arXiv subjects

Jenny E. Greene

Publications and source records attributed to Jenny E. Greene.

At least 217 records · Page 12Linked to original sources

arXiv2021

SQuIGGLE: Studying Quenching in Intermediate-z Galaxies -- Gas, AnguLar Momentum, and Evolution

We describe the SQuIGGLE survey of intermediate-redshift post-starburst galaxies. We leverage the large sky coverage of the SDSS to select ~1300 recently-quenched galaxies at 0.5 75% of SQuIGGLE galaxies formed at least a quarter of their total stellar mass in the recent burst, which ended just ~200Myr before observation. We find that SQuIGGLE galaxies are on average younger and more burst-dominated than most other z<~1 post-starburst samples. This large sample of bright post-starburst galaxies at intermediate redshift opens a wide range of studies into the quenching process. In particular, the full SQuIGGLE survey will investigate the molecular gas reservoirs, morphologies, kinematics, resolved stellar populations, AGN incidence, and infrared properties of this unique sample of galaxies in order to place definitive constraints on the quenching process.

astro-ph.GA↗

arXiv2021

Reaching for the Edge I: Probing the Outskirts of Massive Galaxies with HSC, DECaLS, SDSS, and Dragonfly

The outer light (stellar halos) of massive galaxies has recently emerged as a possible low scatter tracer of dark matter halo mass. To test the robustness of outer light measurements across different data sets, we compare the surface brightness profiles of massive galaxies using four independent data sets: the Hyper Suprime-Cam survey (HSC), the Dark Energy Camera Legacy Survey (DECaLS), the Sloan Digital Sky Survey (SDSS), and the Dragonfly Wide Field Survey (Dragonfly). We use customized pipelines for HSC and DECaLS to achieve better sky background subtraction. For galaxies at $z<0.05$, Dragonfly has the best control of systematics, reaching surface brightness levels of $μ_r \sim 30$ mag/arcsec$^{2}$. At $0.19 200$ kpc without significant bias. At $0.19<z<0.50$, DECaLS and HSC measurements of the stellar mass contained within 100 kpc agree within 0.05 dex. Finally, we use weak gravitational lensing to show that measurements of outer light with DECaLS at $0.19<z<0.50$ show a similar promise as HSC as a low scatter proxy of halo mass. The tests and results from this paper represent an important step forward for accurate measurements of the outer light of massive galaxies and demonstrate that outer light measurements from DECam imaging will be a promising method for finding galaxy clusters for DES and DESI.

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arXiv2021

The Cosmic Ultraviolet Baryon Survey (CUBS) IV: The Complex Multiphase Circumgalactic Medium as Revealed by Partial Lyman Limit Systems

We present a detailed study of two partial Lyman limit systems (pLLSs) of neutral hydrogen column density $N_\mathrm{H\,I}\approx(1-3)\times10^{16}\,\mathrm{cm}^{-2}$ discovered at $z=0.5$ in the Cosmic Ultraviolet Baryon Survey (CUBS). Available far-ultraviolet spectra from the Hubble Space Telescope Cosmic Origins Spectrograph and optical echelle spectra from MIKE on the Magellan Telescopes enable a comprehensive ionization analysis of diffuse circumgalactic gas based on resolved kinematics and abundance ratios of atomic species spanning five different ionization stages. These data provide unambiguous evidence of kinematically aligned multi-phase gas that masquerades as a single-phase structure and can only be resolved by simultaneous accounting of the full range of observed ionic species. Both systems are resolved into multiple components with inferred $α$-element abundance varying from $[α/\text{H}]\approx\!{-0.8}$ to near solar and densities spanning over two decades from $\log n_\mathrm{H}\mathrm{cm}^{-3}\approx\!-2.2$ to $<-4.3$. Available deep galaxy survey data from the CUBS program taken with VLT/MUSE, Magellan/LDSS3-C and Magellan/IMACS reveal that the $z=0.47$ system is located 55 kpc from a star-forming galaxy with prominent Balmer absorption of stellar mass $M_\star\approx2\times10^{10}M_\odot$, while the $z=0.54$ system resides in an over-dense environment of 11 galaxies within 750 kpc in projected distance, with the most massive being a luminous red galaxy of $M_\star\approx2\times10^{11}M_\odot$ at 375 kpc. The study of these two pLLSs adds to an emerging picture of the complex, multiphase circumgalactic gas that varies in chemical abundances and density on small spatial scales in diverse galaxy environments. The inhomogeneous nature of metal enrichment and density revealed in observations must be taken into account in theoretical models of diffuse halo gas.

