The Stellar Populations of Galaxies

The Stellar Populations of Galaxies
Author: B. Barbuy
Publisher: Springer Science & Business Media
Total Pages: 529
Release: 2012-12-06
Genre: Science
ISBN: 9401124345

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One approach to learning about stellar populations is to study them at three different levels of resolution. First in our own Galaxy; secondly from nearby galaxies where stars can still be resolved; and thirdly in remote galaxies in which the stellar population can only be studied in integrated light. This IAU Symposium covered the entire range of galaxies in its study of their stellar populations. Interspersed with theoretical papers, the wealth of observational results provides an important state-of-the-art presentation of the progress that has been made in this field.

The Evolution of Cluster Elliptical Galaxies

The Evolution of Cluster Elliptical Galaxies
Author: Luis Felipe Barrientos
Publisher:
Total Pages: 0
Release: 1999
Genre:
ISBN:

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This thesis work focuses on the understanding of the formation and subsequent evolution of the population of elliptical galaxies in rich galaxy clusters. Elliptical galaxies define a unique and simple laboratory to study the process of galaxy formation and the evolution of stellar populations. Observational data, including a sample of eight clusters observed at Cerro Tololo Inter-American Observatory (CTIO) and ten clusters observed with the Hubble Space Telescope (HST), have been used to conduct several related studies. A surface brightness analysis of the ellipticals in the cores of ten galaxy clusters observed with HST shows that elliptical galaxies are well-represented by an 'r'1/4-law light profile and follow a well-defined relation in the magnitude/size plane, up to 'z' = 1.2. This relation shifts, on average, towards higher luminosities (or equivalently, to smaller sizes) with increasing redshift. If we assume that the size of these galaxies are fixed during the period from 'z' = 1.2 to the present, then these galaxies are evolving monotonically in luminosity. This luminosity evolution amounts to [Delta]'MB' = -1.2 at 'z' = 1.2, when compared to the galaxies in local clusters, and is consistent with that expected for an old and passively evolving stellar population. The luminosity functions for the red galaxies from the eight clusters in the CTIO sample show that are well-represented by a Schechter function, consistent with a single value for their characteristic magnitude (M*). When compared to local cluster luminosity functions, there is evidence for a brightening of a few tenths of a magnitude in M* (the exact value depends on the cosmology). For a low density universe, the brightening observed in the luminosity function, up to 'z' = 0.45, is consistent with that observed from the surface brightness analysis. The cluster elliptical galaxies from the CTIO sample, selected morphologically using a galaxy light profile fitting technique, define a very tight sequence in the colour/magnitude plane. All the clusters are consistent with having a single value for their intrinsic colour dispersions, [delta] = 0.06 ± 0.02, in the restframe ('U' - 'V')/' V' colour relation. These small colour dispersions imply the stars in these galaxies have a typical age dispersion from galaxy to galaxy of ~20% of their age at 'z' = 0.45. Similarly, when comparing the mean colour for the different clusters, it was found that they are consistent with having a single mean colour, ('V' - 'I') = 2.055 ± 0.028. The small dispersion in the mean colours is completely accounted for by sampling uncertainties. With the addition of 'K'-band photometry, and data for local ellipticals, it has been possible to determine the evolutionary vector in the restframe ('U' - 'V')/(' V' - 'H') colour plane from 'z' = 0.45 to 'z' = 0. Predictions of current models have been tested against this observed vector. Most of the more popular models have failed to account for this colour change, and only a more sophisticated model--including infall of primordial gas and chemical enrichment during the assembly of the stellar population--was able to reproduce the observed evolution. The observations in this work strongly suggest that these galaxies are old systems formed at high redshift. However, given the quantitative uncertainties in the observations, population synthesis models, cosmology, and uncertainties in how much synchronicity in formation is reasonable, the observations do not rule out scenarios involving formation at lower redshifts.

Nearly Normal Galaxies

Nearly Normal Galaxies
Author: Sandra M. Faber
Publisher: Springer Science & Business Media
Total Pages: 475
Release: 2012-12-06
Genre: Science
ISBN: 1461247624

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It is sometimes said that astronomy is the crossroads of physics. In the same spirit, it can forcefully be argued that galaxies are the crossroads of astronomy. Internal pro ces ses within galaxies involve all of the fundamental components of astrophysics: stellar evolution, star formation, low-density astrophysics, dynamics, hydrodynamics, and high-energy astrophysics. Indeed, one can hardly name an observational datum in any wavelength range on any kind of celestial object that does not provide a useful clue to galaxy formation and evolution. Although internal processes in galaxies until recently occupied most of our attention, we now know that it is also vital to relate galaxies to their environment. How galaxies congregate in larger structures and are in turn influenced by them are crucial questions for galactic evolution. On a grander level we have also come to regard galaxies as the basic building blocks of the universe, the basic units whereby the large scale structure of the universe is apprehended and quantified. On a grander level still, we also believe strongly that galaxies are the direct descendents of early density irregularities in the Big Bang. Galaxy properties are now viewed as providing a crucial constraint on the physics of the Big Bang and a vital link between the macroscopic and microscopic structure of the universe.

Stellar Populations

Stellar Populations
Author: International Astronomical Union. Symposium
Publisher: Cambridge University Press
Total Pages: 488
Release: 2010
Genre: Galaxies
ISBN: 9780521764841

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IAU Symposium 262 presents reviews on the current understanding of the theories of stellar evolution, galaxy formation and galaxy evolution. It emphasises what we have learned in the past few years from massive surveys covering large portions of the sky (e.g. SDSS, HDF, UDF, GOODS, COSMOS). Several critical aspects of research on stellar populations deserve further effort in order to be brought in tune with other areas of astrophysical research. The next ten years will see the opening of major observatories that will increase the quality and quantity of astronomical data by orders of magnitude. The expected benefits from these instruments for the study of stellar populations are explored. This critical review of state of the art observational and theoretical work will appeal to all those working on stellar populations, from distant galaxies to local resolved galaxies and galactic star clusters.