scholarly journals On the interpretation of the age and chemical composition of composite stellar populations determined with line-strength indices

2007 ◽  
Vol 374 (3) ◽  
pp. 769-774 ◽  
Author(s):  
P. Serra ◽  
S. C. Trager
Keyword(s):  
Chemical Composition ◽  
Line Strength ◽  
Stellar Populations

scholarly journals Chemical evolution and stellar populations in the Sagittarius dwarf Spheroidal Galaxy

2006 ◽  
Vol 2 (S235) ◽  
pp. 330-330 ◽  
Author(s):  
L. Sbordone ◽  
P. Bonifacio ◽  
G. Giuffrida ◽  
G. Marconi ◽  
L. Monaco ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Chemical Evolution ◽  
Large Scale ◽  
Automated Analysis ◽  
Stellar Populations ◽  
Dynamical Analysis ◽  
Complex Object ◽  
Main Body ◽  
Stellar Content ◽  
Chemical Anomalies

AbstractThe closest neighbour of the Milky Way (MW) the Sagittarius dwarf Spheroidal Galaxy (Sgr dSph) is being tidally destroyed by the interaction with our Galaxy, losing its stellar content along a huge stream clearly detectable within the Halo. This makes the Sgr dSph an ideal laboratory to study at the same time the chemical evolution of dwarf galaxies and their role in building bigger structures such as the MW. Since some years we are studying the stellar populations of the Sgr main body and stream, with particular attention to their detailed chemical composition. We collected detailed abundances (up to 22 elements, O to Eu) for 27 stars in the Sgr dSph main body, 5 in the associated globular cluster Terzan 7, and 12 more in the trailing Sgr tidal arm (UVES@VLT and SARG@TNG data). We are also conducting a large FLAMES@VLT chemical and dynamical analysis aimed at obtaining metallicities, alpha-elements content and radial velocities from automated analysis of the spectra. Finally, we just completed the first large scale photometric and spectroscopic survey of the stellar populations across all the dSph main body extension with VIMOS@VLT, aimed at exploring the variations in stellar populations and at deriving radial velocity memberships for future high resolution spectroscopic analysis. The picture emerging from all these studies portraits a large and extremely complex object, with signs of a long and still unclear evolution. Metallicity varies across three orders of magnitude ([Fe/H] from −3 to 0), CMDs change surprisingly from the core to the outskirts of the galaxy, and the chemical composition of the most metal rich objects show a very characteristic signature, with underabundant alpha elements, deficient Na, underabundant Fe-peak Mn, Co, Ni, Cu and Zn, and strongly enhanced n-capture elements La and Nd. This highly peculiar signature can also be effectively used to recognized stripped populations lost by Sgr in favour of the MW system, as clearly showed by the globular Palomar 12, which shows the same chemical anomalies detected in Sgr dSph.

scholarly journals The HR Diagram for Luminous Stars in Nearby Galaxies

1978 ◽  
Vol 80 ◽  
pp. 263-267
Author(s):  
Roberta M. Humphreys
Keyword(s):  
Chemical Composition ◽  
Stellar Evolution ◽  
Milky Way ◽  
Stellar Populations ◽  
Nearby Galaxies ◽  
Hr Diagram

HR diagrams for the stellar populations in other galaxies play a fundamental role in our understanding of the progress of stellar evolution and the effects of possible variations in chemical composition. It is important to compare what little information we have about stars in other galaxies with the same types of stars in our own Milky Way. Basically we are asking - are they the same, and how universal are the processes we observe in our Galaxy?

scholarly journals Ecology of galaxy stellar populations from optical spectroscopic surveys

2009 ◽  
Vol 5 (S262) ◽  
pp. 205-208
Author(s):  
Anna Gallazzi
Keyword(s):  
Star Formation ◽  
Chemical Composition ◽  
Stellar Populations ◽  
Recent Analysis ◽  
Formation Processes ◽  
Population Synthesis ◽  
Full Spectrum ◽  
Large Samples ◽  
New Models ◽  
Insight Into

AbstractThe age and chemical composition of the stars in present-day galaxies carry important clues about their star formation processes. The latest generation of population synthesis models have allowed to derive age and stellar metallicity estimates for large samples of low-redshift galaxies. After reviewing the main results about the distribution in ages and metallicities as a function of galaxy mass, I will concentrate on recent analysis that aims at disentangling the dependences of stellar populations properties on environment and on galaxy stellar mass. Finally, new models that predict the response of the full spectrum to variations in [α/Fe] will allow us to derive accurate estimates of elements abundance ratios and gain deeper insight into the timescales of star formation cessation.

scholarly journals Near-infrared spectroscopic indices for unresolved stellar populations

2019 ◽  
Vol 621 ◽  
pp. A60 ◽  
Author(s):  
P. François ◽  
L. Morelli ◽  
A. Pizzella ◽  
V. D. Ivanov ◽  
L. Coccato ◽  
...  
Keyword(s):  
Galaxy Formation ◽  
Near Infrared ◽  
Spectral Synthesis ◽  
Population Analysis ◽  
Line Strength ◽  
Stellar Populations ◽  
Morphological Type ◽  
Resolving Power ◽  
Data Set ◽  
Hubble Sequence