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arXiv2021

A quasar-based supermassive black hole binary population model: implications for the gravitational-wave background

The nanohertz gravitational wave background (GWB) is believed to be dominated by GW emission from supermassive black hole binaries (SMBHBs). Observations of several dual active galactic nuclei (AGN) strongly suggest a link between AGN and SMBHBs, given that these dual AGN systems will eventually form bound binary pairs. Here we develop an exploratory SMBHB population model based on empirically constrained quasar populations, allowing us to decompose the GWB amplitude into an underlying distribution of SMBH masses, SMBHB number density, and volume enclosing the GWB. Our approach also allows us to self-consistently predict the number of local SMBHB systems from the GWB amplitude. Interestingly, we find the local number density of SMBHBs implied by the common-process signal in the NANOGrav 12.5-yr dataset to be roughly five times larger than previously predicted by other models. We also find that at most $\sim 25 \%$ of SMBHBs can be associated with quasars. Furthermore, our quasar-based approach predicts $\gtrsim 95\%$ of the GWB signal comes from $z \lesssim 2.5$, and that SMBHBs contributing to the GWB have masses $\gtrsim 10^8 M_\odot$. We also explore how different empirical galaxy-black hole scaling relations affect the local number density of GW sources, and find that relations predicting more massive black holes decrease the local number density of SMBHBs. Overall, our results point to the important role that a measurement of the GWB will play in directly constraining the cosmic population of SMBHBs, as well as their connections to quasars and galaxy mergers.

astro-ph.HE↗

arXiv2021

Deep Realistic Extragalactic Model (DREaM) Galaxy Catalogs: Predictions for a Roman Ultra-Deep Field

In the next decade, deep galaxy surveys from telescopes such as the James Webb Space Telescope and Roman Space Telescope will provide transformational data sets that will greatly enhance the understanding of galaxy formation during the epoch of reionization (EoR). In this work, we present the Deep Realistic Extragalactic Model (DREaM) for creating synthetic galaxy catalogs. Our model combines dark matter simulations, subhalo abundance matching and empirical models, and includes galaxy positions, morphologies, and spectral energy distributions (SEDs). The resulting synthetic catalog extends to redshifts $z \sim 12 $, and galaxy masses $\log_{10}(M/M_{\odot}) = 5 $ covering an area of $1\, {\rm deg}^2$ on the sky. We use DREaM to explore the science returns of a $1\, {\rm deg}^2$ \emph{Roman} UDF, and to provide a resource for optimizing ultra-deep survey designs. We find that a \emph{Roman} UDF to $\sim 30\,m_{\rm AB}$ will potentially detect more than $10^6$ $M_{\rm UV}<-17$ galaxies, with more than $10^4$ at redshifts $z>7$, offering an unparalleled dataset for constraining galaxy properties during the EoR. Our synthetic catalogs and simulated images are made publicly available to provide the community with a tool to prepare for upcoming data.

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arXiv2021

The MBHBM$^{\star}$ Project -- II. Molecular Gas Kinematics in the Lenticular Galaxy NGC 3593 Reveal a Supermassive Black Hole

