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arXiv · 0910.4018

Major Merging: The Way to Make a Massive, Passive Galaxy

Arjen van der Wel·Hans-Walter Rix·Bradford P. Holden·Eric F. Bell·Aday R. Robaina
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Abstract

We 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 ~10^{11} M_sol: 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 these mass scales are unrelated. At masses lower than ~10^{11} M_sol, 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 (>10^{11} M_sol), quiescent galaxies, as it inevitably results in spheroids.

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Arjen van der Wel, Hans-Walter Rix, Bradford P. Holden, Eric F. Bell, Aday R. Robaina. 2009-10-21. Major Merging: The Way to Make a Massive, Passive Galaxy. https://doi.org/10.1088/0004-637x/706/1/l120

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