arXiv subjects

Ann I. Zabludoff

Publications and source records attributed to Ann I. Zabludoff.

At least 19 recordsLinked to original sources

arXiv2024

Evolution of Gas Flows along the Starburst to Post-Starburst to Quiescent Galaxy Sequence

We measure velocity offsets in the NaI $λ\lambda5890, 5896$ (Na D) interstellar medium absorption lines to track how neutral galactic winds change as their host galaxies evolve. Our sample of $\sim$80,000 SDSS spectra at $0.010 < z < 0.325$ includes starburst, post-starburst, and quiescent galaxies, forming an evolutionary sequence of declining star formation rate (SFR). We detect bulk flows across this sequence, mostly at higher host stellar masses($log(M_{\star}/M_{\odot})>10$). Along this sequence, the fraction of outflows decreases ($76\pm2\%$ to $65\pm4\%$ to a 3$σ$ upper limit of $34\%$), and the mean velocity offset changes from outflowing to inflowing ($-84.6\pm5.9$ to $-71.6\pm11.4$ to $76.6\pm2.3\,km\,s^{-1}$). Even within the post-starburst sample, wind speed decreases with time elapsed since the starburst ended. These results reveal that outflows diminish as galaxies age. For post-starbursts, there is evidence for an AGN contribution, especially to the speediest outflows: 1) SFR declines faster in time than outflow velocity, a decoupling arguing against massive stellar feedback; 2) of the few outflows strong enough to escape the interstellar medium (9/105), three of the four hosts with measured emission lines are Seyfert galaxies. For disky starburst galaxies, however, the trends suggest flows out of the stellar disk plane (with outflow 1/2-opening angle $> 45$ degree) instead of from the nucleus: the wind velocity decreases as the disk becomes more edge-on, and the outflow fraction, constant at $\sim$90$\%$ for disk inclinations $i<45$ degree, steadily decreases from $\sim$90$%$ to 20$\%$ for $i>45$ degree.

astro-ph.GA↗

arXiv2023

Optical/UV Emission in the Tidal Disruption Event ASASSN-14li: Implications of Disc Modeling

We predict late-time optical/UV emission from tidal disruption events (TDEs) from our slim accretion disc model \citep{Wen20} and explore the impact of the black hole mass $M_\bullet$, black hole spin $a_\bullet$, and accretion disc size. We use these synthetic spectra to successfully fit the multi-band \emph{Swift} observations of ASASSN-14li at >350 days, setting only the host galaxy extinction and outer disc radius as free parameters and employing the $M_\bullet$, $a_\bullet$, disc inclination, and disc accretion rates derived from fitting 10 epochs of ASASSN-14li's X-ray spectra with the slim disc. To address the nature of the \emph{early}-time optical/UV emission, we consider two models: shock dissipation and reprocessing. We find that (1) the predicted late-time optical/UV colour (e.g., $u-w2$) is insensitive to black hole and disc parameters unless the disc spreads quickly; (2) a starburst galaxy extinction model is required to fit the data, consistent with ASASSN-14li's post-starburst host; (3) surprisingly, the outer disc radius is $\approx$2$\times$ the tidal radius and $\sim$constant at late times, showing that viscous spreading is slow or non-existent; (4) the shock model can be self-consistent if $M_\bullet \lesssim 10^{6.75}$M$_\odot$, i.e., on the low end of ASASSN-14li's $M_\bullet$ range ($10^{6.5-7.1}$M$_\odot$; 1$σ$ CL); larger black hole masses require disruption of an unrealistically massive progenitor star; (5) the gas mass needed for reprocessing, whether by a quasi-static or an outflowing layer, can be $<0.5$M$_\odot$, consistent with a (plausible) disruption of a solar-mass star.

