scholarly journals Stellar population properties of ETGs in compact groups of galaxies

2020 ◽  
Vol 493 (3) ◽  
pp. 3238-3254
Author(s):  
Tatiana C Moura ◽  
Reinaldo R de Carvalho ◽  
Sandro B Rembold ◽  
Marina Trevisan ◽  
Andre L B Ribeiro ◽  
...  
Keyword(s):  
Galaxy Evolution ◽  
Stellar Population ◽  
Velocity Dispersion ◽  
Group Velocity Dispersion ◽  
Gas Content ◽  
Dynamical Analysis ◽  
Compact Groups ◽  
Low Mass Stars ◽  
Groups Of Galaxies ◽  
Low Mass

ABSTRACT We present results on the study of the stellar population in early-type galaxies (ETGs) belonging to 151 compact groups (CGs). We also selected a field sample composed of 846 ETGs to investigate environmental effects on galaxy evolution. We find that the dependences of mean stellar ages, [Z/H] and [α/Fe] on central stellar velocity dispersion are similar, regardless where the ETG resides, CGs or field. When compared to the sample of centrals and satellites from the literature, we find that ETGs in CGs behave similarly to centrals, especially those embedded in low-mass haloes ($M_{\mathrm{ h}} \lt 10^ {12.5}\, \mathrm{M}_{\odot }$). Except for the low-mass limit, where field galaxies present a star-forming signature, not seen in CGs, the ionization agent of the gas in CG and field galaxies seem to be similar due to hot, evolved low-mass stars. However, field ETGs present an excess of H α emission relative to ETGs in CGs. Additionally, we performed a dynamical analysis, which shows that CGs present a bimodality in the group velocity dispersion distribution – a high- and low-σ mode. Our results indicate that high-σ groups have a smaller fraction of spirals, shorter crossing times, and a more luminous population of galaxies than the low-σ groups. It is important to emphasize that our findings point to a small environmental impact on galaxies located in CGs. The only evidence we find is the change in gas content, suggesting environmentally driven gas loss.

scholarly journals Compact Groups of Galaxies

1999 ◽  
Vol 186 ◽  
pp. 367-373
Author(s):  
P. Hickson
Keyword(s):  
Galaxy Evolution ◽  
Mass Velocity ◽  
Velocity Dispersion ◽  
Continuous Process ◽  
Physical Nature ◽  
Compact Groups ◽  
Early Type ◽  
Natural Explanation ◽  
Groups Of Galaxies ◽  
Formation And Evolution

This paper reviews some of the outstanding questions concerning compact groups of galaxies. These relate to the physical nature and dynamical status of the groups, their formation and evolution, and their role in galaxy evolution. The picture that emerges is that compact groups are generally physically dense systems, although often contaminated by optical projections. Their evolution is likely a continuous process of infall, interaction and merging. As new galaxies are added, and previous ones merge, the membership of the group evolves. I suggest that while the size of the group changes little, other physical properties such as total mass, gas mass, velocity dispersion, fraction of early-type galaxies increase with time. This picture is at least qualitatively consistent with observations and provides a natural explanation for the strongest correlations found in compact group samples.

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 Tracing interactions in HCGs through the H I

2000 ◽  
Vol 174 ◽  
pp. 167-173 ◽  
Author(s):  
L. Verdes-Montenegro ◽  
M. S. Yun ◽  
B. A. Williams ◽  
W. K. Huchtmeier ◽  
A. Del Olmo ◽  
...  
Keyword(s):  
Velocity Dispersion ◽  
Group Velocity Dispersion ◽  
Dynamical Evolution ◽  
Compact Groups ◽  
High Group ◽  
X Ray ◽  
Hot Gas ◽  
Isolated Galaxies ◽  
Global Study ◽  
Hickson Compact Groups

AbstractWe present a global study of Hɪ spectral line mapping for 16 Hickson Compact Groups (HCGs) combining new and unpublished VLA data, plus the analysis of the Hɪ content of individual galaxies. Sixty percent of the groups show morphological and kinematical signs of perturbations (from multiple tidal features to concentration of the Hɪ in a single enveloping cloud) and sixty five of the resolved galaxies are found to be Hɪ deficient with respect to a sample of isolated galaxies. In total, 77% of the groups suffer interactions among all its members which provides strong evidence of their reality. We find that dynamical evolution does not always produce Hɪ deficiency, but when this deficiency is observed, it appears to correlate with a high group velocity dispersion and in some cases with the presence of a first-ranked elliptical. The X-ray data available for our sample are not sensitive enough for a comparison with the Hɪ mass; however this study does suggest a correlation between Hɪ deficiency and hot gas since velocity dispersions are known from the literature to correlate with X-ray luminosity.

