229 research outputs found
Distinguishing Dark Matter Cusps from Cores using Globular Clusters
Globular Clusters (GCs) provide valuable insight into the properties of their
host galaxies' dark matter halos. Using N-body simulations incorporating
semianalytic dynamical friction and GC-GC merger prescriptions, we study the
evolution of GC radial distributions and mass functions in cuspy and cored dark
matter halos. Modeling the dynamics of the GC-rich system in the dwarf galaxy
UGC7369, we find that friction-induced inspiral and subsequent mergers of
massive GCs can naturally and robustly explain the mass segregation of the GCs
and the existence of a nuclear star cluster (NSC). However, the multiple
mergers required to form the NSC only take place when the dark matter halo is
cuspy. In a cored halo, stalling of the dynamical friction within the core
halts the inspiral of the GCs, and so the GC merger rate falls significantly,
precluding the formation of an NSC. We therefore argue that the presence of an
NSC requires a cusp in UGC7369. More generally, we propose that the presence of
an NSC and the corresponding alteration of the GC mass function due to mergers
may be used as an indicator of a cuspy halo for galaxies in which we expect NSC
formation to be merger-dominated. These observables represent a simple,
powerful complement to other inner halo density profile constraint techniques,
and should allow for straightforward extension to larger samples.Comment: 19 pages, 11 figures. Main results in figures 7 and 8. Submitted to
ApJ, comments are welcome
ELVES III: Environmental Quenching by Milky Way-Mass Hosts
Isolated dwarf galaxies usually exhibit robust star formation but satellite
dwarf galaxies are often devoid of young stars, even in Milky Way-mass groups.
Dwarf galaxies thus offer an important laboratory of the environmental
processes that cease star formation. We explore the balance of quiescent and
star-forming galaxies (quenched fractions) for a sample of ~400 satellite
galaxies around 30 Local Volume hosts from the Exploration of Local VolumE
Satellites (ELVES) Survey. We present quenched fractions as a function of
satellite stellar mass, projected radius, and host halo mass, to conclude that
overall, the quenched fractions are similar to the Milky Way, dropping below
50% at satellite M* ~ 10^8 M_sun. We may see hints that quenching is less
efficient at larger radius. Through comparison with the semi-analytic modeling
code satgen, we are also able to infer average quenching times as a function of
satellite mass in host halo-mass bins. There is a gradual increase in quenching
time with satellite stellar mass rather than the abrupt change from rapid to
slow quenching that has been inferred for the Milky Way. We also generally
infer longer average quenching times than recent hydrodynamical simulations.
Our results are consistent with models that suggest a wide range of quenching
times are possible via ram-pressure stripping, depending on the clumpiness of
the circumgalactic medium, the orbits of the satellites, and the degree of
earlier preprocessing.Comment: 18 pages, 12 figures, replaced post-refereeing, no major change
ELVES IV: The Satellite Stellar-to-Halo Mass Relation Beyond the Milky-Way
Quantifying the connection between galaxies and their host dark matter halos
has been key for testing cosmological models on various scales. Below , such studies have primarily relied on the satellite galaxy
population orbiting the Milky Way. Here we present new constraints on the
connection between satellite galaxies and their host dark matter subhalos using
the largest sample of satellite galaxies in the Local Volume () to date. We use confirmed and candidate dwarf
satellites around 27 Milky Way (MW)-like hosts from the Exploration of Local
VolumE Satellites (ELVES) Survey and use the semi-analytical SatGen model for
predicting the population of dark matter subhalos expected in the same volume.
