Bibcode
Angthopo, James; Ferreras, Ignacio; Silk, Joseph
Referencia bibliográfica
Monthly Notices of the Royal Astronomical Society: Letters, Volume 488, Issue 1, p.L99-L103
Advertised on:
9
2019
Número de citas
22
Número de citas referidas
18
Descripción
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).
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