scholarly journals Stellar Populations in Mixed Pairs of Galaxies

1995 ◽  
Vol 164 ◽  
pp. 434-434 ◽  
Author(s):  
D.F. De Mello ◽  
W.C. Keel ◽  
J.W. Sulentic ◽  
R. Rampazzo
Keyword(s):  
Star Formation ◽  
Stellar Population ◽  
Elliptical Galaxy ◽  
Star Formation History ◽  
Population Synthesis ◽  
Early Type ◽  
Stellar Content ◽  
Stellar Population Synthesis ◽  
History Of ◽  
Early Type Galaxy

The interpration of the interaction in galaxies is simplified in mixed pairs (E+S) because most or all of the cold gas can be traced to an origin in a single galaxy (S). We used spectroscopy, imaging, far–IR, and stellar population synthesis to study the stellar content and history of star formation in the nuclear region of the early–type galaxy in the mixed pair AM0327–285. We used the procedure for stellar population synthesis developed by Bica (1988) to estimate the star-formation history of the nucleus of the elliptical galaxy. The method uses a library of star clusters, and estimates the chemical evolution in a test population with two parameters: age and metallicity; no assumptions on gravity or details of stellar evolution are necessary, and the IMF is implicit in the cluster spectra. The procedure allows one to both determine the chemical enrichment and date successive generations of star formation. The result indicates that the dominant population is old and metal–rich ([Z/Z]⊙=0.3), while ~ 10% of the flux at 5870 Å arises from a young stellar population (age ≤ 5 × 108 yr), confirming that this early-type galaxy had recent star formation as suggested also by photometry and far–IR data (de Mello et al 1994). This age is close to several estimates of the characteristic timescale of the interaction, suggesting that the mass influx associated with this star formation occurred as a result of an earlier phase of the interaction and not as a result of the present geometry of the pair.

scholarly journals The star formation history of the Fornax dwarf spheroidal galaxy

2009 ◽  
Vol 5 (S262) ◽  
pp. 353-354
Author(s):  
Enrico V. Held ◽  
Eline Tolstoy ◽  
Luca Rizzi ◽  
Mary Cesetti ◽  
Andrew A. Cole ◽  
...  
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Stellar Population ◽  
Main Sequence ◽  
Dwarf Galaxy ◽  
Star Formation History ◽  
Stellar Content ◽  
Formation History ◽  
First Results ◽  
History Of

AbstractWe present the first results of a comprehensive HST study of the star-formation history of Fornax dSph, based on WFPC2 imaging of 7 Fornax fields. Our observations reach the oldest main-sequence turnoffs, allowing us to address fundamental questions of dwarf galaxy evolution, such as the spatial variations in the stellar content, and whether the old stellar population is made up of stars formed in a very early burst or the result of a more continuous star formation.

scholarly journals The Star Formation History of the Virgo Early‐Type Galaxy NGC 4435: TheSpitzerMid‐Infrared View

2007 ◽  
Vol 656 (1) ◽  
pp. 206-216 ◽  
Author(s):  
P. Panuzzo ◽  
O. Vega ◽  
A. Bressan ◽  
L. Buson ◽  
M. Clemens ◽  
...  
Keyword(s):  
Star Formation ◽  
Star Formation History ◽  
Early Type ◽  
Formation History ◽  
History Of ◽  
Early Type Galaxy

The star-formation histories of early-type galaxies from ATLAS3D

2011 ◽  
Vol 7 (S284) ◽  
pp. 244-247 ◽  
Author(s):  
Richard M. McDermid ◽  
Katherine Alatalo ◽  
Leo Blitz ◽  
Maxime Bois ◽  
Frédéric Bournaud ◽  
...  
Keyword(s):  
Star Formation ◽  
Stellar Population ◽  
Abundance Ratio ◽  
Star Formation History ◽  
Early Type ◽  
Solar Abundance ◽  
Formation History ◽  
History Of ◽  
Free Parameters ◽  
Star Formation Histories

AbstractWe present an exploration of the integrated stellar populations of early-type galaxies (ETGs) from the ATLAS3D survey. We use two approaches: firstly the application of line-indices interpreted through single stellar population (SSP) models, which provide a single value of age, metallicity and abundance ratio. And secondly, by fitting a linear combination of SSP spectra to our data, smoothly weighted in the free parameters of age and metallicity, thereby inferring a star-formation history of these galaxies. Despite the significant differences in these approaches, we obtain generally consistent results, such that galaxies that are more massive appear older with enhanced abundance ratios using line indices, and have shorter star-formation histories weighted to early times. We highlight two limitations of the index-SSP approach. Firstly the SSP-equivalent ages belie the fact that ETGs are overwhelmingly composed of ancient stars. Secondly, the young stellar contributions implied in our star formation histories are required to obtain realistic UV-optical colours. We remark that, even fitting solar-abundance models, we can recover a star-formation duration that correlates with the measured alpha-enhancement, in agreement with other recent work.

