scholarly journals REVEALING VELOCITY DISPERSION AS THE BEST INDICATOR OF A GALAXY's COLOR, COMPARED TO STELLAR MASS, SURFACE MASS DENSITY, OR MORPHOLOGY

2012 ◽  
Vol 751 (2) ◽  
pp. L44 ◽  
Author(s):  
David A. Wake ◽  
Pieter G. van Dokkum ◽  
Marijn Franx
Keyword(s):  
Velocity Dispersion ◽  
Mass Density ◽  
Stellar Mass ◽  
Surface Mass ◽  
Surface Mass Density

The surface mass density in the solar neighbourhood using red clumps stars in TGASxRAVE

2017 ◽  
Vol 13 (S334) ◽  
pp. 304-305
Author(s):  
Jorrit H. J. Hagen ◽  
Amina Helmi
Keyword(s):  
Vertical Velocity ◽  
Velocity Dispersion ◽  
Mass Density ◽  
Solar Neighbourhood ◽  
Local Distribution ◽  
Surface Mass ◽  
Preliminary Results ◽  
Combining Data ◽  
Surface Mass Density ◽  
Red Clump

AbstractWe investigate the kinematics of red clump stars in the Solar neighbourhood by combining data from the RAVE survey with the TGAS dataset presented in Gaia DR1. Our goal is to put new constraints on the (local) distribution of mass using the Jeans Equations. Here we show the variation of the vertical velocity dispersion as function of height above the mid-plane for both a thin and a thick disk tracer sample and present preliminary results.

scholarly journals Satellite galaxies in the Illustris-1 simulation: anisotropic locations around relatively isolated hosts

2019 ◽  
Vol 489 (1) ◽  
pp. 459-469 ◽  
Author(s):  
Tereasa G Brainerd ◽  
Masaya Yamamoto
Keyword(s):  
Dark Matter ◽  
Mass Density ◽  
Stellar Mass ◽  
Stellar Surface ◽  
Surface Mass ◽  
Degree Of Anisotropy ◽  
Surface Mass Density ◽  
The Mean ◽  
Satellite Galaxies ◽  
Stellar Masses

ABSTRACT We investigate the locations of satellite galaxies in the z = 0 redshift slice of the hydrodynamical Illustris-1 simulation. As expected from previous work, the satellites are distributed anisotropically in the plane of the sky, with a preference for being located near the major axes of their hosts. Due to misalignment of mass and light within the hosts, the degree of anisotropy is considerably less when satellite locations are measured with respect to the hosts’ stellar surface mass density than when they are measured with respect to the hosts’ dark matter surface mass density. When measured with respect to the hosts’ dark matter surface mass density, the mean satellite location depends strongly on host stellar mass and luminosity, with the satellites of the faintest, least massive hosts showing the greatest anisotropy. When measured with respect to the hosts’ stellar surface mass density, the mean satellite location is essentially independent of host stellar mass and luminosity. In addition, the satellite locations are largely insensitive to the amount of stellar mass used to define the hosts’ stellar surface mass density, as long as at least 50–70 per cent of the hosts’ total stellar mass is used. The satellite locations are dependent upon the stellar masses of the satellites, with the most massive satellites having the most anisotropic distributions.

scholarly journals Resolving the Disc–Halo Degeneracy – II: NGC 6946

2020 ◽  
Vol 500 (3) ◽  
pp. 3579-3593
Author(s):  
S Aniyan ◽  
A A Ponomareva ◽  
K C Freeman ◽  
M Arnaboldi ◽  
O E Gerhard ◽  
...  
Keyword(s):  
Vertical Velocity ◽  
Velocity Dispersion ◽  
Mass Density ◽  
Scale Height ◽  
Galactic Rotation ◽  
Dark Halo ◽  
Surface Mass ◽  
Ngc 6946 ◽  
Stellar Velocity ◽  
Surface Mass Density

ABSTRACT The mass-to-light ratio (M/L) is a key parameter in decomposing galactic rotation curves into contributions from the baryonic components and the dark halo of a galaxy. One direct observational method to determine the disc M/L is by calculating the surface mass density of the disc from the stellar vertical velocity dispersion and the scale height of the disc. Usually, the scale height is obtained from near-IR studies of edge-on galaxies and pertains to the older, kinematically hotter stars in the disc, while the vertical velocity dispersion of stars is measured in the optical band and refers to stars of all ages (up to ∼10 Gyr) and velocity dispersions. This mismatch between the scale height and the velocity dispersion can lead to underestimates of the disc surface density and a misleading conclusion of the submaximality of galaxy discs. In this paper, we present the study of the stellar velocity dispersion of the disc galaxy NGC 6946 using integrated star light and individual planetary nebulae as dynamical tracers. We demonstrate the presence of two kinematically distinct populations of tracers that contribute to the total stellar velocity dispersion. Thus, we are able to use the dispersion and the scale height of the same dynamical population to derive the surface mass density of the disc over a radial extent. We find the disc of NGC 6946 to be closer to maximal with the baryonic component contributing most of the radial gravitational field in the inner parts of the galaxy (Vmax(bar) = 0.76(±0.14)Vmax).