astro-ph.HE↗

arXiv2022

The State of the Molecular Gas in Post-Starburst Galaxies

The molecular gas in galaxies traces both the fuel for star formation and the processes that can enhance or suppress star formation. Observations of the molecular gas state can thus point to when and why galaxies stop forming stars. In this study, we present ALMA observations of the molecular gas in galaxies evolving through the post-starburst phase. These galaxies have low current star formation rates, regardless of the SFR tracer used, with recent starbursts ending within the last 600 Myr. We present CO (3-2) observations for three post-starburst galaxies, and dense gas HCN/HCO+/HNC (1-0) observations for six (four new) post-starburst galaxies. The post-starbursts have low excitation traced by the CO spectral line energy distribution (SLED) up to CO (3-2), more similar to early-type than starburst galaxies. The low excitation indicates that lower density rather than high temperatures may suppress star formation during the post-starburst phase. One galaxy displays a blueshifted outflow traced by CO (3-2). MaNGA observations show that the ionized gas velocity is disturbed relative to the stellar velocity field, with a blueshifted component aligned with the molecular gas outflow, suggestive of a multiphase outflow. Low ratios of HCO+/CO, indicating low fractions of dense molecular gas relative to the total molecular gas, are seen throughout post-starburst phase, except for the youngest post-starburst galaxy considered here. These observations indicate that the impact of any feedback or quenching processes may be limited to low excitation and weak outflows in the cold molecular gas during the post-starburst phase.

astro-ph.GA↗

arXiv2022

A Library of Synthetic X-ray Spectra for Fitting Tidal Disruption Events

We present a tabulated version of our slim disk model for fitting tidal disruption events (TDEs). We create a synthetic X-ray spectral library by ray-tracing stationary general relativistic slim disks and including gravitational redshift, Doppler, and lensing effects self-consistently. We introduce the library to reduce computational expense and increase access for fitting future events. Fitting requires interpolation between the library spectra; the interpolation error in the synthetic flux is generally $<10\%$ (it can rise to $40\%$ when the disk is nearly edge-on). We fit the X-ray spectra of the TDEs ASASSN-14li and ASASSN-15oi, successfully reproducing our earlier constraints on black hole mass $M_\bullet$ and spin $a_\bullet$ from full on-the-fly ray-tracing. We use the library to fit mock observational data to explore the degeneracies among parameters, finding that 1) hotter thermal disk and edge-on inclination angle spectra offer tighter constraints on $M_\bullet$ and $a_\bullet$; 2) the constraining power of spectra on $M_\bullet$ and $a_\bullet$ increases as a power-law with the number of X-ray counts, and the index of the power law is higher for hotter thermal disk spectra; 3) multi-epoch X-ray spectra partially break the degeneracy between $M_\bullet$ and $a_\bullet$; 4) the time-dependent level of X-ray absorption can be constrained from spectral fitting. The tabulated model and slim disk model are {\href{https://doi.org/10.25739/hfhz-xn60}{here.}

astro-ph.HE↗

arXiv2022

After The Fall: Resolving the Molecular Gas in Post-Starburst Galaxies

Post-starburst (PSB), or 'E+A', galaxies represent a rapid transitional phase between major, gas-rich mergers and gas-poor, quiescent early-type galaxies. Surprisingly, many PSBs have been shown to host a significant interstellar medium (ISM), despite theoretical predictions that the majority of star-forming gas should be expelled in AGN- or starburst-driven outflows. To-date, the resolved properties of this surviving ISM have remained unknown. We present high resolution ALMA continuum and CO(2$-$1) observations in six gas- and dust-rich PSBs, revealing for the first time the spatial and kinematic structure of their ISM on sub-kpc scales. We find extremely compact molecular reservoirs, with dust and gas surface densities rivaling those found in (ultra-)luminous infrared galaxies. We observe spatial and kinematic disturbances in all sources, with some also displaying disk-like kinematics. Estimates of the internal turbulent pressure in the gas exceed those of normal star-forming disks by at least 2 orders of magnitude, and rival the turbulent gas found in local interacting galaxies, such as the Antennae. Though the source of this high turbulent pressure remains uncertain, we suggest that the high incidence of tidal disruption events (TDEs) in PSBs could play a role. The star formation in these PSBs' turbulent central molecular reservoirs is suppressed, forming stars only 10% as efficiently as starburst galaxies with similar gas surface densities. "The fall" of star formation in these galaxies was not precipitated by complete gas expulsion or redistribution. Rather, this high-resolution view of PSBs' ISM indicates that star formation in their remaining compact gas reservoirs is suppressed by significant turbulent heating.

