arXiv subjects

Richard Donnerstein

Publications and source records attributed to Richard Donnerstein.

27 records · Page 2Linked to original sources

arXiv2023

An Enigmatic 380 kpc Long Linear Collimated Galactic Tail

We present an intriguing, serendipitously-detected system consisting of an S0/a galaxy, which we refer to as the "Kite", and a highly-collimated tail of gas and stars that extends over 380 kpc and contains pockets of star formation. In its length, narrowness, and linearity the Kite's tail is an extreme example relative to known tails. The Kite (PGC 1000273) has a companion galaxy, Mrk 0926 (PGC 070409), which together comprise a binary galaxy system in which both galaxies host active galactic nuclei. Despite this systems being previously searched for signs of tidal interactions, the tail had not been discovered prior to our identification as part of the validation process of the SMUDGes survey for low surface brightness galaxies. We confirm the kinematic association between various H$α$ knots along the tail, a small galaxy, and the Kite galaxy using optical spectroscopy obtained with the Magellan telescope and measure a velocity gradient along the tail. The Kite shares characteristics common to those formed via ram pressure stripping ("jellyfish" galaxies) and formed via tidal interactions. However, both scenarios face significant challenges that we discuss, leaving open the question of how such an extreme tail formed. We propose that the tail resulted from a three-body interaction from which the lowest-mass galaxy was ejected at high velocity.

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arXiv2023

Systematically Measuring Ultra-Diffuse Galaxies (SMUDGes). IV. Ultra-Diffuse Satellites of Milky Way Analogs

To better understand the formation of large, low surface brightness galaxies, we measure the correlation function between ultra-diffuse galaxy (UDG) candidates and Milky Way analogs (MWAs). We find that (1) the projected radial distribution of UDG satellites (projected surface density $\propto r^{-0.84\pm0.06}$) is consistent with that of normal satellite galaxies, (2) the number of UDG satellites per MWA ($S_{\rm UDG}$) is $\sim 0.5\pm0.1$ over projected radii from 20 to 250 kpc and $-17< M_r < -13.5$, (3) $S_{\rm UDG}$ is consistent with a linear extrapolation of the relationship between the number of UDGs per halo vs. halo mass obtained over galaxy group and cluster scales, (4) red UDG satellites dominate the population of UDG satellites ($\sim80$%), (5) over the range of satellite magnitudes studied, UDG satellites comprise $\sim$ 10% of the satellite galaxy population of MWAs, (6) a significant fraction of these ($\sim$13%) have estimated total masses $>$ 10$^{10.9}$ M$_\odot$ or, equivalently, at least half the halo mass of the LMC, and populate a large fraction ($\sim$ 18%) of the expected subhalos down to these masses. All of these results suggest a close association between the overall low mass galaxy population and UDGs, which we interpret as favoring models where UDG formation principally occurs within the general context of low mass galaxy formation over models invoking more exotic physical processes specifically invoked to form UDGs.

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arXiv2022

Systematically Measuring Ultra-Diffuse Galaxies (SMUDGes). III. The Southern SMUDGes Catalog

We present a catalog of 5598 ultra-diffuse galaxy (UDG) candidates with effective radius $r_e > 5.3$ arcsec distributed throughout the southern portion of the DESI Legacy Imaging Survey covering $\sim$ 15000 deg$^2$. The catalog is most complete for physically large ($r_e > 2.5$ kpc) UDGs lying in the redshift range $1800 \lesssim cz/{\rm km\ s}^{-1} \lesssim 7000$, where the lower bound is defined by where incompleteness becomes significant for large objects on the sky and the upper bound by our minimum angular size selection criterion. Because physical size is integral to the definition of a UDG, we develop a method {of distance estimation} using existing redshift surveys. With three different galaxy samples, two of which contain UDGs with spectroscopic redshifts, we estimate that the method has a redshift accuracy of $\sim$ 75% when the method converges, although larger, more representative spectroscopic UDG samples are needed to fully understand the behavior of the method. We are able to estimate distances for 1079 of our UDG candidates (19%). Finally, to illustrate uses of the catalog, we present distance independent and dependent results. In the latter category we establish that the red sequence of UDGs lies on the extrapolation of the red sequence relation for bright ellipticals and that the environment-color relation is at least qualitatively similar to that of high surface brightness galaxies. Both of these results challenge some of the models proposed for UDG evolution.

