Using galaxy pairs to probe star formation during major halo mergers

作者：Behroozi Peter S^*; Zhu Guangtun; Ferguson Henry C; Hearin Andrew P; Lotz Jennifer; Silk Joseph; Kassin Susan; Lu Yu; Croton Darren; Somerville Rachel S; Watson Douglas F

来源：Monthly Notices of the Royal Astronomical Society, 2015, 450(2): 1546-1564.

DOI：10.1093/mnras/stv728

• galaxies: formation
• galaxies: haloes

Currently-proposed galaxy quenching mechanisms predict very different behaviours during major halo mergers, ranging from significant quenching enhancement (e.g. clump-induced gravitational heating models) to significant star formation enhancement (e.g. gas starvation models). To test real galaxies' behaviour, we present an observational galaxy pair method for selecting galaxies whose host haloes are preferentially undergoing major mergers. Applying the method to central L* (10(10) M-circle dot < M-* < 10(10.5) M-circle dot) galaxies in the Sloan Digital Sky Survey at z < 0.06, we find that major halo mergers can at most modestly reduce the star-forming fraction, from 59 to 47 per cent. Consistent with past research, however, mergers accompany enhanced specific star formation rates for star-forming L* centrals: similar to 10 per cent when a paired galaxy is within 200 kpc (approximately the host halo's virial radius), climbing to similar to 70 per cent when a paired galaxy is within 30 kpc. No evidence is seen for even extremely close pairs (< 30 kpc separation) rejuvenating star formation in quenched galaxies. For galaxy formation models, our results suggest: (1) quenching in L* galaxies likely begins due to decoupling of the galaxy from existing hot and cold gas reservoirs, rather than a lack of available gas or gravitational heating from infalling clumps, (2) state-of-the-art semi-analytic models currently overpredict the effect of major halo mergers on quenching, and (3) major halo mergers can trigger enhanced star formation in non-quenched central galaxies.

• 出版日期2015-6-21
• 单位rutgers