Properties Of Satellite Galaxies Research Articles

Orbital evolution of satellite galaxies in self-interacting dark matter models

Dark matter self-interactions can leave distinctive signatures on the properties of satellite galaxies around Milky Way--like hosts through their impact on tidal stripping, ram pressure, and gravothermal collapse. We delineate the regions of self-interacting dark matter parameter space---specified by interaction cross section and a velocity scale---where each of these effects dominates and show how the relative mass loss depends on the satellite's initial mass, density profile, and orbit. We obtain novel, conservative constraints in this parameter space using Milky Way satellite galaxies with notably high central densities and small pericenter distances. Our results for self-interacting dark matter models, in combination with constraints from clusters of galaxies, favor either velocity-dependent cross sections that lead to gravothermal core collapse in the densest satellites or small cross sections which more closely resemble cold and collisionless dark matter.

Sussing merger trees: the impact of halo merger trees on galaxy properties in a semi-analytic model

A halo merger tree forms the essential backbone of a semi-analytic model for galaxy formation and evolution. Recent studies have pointed out that extracting merger trees from numerical simulations of structure formation is non-trivial; different tree building algorithms can give differing merger histories. These differences should be carefully understood before merger trees are used as input for models of galaxy formation. We investigate the impact of different halo merger trees on a semi-analytic model. We find that the z=0 galaxy properties in our model show differences between trees when using a common parameter set. The star formation history of the Universe and the properties of satellite galaxies can show marked differences between trees with different construction methods. Independently calibrating the semi-analytic model for each tree can reduce the discrepancies between the z=0 global galaxy properties, at the cost of increasing the differences in the evolutionary histories of galaxies. Furthermore, the underlying physics implied can vary, resulting in key quantities such as the supernova feedback efficiency differing by factors of 2. Such a change alters the regimes where star formation is primarily suppressed by supernovae. Therefore, halo merger trees extracted from a common halo catalogue using different, but reliable, algorithms can result in a difference in the semi-analytic model. Given the uncertainties in galaxy formation physics, however, these differences may not necessarily be viewed as significant.

MEASURABLE RELATIONSHIP BETWEEN BRIGHT GALAXIES AND THEIR FAINT COMPANIONS IN WHL J085910.0+294957, A GALAXY CLUSTER ATz= 0.30: VESTIGES OF INFALLEN GROUPS?

The properties of satellite galaxies are closely related to their host galaxies in galaxy groups. In cluster environments, on the other hand, the interaction between close neighbors is known to be limited. Our goal is to examine the relationships between host and satellite galaxies in the harsh environment of a galaxy cluster. To achieve this goal, we study a galaxy cluster WHL J085910.0+294957 at z = 0.30 using deep images obtained with CQUEAN CCD camera mounted on the 2.1-m Otto Struve telescope. After member selection based on the scaling relations of photometric and structural parameters, we investigate the relationship between bright (M_i < -18) galaxies and their faint (-18 < M_i < -15) companions. The weighted mean color of faint companion galaxies shows no significant dependence (< 1 sigma to Bootstrap uncertainties) on cluster-centric distance and local luminosity density as well as the luminosity and concentration of an adjacent bright galaxy. However, the weighted mean color shows marginal dependence (~ 2.2 sigma) on the color of an adjacent bright galaxy, when the sample is limited to bright galaxies with at least 2 faint companions. By using a permutation test, we confirm that the correlation in color between bright galaxies and their faint companions in this cluster is statistically significant with a confidence level of 98.7%. The statistical significance increases if we additionally remove non-members using the SDSS photometric redshift information (~ 2.6 sigma and 99.3%). Our results suggest three possible scenarios: (1) vestiges of infallen groups, (2) dwarf capturing, and (3) tidal tearing of bright galaxies.

EVOLUTION OF THE GALAXY–DARK MATTER CONNECTION AND THE ASSEMBLY OF GALAXIES IN DARK MATTER HALOS

We present a new model to describe the galaxy-dark matter connection across cosmic time, which unlike the popular subhalo abundance matching technique is self-consistent in that it takes account of the facts that (i) subhalos are accreted at different times, and (ii) the properties of satellite galaxies may evolve after accretion. Using observations of galaxy stellar mass functions out to $z \sim 4$, the conditional stellar mass function at $z\sim 0.1$ obtained from SDSS galaxy group catalogues, and the two-point correlation function (2PCF) of galaxies at $z \sim 0.1$ as function of stellar mass, we constrain the relation between galaxies and dark matter halos over the entire cosmic history from $z \sim 4$ to the present. This relation is then used to predict the median assembly histories of different stellar mass components within dark matter halos (central galaxies, satellite galaxies, and halo stars). We also make predictions for the 2PCFs of high-$z$ galaxies as function of stellar mass. Our main findings are the following: (i) Our model reasonably fits all data within the observational uncertainties, indicating that the $\Lambda$CDM concordance cosmology is consistent with a wide variety of data regarding the galaxy population across cosmic time. (ii) ... [abridged]

Observational Evidence for an Age Dependence of Halo Bias

We study the dependence of the cross-correlation between galaxies and galaxy groups on group properties. Confirming previous results, we find that the correlation strength is stronger for more massive groups, in good agreement with the expected mass dependence of halo bias. We also find, however, that for groups of the same mass, the correlation strength depends on the star formation rate (SFR) of the central galaxy: at fixed mass, the bias of galaxy groups decreases as the SFR of the central galaxy increases. We discuss these findings in light of the recent findings by Gao et al. that halo bias depends on halo formation time, in that halos that assemble earlier are more strongly biased. We also discuss the implication for galaxy formation and address a possible link to galaxy conformity, the observed correlation between the properties of satellite galaxies and those of their central galaxy.