scholarly journals New results on the structure and stellar content of the outer regions of the SMC

1991 ◽  
Vol 148 ◽  
pp. 51-52
Author(s):  
L. T. Gardiner ◽  
M.R.S. Hawkins
Keyword(s):  
Evolutionary History ◽  
Large Scale ◽  
Stellar Population ◽  
Main Sequence ◽  
Population Synthesis ◽  
Stellar Content ◽  
Surface Distribution ◽  
Contour Maps ◽  
Stellar Population Synthesis ◽  
History Of

Surface distribution contour maps of the HB/clump population and the < 1 Gyr main sequence population for the outer regions of the Small Magellanic Cloud (SMC) are presented. Aspects of the stellar population synthesis, large-scale structure and evolutionary history of the SMC halo are discussed.

scholarly journals The Structure and Star Formation History of Early‐Type Galaxies in the Ultra Deep Field/GRAPES Survey

2006 ◽  
Vol 636 (1) ◽  
pp. 115-133 ◽  
Author(s):  
A. Pasquali ◽  
I. Ferreras ◽  
N. Panagia ◽  
E. Daddi ◽  
S. Malhotra ◽  
...  
Keyword(s):  
Star Formation ◽  
Star Formation History ◽  
Early Type ◽  
Formation History ◽  
History Of

scholarly journals Tracers of Star Formation in the Near Infrared

2009 ◽  
Vol 5 (S262) ◽  
pp. 383-384
Author(s):  
L. Martins ◽  
A. Ardila ◽  
R. Gruenwald ◽  
R. de Souza
Keyword(s):  
Star Formation ◽  
Stellar Population ◽  
Near Infrared ◽  
Agb Stars ◽  
Population Synthesis ◽  
Near Ir ◽  
Stellar Population Synthesis ◽  
First Time ◽  
Absorption Features ◽  
Empirical Database

AbstractStarburst features in the optical are nowadays well known, but the use of this knowledge is not always possible (e.g. objects heavily obscured). In this case the near-IR is of unprecedented value. Recent models show that TP-AGB stars should dominate the NIR spectra of populations 0.3 to 2 Gyr old. While the optical spectra is insensitive to the presence of these stars, the near-IR changes dramatically. Not only does the absolute flux in the near-IR is affected, but also peculiar absorption features appear. These features can be used as indicators of 1 Gyr stellar population. In this work we used the IRTF Spex to create the first empirical database of NIR spectra of carefully selected starbursts, to test for the first time and in a consistent way the new stellar population models that account for the TP-AGB. The methodology used is to do stellar population synthesis in the optical and in the NIR, and compare the predictions of both spectral regions. We also compare the strength of important features of the TP-AGB stars, like the CN (1.1 microns) and CO (2.3 microns) bands with optical diagnostics.

scholarly journals The Massive stellar Population at the Galactic Center

2016 ◽  
Vol 12 (S329) ◽  
pp. 287-291
Author(s):  
Francisco Najarro ◽  
Diego de la Fuente ◽  
Tom R. Geballe ◽  
Don F. Figer ◽  
D. John Hillier
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
Stellar Population ◽  
Milky Way ◽  
Local Group ◽  
Galactic Center ◽  
Spectroscopic Studies ◽  
Star Formation History ◽  
Stellar Content ◽  
Formation History

AbstractWe present results from our ongoing infrared spectroscopic studies of the massive stellar content at the Center of the Milky Way. This region hosts a large number of apparently isolated massive stars as well as three of the most massive resolved young clusters in the Local Group. Our survey seeks to infer the presence of a possible top-heavy recent star formation history and to test massive star formation channels: clusters vs isolation.

scholarly journals Stellar population synthesis: Application To Galactic Bulges

1993 ◽  
Vol 153 ◽  
pp. 133-150
Author(s):  
N. Arimoto
Keyword(s):  
Observational Data ◽  
Stellar Population ◽  
Stellar Populations ◽  
Population Synthesis ◽  
Firm Conclusion ◽  
Formation History ◽  
Stellar Population Synthesis ◽  
Central Regions ◽  
History Of ◽  
Metallicity Distribution

The stellar populations give traces of the formation history of the bulges. The metallicity distribution of K-giants in the Galactic bulge resembles to that of the giant ellipticals. There seems to be no conspicuous colour-magnitude relation intrinsic to the bulges. This can be explained if the bulges formed by the dissipative collapse of central regions of proto-galaxies followed by the supernova-driven bulge wind which was induced later than the dwarf ellipticals of the similar mass (the biased wind). Unfortunately, the observational data available at present of stellar populations of the bulges are not yet sufficient to get a firm conclusion on the origin of the bulges.

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