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arXiv2022

Implications for Galaxy Formation Models from Observations of Globular Clusters around Ultra-Diffuse Galaxies

We present an analysis of Hubble Space Telescope observations of globular clusters (GCs) in six ultra-diffuse galaxies (UDGs) in the Coma cluster, a sample that represents UDGs with large effective radii ($R_{\rm e}$), and use the results to evaluate competing formation models. We eliminate two significant sources of systematic uncertainty in the determination of the number of GCs, $N_{\rm GC}$ by using sufficiently deep observations that (i) reach the turnover of the GC luminosity function and (ii) provide a sufficient number of GCs with which to measure the GC number radial distribution. We find that $N_{\rm GC}$ for these galaxies is on average $\sim$20, which implies an average total mass, $M_{\rm total}$, $\sim$ $10^{11}$ $M_{\odot}$ when applying the relation between $N_{\rm GC}$ and $M_{\rm total}$. This value of $N_{\rm GC}$ lies at the upper end of the range observed for dwarf galaxies of the same stellar mass and is roughly a factor of two larger than the mean. The GC luminosity function, radial profile and average colour are more consistent with those observed for dwarf galaxies than with those observed for the more massive ($L^*$) galaxies, while both the radial and azimuthal GC distributions closely follow those of the stars in the host galaxy. Finally, we discuss why our observations, specifically the GC number and GC distribution around these six UDGs, pose challenges for several of the currently favoured UDG formation models.

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arXiv2021

Systematically Measuring Ultra-Diffuse Galaxies (SMUDGes). II. Expanded Survey Description and the Stripe 82 Catalog

We present 226 large ultra-diffuse galaxy (UDG) candidates ($r_e > 5.3$\arcsec, $μ_{0,g} > 24$ mag arcsec$^{-2}$) in the SDSS Stripe 82 region recovered using our improved procedure developed in anticipation of processing the entire Legacy Surveys footprint. The advancements include less constrained structural parameter fitting, expanded wavelet filtering criteria, consideration of Galactic dust, estimates of parameter uncertainties and completeness based on simulated sources, and refinements of our automated candidate classification. We have a sensitivity $\sim$1 mag fainter in $μ_{0,g}$ than the largest published catalog of this region. Using our completeness-corrected sample, we find that (1) there is no significant decline in the number of UDG candidates as a function of $μ_{0,g}$ to the limit of our survey ($\sim$ 26.5 mag arcsec$^{-2}$); (2) bluer candidates have smaller Sérsic $n$; (3) most blue ($g-r < 0.45$ mag) candidates have $μ_{0,g} \lesssim 25$ mag arcsec$^{-2}$ and will fade to populate the UDG red sequence we observe to $\sim 26.5$ mag arcsec$^{-2}$; (4) any red UDGs that exist significantly below our $μ_{0,g}$ sensitivity limit are not descended from blue UDGs in our sample; and (5) candidates with lower $μ_{0,g}$ tend to smaller $n$. We anticipate that the final SMUDGes sample will contain $\sim$ 30$\times$ as many candidates.

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arXiv2020

Systematically Measuring Ultra Diffuse Galaxies in HI: Results from the Pilot Survey

We present neutral hydrogen (HI) observations using the Robert C. Byrd Green Bank Telescope (GBT) of 70 optically-detected UDG candidates in the Coma region from the Systematically Measuring Ultra-Diffuse Galaxies survey (SMUDGes). We detect HI in 18 targets, confirming 9 to be gas-rich UDGs and the remainder to be foreground dwarfs. None of our HI-detected UDGs are Coma Cluster members and all but one are in low-density environments. The HI-detected UDGs are bluer and have more irregular morphologies than the redder, smoother candidates not detected in HI, with the combination of optical color and morphology being a better predictor of gas richness than either parameter alone. There is little visual difference between the gas-rich UDGs and the foreground dwarfs in the SMUDGes imaging, and distances are needed to distinguish between them. We find that the gas richnesses of our HI-confirmed UDGs and those from other samples scale with their effective radii in two stellar mass bins, possibly providing clues to their formation. We attempt to place our UDGs on the baryonic Tully-Fisher relation (BTFR) using optical ellipticities and turbulence-corrected HI linewidths to estimate rotation velocities, but the potential systematics associated with fitting smooth $\mathrm{S\acute{e}rsic}$ profiles to clumpy, low-inclination low surface brightness disks precludes a meaningful analysis of potential BTFR offsets. These observations are a pilot for a large campaign now underway at the GBT to use the HI properties of gas-rich UDGs to quantitatively constrain how these galaxies form and evolve.