As part of the Measuring Black Holes in Below Milky Way-mass (M$^\star$) galaxies (MBHBM$^\star$) Project, we present a dynamical measurement of the supermassive black hole (SMBH) mass in the nearby lenticular galaxy NGC 3593, using cold molecular gas $^{12}$CO(2-1) emission observed at an angular resolution of $\approx0''.3$ ($\approx10$ pc) with the Atacama Large Millimeter/submillimeter Array (ALMA). Our ALMA observations reveal a circumnuclear molecular gas disc (CND) elongated along the galaxy major axis and rotating around the SMBH. Using dynamical modelling, the molecular gas kinematics allow us to infer a SMBH mass $M_{\rm BH}=2.40_{-1.05}^{+1.87}\times10^6$ M$_\odot$ (only statistical uncertainties at the $3σ$ level). We also detect a massive core of cold molecular gas (CMC) of mass $M_{\rm CMC}=(5.4\pm1.2)\times10^6$ M$_\odot$ and effective (half-mass) radius $r_{\rm CMC,e}=11.2\pm2.8$ pc, co-spatial with a nuclear star cluster (NSC) of mass $M_{\rm NSC}=(1.67\pm0.48)\times10^7$ M$_\odot$ and effective radius $r_{\rm NSC,e}=5.0\pm1.0$~pc (or $0''.15\pm0''.03$). The mass profiles of the CMC and NSC are well described by Sérsic functions with indices $1-1.4$. Our $M_{\rm BH}$ and $M_{\rm NSC}$ estimates for NGC 3593 agree well with the recently compiled $M_{\rm BH}$-$M_{\rm NSC}$ scaling relation. Although the $M_{\rm NSC}$ uncertainty is twice the inferred $M_{\rm BH}$, the rapid central rise of the rotation velocities of the CND (as the radius decreases) clearly suggests a SMBH. Indeed, our dynamical models show that even if $M_{\rm NSC}$ is at the upper end of its allowed range, the evidence for a black hole does not vanish, but remains with a lower limit of $M_{\rm BH}>3\times10^5$ M$_\odot$.

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arXiv2021

Galaxy Core Formation by Supermassive Black Hole Binaries: the Importance of Realistic Initial Conditions and Galaxy Morphology

The binding energy liberated by the coalescence of supermassive black hole (SMBH) binaries during galaxy mergers is thought to be responsible for the low density cores often found in bright elliptical galaxies. We use high-resolution $N$-body and Monte Carlo techniques to perform single and multi-stage galaxy merger simulations and systematically study the dependence of the central galaxy properties on the binary mass ratio, the slope of the initial density cusps, and the number of mergers experienced. We study both the amount of depleted stellar mass (or ``mass deficit'), $M_{\rm def}$, and the radial extent of the depleted region, $r_{\rm b}$. We find that $r_{\rm b}\simeq r_{\rm SOI}$ and that $M_{\rm def}$ varies in the range $0.5$ to $4M_{\bullet}$, with $r_{\rm SOI}$ the influence radius of the remnant SMBH and $M_{\bullet}$ its mass. The coefficients in these relations depend weakly on the binary mass ratio and remain remarkably constant through subsequent mergers. We conclude that the core size and mass deficit do not scale linearly with the number of mergers, making it hard to infer merger histories from observations. On the other hand, we show that both $M_{\rm def}$ and $r_{\rm b}$ are sensitive to the morphology of the galaxy merger remnant, and that adopting spherical initial conditions, as done in early work, leads to misleading results. Our models reproduce the range of values for $M_{\rm def}$ found in most observational work, but span nearly an order of magnitude range around the true ejected stellar mass.

