scholarly journals Implications and Applications of Kinematic Galaxy Scaling Relations

2012 ◽  
Vol 2012 ◽  
pp. 1-15 ◽  
Author(s):  
Dennis Zaritsky
Keyword(s):  
Galaxy Formation ◽  
Mass Function ◽  
Initial Mass Function ◽  
Scaling Relations ◽  
Disk Galaxies ◽  
Lenticular Galaxies ◽  
Stellar Initial Mass Function ◽  
Low Mass ◽  
Apparent Shift ◽  
Cross Calibration

Galaxy scaling relations, which describe a connection between ostensibly unrelated physical characteristics, testify to an underlying order in galaxy formation that requires understanding. I review the development of a scaling relation that (1) unites the well-known fundamental plane (FP) relation of giant elliptical galaxies and Tully-Fisher (TF) relation of disk galaxies, (2) fits low mass spheroidal galaxies, including the ultrafaint satellites of our galaxy, (3) explains the apparent shift of lenticular galaxies relative to both FP or TF, (4) describes all stellar dynamical systems, including systems with no dark matter (stellar clusters), (5) associates explicitly the numerical coefficients that account for the apparent tilt of the FP away from the expectation drawn from the virial theorem with variations in the total mass-to-light ratio of galaxies within the half-light radius, (6) connects with results that demonstrate the robustness of mass estimators when applied at the half-light radius, and (7) results in smaller scatter for disk galaxies than the TF relation. I review two applications: (1) the cross-calibration of distance measurement methods and (2) the determination of mass-to-light ratios of simple stellar populations and implications for the stellar initial mass function.

scholarly journals Mass to Light Ratio, Initial Mass Function, and Chemical Evolution in Disk Galaxies

2004 ◽  
Vol 21 (2) ◽  
pp. 144-147 ◽  
Author(s):  
L. Portinari ◽  
J. Sommer-Larsen ◽  
R. Tantalo
Keyword(s):  
Galaxy Formation ◽  
Chemical Properties ◽  
Zero Point ◽  
Mass Function ◽  
Initial Mass Function ◽  
Initial Mass ◽  
Disk Galaxies ◽  
Stellar Component ◽  
Low Mass ◽  
Fisher Relation

AbstractCosmological simulations of disk galaxy formation, when compared to the observed Tully–Fisher relation, suggest a low mass to light (M/L) ratio for the stellar component in spirals. We show that a number of 'bottom-light' initial mass functions (IMFs) suggested independently in the literature, do imply M/L ratios as low as required, at least for late type spirals (Sbc–Sc). However the typical M/L ratio, and correspondingly the zero point of the Tully–Fisher relation, is expected to vary considerably with Hubble type.Bottom-light IMFs tend to have a metal production in excess of what is typically estimated for spiral galaxies. Suitable tuning of the IMF slope and mass limits, post-supernova fallback of metals onto black holes or metal outflows must then be invoked, to reproduce the observed chemical properties of disk galaxies.

scholarly journals The Stellar Initial Mass Function in Starburst Galaxies

1999 ◽  
Vol 186 ◽  
pp. 243-250
Author(s):  
Claus Leitherer
Keyword(s):  
Massive Stars ◽  
Mass Function ◽  
Starburst Galaxies ◽  
Initial Mass Function ◽  
Initial Mass ◽  
H Ii Regions ◽  
Environmental Properties ◽  
Stellar Initial Mass Function ◽  
Low Mass ◽  
Star Formation Histories

Starburst galaxies are currently forming massive stars at prodigious rates. I discuss the star-formation histories and the shape of the initial mass function, with particular emphasis on the high- and on the low-mass end. The classical Salpeter IMF is consistent with constraints from observations of the most massive stars, irrespective of environmental properties. The situation at the low-mass end is less clear: direct star counts in nearby giant H II regions show stars down to ~1 M⊙, whereas dynamical arguments in some starburst galaxies suggest a deficit of such stars.

scholarly journals The star formation timescale of elliptical galaxies

2019 ◽  
Vol 632 ◽  
pp. A110 ◽  
Author(s):  
Zhiqiang Yan ◽  
Tereza Jerabkova ◽  
Pavel Kroupa
Keyword(s):  
Star Formation ◽  
Stellar Population ◽  
Mass Function ◽  
Elliptical Galaxies ◽  
Initial Mass Function ◽  
Different Types ◽  
The Galaxy ◽  
Stellar Initial Mass Function ◽  
Low Mass ◽  
Natural Solution