Through a Bayesian model comparison of the observed and the forward-modeled
satellite stellar mass functions (SSMF), we infer the satellite stellar-to-halo
mass relation. We find that the observed SSMF is best reproduced when subhalos
at the low mass end are populated by a relation of the form , with a moderate slope of and a low scatter, constant as a function of the peak halo mass, of
. A model with a steeper slope
() and a scatter that grows with decreasing
is also consistent with the observed SSMF but is not
required. Our new model for the satellite-subhalo connection, based on hundreds
of Local Volume satellite galaxies, is in line with what was previously derived
using only the Milky Way satellites.Comment: Accepted for publication in ApJ. Figure 8 shows the key result -- the
Satellite Stellar to Halo Mass relation obtained in this work, in comparison
to previous studie
A Tip of the Red Giant Branch Distance to the Dark Matter Deficient Galaxy NGC1052-DF4 from Deep Hubble Space Telescope Data
Previous studies have shown that the large, diffuse galaxies NGC1052-DF2 and
NGC1052-DF4 both have populations of unusually luminous globular clusters as
well as a very low dark matter content. Here we present newly-obtained deep
Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) imaging of one
of these galaxies, NGC1052-DF4. We use these data to measure the distance of
the galaxy from the location of the tip of the red giant branch (TRGB). We find
a rapid increase in the number of detected stars fainter than , which we identify as the onset of the red giant branch. Using a forward
modeling approach that takes the photometric uncertainties into account, we
find a TRGB magnitude of . The inferred
distance, including the uncertainty in the absolute calibration, is Mpc. The TRGB distance of NGC1052-DF4 is consistent with
the previously-determined surface brightness fluctuation distance of Mpc to NGC1052-DF2 and is consistent with the distance of the
bright elliptical galaxy NGC1052. We conclude that the unusual properties of
these galaxies cannot be explained by distance errors.Comment: Accepted for publication in ApJ Letters, in press. Figure 1 shows the
color image of the galaxy. The main result is shown in Figure
Light from the Darkness: Detecting Ultra-diffuse Galaxies in the Perseus Cluster through Over-densities of Globular Clusters with a Log-Gaussian Cox Process
We introduce a new method for detecting ultra-diffuse galaxies by searching for over-densities in intergalactic globular cluster populations. Our approach is based on an application of the log-Gaussian Cox process, which is a commonly used model in the spatial statistics literature but rarely used in astronomy. This method is applied to the globular cluster data obtained from the PIPER survey, a Hubble Space Telescope imaging program targeting the Perseus cluster. We successfully detect all confirmed ultra-diffuse galaxies with known globular cluster populations in the survey. We also identify a potential galaxy that has no detected diffuse stellar content. Preliminary analysis shows that it is unlikely to be merely an accidental clump of globular clusters or other objects. If confirmed, this system would be the first of its kind. Simulations are used to assess how the physical parameters of the globular cluster systems within ultra-diffuse galaxies affect their detectability using our method. We quantify the correlation of the detection probability with the total number of globular clusters in the galaxy and the anticorrelation with increasing half-number radius of the globular cluster system. The Sérsic index of the globular cluster distribution has little impact on detectability
Haptoglobin Genotype Is a Consistent Marker of Coronary Heart Disease Risk Among Individuals With Elevated Glycosylated Hemoglobin
ObjectivesThis study sought to investigate into the biologically plausible interaction between the common haptoglobin (Hp) polymorphism rs#72294371 and glycosylated hemoglobin (HbA1c) on risk of coronary heart disease (CHD).BackgroundStudies of the association between the Hp polymorphism and CHD report inconsistent results. Individuals with the Hp2-2 genotype produce Hp proteins with an impaired ability to prevent oxidative injury caused by elevated HbA1c.MethodsHbA1c concentration and Hp genotype were determined for 407 CHD cases matched 1:1 to controls (from the NHS [Nurses' Health Study]) and in a replication cohort of 2,070 individuals who served as the nontreatment group in the ICARE (Prevention of Cardiovascular Complications in Diabetic Patients With Vitamin E Treatment) study, with 29 CHD events during follow-up. Multivariate models were adjusted for lifestyle and CHD risk factors as appropriate. A pooled analysis was conducted of NHS, ICARE, and the 1 previously published analysis (a cardiovascular disease case-control sample from the Strong Heart Study).ResultsIn the NHS, Hp2-2 genotype (39% frequency) was strongly related to CHD risk only among individuals with elevated HbA1c (≥6.5%), an association that was similar in the ICARE trial and the Strong Heart Study. In a pooled analysis, participants with both the Hp2-2 genotype and elevated HbA1c had a relative risk of 7.90 (95% confidence interval: 4.43 to 14.10) for CHD compared with participants with both an Hp1 allele and HbA1c <6.5% (p for interaction = 0.004), whereas the Hp2-2 genotype with HbA1c <6.5% was not associated with risk (relative risk: 1.34 [95% confidence interval: 0.73 to 2.46]).ConclusionsHp genotype was a significant predictor of CHD among individuals with elevated HbA1c
Beyond Ultra-Diffuse Galaxies I: Mass-Size Outliers Among the Satellites of Milky Way Analogs
Large diffuse galaxies are hard to find, but understanding the environments
where they live, their numbers, and ultimately their origins, is of intense
interest and importance for galaxy formation and evolution. Using Subaru's
Hyper Suprime-Cam Strategic Survey Program, we perform a systematic search for
low surface brightness galaxies and present novel and effective methods for
detecting and modeling them. As a case study, we surveyed 922 Milky Way analogs
in the nearby Universe () and build a large sample of
satellite galaxies that are outliers in the mass-size relation. These
``ultra-puffy'' galaxies (UPGs), defined to be above the average
mass-size relation, represent the tail of the satellite size distribution. We
find that each MW analog hosts ultra-puffy
galaxies on average, which is consistent with but slightly lower than the
observed abundance at this halo mass in the Local Volume. We also construct a
sample of ultra-diffuse galaxies (UDGs) in MW analogs and find an abundance of
per host. With literature results, we confirm that
the UDG abundance scales with the host halo mass following a sublinear power
law. We argue that our definition for ultra-puffy galaxies, which is based on
the mass-size relation, is more physically-motivated than the common definition
of ultra-diffuse galaxies, which depends on surface brightness and size cuts
and thus yields different surface mass density cuts for quenched and
star-forming galaxies.Comment: 19 pages, 7 figures, submitted to Ap
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