Digital Sky Survey (SDSS). We first identify star-forming early-type galaxies from the SDSS sample, which are morphologically early-type but show current star formation activity in their optical spectra. We then construct comparison samples with different combinations of star formation activity and morphology, which include star-forming late-type galaxies, quiescent early-type galaxies, and quiescent late-type galaxies. Our analysis of the optical spectra reveals that the star-forming early-type galaxies have two distinctive episodes of star formation, which is similar to late-type galaxies but different from quiescent early-type galaxies with a single star formation episode. Star-forming early-type galaxies have properties in common with star-forming late-type galaxies, which include stellar population, gas and dust content, mass, and environment. However, the physical properties of star-forming early-type galaxies derived from spatially resolved spectroscopy differ from those of star-forming late-type galaxies in the sense that the gas in star-forming early-type galaxies is more concentrated than their stars, and is often kinematically misaligned with stars. The age gradient of star-forming early-type galaxies also differs from those of star-forming late-type galaxies. Our findings suggest that the current star formation in star-forming early-type galaxies has an external origin including galaxy mergers or accretion gas from the cosmic web.

Astronomy & Astrophysics↗