The alpha element to iron peak element ratio, for example [Mg/Fe], is a commonly applied indicator of the galaxy star formation timescale (SFT) since the two groups of elements are mainly produced by different types of supernovae that explode over different timescales. However, it is insufficient to consider only [Mg/Fe] when estimating the SFT. The [Mg/Fe] yield of a stellar population depends on its metallicity. Therefore, it is possible for galaxies with different SFTs and at the same time different total metallicity to have the same [Mg/Fe]. This effect has not been properly taken into consideration in previous studies. In this study, we assume the galaxy-wide stellar initial mass function (gwIMF) to be canonical and invariant. We demonstrate that our computation code reproduces the SFT estimations of previous studies, where only the [Mg/Fe] observational constraint is applied. We then demonstrate that once both metallicity and [Mg/Fe] observations are considered, a more severe “downsizing relation” is required. This means that either low-mass ellipticals have longer SFTs (> 4 Gyr for galaxies with mass below 1010 M⊙) or massive ellipticals have shorter SFTs (≈200 Myr for galaxies more massive than 1011 M⊙) than previously thought. This modification increases the difficulty in reconciling such SFTs with other observational constraints. We show that applying different stellar yield modifications does not relieve this formation timescale problem. The quite unrealistically short SFT required by [Mg/Fe] and total metallicity would be prolonged if a variable stellar gwIMF were assumed. Since a systematically varying gwIMF has been suggested by various observations this could present a natural solution to this problem.

scholarly journals Variation in the Stellar Initial Mass Function from the Chromospheric Activity of M Dwarfs in Early-type Galaxies

2021 ◽  
Vol 923 (1) ◽  
pp. 43
Author(s):  
Pieter van Dokkum ◽  
Charlie Conroy
Keyword(s):  
Mass Function ◽  
Initial Mass Function ◽  
Initial Mass ◽  
Early Type ◽  
M Dwarfs ◽  
Low Mass Stars ◽  
Chromospheric Activity ◽  
Stellar Initial Mass Function ◽  
Low Mass ◽  
The Imf

Abstract Mass measurements and absorption-line studies indicate that the stellar initial mass function (IMF) is bottom-heavy in the central regions of many early-type galaxies, with an excess of low-mass stars compared to the IMF of the Milky Way. Here we test this hypothesis using a method that is independent of previous techniques. Low-mass stars have strong chromospheric activity characterized by nonthermal emission at short wavelengths. Approximately half of the UV flux of M dwarfs is contained in the λ1215.7 Lyα line, and we show that the total Lyα emission of an early-type galaxy is a sensitive probe of the IMF with a factor of ∼2 flux variation in response to plausible variations in the number of low-mass stars. We use the Cosmic Origins Spectrograph on the Hubble Space Telescope to measure the Lyα line in the centers of the massive early-type galaxies NGC 1407 and NGC 2695. We detect Lyα emission in both galaxies and demonstrate that it originates in stars. We find that the Lyα to i-band flux ratio is a factor of 2.0 ± 0.4 higher in NGC 1407 than in NGC 2695, in agreement with the difference in their IMFs as previously determined from gravity-sensitive optical absorption lines. Although a larger sample of galaxies is required for definitive answers, these initial results support the hypothesis that the IMF is not universal but varies with environment.

scholarly journals Stellar initial mass function variation in massive early-type galaxies: the potential role of the deuterium abundance

2020 ◽  
Vol 498 (3) ◽  
pp. 4051-4059 ◽  
Author(s):  
Timothy A Davis ◽  
Freeke van de Voort
Keyword(s):  
Mass Loss ◽  
Cosmic Time ◽  
Mass Function ◽  
Stellar Mass ◽  
Initial Mass Function ◽  
Initial Mass ◽  
Early Type ◽  
Root Cause ◽  
Stellar Initial Mass Function ◽  
Low Mass

