26 research outputs found
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
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
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
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.Comment: Accepted by ApJ. Revisions include updated versions of Figures 3-9,
new table 5, and expanded discussion. Conclusions unchanged. Figures 6-8 will
be available in higher resolution in the published versio
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Ultra-diffuse Galaxies at Ultraviolet Wavelengths
We measure near-ultraviolet (NUV) aperture magnitudes from Galaxy Evolution Explorer images for 258 ultra-diffuse galaxy (UDG) candidates drawn from the initial Systematically Measuring Ultra-Diffuse Galaxies (SMUDGes) survey of similar to 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 far-ultraviolet (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.NASA [NAS5-26555]; National Science Foundation [NSF AAG-171384]This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
Systematically Measuring Ultra-Diffuse Galaxies (SMUDGes). V. The Complete SMUDGes Catalog and the Nature of Ultra-Diffuse Galaxies
We present the completed catalog of ultra-diffuse galaxy (UDG) candidates
(7070 objects) from our search of the DR9 Legacy Survey images, including
distance and total mass estimates for 1529 and 1436 galaxies, respectively,
that we provide and describe in detail. From the sample with estimated
distances, we obtain a sample of 585 UDGs ( mag arcsec
and kpc) over 20,000 sq. deg of sky in various environments. We
conclude that UDGs in our sample are limited to
M/M and are on average a factor of 1.5 to 7
deficient in stars relative to the general population of galaxies of the same
total mass. That factor increases with increasing galaxy size and mass up to a
factor of 10 when the total mass of the UDG increases beyond M M. We do not find evidence that this factor has a dependence
on the UDG's large-scale environment.Comment: 21 pages, accepted for publication in ApJS, full catalog available
upon reques
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 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.Comment: Submitted to publication in MNRAS (comments welcome
One hundred SMUDGes in S-PLUS: ultra-diffuse galaxies flourish in the field
We present the first systematic study of the stellar populations of ultra-diffuse galaxies (UDGs) in the field, integrating the large area search and characterization of UDGs by the SMUDGes survey with the twelve-band optical photometry of the S-PLUS survey. Based on Bayesian modeling of the optical colors of UDGs, we determine the ages, metallicities and stellar masses of 100 UDGs distributed in an area of deg in the Stripe 82 region. We find that the stellar masses and metallicities of field UDGs are similar to those observed in clusters and follow the trends previously defined in studies of dwarf and giant galaxies. However, field UDGs have younger luminosity-weighted ages than do UDGs in clusters. We interpret this result to mean that field UDGs have more extended star formation histories, including some that continue to form stars at low levels to the present time. Finally, we examine stellar population scaling relations that show that UDGs are, as a population, similar to other low-surface brightness galaxies.Instituto de Astrofísica de La PlataFacultad de Ciencias Astronómicas y Geofísica
Systematically Measuring Ultradiffuse Galaxies (SMUDGes). IV. Ultradiffuse Satellites of Milky Way Analogs
To better understand the formation of large, low-surface-brightness galaxies, we measure the correlation function between ultradiffuse galaxy (UDG) candidates and Milky Way analogs (MWAs). We find that: (1) the projected radial distribution of UDG satellites (projected surface density ∝ r ^−0.84±0.06 ) is consistent with that of normal satellite galaxies; (2) the number of UDG satellites per MWA ( S _UDG ) is ∼0.5 ± 0.1 over projected radii from 20 to 250 kpc and −17 10 ^10.9 M _⊙ or, equivalently, at least half the halo mass of the LMC, and populate a large fraction (∼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