Properties of galaxy groups in the Sloan Digital Sky Survey -- I. The dependence of colour, star formation and morphology on halo mass

Using a large galaxy group catalogue constructed from the Sloan Digital Sky Survey Data Release 2, we investigate the correlation between various galaxy properties and halo mass. We split the population of galaxies in early-types, late-types and intermediate-types, based on their colour and specific star formation rate. At fixed luminosity, the late- (early-)type fraction of galaxies increases (decreases) with decreasing halo mass. Most importantly, this mass dependence is smooth and persists over the entire mass range probed, without any break or feature at any mass-scale. We argue that the previous claim of a characteristic feature on galaxy group scales is an artefact of the environment estimators used. At fixed halo mass, the luminosity dependence of the type fractions is surprisingly weak, especially over the range 0.25? L/L*? 2.5: galaxy type depends more strongly on halo mass than on luminosity. In agreement with previous studies, the late- (early-)type fraction increases (decreases) with increasing halocentric radius. However, we find that this radial dependence is present in haloes of all masses probed (down to 10 12 h -1 M ⊙ ), while previous studies did not find any radial dependence in haloes with M? 10 13.5 h -1 M ⊙ . We argue that this discrepancy owes to the fact that we have excluded central galaxies from our analysis. We also find that the properties of satellite galaxies are strongly correlated with those of their central galaxy. In particular, the early-type fraction of satellites is significantly higher in a halo with an early-type central galaxy than in a halo of the same mass but with a late-type central galaxy. This phenomenon, which we call 'galactic conformity', is present in haloes of all masses and for satellites of all luminosities. Finally, the fraction of intermediate-type galaxies is always ∼20 per cent, independent of luminosity, independent of halo mass, independent of halocentric radius, and independent of whether the galaxy is a central galaxy or a satellite galaxy. We discuss the implicat ns of all these findings for galaxy formation and evolution.

The Properties of Satellite Galaxies in External Systems. II. Photometry and Colors

In this second paper dedicated to the study of satellite galaxies we present broadband photometry in the B, V, R, and I filters of 49 satellite galaxies orbiting giant isolated spiral galaxies. First analysis of the properties of these objects are presented by means of color-color and color-magnitude diagrams for early- and late-type satellites. Although we find differences in the slope of the V - I versus Mv color magnitude diagram, as a whole, the relations are in agreement with the trends known to date for galaxies of similar magnitudes in nearby clusters of galaxies. Comparison with the relations found for satellites in the Local Group allows us to sample better the bright end of the luminosity function of satellite galaxies and extends for brighter objects the validity of the color-magnitude relation found for dwarf galaxies in the Local Group. Most of the E/S0 galaxies in our sample show a negative color gradient with values similar to those known for early-type galaxies in other environments.

The Properties of Satellite Galaxies in External Systems. I. Morphology and Structural Parameters

We present the first results of an ongoing project to study the morphological, kinematical, dynamical, and chemical properties of satellite galaxies of external giant spiral galaxies. The sample of objects has been selected from the catalog by Zaritsky et al. The paper analyzes the morphology and structural parameters of a subsample of 60 such objects. The satellites span a great variety of morphologies and surface brightness profiles. About two-thirds of the sample are spirals and irregulars, the remaining third being early-types. Some cases showing interaction between pairs of satellites are presented and briefly discussed.

The effects of photoionization on galaxy formation - II. Satellite galaxies in the Local Group

We use a self-consistent model of galaxy formation and the evolution of the intergalactic medium to study the effects of the reionization of the Universe at high redshift on the properties of satellite galaxies like those seen around the Milky Way. Photoionization suppresses the formation of small galaxies, so that surviving satellites are preferentially those that formed before the Universe reionized. As a result, the number of satellites expected today is about an order of magnitude smaller than the number inferred by identifying satellites with subhaloes of the same circular velocity in high-resolution simulations of the dark matter. The resulting satellite population has an abundance similar to that observed in the Local Group, although the distribution of circular velocities differs somewhat from the available data. We explore many other properties of satellite galaxies, including their gas content, metallicity and star formation rate, and find generally good agreement with available data. Our model predicts the existence of many as yet undetected satellites in the Local Group. We quantify their observability in terms of their apparent magnitude and surface brightness, and also in terms of their constituent stars. A near-complete census of the Milky Way's satellites would require imaging to V≈20 and to a surface brightness fainter than 26 V-band magnitudes per square arcsecond. Satellites with integrated luminosity V=15 should contain of order 100 stars brighter than B=26, with central stellar densities of a few tens per square arcminute. Discovery of a large population of faint satellites would provide a strong test of current models of galaxy formation.