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arXiv2021

The Detection of Ionized Carbon Emission at z~8

We present deep Keck/MOSFIRE $H$-band spectroscopic observations covering the [CIII],CIII]$λ\lambda1907,1909$ doublet for three $z\sim8$ galaxy candidates in the AEGIS field. Along with non-detections in two galaxies, we obtain one of the highest-redshift detections to-date of [CIII]$λ1907$ for the galaxy AEGIS-33376, finding $z_{\rm spec}=7.945\pm0.001$. We measure a [CIII]$λ$1907 flux of $2.24\pm0.71\times10^{-18} \mbox{ erg}\mbox{ s}^{-1} \mbox{ cm}^{-2}$, corresponding to a rest-frame equivalent width of $20.3\pm6.5 \unicode{x212B}$ for the single line. Given the not very constraining upper limit for CIII]$λ1909$ based on strong sky-line contamination, we assume a [CIII]$λ$1907/CIII]$λ1909$ doublet ratio of 1.5 and infer a total [CIII],CIII]$λ\lambda1907,1909$ equivalent width of $33.7\pm 10.8 \unicode{x212B}$. We repeat the same reductions and analysis on multiple subsets of our raw data divided on the basis of time and observing conditions, verifying that the [CIII]$λ1907$ emission is present for AEGIS-33376 throughout our observations. We also confirm that the significance of the [CIII]$λ1907$ detection in different subsets of our data tracks that of brighter emission features detected on the same multi-slit mask. These multiple tests suggest that the observed emission line is real and associated with the $z\sim 8$ target. The strong observed [CIII],CIII]$λ\lambda1907,1909$ in AEGIS-33376 likely indicates ISM conditions of low metallicity, high ionization parameter, and a hard ionizing spectrum, although AGN contributions are possible. This single detection represents a sizable increase in the current sample [CIII],CIII]$λ\lambda1907,1909$ detections at $z>7$, while $\textit{JWST}$ will provide the first statistical samples of such measurements at these redshifts.

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arXiv2021

The Intrinsic Shapes of Low Surface Brightness Galaxies: a Discriminant of LSBG Formation Mechanisms

We use the low surface brightness galaxy (LSBG) samples created from the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP, 781 galaxies), the Dark Energy Survey (DES, 20977 galaxies), and the Legacy Survey (selected via HI detection in the Arecibo Legacy Fast ALFA Survey, 188 galaxies) to infer the intrinsic shape distribution of the low surface brightness galaxy population. To take into account the effect of the surface brightness cuts employed when constructing LSBG samples, we simultaneously model both the projected ellipticity and the apparent surface brightness in our shape inference. We find that the LSBG samples are well-characterized by oblate spheroids, with no significant difference between red and blue LSBGs. This inferred shape distribution is in good agreement with similar inferences made for ultra-diffuse cluster galaxy samples, indicating that environment does not play a key role in determining the intrinsic shape of low surface brightness galaxies. We also find some evidence that LSBGs are more thickened than similarly massive high surface brightness dwarfs. We compare our results to intrinsic shape measures from contemporary cosmological simulations, and find that the observed LSBG intrinsic shapes place considerable constraints on the formation path of such galaxies. In particular, LSBG production via the migration of star formation to large radii produces intrinsic shapes in good agreement with our observational findings.

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arXiv2021

The nucleation fraction of Local Volume galaxies

Nuclear star clusters (NSCs) are a common phenomenon in galaxy centres and are found in a vast majority of galaxies of intermediate stellar mass $10^{9}$ M$_{\odot}$. Recent investigations suggest that they are rarely found in the least and most massive galaxies and that the nucleation fraction increases in dense environments. It is unclear whether this trend holds true for field galaxies due to the limited data currently available. Here we present our results on the nucleation fraction for 601 galaxies in the Local Volume ($\lesssim 12$ Mpc). Covering more than eight orders of magnitude in stellar mass, this is the largest sample of galaxies analysed in a low-density environment. Within the Local Volume sample we find a strong dependence of the nucleation fraction on galaxy stellar mass, in agreement with previous work. We also find that for galaxies with $M_{\star} < 10^{9}$ M$_{\odot}$, early-type galaxies have a higher nucleation fraction than late-types. The nucleation fraction in the Local Volume correlates independently with stellar mass, Hubble type, and local environmental density. We compare our data to those in galaxy cluster environments (Coma, Fornax, and Virgo) by compiling previous results and calculating stellar masses in a homogeneous way. We find significantly lower nucleation fractions (up to 40$\%$) in galaxies with $M_{\star} \lesssim 10^{9.5}$ M$_{\odot}$, in agreement with previous work. Our results reinforce the connection between globular clusters and NSCs, but it remains unclear if it can explain the observed trends with Hubble type and local environment. We speculate that correlation between the nucleation fraction and cluster environment weakens for the densest clusters like Coma and Virgo.