astro-ph.GA↗

arXiv2021

Mass, Spin, and Ultralight Boson Constraints from the Intermediate Mass Black Hole in the Tidal Disruption Event 3XMM J215022.4-055108

We simultaneously and successfully fit the multi-epoch X-ray spectra of the tidal disruption event (TDE) 3XMM J215022.4-055108 using a modified version of our relativistic slim disk model that now accounts for angular momentum losses from radiation. We explore the effects of different disk properties and of uncertainties in the spectral hardening factor fc and redshift z on the estimation of the black hole mass M and spin a. Across all choices of theoretical priors, we constrain M to less than 2.2e4 Ms at 1 sigma confidence. Assuming that the TDE host is a star cluster associated with the adjacent, brighter, barred lenticular galaxy at z=0.055, we constrain M and a to be (1.75+0.45-0.05)e4 Ms and 0.8+0.12-0.02, respectively, at 1 sigma confidence. The high, but sub-extremal, spin suggests that, if this intermediate mass black hole (IMBH) has grown significantly since formation, it has acquired its last e-fold in mass in a way incompatible with both the standard and chaotic limits of gas accretion. Ours is the first clear IMBH with a spin measurement. As such, this object represents a novel laboratory for astro-particle physics; its M and a place tight limits on the existence of ultralight bosons, ruling out those with masses 1.0e-15 to 1.0e-16 eV.

astro-ph.HE↗

arXiv2021

Discovery of a Possible Splashback Feature in the Intracluster Light of MACS J1149.5+2223

We present an analysis of the intracluster light in the Frontier Field Cluster MACS J1149.5+2223 (z=0.544), which combines new and archival Hubble WFC3/IR imaging to provide continuous radial coverage out to 2.8 Mpc from the brightest cluster galaxy. Employing careful treatment of potential systematic biases and using data at the largest radii to determine the background sky level, we reconstruct the surface brightness profile out to a radius of 2 Mpc. This radius is the largest to which the intracluster light (ICL) has been measured for an individual cluster. Within this radius, we measure a total luminosity of 1.5e13 Lsun for the brightest cluster galaxy plus ICL light. From the profile and its logarithmic slope, we identify the transition from the brightest cluster galaxy to ICL at r~70 kpc. Remarkably, we also detect an inflection in the profile centered in the 1.2-1.7 Mpc (0.37-0.52 r200m) radial bin, a signature of an infall caustic in the stellar distribution. Based upon the shape and strength of the feature, we interpret it as potentially being at the splashback radius, although the radius is smaller than theoretical predictions. If this is the splashback radius, then it is the first such detection in the ICL and the first detection of the splashback radius for an individual cluster. Similar analyses should be possible with the other Frontier Field clusters, and eventually with clusters from the Euclid and Roman missions.

astro-ph.CO↗

arXiv2020

Continuum-Fitting the X-ray Spectra of Tidal Disruption Events

We develop a new model for X-ray emission from tidal disruption events (TDEs), applying stationary general relativistic ``slim disk'' accretion solutions to supermassive black holes (SMBHs) and then ray-tracing the photon trajectories from the image plane to the disk surface, including gravitational redshift, Doppler, and lensing effects self-consistently. We simultaneously and successfully fit the multi-epoch XMM-Newton X-ray spectra for two TDEs: ASASSN-14li and ASASSN-15oi. We test explanations for the observed, unexpectedly slow X-ray brightening of ASASSN-15oi, including delayed disk formation and variable obscuration by a reprocessing layer. We propose a new mechanism that better fits the data: a ``Slimming Disk'' scenario in which accretion onto an edge-on disk slows, reducing the disk height and exposing more X-rays from the inner disk to the sightline over time.For ASASSN-15oi, we constrain the SMBH mass to $4.0^{+2.5}_{-3.1} \times 10^6M_\odot$. For ASASSN-14li, the SMBH mass is $10^{+1}_{-7}\times 10^6M_\odot$ and the spin is $>0.3$. For both TDEs, our fitted masses are consistent with independent estimates; for ASASSN-14li, application of the external mass constraint narrows our spin constraint to $>0.85$. The mass accretion rate of ASASSN-14li decays slowly, as $\propto t^{-1.1}$, perhaps due to inefficient debris circularization. Over $\approx$1100 days, its SMBH has accreted $ΔM \approx 0.17 M_\odot$, implying a progenitor star mass of $> 0.34 M_\odot$, i.e., no ``missing energy problem.'' For both TDEs, the hydrogen column density declines to the host galaxy plus Milky Way value after a few hundred days, suggesting a characteristic timescale for the depletion or removal of obscuring gas.