scholarly journals Poor Groups Around Strong Gravitational Lenses

2006 ◽  
Vol 2 (S235) ◽  
pp. 230-230
Author(s):  
Ivelina Momcheva ◽  
Kurtis Williams ◽  
Ann Zabludoff ◽  
Charles Keeton
Keyword(s):  
Galaxy Evolution ◽  
Velocity Dispersion ◽  
Gravitational Lenses ◽  
Local Universe ◽  
Groups Of Galaxies ◽  
Hot Gas ◽  
Gas Kinematics ◽  
The Galaxy ◽  
Group Centroid ◽  
Group Galaxy

AbstractPoor groups are common and interactive environments for galaxies, and thus are important laboratories for studying galaxy evolution. Unfortunately, little is known about groups at z ≥ 0.1, because of the difficulty in identifying them in the first place. Here we present results from our ongoing survey of the environments of strong gravitational lenses, in which we have so far discovered six distant (z ≥ 0.5) groups of galaxies. As in the local Universe, the highest velocity dispersion groups contain a brightest member spatially coincident with the group centroid, whereas lower-dispersion groups tend to have an offset brightest group galaxy. This suggests that higher-dispersion groups are more dynamically relaxed than lower-dispersion groups and that at least some evolved groups exist by z ~ 0.5. We also compare the galaxy and hot gas kinematics with those of similarly distant clusters and of nearby groups.

scholarly journals Core-hydrogen-burning RSGs in the early globular clusters

2015 ◽  
Vol 11 (A29B) ◽  
pp. 473-473
Author(s):  
Dorottya Szécsi ◽  
Jonathan Mackey ◽  
Norbert Langer
Keyword(s):  
Globular Clusters ◽  
Stellar Population ◽  
Massive Stars ◽  
Shell Formation ◽  
Low Mass Stars ◽  
Hydrogen Burning ◽  
The Core ◽  
Anomalous Surface ◽  
Low Metallicity ◽  
Low Mass

AbstractThe first stellar generation in galactic globular clusters contained massive low-metallicity stars (Charbonnel et al. 2014). We modelled the evolution of this massive stellar population and found that such stars with masses 100-600 M⊙ evolve into cool RSGs (Szécsi et al. 2015). These RSGs spend not only the core-He-burning phase but even the last few 105 years of the core-H-burning phase on the SG branch. Due to the presence of hot massive stars in the cluster at the same time, we show that the RSG wind is trapped into photoionization confined shells (Mackey et al. 2014). We simulated the shell formation around such RSGs and find them to become gravitationally unstable (Szécsi et al. 2016). We propose a scenario in which these shells are responsible for the formation of the second generation low-mass stars in globular clusters with anomalous surface abundances.

scholarly journals Simulations of Compact Groups of Galaxies with Halos

1987 ◽  
Vol 117 ◽  
pp. 281-281
Author(s):  
T. Ishizawa
Keyword(s):  
Velocity Dispersion ◽  
Big Bang ◽  
Compact Groups ◽  
Maximum Expansion ◽  
Groups Of Galaxies ◽  
Elapsed Time ◽  
Self Consistent ◽  
The Big Bang ◽  
Hubble Time

Self-consistent simulations of seven groups are performed from the maximum expansion to the present using Aarseth's N-body code. An initial galaxy consists of 100 stars. Its mass, half-mass radius, and central velocity dispersion are 1, 0.41, and 0.96. Units of mass, length, velocity, and time are 1.4×101 2M⊙, 100 kpc, 245 kms−1 and 4.0×108y. Table 1 gives the elapsed time from the Big Bang to the formation of a multiple merger tm+Tc*/2. For H0=80 kms−1Mpc−1, the Hubble time H0−1=30.6 in our units. Dense groups except B form multiple mergers in a Hubble time.