astro-ph.GA↗

arXiv2021

The Cosmic Ultraviolet Baryon Survey (CUBS) -- III. Physical properties and elemental abundances of Lyman limit systems at $z<1$

(Abridged) We present a systematic investigation of physical conditions and elemental abundances in four optically thick Lyman-limit systems (LLSs) at $z=0.36-0.6$ discovered within the Cosmic Ultraviolet Baryon Survey (CUBS). CUBS LLSs exhibit multi-component kinematic structure and a complex mix of multiphase gas, with associated metal transitions from multiple ionization states that span several hundred km/s in line-of-sight velocity. Specifically, higher column density components (log N(HI)>16) in all four absorbers comprise dynamically cool gas with $\langle T \rangle =(2\pm1) \times10^4\,$K and modest non-thermal broadening of $5\pm3\,$ km/s. The high quality of the QSO absorption spectra allows us to infer the physical conditions of the gas, using a detailed ionization modeling that takes into account the resolved component structures of HI and metal transitions. The range of inferred gas densities indicates that these absorbers consist of spatially compact clouds with a median line-of-sight thickness of $160^{+140}_{-50}$ pc. While obtaining robust metallicity constraints for the low-density, highly ionized phase remains challenging due to the uncertain N(HI), we demonstrate that the cool-phase gas in LLSs has a median metallicity of $\mathrm{[α/H]_{1/2}}=-0.7^{+0.1}_{-0.2}$, with a 16-84 percentile range of $\mathrm{[α/H]}=(-1.3,-0.1)$. Furthermore, the wide range of inferred elemental abundance ratios ($\mathrm{[C/α]}$, $\mathrm{[N/α]}$, and $\mathrm{[Fe/α]}$) indicate a diversity of chemical enrichment histories. Combining the absorption data with deep galaxy survey data characterizing the galaxy environment of these absorbers, we discuss the physical connection between star-forming regions in galaxies and diffuse gas associated with optically thick absorption systems in the $z<1$ circumgalactic medium.

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arXiv2021

Discovery and origins of giant optical nebulae surrounding quasar PKS 0454-22

We report optical integral-field spectroscopy in the field of one of the most luminous quasars in the $z < 1$ Universe, PKS0454-22, with the Multi-Unit Spectroscopic Explorer. These data enable the discovery of three large ionized nebulae emitting in [O II], H$β$, and [O III] with projected areas of $1720, \ 1520,$ and $130 \ \mathrm{pkpc}^2$, which we refer to as N1, N2, and N3, respectively. N1 spatially and kinematically surrounds the quasar host and five nearby galaxies. The morphology and kinematics of N1 are most consistent with stripped interstellar medium resulting from ongoing interactions. Its ionization properties can be explained by quasar photoionization. N2 spatially and kinematically surrounds two galaxies which are at projected distances of $d \approx 90 \ \mathrm{pkpc}$ and line-of-sight velocities of $Δv \approx +1410\ \mathrm{km\ s^{-1}}$ from the quasar. The morphology and kinematics of N2 are also consistent with stripped interstellar medium. However, its ionization state requires additional ionization sources beyond the quasar, likely from fast shocks as it moves through the hot halo associated with a galaxy over-density around the quasar. N3 is not coincident with any galaxies with secure redshifts, and may arise from a cool gas structure in the intragroup medium or a dwarf galaxy. These large ionized nebulae demonstrate that interactions can produce cool gas structures on halo scales, while also possibly facilitating quasar fueling. The growing availability of wide-area integral field spectroscopic data will continue to reveal the morphologies, kinematics, and conditions of the gas flows, which may fuel galaxy and black hole growth.