ABSTRACT The observed stellar initial mass function (IMF) appears to vary, becoming bottom-heavy in the centres of the most massive, metal-rich early-type galaxies. It is still unclear what physical processes might cause this IMF variation. In this paper, we demonstrate that the abundance of deuterium in the birth clouds of forming stars may be important in setting the IMF. We use models of disc accretion on to low-mass protostars to show that those forming from deuterium-poor gas are expected to have zero-age main-sequence masses significantly lower than those forming from primordial (high deuterium fraction) material. This deuterium abundance effect depends on stellar mass in our simple models, such that the resulting IMF would become bottom-heavy – as seen in observations. Stellar mass loss is entirely deuterium free and is important in fuelling star formation across cosmic time. Using the Evolution and Assembly of GaLaxies and their Environments (EAGLE) simulation we show that stellar mass-loss-induced deuterium variations are strongest in the same regions where IMF variations are observed: at the centres of the most massive, metal-rich, passive galaxies. While our analysis cannot prove that the deuterium abundance is the root cause of the observed IMF variation, it sets the stage for future theoretical and observational attempts to study this possibility.

scholarly journals THE LOW-MASS STELLAR POPULATION IN L1641: EVIDENCE FOR ENVIRONMENTAL DEPENDENCE OF THE STELLAR INITIAL MASS FUNCTION

2012 ◽  
Vol 752 (1) ◽  
pp. 59 ◽  
Author(s):  
Wen-Hsin Hsu ◽  
Lee Hartmann ◽  
Lori Allen ◽  
Jesús Hernández ◽  
S. T. Megeath ◽  
...  
Keyword(s):  
Stellar Population ◽  
Mass Function ◽  
Initial Mass Function ◽  
Initial Mass ◽  
Stellar Initial Mass Function ◽  
Low Mass ◽  
Environmental Dependence

HI gas component in dwarf and disk galaxies in the view of semi-analytic models

2018 ◽  
Vol 14 (S344) ◽  
pp. 274-275
Author(s):  
Jian Fu
Keyword(s):  
Galaxy Formation ◽  
Recent Progress ◽  
Milky Way ◽  
Mass Function ◽  
The Other ◽  
Disk Galaxies ◽  
Model Based ◽  
Low Mass ◽  
Analytic Models ◽  
Gas Component

AbstractWe show our recent progress on the L-Galaxies semi-analytic models of galaxy formation, which focuses on the HI gas in low mass galaxies. We find that the model based on ELUCID haloes can reproduce the HI mass function from ALFALFA 100 at low mass end. On the other hand, our models predict some gas rich low mass galaxies around the Milky Way, which may offer opportunities for future HI 21cm survey in nearby universe by FAST and SKA-1.

The stellar initial mass function in the early universe revealed from old stellar populations in our neighbourhood

2012 ◽  
Vol 8 (S295) ◽  
pp. 322-322
Author(s):  
Yutaka Komiya ◽  
Shimako Yamada ◽  
Takuma Suda ◽  
Masayuki Y. Fujimoto
Keyword(s):  
Early Universe ◽  
Galactic Halo ◽  
Stellar Populations ◽  
Mass Function ◽  
Initial Mass Function ◽  
New Method ◽  
Elemental Abundances ◽  
Stellar Initial Mass Function ◽  
Low Mass ◽  
The Imf

AbstractWe present a new method to investigate the IMF in the early universe from observations of extremely metal-poor (EMP) stars. EMP stars are the low-mass survivors of stars which are formed in the early universe. We can give constraints on the IMF from statistics of the elemental abundances of the EMP stars in the Galactic halo.

scholarly journals LOW-MASS X-RAY BINARIES INDICATE A TOP-HEAVY STELLAR INITIAL MASS FUNCTION IN ULTRACOMPACT DWARF GALAXIES

2012 ◽  
Vol 747 (1) ◽  
pp. 72 ◽  
Author(s):  
Jörg Dabringhausen ◽  
Pavel Kroupa ◽  
Jan Pflamm-Altenburg ◽  
Steffen Mieske
Keyword(s):  
Dwarf Galaxies ◽  
Mass Function ◽  
Initial Mass Function ◽  
Initial Mass ◽  
X Ray ◽  
Stellar Initial Mass Function ◽  
Low Mass ◽  
X Ray Binaries
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