astro-ph.HE↗

arXiv2020

The Host Galaxies of Tidal Disruption Events

Recent studies of Tidal Disruption Events (TDEs) have revealed unexpected correlations between the TDE rate and the large-scale properties of the host galaxies. In this review, we present the host galaxy properties of all TDE candidates known to date and quantify their distributions. We consider throughout the differences between observationally-identified types of TDEs and differences from spectroscopic control samples of galaxies. We focus here on the black hole and stellar masses of TDE host galaxies, their star formation histories and stellar populations, the concentration and morphology of the optical light, the presence of AGN activity, and the extra-galactic environment of the TDE hosts. We summarize the state of several possible explanations for the links between the TDE rate and host galaxy type. We present estimates of the TDE rate for different host galaxy types and quantify the degree to which rate enhancement in some types results in rate suppression in others. We discuss the possibilities for using TDE host galaxies to assist in identifying TDEs in upcoming large transient surveys and possibilities for TDE observations to be used to study their host galaxies.

astro-ph.HE↗

arXiv2020

The Structure of Tidal Disruption Event Host Galaxies on Scales of Tens to Thousands of Parsecs

We explore the galaxy structure of four tidal disruption event (TDE) host galaxies on 30 pc to kpc scales using HST WFC3 multi-band imaging. The star formation histories of these hosts are diverse, including one post-starburst galaxy (ASASSN-14li), two hosts with recent weak starbursts (ASASSN-14ae and iPTF15af), and one early type (PTF09ge). Compared to early type galaxies of similar stellar masses, the TDE hosts have higher central surface brightnesses and stellar mass surface densities on 30-100 pc scales. The TDE hosts do not show the large, kpc-scale tidal disruptions seen in some post-starburst galaxies; the hosts have low morphological asymmetries similar to those of early type galaxies. The lack of strong asymmetries are inconsistent with a recent major (~1:1 mass) merger, although minor ($\lesssim$1:3) mergers are possible. Given the time elapsed since the end of the starbursts in the three post-burst TDE hosts and the constraints on the merger mass ratios, it is unlikely that a bound supermassive black hole binary (SMBHB) has had time to coalesce. The TDE hosts have low central (<140 pc) ellipticities compared to early type galaxies. The low central ellipticities disfavor a strong radial anisotropy as the cause for the enhanced TDE rate, although we cannot rule out eccentric disks at the scale of the black hole gravitational radius of influence (~1 pc). These observations suggest that the high central stellar densities are a more important driver than SMBHBs or radial anisotropies in increasing the TDE rate in galaxies with recent starbursts.

astro-ph.HE↗

arXiv2019

The Next Generation Virgo Cluster Survey. XVII. A Search for Planetary Nebulae in Virgo Cluster Globular Clusters