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arXiv2021

Infrared Surface Brightness Fluctuation Distances for MASSIVE and Type Ia Supernova Host Galaxies

We measured high-quality surface brightness fluctuation (SBF) distances for a sample of 63 massive early-type galaxies using the WFC3/IR camera on the Hubble Space Telescope. The median uncertainty on the SBF distance measurements is 0.085 mag, or 3.9% in distance. Achieving this precision at distances of 50 to 100 Mpc required significant improvements to the SBF calibration and data analysis procedures for WFC3/IR data. Forty-two of the galaxies are from the MASSIVE Galaxy Survey, a complete sample of massive galaxies within ~100 Mpc; the SBF distances for these will be used to improve the estimates of the stellar and central supermassive black hole masses in these galaxies. Twenty-four of the galaxies are Type Ia supernova hosts, useful for calibrating SN Ia distances for early-type galaxies and exploring possible systematic trends in the peak luminosities. Our results demonstrate that the SBF method is a powerful and versatile technique for measuring distances to galaxies with evolved stellar populations out to 100 Mpc and constraining the local value of the Hubble constant.

astro-ph.CO↗

arXiv2021

A Chandra and HST View of WISE-Selected AGN Candidates in Dwarf Galaxies

Reliably identifying active galactic nuclei (AGNs) in dwarf galaxies is key to understanding black hole demographics at low masses and constraining models for black hole seed formation. Here we present Chandra X-ray Observatory observations of eleven dwarf galaxies that were chosen as AGN candidates using Wide-field Infrared Survey Explorer (WISE) mid-infrared (mid-IR) color-color selection. Hubble Space Telescope images are also presented for ten of the galaxies. Based on Sloan Digital Sky Survey spectroscopy, six galaxies in our sample have optical evidence for hosting AGNs and five are classified as star-forming. We detect X-ray point sources with luminosities above that expected from X-ray binaries in the nuclei of five of the six galaxies with optical evidence of AGNs. However, the X-ray emission from these AGNs is generally much lower than expected based on AGN scaling relations with infrared and optical tracers. We do not find compelling evidence for AGNs in the five optically-selected star-forming galaxies despite having red mid-IR colors. Only two are detected in X-rays and their properties are consistent with stellar-mass X-ray binaries. Based on this multiwavelength study, we conclude that two-color mid-IR AGN diagnostics at the resolution of WISE cannot be used to reliably select AGNs in optically-star-forming dwarf galaxies. Future observations in the infrared with the James Webb Space Telescope offer a promising path forward.

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arXiv2021

A Search for Wandering Black Holes in the Milky Way with Gaia and DECaLS

We present a search for "hyper-compact" star clusters in the Milky Way using a combination of Gaia and the Dark Energy Camera Legacy Survey (DECaLS). Such putative clusters, with sizes of ~1 pc and containing 500-5000 stars, are expected to remain bound to intermediate-mass black holes (Mbh~10^3-10^5 M-sun) that may be accreted into the Milky Way halo within dwarf satellites. Using the semi-analytic model SatGen we find an expected ~100 wandering intermediate-mass black holes with if every infalling satellite hosts a black hole. We do not find any such clusters in our search. Our upper limits rule out 100% occupancy, but do not put stringent constraints on the occupation fraction. Of course, we need stronger constraints on the properties of the putative star clusters, including their assumed sizes as well as the fraction of stars that would be compact remnants.

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arXiv2021

ELVES I: Structures of Dwarf Satellites of MW-like Galaxies; Morphology, Scaling Relations, and Intrinsic Shapes

The structure of a dwarf galaxy is an important probe into the effects of stellar feedback and environment. Using an unprecedented sample of 223 low-mass satellites from the ongoing Exploration of Local VolumE Satellites (ELVES) Survey, we explore the structures of dwarf satellites in the mass range $10^{5.5}<M_\star<10^{8.5}$M$_\odot$. We survey satellites around $80\%$ of the massive, $M_K<-22.4$ mag, hosts in the Local Volume. Our sample of dwarf satellites is complete to luminosities of $M_V<-9$ mag and surface brightness $μ_{0,V}<26.5$ mag arcsec$^{-2}$ within at least $\sim200$ projected kpc. We separate the satellites into late- and early-type, finding the mass-size relations are very similar between them, to within $\sim5\%$. This similarity indicates that the quenching and transformation of a late-type dwarf into an early-type involves only very mild size evolution. Considering the distribution of apparent ellipticities, we infer the intrinsic shapes of the early- and late-type samples. Combining with literature samples, we find that both types of dwarfs get thicker at fainter luminosities but early-types are always rounder at fixed luminosity. Finally, we compare the LV satellites with dwarf samples from the cores of the Virgo and Fornax clusters. We find that the cluster satellites show similar scaling relations to the LV early-type dwarfs but are roughly $10\%$ larger at fixed mass, which we interpret as being due to tidal heating in the cluster environments. The dwarf structure results presented here are a useful reference for simulations of dwarf galaxy formation and the transformation of dwarf irregulars into spheroidals.

