Galaxies: evolution

Abstract. This aims to be an overview of what detailed observations of individual stars in nearby dwarf galaxies may teach us about galaxy evolution. This includes some early results from the DART (Dwarf Abundances and Radial velocity Team) Large Programme at ESO. This project has used 2.2m/WFI and VLT/FLAMES to obtain spectra of large samples of individual stars in nearby dwarf spheroidal galaxies and determine accurate abundances and kinematics. These results can be used to trace the formation and evolution of nearby galaxies from the earliest times to the present. 

The abundance patterns of individual stars of different ages and environments enable us to unlock the evolutionary history of galaxies. Many physical characteristics of a galaxy may change over time, such as shape and colour, however the metal content and abundance ratios of stellar atmospheres are not so easy to tamper with. Stars retain the chemical imprint of the interstellar gas out of which they formed, and metals can only increase with time. This method to study galaxy evolution has been elegantly named Chemical Tagging [2],... 

In the next very few years stellar abundances and kinematics will be available for as many stars as redshifts are now available for galaxies. This abundance of information can, provided we approach the analysis and interpretation with due imagination, advance the astrophysics of galaxy formation as much as Cosmology has advanced over the last few decades. No doubt our image of galaxy evolution will be similarly revolutionised. 

This could have occurred as a wind in the early, vigorously star-forming phase of galaxy evolution. This inference has additional credence from the facts that the mass in hitherto undetected baryons is comparable to that observed in stars and that the WHIM is observed to exist outside of rich clusters... 

Langer, N. Woosley, S. E., 1996, in From Stars to Galaxies — The Impact of Stellar Physics on Galaxy Evolution, eds. C. Leitherer, U. Fritze-von Alvensleben, J. Huchra, ASP Conf. Series Vol. 98, p. 220... 

Beyond galaxy evolution, abundance measurements provide important ancillary information relevant to other very important astrophysical problems, including ... 

Mosaiced images of a medium red shift (z = 0.165) cluster of galaxies A1553 were obtained in an area of 9 X 9 at J, H and K bands with the integration over 1500 seconds. We detected 200 galaxies. The data will be used to study the galaxy evolution. 

Figure 2 shows projected performance levels at 100/um, calculated for no galaxy evolution and effective beam diameters of 1.2XjD (upper curve) and... 

Another argument puts a stronger constraint on host galaxy evolution. We note that most of the iron in the solar neighborhood was produced by type la supemovae (e.g. Matteucd and Greggio 1986). These objects have an enrichment timescale 1 Gyr. For qo =, the start of star formation must be z > 9.0 for a universe with Ho = 50, and is inconsistent with Ho = 100. If indeed iron enrichment requires 1 Gyr, the large Ho values require qo <. ... 

Key words Galaxies Stellax Content - Galaxies Formation - Galaxies Evolution... 

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