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Galaxies mass-luminosity relation

When the light is dominated by massive stars, e.g. in starburst galaxies, the luminosity is related in turn to the rate of metal production, since virtually all processed material is ejected in the form of metals (and some helium). Thus there is a relationship between the total co-moving luminosity density, the monochromatic luminosity density (deduced from star-forming galaxy redshift surveys with appropriate corrections for absorption) in a fixed frequency bandwidth (anywhere between 912 and about 2000 A in the rest frame) and the mass going into nucleosynthesis ... [Pg.381]

The luminosity L of a star provides astronomers with much information. For example, the lifetime T of a star is proportional (°c) to its energy supply divided by the rate at which it is used. Because energy supply is proportional to mass, and the rate is proportional to luminosity, we find that X = MIL. Similarly, because luminosity is proportional to the mass to the 3.5 power (L °c M3 5, an average relation described by James Kaler)5 we can approximate stellar lifetime by x (1/M)2-5. This means, for example, that Vega, a typical A-type dwarf star, which is 2.5 times the mass of our Sun will live (1/2.5)25=1/10 as long as the Sun. There are stars in our Universe that only survive for a few million years while others that are less than 0.8 solar masses have lifetimes longer the age of the Galaxy. [Pg.68]

The basic data for stochastic simulations of galaxies and their constituent populations and metallicity evolution is the initial mass function (IMF), which represents the mass distribution with which stars are presumed to form. Its derivation from the observed distribution of luminosity among field stars (refs. 57 and 58 and references therein) and from star clusters involves many detailed corrections for both stellar evolution and abundance variations among the observed population. The methods for achieving the IMF from the observed distribution are most thoroughly outlined by Miller and Scalo but can be stated briefly, since they also relate to an accurate testing of various proposed stochastic methods. It should first be noted that the problems encountered for stellar distributions are quite similar to those with which studies of galaxies and thdr intrinsic properties have to deal. [Pg.497]

The idea of dark matter was first mooted to resolve Zwicky s paradox, which relates to different estimates of galactic mass, based on luminosity and rotational models respectively. Rotational analysis consistently predicts excess mass, compared to the total luminous mass within the assumed limiting size of a galaxy, as defined by its so-called Holmberg radius. The subsequent discovery of massive clouds of both atomic and molecular hydrogen around typical galaxies and clusters may well account for this missing mass. [Pg.217]

Detailed studies have provided solid evidence for the existence of dark halos around disk galaxies of any morphological type, luminosity, and environmoit (e.g., Rubin et cU. 1985 Kent 1988). Nevertheless, quantitative assessmmt of the size and importance of the various dynamical components (e.g., disk, bulge, halo, and their M/L ratios) suffers from the limited validity of certain premises. One questionable assumption is that of constant M/L ratios for the bulge and disk components. Another question is about the mass distribution inferred from optical emission-line rotation curves, which are related to the kinematics of the ionized gas, so that rotation curves in bulge-dominated regions may not measure true rotational velocities (Kent 1988 Kormendy Westpfahl 1989). [Pg.129]


See other pages where Galaxies mass-luminosity relation is mentioned: [Pg.236]    [Pg.238]    [Pg.346]    [Pg.357]    [Pg.365]    [Pg.202]    [Pg.193]    [Pg.49]    [Pg.267]    [Pg.269]    [Pg.151]    [Pg.190]    [Pg.191]    [Pg.245]    [Pg.251]    [Pg.193]   
See also in sourсe #XX -- [ Pg.357 , Pg.358 , Pg.362 , Pg.364 , Pg.373 ]




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Mass-luminosity relation

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