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arXiv2021

ELVES II: GCs and Nuclear Star Clusters of Dwarf Galaxies; The Importance of Environment

We present the properties of the globular clusters (GCs) and nuclear star clusters (NSCs) of low-mass ($10^{5.5}<M_\star<10^{8.5}$ $M_\odot$) early-type satellites of Milky Way-like and small group hosts in the Local Volume (LV) using deep, ground-based data from the ongoing Exploration of Local VolumE Satellites (ELVES) Survey. This sample of 177 dwarfs significantly increases the statistics for studying the star clusters of dwarfs in low-density environments, offering an important comparison to samples from nearby galaxy clusters. The LV dwarfs exhibit significantly lower nucleation fractions at fixed galaxy mass than dwarfs in nearby clusters. The mass of NSCs of LV dwarfs show a similar scaling of $M_{\star,\mathrm{NSC}}\propto M_{\star,\mathrm{gal}}^{0.4}$ as that found in clusters but offset to lower NSC masses. To deal with foreground/background contamination in the GC analysis, we employ both a statistical subtraction and Bayesian approach to infer the average GC system properties from all dwarfs simultaneously. We find that the GC occupation fraction and average abundance are both increasing functions of galaxy stellar mass, and the LV dwarfs show significantly lower average GC abundance at fixed galaxy mass than a comparable sample of Virgo dwarfs analyzed in the same way, demonstrating that GC prevalence also shows an important secondary dependence on the dwarf's environment. This result strengthens the connection between GCs and NSCs in low-mass galaxies. We discuss these observations in the context of modern theories of GC and NSC formation, finding that the environmental dependencies can be well-explained by these models.

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arXiv2021

The Cosmic Ultraviolet Baryon Survey (CUBS) II: Discovery of an H$_{2}$-Bearing DLA in the Vicinity of an Early-Type Galaxy at z = 0.576

We report the serendipitous detection of an H$_{2}$-bearing damped Lyman-$α$ absorber at z = 0.576 in the spectrum of the QSO J0111-0316 in the Cosmic Ultraviolet Baryon Survey. Spectroscopic observations from HST-COS in the far-ultraviolet reveal a damped absorber with log[N(HI)/cm^-2] = 20.1 +/- 0.2 and log[N(H$_{2}$)/cm^-2] = 18.97 (-0.06, +0.05). The diffuse molecular gas is found in two velocity components separated by dv = 60 km/s, with >99.9% of the total H$_{2}$ column density concentrated in one component. At a metallicity of $\approx$ 50% of solar, there is evidence for Fe enhancement and dust depletion, with a dust-to-gas ratio $κ_{\text{O}} \approx$ 0.4. A galaxy redshift survey conducted with IMACS and LDSS-3C on Magellan reveals an overdensity of nine galaxies at projected distance d <= 600 proper kpc (pkpc) and line-of-sight velocity offset dv$_{g}$ <= 300 km/s from the absorber. The closest is a massive, early-type galaxy at d = 41 pkpc which contains $\approx$ 70% of the total stellar mass identified at d <= 310 pkpc of the H$_{2}$ absorber. The close proximity of the H$_{2}$-bearing gas to the quiescent galaxy and the Fe-enhanced chemical abundance pattern of the absorber suggest a physical connection, in contrast to a picture in which DLAs are primarily associated with gas-rich dwarfs. This case study illustrates that deep galaxy redshift surveys are needed to gain insight into the diverse environments that host dense and potentially star-forming gas.

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