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arXiv2019

Ultra-Diffuse Galaxies at Ultraviolet Wavelengths

We measure NUV aperture magnitudes from {\sl GALEX} images for 258 ultra-diffuse galaxy (UDG) candidates drawn from the initial SMUDGes survey of $\sim 300$ square degrees surrounding, and including, the Coma galaxy cluster. For the vast majority, 242 of them, we present flux upper limits due either to a lack of significant flux in the aperture or confusion with other objects projected within the aperture. These limits often place interesting constraints on the UDG candidates, indicating that they are non-star forming or quiescent. In particular, we identify field, quiescent UDG candidates, which are a challenge for formation models and are therefore compelling prospects for spectroscopic follow-up and distance determinations. We present FUV and NUV magnitudes for 16 detected UDG candidates and compare those galaxies to the local population of galaxies on color-magnitude and specific star formation rate diagrams. The NUV detected UDG candidates form mostly an extension toward lower stellar masses of the star forming galaxy sequence and none of these lie within regions of high local galaxy density. UDG candidates span a range of properties, although almost all are consistent with being quiescent, low surface brightness galaxies, regardless of environment.

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arXiv2018

Systematically Measuring Ultra Diffuse Galaxies (SMUDGes). I. Survey Description and First Results in the Coma Galaxy Cluster and Environs

We present a homogeneous catalog of 275 large (effective radius $\gtrsim$ 5.3 arcsec) ultra-diffuse galaxy (UDG) candidates lying within an $\approx$ 290 square degree region surrounding the Coma cluster. The catalog results from our automated postprocessing of data from the Legacy Surveys, a three-band imaging survey covering 14,000 square degrees of the extragalactic sky. We describe a pipeline that identifies UDGs and provides their basic parameters. The survey is as complete in these large UDGs as previously published UDG surveys of the central region of the Coma cluster. We conclude that the majority of our detections are at roughly the distance of the Coma cluster, implying effective radii $\ge 2.5$ kpc, and that our sample contains a significant number of analogs of DF 44, where the effective radius exceeds 4 kpc, both within the cluster and in the surrounding field. The $g-z$ color of our UDGs spans a large range, suggesting that even large UDGs may reflect a range of formation histories. A majority of the UDGs are consistent with being lower stellar mass analogs of red sequence galaxies, but we find both red and blue UDG candidates in the vicinity of the Coma cluster and a relative overabundance of blue UDG candidates in the lower density environments and the field. Our eventual processing of the full Legacy Surveys data will produce the largest, most homogeneous sample of large UDGs.

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arXiv2015

The Contribution of Faint Galaxy Wings to Source-subtracted Near-infrared Background Fluctuations

The source-subtracted, 1.1 and 1.6 μm NICMOS images used in earlier analyses of the near-infrared Hubble Ultra Deep Field contained residual flux in extended wings of identified sources that contributed an unknown amount to fluctuation power. When compared to the original results, a reanalysis after subtracting this residual flux shows that mean-square and rms fluctuations decrease a maximum of 52 and 31 per cent at 1.6 μm and 50 and 30 per cent at 1.1 μm. However, total mean-square fluctuations above 0.5 arcsec only decrease 6.5 and 1.4 per cent at 1.6 and 1.1 μm, respectively. These changes would not affect any published conclusions based on the prior analyses. These results exclude previous suggestions that extended wings of detected galaxies may be a major contributor to the source-subtracted near-infrared background and confirm that most fluctuation power in these images must be explained by other means.

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