A detailed look at the stellar populations in green valley galaxies. Issue 3 (13th May 2020)

• Record Type: Journal Article
• Authors: Angthopo, James; Ferreras, Ignacio; Silk, Joseph
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 495:Issue 3(2020)
• Page Start: 2720
• Page End: 2737
• Publication Date: 2020-05-13
• Subjects: galaxies: evolution -- galaxies: formation -- galaxies: interactions -- galaxies: stellar content; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/staa1276
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: The green valley (GV) represents an important transitional state from actively star-forming galaxies to passively evolving systems. Its traditional definition, based on colour, rests on a number of assumptions that can be subjected to non-trivial systematics. In Angthopo, Ferreras & Silk (2019 ), we proposed a new definition of the GV based on the 4000 Å break strength. In this paper, we explore in detail the properties of the underlying stellar populations by use of ∼230 thousand high-quality spectra from the Sloan Digital Sky Survey (SDSS), contrasting our results with a traditional approach via dust-corrected colours. We explore high-quality stacked SDSS spectra, and find a population trend that suggests a substantial difference between low- and high-mass galaxies, with the former featuring younger populations with star formation quenching, and the latter showing older (post-quenching) populations that include rejuvenation events. Subtle but measurable differences are found between a colour-based approach and our definition, especially as our selection of GV galaxies produces a cleaner 'stratification' of the GV, with more homogeneous population properties within sections of the GV. Our definition based on 4000 Å break strength gives a clean representation of the transition to quiescence, easily measurable in the upcoming and future spectroscopic surveys.