QUENCHING STAR FORMATION AT INTERMEDIATE REDSHIFTS: DOWNSIZING OF THE MASS FLUX DENSITY IN THE GREEN VALLEY

• Published in: The Astrophysical journal Vol. 759; no. 1; pp. 1 - 12
• Main Authors: GONCALVES, Thiago S, CHRISTOPHER MARTIN, D, MENENDEZ-DELMESTRE, Karín, WYDER, Ted K, KOEKEMOER, Anton
• Format: Journal Article
• Language: English
• Published: Bristol IOP 01-11-2012
• Subjects: ASTRONOMY; ASTROPHYSICS; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; Clouds; COSMOLOGY; Downsizing; Earth, ocean, space; EMISSION SPECTROSCOPY; Exact sciences and technology; Flux; FLUX DENSITY; GALACTIC EVOLUTION; GALAXIES; LUMINOSITY; MASS; QUENCHING; RED SHIFT; Star formation; STARS; TELESCOPES; UNIVERSE; Valleys; Galaxy evolution; Spectroscopy; Red shift; Deimos; Galaxies; galaxies: luminosity function; galaxies: evolution; Mass transfer; Mars satellite; Flux density; Mass function; Star formation; Stellar mass; Age; Luminosity function
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1088/0004-637X/759/1/67

The bimodality in galaxy properties has been observed at low and high redshifts, with a clear distinction between star-forming galaxies in the blue cloud and passively evolving objects in the red sequence; the absence of galaxies with intermediate properties indicates that the quenching of star formation and subsequent transition between populations must happen rapidly. In this paper, we present a study of over 100 transiting galaxies in the so-called green valley at intermediate redshifts (z ~ 0.8). By using very deep spectroscopy with the DEIMOS instrument at the Keck telescope we are able to infer the star formation histories of these objects and measure the stellar mass flux density transiting from the blue cloud to the red sequence when the universe was half its current age. Our results indicate that the process happened more rapidly and for more massive galaxies in the past, suggesting a top-down scenario in which the massive end of the red sequence is forming first. This represents another aspect of downsizing, with the mass flux density moving toward smaller galaxies in recent times.