scholarly journals The Dark Side of Globular Clusters

1996 ◽  
Vol 174 ◽  
pp. 377-378
Author(s):  
P.-Y. Longaretti ◽  
R. Taillet ◽  
P. Salati
Keyword(s):  
Globular Clusters ◽  
Mass Function ◽  
Dynamical Analysis ◽  
Dark Side ◽  
Low Mass Stars ◽  
First Results ◽  
Low Mass ◽  
Non Parametric

Searches of low-mass stars have become possible in globular clusters, and the first results suggest that the mass function turns up below ∼ 0.4 M⊙ (Fahlman et al. 1989; Richer et al., 1990; Richer et al. 1991; G. Piotto, these proceedings). This conclusion is independently supported by the non-parametric dynamical analysis of four clusters by Gebhardt and Fisher 1995.

scholarly journals Truncated Star Formation in Compact Groups of Galaxies: A Stellar Population Study

2006 ◽  
Vol 133 (1) ◽  
pp. 330-346 ◽  
Author(s):  
Ignacio G. de la Rosa ◽  
Reinaldo R. de Carvalho ◽  
Alexandre Vazdekis ◽  
Beatriz Barbuy
Keyword(s):  
Star Formation ◽  
Population Study ◽  
Stellar Population ◽  
Compact Groups ◽  
Groups Of Galaxies

scholarly journals The effect of ram-pressure stripping on dwarf galaxies

2020 ◽  
Vol 494 (1) ◽  
pp. 1114-1127 ◽  
Author(s):  
P Steyrleithner ◽  
G Hensler ◽  
A Boselli
Keyword(s):  
Galaxy Clusters ◽  
Stellar Population ◽  
Velocity Dispersion ◽  
Spiral Galaxies ◽  
Dwarf Galaxies ◽  
Gas Content ◽  
Gas Reservoirs ◽  
Interstellar Gas ◽  
Internal Structures ◽  
Ram Pressure

ABSTRACT Ram-pressure stripping (RPS) is a well observed phenomenon of massive spiral galaxies passing through the hot intracluster medium (ICM) of galaxy clusters. For dwarf galaxies (DGs) within a cluster, the transformation from gaseous to gas-poor systems by RPS is not easily observed and must happen in the outskirts of clusters. In a few objects in close by galaxy clusters and the field, RPS has been observed. Since cluster early-type DGs also show a large variety of internal structures (unexpected central gas reservoirs, blue stellar cores, composite radial stellar profiles), we aim in this study to investigate how ram pressure (RP) affects the interstellar gas content and therefore the star formation (SF) activity. Using a series of numerical simulations, we quantify the dependence of the stripped-off gas on the velocity of the infalling DGs and on the ambient ICM density. We demonstrated that SF can be either suppressed or triggered by RP depending on the ICM density and the DGs mass. Under some conditions, RP can compress the gas, so that it is unexpectedly retained in the central DG region and forms stars. When gas clouds are still bound against stripping but lifted from a thin disc and fall back, their new stars form an ellipsoidal (young) stellar population already with a larger velocity dispersion without the necessity of harassment. Most spectacularly, star clusters can form downstream in stripped-off massive gas clouds in the case of strong RP. We compare our results to observations.

scholarly journals Disk Mass From Large-Scale Dynamics

1998 ◽  
Vol 11 (1) ◽  
pp. 410-411
Author(s):  
J.A. Sellwood
Keyword(s):  
Dark Matter ◽  
Large Scale ◽  
Stellar Population ◽  
Milky Way ◽  
Low Mass Stars ◽  
Rutgers University ◽  
Disk Mass ◽  
Low Mass ◽  
The Individual ◽  
Inner Parts

The radial distribution of mass in a disk galaxy is strongly constrained by its rotation curve. The separate contributions from the individual stellar populations and dark matter (DM) are not easily disentangled, however, especially since there is generally no feature to indicate where the component dominating the central attraction switches from luminous to dark matter. Here I summarize three recent thesis projects at Rutgers University which all suggest that DM has a low density in the inner parts of bright galaxies, and that most of the mass therefore resides in the disk. In addition, I present some preliminary work on the Milky Way. If we are able to determine the M/L of a typical disk stellar population, it should provide a useful constraint on the numbers of low mass stars.

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