The occurrence of planetary nebulae (PNe) in globular clusters (GCs) provides an excellent chance to study low-mass stellar evolution in a special (low-metallicity, high stellar density) environment. We report a systematic spectroscopic survey for the [O{\sc iii}] 5007 emission line of PNe in 1469 Virgo GCs and 121 Virgo ultra-compact dwarfs (UCDs), mainly hosted in the giant elliptical galaxies M87, M49, M86, and M84. We detected zero PNe in our UCD sample and discovered one PN ($M_{5007} = -4.1$ mag) associated with an M87 GC. We used the [O{\sc iii}] detection limit for each GC to estimate the luminosity-specific frequency of PNe, $α$, and measured $α$ in the Virgo cluster GCs to be $α\sim 3.9_{-0.7}^{+5.2}\times 10^{-8}\mathrm{PN}/L_\odot$. $α$ in Virgo GCs is among the lowest values reported in any environment, due in part to the large sample size, and is 5--6 times lower than that for the Galactic GCs. We suggest that $α$ decreases towards brighter and more massive clusters, sharing a similar trend as the binary fraction, and the discrepancy between the Virgo and Galactic GCs can be explained by the observational bias in extragalactic surveys toward brighter GCs. This low but non-zero efficiency in forming PNe may highlight the important role played by binary interactions in forming PNe in GCs. We argue that a future survey of less massive Virgo GCs will be able to determine whether PN production in Virgo GCs is governed by internal process (mass, density, binary fraction), or is largely regulated by external environment.

astro-ph.GA↗

arXiv2019

The Evolution of the Interstellar Medium in Post-Starburst Galaxies

We derive dust masses ($M_{\rm dust}$) from the spectral energy distributions of 58 post-starburst galaxies (PSBs). There is an anticorrelation between specific dust mass ($M_{\rm dust}$/$M_{\star}$) and the time elapsed since the starburst ended, indicating that dust was either destroyed, expelled, or rendered undetectable over the $\sim$1 Gyr after the burst. The $M_{\rm dust}$/$M_{\star}$ depletion timescale, 205$^{+58}_{-37}$ Myr, is consistent with that of the CO-traced $M_{\rm H_2}/M_{\star}$, suggesting that dust and gas are altered via the same process. Extrapolating these trends leads to the $M_{\rm dust}/M_{\star}$ and $M_{\rm H_2}/M_{\star}$ values of early-type galaxies (ETGs) within 1-2 Gyr, a timescale consistent with the evolution of other PSB properties into ETGs. Comparing $M_{\rm dust}$ and $M_{\rm H_2}$ for PSBs yields a calibration, log $M_{\rm H_2}$ = 0.45 log $M_{\rm dust}$ + 6.02, that allows us to place 33 PSBs on the Kennicutt-Schmidt (KS) plane, $Σ\rm SFR-ΣM_{\rm H_2}$. Over the first $\sim$200-300 Myr, the PSBs evolve down and off of the KS relation, as their star formation rate (SFR) decreases more rapidly than $M_{\rm H_2}$. Afterwards, $M_{\rm H_2}$ continues to decline whereas the SFR levels off. These trends suggest that the star-formation efficiency bottoms out at 10$^{-11}\ \rm yr^{-1}$ and will rise to ETG levels within 0.5-1.1 Gyr afterwards. The SFR decline after the burst is likely due to the absence of gas denser than the CO-traced H$_2$. The mechanism of the $M_{\rm dust}/M_{\star}$ and$M_{\rm H_2}/M_{\star}$ decline, whose timescale suggests active galactic nucleus (AGN) or low-ionization nuclear emission-line region (LINER) feedback, may also be preventing the large CO-traced molecular gas reservoirs from collapsing and forming denser star forming clouds.

astro-ph.GA↗

arXiv2019

Type Ibn Supernovae May not all Come from Massive Stars

Because core-collapse supernovae are the explosions of massive stars, which have relatively short lifetimes, they occur almost exclusively in galaxies with active star formation. On the other hand, the Type Ibn supernova PS1-12sk exploded in an environment much more typical of thermonuclear (Type Ia) supernovae: on the outskirts of the brightest elliptical galaxy in a galaxy cluster. The lack of any obvious star formation at that location presented a challenge to models of Type Ibn supernovae as the explosions of very massive Wolf-Rayet stars. Here we present a supplementary search for star formation at the site of PS1-12sk, now that the supernova has faded, via deep ultraviolet imaging of the host cluster with the Hubble Space Telescope. We do not detect any ultraviolet emission within 1 kpc of the supernova location, which allows us deepen the limit on star formation rate by an order of magnitude compared to the original study on this event. In light of this new limit, we discuss whether the progenitors of Type Ibn supernovae can be massive stars and what reasonable alternatives have been proposed.

