Galaxies luminosities

Fig. 3.44. Metallicities in gas-poor galaxies (open symbols) and oxygen abundances at a representative radius in gas-rich disk galaxies (filled symbols), as a function of galaxy luminosity in blue light. The dotted lines in each panel represent identical trends for [Fe/H] and [O/H] and the ordinate 0.0 represents solar composition. Adapted from Zaritsky, Kennicutt and Huchra (1994).

Besides the nearby cluster detections (z O.l) that are using simple galaxy density criteria, the combination of such galaxy densities over the sky and of the shape of the galaxy luminosity function allows cluster detections up to 1... 

Figure 8.30. Cumulative number distribution for the galaxies in the Universe. Mass is assumed proportional to absolute luminosity (units solar luminosity x 10 ). From Brown et al. (1983).

Scl is a close companion of the Milky Way, at a distance of 72 5 kpc [7], with a low total (dynamical) mass, (1.4 0.6) x 107Mq [8], and modest luminosity, My = —10.7 0.5, and central surface brightness, Soy = 23.5 0.5 mag/arcsec2 [9] with no HI gas [10]. CMD analysis, including the oldest Main Sequence turnoffs, has determined that this galaxy is predominantly old and that the entire star formation history can have lasted only a few Gyr [11]. 

The Metallicity-Luminosity Relation for Local Group Dwarf Galaxies... 

The accretion history of a parent galaxy is constructed using a semi-analytical code. The full phase-space evolution during each accretion event is then followed separately with numerical simulations [2]. Star-formation and chemical evolution models are implemented within each satellite. The star formation prescription matches the number and luminosity of present-day galaxies in the Local Group, whereas the chemical evolution model takes into account the metal enrichment of successive stellar populations as well as feedback processes. Below we present results of a sample of four such simulated galaxy halos, denoted as Halos HI, H2, H3 and H4. 

Spergel et al. 2007), but greatly exceeds the smoothed-out cosmological density of luminous matter deduced from galaxy redshift surveys, which give a luminosity density in blue light... 

Fig. 8.12. Relation between oxygen abundance of H II regions in irregular (open squares) and spiral galaxies (filled circles, taking abundances at 0.4 of the de Vaucouleurs isophotal radius R25) plotted against the gas fraction, after Pilyugin, Vilchez and Contini (2004). The heavy curve shows expectation from the Simple model with an oxygen yield of 0.0027 (or about 0.5 Z ) and the broken curves show the same with the yield 1.5 x higher or lower, whereas the dotted curve shows a yield 4 x lower. The effective yield, defined as Zo/(— ln/z), increases systematically with luminosity, and the gas fraction decreases.

A relationship also exists between abundances and luminosity of the host galaxy, whether gas-rich or otherwise (Fig. 3.44), and especially with the rotational velocity in disk galaxies (Fig. 8.13). Similarly, studies of elliptical galaxies in general suggest that the primary factor fixing the mean metallicity of their stellar... 

Fig. 11.2. Mean stellar iron abundances as a function of luminosity in dwarf spheroidals (filled circles), dwarf ellipticals (open circles), dSph/dlrr transition galaxies (filled diamonds) and dwarf irregulars (open diamonds). Baryonic luminosity in the right panel includes the additional luminosity that irregulars would have if their gas were converted into stars. After Grebel, Gallagher and Harbeck (2003).

Fig. 11.18. Gas mass in clusters of galaxies plotted against the total luminosity of elliptical and lenticular (SO) galaxies in the cluster. The la error in the slope a is 0.25. After Arnaud et al. (1992). Courtesy Monique Arnaud.

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