Erratum: Resolving the age bimodality of galaxy stellar populations on kpc scales

The Hipparcos catalogue provides an accurate and extensive sampling of the solar neighbourhood HR diagram. The morphology of this diagram depends on selection criteria of the catalogue such as the limiting magnitude, angular separation and on the characteristics of the stellar populations near the sun (space density, metallicity, star formation rate, etc). Since the Hipparcos data are so accurate, one needs to model precisely the different selection bias and, at the same time, parametrize models of the galactic stellar populations with sufficient flexibility that as much information as possible can be grasped from the catalogue. Comparisons between our model and the Hipparcos catalogue will be presented elsewhere. Since the quantity of information contained in the Hipparcoscatalogue is so important, models ought to be complex, and external contraints, obtained prior to any general comparison with the model, are welcome. A major factor that influences the distribution of the stars in the HR diagram is the metallicity. For the late type stars, the metallicity distribution can be best studied by re-analysing a volume-limited sample of stars from the catalogue.

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The weak imprint of environment on the stellar populations of galaxies

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3545 ◽

2020 ◽

Vol 500 (4) ◽

pp. 4469-4490 ◽

Cited By ~ 1

Author(s):

James Trussler ◽

Roberto Maiolino ◽

Claudia Maraston ◽

Yingjie Peng ◽

Daniel Thomas ◽

...

Keyword(s):

Environmental Effects ◽

Unique Feature ◽

Stellar Populations ◽

Stellar Mass ◽

Sloan Digital Sky Survey ◽

Star Forming ◽

Sky Survey ◽

Satellite Galaxies ◽

Projected Distance ◽

Environmental Dependence

ABSTRACT We investigate the environmental dependence of the stellar populations of galaxies in Sloan Digital Sky Survey Data Release 7 (SDSS DR7). Echoing earlier works, we find that satellites are both more metal-rich (<0.1 dex) and older (<2 Gyr) than centrals of the same stellar mass. However, after separating star-forming, green valley, and passive galaxies, we find that the true environmental dependence of both stellar metallicity (<0.03 dex) and age (<0.5 Gyr) is in fact much weaker. We show that the strong environmental effects found when galaxies are not differentiated result from a combination of selection effects brought about by the environmental dependence of the quenched fraction of galaxies, and thus we strongly advocate for the separation of star-forming, green valley, and passive galaxies when the environmental dependence of galaxy properties are investigated. We also study further environmental trends separately for both central and satellite galaxies. We find that star-forming galaxies show no environmental effects, neither for centrals nor for satellites. In contrast, the stellar metallicities of passive and green valley satellites increase weakly (<0.05 and <0.08 dex, respectively) with increasing halo mass, increasing local overdensity and decreasing projected distance from their central; this effect is interpreted in terms of moderate environmental starvation (‘strangulation’) contributing to the quenching of satellite galaxies. Finally, we find a unique feature in the stellar mass–stellar metallicity relation for passive centrals, where galaxies in more massive haloes have larger stellar mass (∼0.1 dex) at constant stellar metallicity; this effect is interpreted in terms of dry merging of passive central galaxies and/or progenitor bias.

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Kinematical evolution of Globular Clusters

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319009207 ◽

2019 ◽

Vol 14 (S351) ◽

pp. 524-527

Author(s):

Maria A. Tiongco ◽

Enrico Vesperini ◽

Anna Lisa Varri

Keyword(s):

Angular Momentum ◽

Structural Properties ◽

Globular Clusters ◽

Velocity Dispersion ◽

Three Dimensional ◽

Stellar Populations ◽

Velocity Space ◽

Fundamental Understanding

AbstractWe present several results of the study of the evolution of globular clusters’ internal kinematics, as driven by two-body relaxation and the interplay between internal angular momentum and the external Galactic tidal field. Via a large suite of N-body simulations, we explored the three-dimensional velocity space of tidally perturbed clusters, by characterizing their degree of velocity dispersion anisotropy and their rotational properties. These studies have shown that a cluster’s kinematical properties contain distinct imprints of the cluster’s initial structural properties, dynamical history, and tidal environment. Building on this fundamental understanding, we then studied the dynamics of multiple stellar populations in globular clusters, with attention to the largely unexplored role of angular momentum.

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Stellar Populations

Physics Today ◽

10.1063/1.3060988 ◽

1959 ◽

Vol 12 (9) ◽

pp. 65-68

Author(s):

D. J. K. O'Connell ◽

E. J. Öpik

Keyword(s):

Stellar Populations

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The IMF-SFH connection in massive early-type galaxies

Proceedings of the International Astronomical Union ◽

10.1017/s1743921316007808 ◽

2015 ◽

Vol 11 (S315) ◽

Author(s):

I. Ferreras ◽

C. Weidner ◽

A. Vazdekis ◽

F. La Barbera

Keyword(s):

Age Distribution ◽

Stellar Populations ◽

Mass Function ◽

Initial Mass Function ◽

Population Synthesis ◽

Early Type ◽

Massive Galaxies ◽

Stellar Initial Mass Function ◽

The Many ◽

The Imf

The stellar initial mass function (IMF) is one of the fundamental pillars in studies of stellar populations. It is the mass distribution of stars at birth, and it is traditionally assumed to be universal, adopting generic functions constrained by resolved (i.e. nearby) stellar populations (e.g., Salpeter 1955; Kroupa 2001; Chabrier 2003). However, for the vast majority of cases, stars are not resolved in galaxies. Therefore, the interpretation of the photo-spectroscopic observables is complicated by the many degeneracies present between the properties of the unresolved stellar populations, including IMF, age distribution, and chemical composition. The overall good match of the photometric and spectroscopic observations of galaxies with population synthesis models, adopting standard IMF choices, made this issue a relatively unimportant one for a number of years. However, improved models and observations have opened the door to constraints on the IMF in unresolved stellar populations via gravity-sensitive spectral features. At present, there is significant evidence of a non-universal IMF in early-type galaxies (ETGs), with a trend towards a dwarf-enriched distribution in the most massive systems (see, e.g., van Dokkum & Conroy 2010; Ferreras et al. 2013; La Barbera et al. 2013). Dynamical and strong-lensing constraints of the stellar M/L in similar systems give similar results, with heavier M/L in the most massive ETGs (see, e.g., Cappellari et al. 2012; Posacki et al. 2015). Although the interpretation of the results is still open to discussion (e.g., Smith 2014; La Barbera 2015), one should consider the consequences of such a bottom-heavy IMF in massive galaxies.

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Gaia unveils the kinematics of multiple stellar populations in 47 Tucanae

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/sty1873 ◽

2018 ◽

Vol 479 (4) ◽

pp. 5005-5011 ◽

Cited By ~ 24

Author(s):

A P Milone ◽

A F Marino ◽

A Mastrobuono-Battisti ◽

E P Lagioia

Keyword(s):

Stellar Populations

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