astro-ph.HE↗

arXiv2018

Identifying Tidal Disruption Events via Prior Photometric Selection of Their Preferred Hosts

A nuclear transient detected in a post-starburst galaxy or other quiescent galaxy with strong Balmer absorption is likely to be a Tidal Disruption Event (TDE). Identifying such galaxies within the planned survey footprint of the Large Synoptic Survey Telescope (LSST)---before a transient is detected---will make TDE classification immediate and follow-up more efficient. Unfortunately, spectra for identifying most such galaxies are unavailable, and simple photometric selection is ineffective; cutting on "green valley" UV/optical/IR colors produces samples that are highly contaminated and incomplete. Here we propose a new strategy using only photometric optical/UV/IR data from large surveys. Applying a machine learning Random Forest classifier to a sample of ~400k SDSS galaxies with GALEX and WISE photometry, including 13,592 quiescent Balmer-strong galaxies, we achieve 53-61% purity and 8-21% completeness, given the range in redshift. For the subset of 1299 post-starburst galaxies, we achieve 63-73% purity and 5-12% completeness. Given these results, the range of likely TDE and supernova rates, and that 36-75% of TDEs occur in quiescent Balmer-strong hosts, we estimate that 13-99% of transients observed in photometrically-selected host galaxies will be TDEs and that we will discover 119-248 TDEs per year with LSST. Using our technique, we present a new catalog of 67,484 candidate galaxies expected to have a high TDE rate, drawn from the SDSS, Pan-STARRS, DES, and WISE photometric surveys. This sample is 3.5x larger than the current SDSS sample of similar galaxies, thereby providing a new path forward for transient science and galaxy evolution studies.

astro-ph.GA↗

arXiv2018

Clocking the Evolution of Post-Starburst Galaxies: Methods and First Results

Detailed modeling of the recent star formation histories (SFHs) of post-starburst (or "E+A") galaxies is impeded by the degeneracy between the time elapsed since the starburst ended (post-burst age), the fraction of stellar mass produced in the burst (burst strength), and the burst duration. To resolve this issue, we combine GALEX ultraviolet photometry, SDSS photometry and spectra, and new stellar population synthesis models to fit the SFHs of 532 post-starburst galaxies. In addition to an old stellar population and a recent starburst, 48% of the galaxies are best fit with a second recent burst. Lower stellar mass galaxies (log M$_\star$/M$_\odot<10.5$) are more likely to experience two recent bursts, and the fraction of their young stellar mass is more strongly anti-correlated with their total stellar mass. Applying our methodology to other, younger post-starburst samples, we identify likely progenitors to our sample and examine the evolutionary trends of molecular gas and dust content with post-burst age. We discover a significant (4$σ$) decline, with a 117-230 Myr characteristic depletion time, in the molecular gas to stellar mass fraction with the post-burst age. The implied rapid gas depletion rate of 2-150 M$_\odot$yr$^{-1}$ cannot be due to current star formation, given the upper limits on the current SFRs in these post-starbursts. Nor are stellar winds or SNe feedback likely to explain this decline. Instead, the decline points to the expulsion or destruction of molecular gas in outflows, a possible smoking gun for AGN feedback.

astro-ph.GA↗

arXiv2018

Why Post-Starburst Galaxies are Now Quiescent

Post-starburst or "E+A" galaxies are rapidly transitioning from star-forming to quiescence. While the current star formation rate of post-starbursts is already at the level of early type galaxies, we recently discovered that many have large CO-traced molecular gas reservoirs consistent with normal star forming galaxies. These observations raise the question of why these galaxies have such low star formation rates. Here we present an ALMA search for the denser gas traced by HCN (1--0) and HCO+ (1--0) in two CO-luminous, quiescent post-starburst galaxies. Intriguingly, we fail to detect either molecule. The upper limits are consistent with the low star formation rates and with early-type galaxies. The HCN/CO luminosity ratio upper limits are low compared to star-forming and even many early type galaxies. This implied low dense gas mass fraction explains the low star formation rates relative to the CO-traced molecular gas and suggests the state of the gas in post-starburst galaxies is unusual, with some mechanism inhibiting its collapse to denser states. We conclude that post-starbursts galaxies are now quiescent because little dense gas is available, in contrast to the significant CO-traced lower density gas reservoirs that still remain.