Context. A new generation of spectral synthesis models has been developed in recent years, but there is no matching set of template galaxy spectra, in terms of quality and resolution, for testing and refining the new models. Aims. Our main goal is to find and calibrate new near-infrared spectral indices along the Hubble sequence of galaxies which will be used to obtain additional constraints to the population analysis based on medium-resolution integrated spectra of galaxies. Methods. Spectra of previously studied and well-understood galaxies with relatively simple stellar populations (e.g., ellipticals or bulge dominated galaxies) are needed to provide a baseline data set for spectral synthesis models. Results. X-shooter spectra spanning the optical and infrared wavelengths (350–2400 nm) of bright nearby elliptical galaxies with a resolving power of R ∼ 4000–5400 were obtained. Heliocentric systemic velocity, velocity dispersion, and Mg, Fe, and Hβ line-strength indices are presented. Conclusions. We present a library of very-high-quality spectra of galaxies covering a large range of age, metallicity, and morphological type. Such a dataset of spectra will be crucial to addressing important questions of the modern investigation concerning galaxy formation and evolution.

scholarly journals Investigating the Scatter in the V26 – log σ relation

1987 ◽  
Vol 127 ◽  
pp. 387-388
Author(s):  
Michael Gregg ◽  
Alan Dressler
Keyword(s):  
Dispersion Relation ◽  
Velocity Dispersion ◽  
Line Strength ◽  
Stellar Populations ◽  
Elliptical Galaxies ◽  
The Family ◽  
Secondary Parameter

The nature and existence of a second parameter needed to characterize the family of normal elliptical galaxies has been much discussed. The need for a second parameter has been demonstrated by the correlation of the residuals from the well–known magnitude–velocity dispersion relation for ellipticals with other observables such as ellipticity, mass–to–light ratio and Mg line strength or metallicity. Here, evidence for a correlation between residuals in the V26 – log σ relation and the strength of Hβ is presented, suggesting that variations in the stellar populations in Virgo elliptical cores may be an important secondary parameter.

scholarly journals The Stellar Ages of Elliptical Galaxies

1995 ◽  
Vol 164 ◽  
pp. 249-257 ◽  
Author(s):  
S.M. Faber ◽  
S.C. Trager ◽  
J.J. Gonzalez ◽  
Guy Worthey
Keyword(s):  
Line Strength ◽  
Broad Band ◽  
Stellar Populations ◽  
Elliptical Galaxies ◽  
Age Effects ◽  
Color Line ◽  
Stellar Ages ◽  
The Mean

Integrated broad-band colors and metallic lines cannot discriminate clearly between the effects of age and Z in old stellar populations. Such data are more sensitive to Z than to age. The Hβ feature provides a way to break this degeneracy. New measurements indicate that the mean stellar ages of typical E galaxy nuclei are fairly young, ranging from 2 to ~12 Gyr. The outer parts of E galaxies are both older and more metal-poor than nuclei, consistent with the formation of E galaxies via mergers and starbursts. Age effects contribute strongly to the classic color-line strength sequence of E galaxies.

scholarly journals KINEMATIC PROPERTIES AND STELLAR POPULATIONS OF FAINT EARLY-TYPE GALAXIES. II. LINE-STRENGTH MEASUREMENTS OF CENTRAL COMA GALAXIES

2009 ◽  
Vol 691 (2) ◽  
pp. 1862-1878 ◽  
Author(s):  
A. Matković ◽  
R. Guzmán ◽  
P. Sánchez-Blázquez ◽  
J. Gorgas ◽  
N. Cardiel ◽  
...  
Keyword(s):  
Line Strength ◽  
Stellar Populations ◽  
Early Type ◽  
Kinematic Properties

scholarly journals The SAURON project - XI. Stellar populations from absorption-line strength maps of 24 early-type spirals

2007 ◽  
Vol 379 (2) ◽  
pp. 445-468 ◽  
Author(s):  
R. F. Peletier ◽  
J. Falcon-Barroso ◽  
R. Bacon ◽  
M. Cappellari ◽  
R. L. Davies ◽  
...  
Keyword(s):  
Absorption Line ◽  
Line Strength ◽  
Stellar Populations ◽  
Early Type

scholarly journals The chemical composition of the accretion disc and donor star in ultra-compact X-ray binaries: A comprehensive X-ray analysis

2020 ◽  
Vol 501 (1) ◽  
pp. 548-563 ◽  
Author(s):  
Filippos Koliopanos ◽  
Mathias Péault ◽  
Georgios Vasilopoulos ◽  
Natalie Webb
Keyword(s):  
Chemical Composition ◽  
Line Strength ◽  
Accretion Disc ◽  
Accretion Discs ◽  
Type I ◽  
Iron Line ◽  
X Ray ◽  
Theoretical Predictions ◽  
History Of ◽  
X Ray Binaries

ABSTRACT We have analysed the X-ray spectra of all known Ultra-Compact X-ray Binaries (UCXBs), with the purpose of constraining the chemical composition of their accretion disc and donor star. Our investigation was focused on the presence (or absence) of the Fe Kα emission line, which was used as the probe of chemical composition of the disc, based on previously established theoretical predictions for the reflection of X-ray radiation off the surface of C/O-rich or He-rich accretion discs in UCXBs. We have contrasted the results of our spectral analysis to the history of type I X-ray bursts from these systems, which can also indicate donor star composition. We found that UCXBs with prominent and persistent iron Kα emission also featured repeat bursting activity. On the other hand, the UCXBs for which no iron line was detected, appear to have few or no type I X-ray bursts detected over more than a decade of monitoring. Based on Monte Carlo simulations, demonstrating a strong correlation between the Fe Kα line strength and the abundance of C and O in the accretion disc material and given the expected correlation between the H/He abundance and the recurrence rate of type I X-ray bursts, we propose that there is a considerable likelihood that UCXBs with persistent iron emission have He-rich donors, while those that do not, likely have C/O or O/Ne/Mg-rich donors. Our result strongly advocate for the development of more sophisticated simulations of X-ray reflection from hydrogen-poor accretion discs.

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