scholarly journals IMF radial gradients in most massive early-type galaxies

2019 ◽  
Vol 489 (3) ◽  
pp. 4090-4110 ◽  
Author(s):  
F La Barbera ◽  
A Vazdekis ◽  
I Ferreras ◽  
A Pasquali ◽  
C Allende Prieto ◽  
...  
Keyword(s):  
Stellar Population ◽  
Velocity Dispersion ◽  
Mass Density ◽  
Initial Mass Function ◽  
Early Type ◽  
Low Mass Stars ◽  
Surface Mass ◽  
Low Mass ◽  
Surface Mass Density ◽  
The Imf

ABSTRACT Using new long-slit spectroscopy obtained with X-Shooter at ESO-VLT, we study, for the first time, radial gradients of optical and near-infrared initial mass function (IMF)-sensitive features in a representative sample of galaxies at the very high mass end of the galaxy population. The sample consists of seven early-type galaxies (ETGs) at z ∼ 0.05, with central velocity dispersion in the range 300 ≲ σ ≲ 350 km s−1. Using state-of-the-art stellar population synthesis models, we fit a number of spectral indices, from different chemical species (including TiO and Na indices), to constrain the IMF slope (i.e. the fraction of low-mass stars), as a function of galactocentric distance, over a radial range out to ∼4 kpc. ETGs in our sample show a significant correlation of IMF slope and surface mass density. The bottom-heavy population (i.e. an excess of low-mass stars in the IMF) is confined to central galaxy regions with surface mass density above $\rm \sim 10^{10}\, M_\odot \, kpc^{-2}$, or, alternatively, within a characteristic radius of ∼2 kpc. Radial distance, in physical units, and surface mass density are the best correlators to IMF variations, with respect to other dynamical (e.g. velocity dispersion) and stellar population (e.g. metallicity) properties. Our results for the most massive galaxies suggest that there is no single parameter that fully explains variations in the stellar IMF, but IMF radial profiles at z ∼ 0 rather result from the complex formation and mass accretion history of galaxy inner and outer regions.

scholarly journals Resolving the Disk-Halo Degeneracy: A look at M74

2016 ◽  
Vol 11 (S321) ◽  
pp. 267-267
Author(s):  
S. Aniyan ◽  
K. C. Freeman ◽  
M. Arnaboldi ◽  
O. Gerhard ◽  
L. Coccato ◽  
...  
Keyword(s):  
Surface Density ◽  
Rotation Curve ◽  
Velocity Dispersion ◽  
Mass Density ◽  
Disk Surface ◽  
Scale Height ◽  
Dark Halo ◽  
Conceptual Problem ◽  
Surface Mass ◽  
Surface Mass Density

AbstractThe decomposition of the 21 cm rotation curve of galaxies into contribution from the disk and dark halo depends on the adopted mass to light ratio (M/L) of the disk. Given the vertical velocity dispersion (σz) of stars in the disk and its scale height (h), the disk surface density and hence the M/L can be estimated. Earlier works have used this technique to conclude that galaxy disks are submaximal. Here we address an important conceptual problem: σz and h must pertain to the same population. Our analysis concludes that previous studies underestimate the disk surface mass density by ~ 2, sufficient to make a maximal disk for M74 appear like a submaximal disk.

scholarly journals Gravitational Microlensing By Random Motion Of Stars: Movie and Analysis of Light Curves

1996 ◽  
Vol 173 ◽  
pp. 287-288
Author(s):  
Joachim Wambsganss ◽  
Tomislav Kundić
Keyword(s):  
Velocity Dispersion ◽  
Mass Density ◽  
Random Motion ◽  
Light Curves ◽  
Short Version ◽  
Full Paper ◽  
Surface Mass ◽  
Bulk Motion ◽  
The Galaxy ◽  
Surface Mass Density

We present a quantitative analysis of the effect of microlensing caused by random motion of individual stars in a galaxy lensing a background quasar. We calculate a large number of magnification patterns for positions of the stars slightly offset from one frame to the next, and thus obtain light curves for fixed quasar and galaxy positions, only due to the change in the relative star positions. These light curves are analyzed to identify microlensing events, which are then classified with respect to height, duration, and slope. These random motion microlensing events are compared with the corresponding ones caused by the bulk motion of the galaxy.We find that microlensing events produced by random motion of stars are shorter, steeper, and more frequent than bulk motion events, assuming the velocity dispersion of the stars equals the bulk velocity of the galaxy. The reason for this difference is that in the case of random motion, caustics can move with an arbitrarily high velocity, producing very short events, whereas in the comparison case for bulk motion a microlensing event can never be shorter than it takes a fold caustic, which moves with the velocity of the lensing galaxy projected onto the quasar plane, to cross the quasar. An accompanying video illustrates these results. For three different values of the surface mass density κ, it shows time sequences of 1000 magnification patterns for slowly changing lens positions, together with the positions and velocity vectors of the microlensing stars. The full paper including the video can be found in Wambsganss & Kundić (1995). A short version of the video is available as an MPEG movie under anonymous ftp at astro.princeton.edu, in the directory jkw/microlensing/moving_stars.

