Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userDynamical evidence for a morphology-dependent relation between the stellar and halo masses of galaxies
134
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We derive the stellar-to-halo mass relation (SHMR), namely $f_starpropto M_star/M_{rm h}$ versus $M_star$ and $M_{rm h}$, for early-type galaxies from their near-IR luminosities (for $M_star$) and the position-velocity distributions of their globular cluster systems (for $M_{rm h}$). Our individual estimates of $M_{rm h}$ are based on fitting a dynamical model with a distribution function expressed in terms of action-angle variables and imposing a prior on $M_{rm h}$ from the concentration-mass relation in the standard $Lambda$CDM cosmology. We find that the SHMR for early-type galaxies declines with mass beyond a peak at $M_starsim 5times 10^{10}M_odot$ and $M_{rm h}sim 10^{12}M_odot$ (near the mass of the Milky Way). This result is consistent with the standard SHMR derived by abundance matching for the general population of galaxies, and with previous, less robust derivations of the SHMR for early types. However, it contrasts sharply with the monotonically rising SHMR for late types derived from extended HI rotation curves and the same $Lambda$CDM prior on $M_{rm h}$ as we adopt for early types. The SHMR for massive galaxies varies more or less continuously, from rising to falling, with decreasing disc fraction and decreasing Hubble type. We also show that the different SHMRs for late and early types are consistent with the similar scaling relations between their stellar velocities and masses (Tully-Fisher and Faber-Jackson relations). Differences in the relations between the stellar and halo virial velocities account for the similarity of the scaling relations. We argue that all these empirical findings are natural consequences of a picture in which galactic discs are built mainly by smooth and gradual inflow, regulated by feedback from young stars, while galactic spheroids are built by a cooperation between merging, black-hole fuelling, and feedback from AGNs.
rate research
Read More
For many massive compact galaxies, their dynamical masses ($M_mathrm{dyn} propto sigma^2 r_mathrm{e}$) are lower than their stellar masses ($M_star$). We analyse the unphysical mass discrepancy $M_star / M_mathrm{dyn} > 1$ on a stellar-mass-selected sample of early-type galaxies ($M_star gtrsim 10^{11} mathrm{M_odot}$) at redshifts $z sim 0.2$ to $z sim 1.1$. We build stacked spectra for bins of redshift, size and stellar mass, obtain velocity dispersions, and infer dynamical masses using the virial relation $M_mathrm{dyn} equiv K sigma_mathrm{e}^2 r_mathrm{e} / G$ with $K = 5.0$; this assumes homology between our galaxies and nearby massive ellipticals. Our sample is completed using literature data, including individual objects up to $z sim 2.5$ and a large local reference sample from the Sloan Digital Sky Survey (SDSS). We find that, at all redshifts, the discrepancy between $M_star$ and $M_mathrm{dyn}$ grows as galaxies depart from the present-day relation between stellar mass and size: the more compact a galaxy, the larger its $M_star / M_mathrm{dyn}$. Current uncertainties in stellar masses cannot account for values of $M_star / M_mathrm{dyn}$ above 1. Our results suggest that the homology hypothesis contained in the $M_mathrm{dyn}$ formula above breaks down for compact galaxies. We provide an approximation to the virial coefficient $K sim 6.0 left[ r_mathrm{e} / (3.185 mathrm{kpc}) right]^{-0.81} left[ M_star / (10^{11} mathrm{M_odot}) right]^{0.45}$, which solves the mass discrepancy problem. A rough approximation to the dynamical mass is given by $M_mathrm{dyn} sim left[ sigma_mathrm{e} / (200 mathrm{km s^{-1}}) right]^{3.6} left[ r_mathrm{e} / (3 mathrm{kpc}) right]^{0.35} 2.1 times 10^{11} mathrm{M_odot}$.
We use the SPARC (Spitzer Photometry & Accurate Rotation Curves) database to study the relation between the central surface density of stars Sstar and dynamical mass Sdyn in 135 disk galaxies (S0 to dIrr). We find that Sdyn correlates tightly with Sstar over 4 dex. This central density relation can be described by a double power law. High surface brightness galaxies are consistent with a 1:1 relation, suggesting that they are self-gravitating and baryon dominated in the inner parts. Low surface brightness galaxies systematically deviate from the 1:1 line, indicating that the dark matter contribution progressively increases but remains tightly coupled to the stellar one. The observed scatter is small (~0.2 dex) and largely driven by observational uncertainties. The residuals show no correlations with other galaxy properties like stellar mass, size, or gas fraction.
In this study we demonstrate that stellar masses of galaxies (Mstar) are universally correlated through a double power law function with the product of the dynamical velocities (Ve) and sizes to one-fourth power (Re^0.25) of galaxies, both measured at the effective radii. The product VeRe^0.25 represents the fourth root of the total binding energies within effective radii of galaxies. This stellar mass-binding energy correlation has an observed scatter of 0.14 dex in log(VeRe^0.25) and 0.46 dex in log(Mstar). It holds for a variety of galaxy types over a stellar mass range of nine orders of magnitude, with little evolution over cosmic time. A toy model of self-regulation between binding energies and supernovae feedback is shown to be able to reproduce the observed slopes, but the underlying physical mechanisms are still unclear. The correlation can be a potential distance estimator with an uncertainty of 0.2 dex independent of the galaxy type.
The 2020s are poised to continue the past two decades of significant advances based on observations of dwarf galaxies in the nearby universe. Upcoming wide-field photometric surveys will probe substantially deeper than previous data sets, pushing the discovery frontier for new dwarf galaxies to fainter magnitudes, lower surface brightnesses, and larger distances. These dwarfs will be compelling targets for testing models of galaxy formation and cosmology, including the properties of dark matter and possible modifications to gravity. However, most of the science that can be extracted from nearby dwarf galaxies relies on spectroscopy with large telescopes. We suggest that maximizing the scientific impact of near-future imaging surveys will require both major spectroscopic surveys on 6-10m telescopes and multiplexed spectroscopy with even larger apertures.
We investigate the relation between the projected morphology (b/a) and the velocity dispersion (sigma_v) of groups of galaxies using two recently compiled group catalogs, one based on the 2MASS redshift survey and the other on the SDSS Data Release 5 galaxy catalog. We find that the sigma_v of groups is strongly correlated with the group projected b/a and size, with elongated and larger groups having a lower sigma_v. Such a correlation could be attributed to the dynamical evolution of groups, with groups in the initial stages of formation, having small sigma_v, a large size and an elongated shape that reflects the anisotropic accretion of galaxies along filamentary structures. The same sort of correlations, however, could also be reproduced in prolate-like groups, if the net galaxy motion is preferentially along the group elongation, since then the groups oriented close to the line of sight will appear more spherical, will have a small projected size and large sigma_v, while groups oriented close to the sky-plane will appear larger in projection, more elongated, and will have smaller sigma_v. We perform tests that relate only to the dynamical evolution of groups (eg., calculating the fraction of early type galaxies in groups) and indeed we find a strong positive (negative) correlation between the group sigma_v (projected major axis) with the fraction of early type galaxies. We conclude that (a) the observed dependencies of the group sigma_v on the group projected size and b/a, should be attributed mostly to the dynamical state of groups and (b) groups in the local universe do not constitute a family of objects in dynamical equilibrium, but rather a family of cosmic structures that are presently at various stages of their virialization process.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
