2018/10/31 by Ruby J. Wright, Claudia del P. Lagos, Luke J. M. Davies +3
Physics and Astronomy · #astro-ph.GA
paper · pdf · doi:10.1093/mnras/stz1410
Final version accepted to MNRAS. 18 pages, 16 figures
arxiv created 2019/05/18 · arxiv updated 2019/06/05
We use the \eagle simulations to study the connection between the quenching timescale, τ\rm Q, and the physical mechanisms that transform star-forming galaxies into passive galaxies. By quantifying τ\rm Q 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 τ\rm Q distribution of high-mass centrals, low-mass centrals and satellites are divergent. In the low stellar mass regime where M⋆<109.6M\odot, centrals exhibit systematically longer quenching timescales 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 τ\rm Q\gtrsim 3~Gyr. At intermediate stellar masses where 109.7 \rm M\odot<M⋆<1010.3 \rm M\odot, τ\rm Q are the longest for both centrals and satellites, particularly for galaxies with higher gas fractions. At M⋆\gtrsim 1010.3 \rm M\odot, galaxy merger counts and black hole activity increase steeply for all galaxies. Quenching timescales for centrals and satellites decrease with stellar mass in this regime to τ\rm Q\lesssim2~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 τ\rm Q 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.