scholarly journals A Dependence of the Tidal Disruption Event Rate on Global Stellar Surface Mass Density and Stellar Velocity Dispersion

2018 ◽  
Vol 853 (1) ◽  
pp. 39 ◽  
Author(s):  
Or Graur ◽  
K. Decker French ◽  
H. Jabran Zahid ◽  
James Guillochon ◽  
Kaisey S. Mandel ◽  
...  
Keyword(s):  
Velocity Dispersion ◽  
Event Rate ◽  
Mass Density ◽  
Stellar Surface ◽  
Tidal Disruption ◽  
Surface Mass ◽  
Stellar Velocity ◽  
Surface Mass Density ◽  
Disruption Event

scholarly journals The SAMI Galaxy Survey: stellar population and structural trends across the Fundamental Plane

2021 ◽  
Author(s):  
Francesco D’Eugenio ◽  
Matthew Colless ◽  
Nicholas Scott ◽  
Arjen van der Wel ◽  
Roger L Davies ◽  
...  
Keyword(s):  
Stellar Population ◽  
Mass Density ◽  
Empirical Relation ◽  
Zero Point ◽  
High Signal ◽  
Fundamental Plane ◽  
Surface Mass ◽  
Integral Field Spectroscopy ◽  
Surface Mass Density ◽  
Photometric Measurements

Abstract We study the Fundamental Plane (FP) for a volume- and luminosity-limited sample of 560 early-type galaxies from the SAMI survey. Using r −band sizes and luminosities from new Multi-Gaussian Expansion (MGE) photometric measurements, and treating luminosity as the dependent variable, the FP has coefficients a = 1.294 ± 0.039, b = 0.912 ± 0.025, and zero-point c = 7.067 ± 0.078. We leverage the high signal-to-noise of SAMI integral field spectroscopy, to determine how structural and stellar-population observables affect the scatter about the FP. The FP residuals correlate most strongly (8σ significance) with luminosity-weighted simple-stellar-population (SSP) age. In contrast, the structural observables surface mass density, rotation-to-dispersion ratio, Sérsic index and projected shape all show little or no significant correlation. We connect the FP residuals to the empirical relation between age (or stellar mass-to-light ratio ϒ⋆ ) and surface mass density, the best predictor of SSP age amongst parameters based on FP observables. We show that the FP residuals (anti-)correlate with the residuals of the relation between surface density and ϒ⋆ . This correlation implies that part of the FP scatter is due to the broad age and ϒ⋆ distribution at any given surface mass density. Using virial mass and ϒ⋆ we construct a simulated FP and compare it to the observed FP. We find that, while the empirical relations between observed stellar population relations and FP observables are responsible for most (75 per cent) of the FP scatter, on their own they do not explain the observed tilt of the FP away from the virial plane.

scholarly journals Resolving the Disk-Halo Degeneracy using Planetary Nebulae

2016 ◽  
Vol 12 (S323) ◽  
pp. 284-287
Author(s):  
S. Aniyan ◽  
K. C. Freeman ◽  
M. Arnaboldi ◽  
O. Gerhard ◽  
L. Coccato ◽  
...  
Keyword(s):  
Vertical Velocity ◽  
Velocity Dispersion ◽  
Mass Density ◽  
Planetary Nebulae ◽  
Disk Surface ◽  
Scale Height ◽  
Dark Halo ◽  
Surface Mass ◽  
Star Forming ◽  
Light Spectra

AbstractThe decomposition of the 21 cm rotation curve of galaxies into contribution from the disk and dark halo depends on the adopted mass to light ratio (M/L) of the disk. Given the vertical velocity dispersion (σz) of stars in the disk and its scale height (hz), the disk surface density and hence the M/L can be estimated. Earlier works have used this technique to conclude that galaxy disks are submaximal. Here we address an important conceptual problem: star-forming spirals have an old (kinematically hot) disk population and a young cold disk population. Both of these populations contribute to the integrated light spectra from which σz is measured. The measured scale height hz is for the old disk population. In the Jeans equation, σz and hz must pertain to the same population. We have developed techniques to extract the velocity dispersion of the old disk from integrated light spectra and from samples of planetary nebulae. We present the analysis of the disk kinematics of the galaxy NGC 628 using IFU data in the inner regions and planetary nebulae as tracers in the outer regions of the disk. We demonstrate that using the scale height of the old thin disk with the vertical velocity dispersion of the same population, traced by PNe, results in a maximal disk for NGC 628. Our analysis concludes that previous studies underestimate the disk surface mass density by ~ 2, sufficient to make a maximal disk for NGC 628 appear like a submaximal disk.

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