Quenching time-scales of galaxies in the EAGLE simulations
Abstract
We use the EAGLE simulations to study the connection between the quenching time-scale, τQ, and the physical mechanisms that transform star-forming galaxies into passive galaxies. By quantifying τQ in two complementary ways - as the time over which (i) galaxies traverse the green valley on the colour-mass diagram, or (ii) leave the main sequence of star formation and subsequently arrive on the passive cloud in specific star formation rate (SSFR)-mass space - we find that the τQ distribution of high-mass centrals, low-mass centrals, and satellites are divergent. In the low stellar mass regime where M⋆ < 109.6 M⊙, centrals exhibit systematically longer quenching time-scales than satellites (≈4 Gyr compared to ≈2 Gyr). Satellites with low stellar mass relative to their halo mass cause this disparity, with ram pressure stripping quenching these galaxies rapidly. Low-mass centrals are quenched as a result of stellar feedback, associated with long τQ ≳ 3 Gyr. At intermediate stellar masses where 10^{9.7}< M_{\star }< 10^{10.3} M_{\odot }, τQ are the longest for both centrals and satellites, particularly for galaxies with higher gas fractions. At M_{\star }≳ 10^{10.3} M_{\odot }, galaxy merger counts and black hole activity increase steeply for all galaxies. Quenching time-scales for centrals and satellites decrease with stellar mass in this regime to τQ ≲ 2 Gyr. In anticipation of new intermediate redshift observational galaxy surveys, we analyse the passive and star-forming fractions of galaxies across redshift, and find that the τQ peak at intermediate stellar masses is responsible for a peak (inflection point) in the fraction of green valley central (satellite) galaxies at z ≈ 0.5-0.7.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- August 2019
- DOI:
- 10.1093/mnras/stz1410
- arXiv:
- arXiv:1810.07335
- Bibcode:
- 2019MNRAS.487.3740W
- Keywords:
-
- galaxies: evolution;
- galaxies: formation;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- Final version accepted to MNRAS. 18 pages, 16 figures