%0 Journal Article %T Exploring a new definition of the green valley and its implications %+ Institut d'Astrophysique de Paris (IAP) %A Angthopo, James %A Ferreras, Ignacio %A Silk, Joseph %< avec comité de lecture %@ 1745-3933 %J Monthly Notices of the Royal Astronomical Society: Letters %I Oxford Journals %V 488 %P L99-L103 %8 2019 %D 2019 %Z 1907.02093 %Z 2019MNRAS.488L..99A %R 10.1093/mnrasl/slz106 %K galaxies: evolution %K galaxies: formation %K galaxies: interactions %K galaxies: stellar content %K Astrophysics - Astrophysics of Galaxies %Z Sciences of the Universe [physics] %Z Sciences of the Universe [physics]/Astrophysics [astro-ph]Journal articles %X The distribution of galaxies on a colour-magnitude diagram reveals a bimodality, featuring a passively evolving red sequence and a star-forming blue cloud. The region between these two, the green valley (GV), represents a fundamental transition where quenching processes operate. We exploit an alternative definition of the GV using the 4000 Å break strength, an indicator that is more resilient than colour to dust attenuation. We compare and contrast our GV definition with the traditional one, based on dust-corrected colour, making use of data from the Sloan Digital Sky Survey. Our GV selection - that does not need a dust correction and thus does not carry the inherent systematics - reveals very similar trends regarding nebular activity (star formation, AGN, quiescence) to the standard dust-corrected 0.1(g - r). By use of high-SNR stacked spectra of the quiescent GV subsample, we derive the simple stellar population (SSP) age difference across the GV, a rough proxy of the quenching time-scale (Δt). We obtain an increasing trend with velocity dispersion (σ), from Δt ∼ 1.5 Gyr at σ = 100 km s-1, up to 3.5 Gyr at σ = 200 km s-1, followed by a rapid decrease in the most massive GV galaxies (Δt ∼ 1 Gyr at σ = 250 km s-1), suggesting two different modes of quenching, or the presence of an additional channel (rejuvenation). %G English %2 https://insu.hal.science/insu-03747920/document %2 https://insu.hal.science/insu-03747920/file/slz106.pdf %L insu-03747920 %U https://insu.hal.science/insu-03747920 %~ INSU %~ CNRS %~ IAP %~ SORBONNE-UNIVERSITE %~ SORBONNE-UNIV %~ SU-SCIENCES %~ SU-TI %~ ALLIANCE-SU