astro-ph.GA↗

arXiv2017

A dependence of the tidal disruption event rate on global stellar surface mass density and stellar velocity dispersion

The rate of tidal disruption events (TDEs), $R_\text{TDE}$, is predicted to depend on stellar conditions near the super-massive black hole (SMBH), which are on difficult-to-measure sub-parsec scales. We test whether $R_\text{TDE}$ depends on kpc-scale global galaxy properties, which are observable. We concentrate on stellar surface mass density, $Σ_{M_\star}$, and velocity dispersion, $σ_v$, which correlate with the stellar density and velocity dispersion of the stars around the SMBH. We consider 35 TDE candidates, with and without known X-ray emission. The hosts range from star-forming to quiescent to quiescent with strong Balmer absorption lines. The last (often with post-starburst spectra) are overrepresented in our sample by a factor of $35^{+21}_{-17}$ or $18^{+8}_{-7}$, depending on the strength of the H$δ$ absorption line. For a subsample of hosts with homogeneous measurements, $Σ_{M_\star}=10^9$-$10^{10}~{\rm M_\odot / kpc^2}$, higher on average than for a volume-weighted control sample of Sloan Digital Sky Survey galaxies with similar redshifts and stellar masses. This is because: (1) most of the TDE hosts here are quiescent galaxies, which tend to have higher $Σ_{M_\star}$ than the star-forming galaxies that dominate the control, and (2) the star-forming hosts have higher average $Σ_{M_\star}$ than the star-forming control. There is also a weak suggestion that TDE hosts have lower $σ_v$ than for the quiescent control. Assuming that $R_{\rm TDE}\propto Σ_{M_\star}^α\times σ_v^β$, and applying a statistical model to the TDE hosts and control sample, we estimate $\hatα=0.9 \pm 0.2$ and $\hatβ=-1.0 \pm 0.6$. This is broadly consistent with $R_\text{TDE}$ being tied to the dynamical relaxation of stars surrounding the SMBH.

astro-ph.HE↗

arXiv2017

A Spectroscopic Survey of the Fields of 28 Strong Gravitational Lenses: The Group Catalog

With a large, unique spectroscopic survey in the fields of 28 galaxy-scale strong gravitational lenses, we identify groups of galaxies in the 26 adequately-sampled fields. Using a group finding algorithm, we find 210 groups with at least five member galaxies; the median number of members is eight. Our sample spans redshifts of 0.04 $\le z_{grp} \le$ 0.76 with a median of 0.31, including 174 groups with $0.1 < z_{grp} < 0.6$. Groups have radial velocity dispersions of 60 $\le σ_{grp} \le$ 1200 km s$^{-1}$ with a median of 350 km s$^{-1}$. We also discover a supergroup in field B0712+472 at $z =$ 0.29 consisting of three main groups. We recover groups similar to $\sim$ 85% of those previously reported in these fields within our redshift range of sensitivity and find 187 new groups with at least five members. The properties of our group catalog, specifically 1) the distribution of $σ_{grp}$, 2) the fraction of all sample galaxies that are group members, and 3) the fraction of groups with significant substructure, are consistent with those for other catalogs. The distribution of group virial masses agrees well with theoretical expectations. Of the lens galaxies, 12 of 26 (46%) (B1422+231, B1600+434, B2114+022, FBQS J0951+2635, HE0435-1223, HST J14113+5211, MG0751+2716, MGJ1654+1346, PG 1115+080, Q ER 0047-2808, RXJ1131-1231, and WFI J2033-4723) are members of groups with at least five galaxies, and one more (B0712+472) belongs to an additional, visually identified group candidate. There are groups not associated with the lens that still are likely to affect the lens model; in six of 25 (24%) fields (excluding the supergroup), there is at least one massive ($σ_{grp} \ge$ 500 km s$^{-1}$) group or group candidate projected within 2$^{\prime}$ of the lens.

astro-ph.GA↗