Arjen van der Wel et al 2009 ApJ 706 L120 doi:10.1088/0004-637X/706/1/L120
Arjen van der Wel1, Hans-Walter Rix1, Bradford P. Holden2, Eric F. Bell1,3 and Aday R. Robaina1
Show affiliationsWe analyze the projected axial ratio distribution, p(b/a), of galaxies that were spectroscopically selected from the Sloan Digital Sky Survey (DR6) to have low star formation rates. For these quiescent galaxies we find a rather abrupt change in p(b/a) at a stellar mass of ~1011 M ☉: at higher masses there are hardly any galaxies with b/a < 0.6, implying that essentially none of them have disk-like intrinsic shapes and must be spheroidal. This transition mass is ~3-4 times higher than the threshold mass above which quiescent galaxies dominate in number over star-forming galaxies, which suggests that these mass scales are unrelated. At masses lower than ~1011 M ☉, quiescent galaxies show a large range in axial ratios, implying a mix of bulge- and disk-dominated galaxies. Our result strongly suggests that major merging is the most important, and perhaps only relevant, evolutionary channel to produce massive (>1011 M ☉), quiescent galaxies, as it inevitably results in spheroids.
galaxies: elliptical and lenticular, cD; galaxies: formation; galaxies: fundamental parameters; galaxies: statistics; galaxies: structure
98.62.Ai Origin, formation, evolution, age, and star formation
98.62.Ck Masses and mass distribution
98.52.Lp Lenticular (S0) galaxies
98.62.Js Galactic nuclei (including black holes), circumnuclear matter, and bulges
98.62.Py Distances, redshifts, radial velocities; spatial distribution of galaxies
Issue 1 (2009 November 20)
Received 2009 August 28, accepted for publication 2009 October 20
Published 2009 November 2
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