Mass and Environment as Drivers of Galaxy Evolution in SDSS and zCOSMOS and the Origin of the Schechter Function

• Published in: The Astrophysical journal 2010-09, Vol.721 (1), p.193-221
• Main Authors: Peng, Ying-jie, Lilly, Simon J, Kovač, Katarina, Bolzonella, Micol, Pozzetti, Lucia, Renzini, Alvio, Zamorani, Gianni, Ilbert, Olivier, Knobel, Christian, Iovino, Angela, Maier, Christian, Cucciati, Olga, Tasca, Lidia, Carollo, C. Marcella, Silverman, John, Kampczyk, Pawel, de Ravel, Loic, Sanders, David, Scoville, Nicholas, Contini, Thierry, Mainieri, Vincenzo, Scodeggio, Marco, Kneib, Jean-Paul, Le Fèvre, Olivier, Bardelli, Sandro, Bongiorno, Angela, Caputi, Karina, Coppa, Graziano, de la Torre, Sylvain, Franzetti, Paolo, Garilli, Bianca, Lamareille, Fabrice, Le Borgne, Jean-Francois, Le Brun, Vincent, Mignoli, Marco, Montero, Enrique Perez, Pello, Roser, Ricciardelli, Elena, Tanaka, Masayuki, Tresse, Laurence, Vergani, Daniela, Welikala, Niraj, Zucca, Elena, Oesch, Pascal, Abbas, Ummi, Barnes, Luke, Bordoloi, Rongmon, Bottini, Dario, Cappi, Alberto, Cassata, Paolo, Cimatti, Andrea, Fumana, Marco, Hasinger, Gunther, Koekemoer, Anton, Leauthaud, Alexei, Maccagni, Dario, Marinoni, Christian, McCracken, Henry, Memeo, Pierdomenico, Meneux, Baptiste, Nair, Preethi, Porciani, Cristiano, Presotto, Valentina, Scaramella, Roberto
• Format: Article
• Language: English
• Subjects: ABUNDANCE; Astronomy; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; COSMOLOGY; Earth, ocean, space; ELEMENT ABUNDANCE; EVOLUTION; Exact sciences and technology; GALACTIC EVOLUTION; GALAXIES; MASS; RED SHIFT; SATELLITES; STAR EVOLUTION; STARS; UNIVERSE
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1088/0004-637X/721/1/193

We explore the simple inter-relationships between mass, star formation rate, and environment in the SDSS, zCOSMOS, and other deep surveys. We take a purely empirical approach in identifying those features of galaxy evolution that are demanded by the data and then explore the analytic consequences of these. We show that the differential effects of mass and environment are completely separable to z {approx} 1, leading to the idea of two distinct processes of 'mass quenching' and 'environment quenching'. The effect of environment quenching, at fixed over-density, evidently does not change with epoch to z {approx} 1 in zCOSMOS, suggesting that the environment quenching occurs as large-scale structure develops in the universe, probably through the cessation of star formation in 30%-70% of satellite galaxies. In contrast, mass quenching appears to be a more dynamic process, governed by a quenching rate. We show that the observed constancy of the Schechter M* and {alpha}{sub s} for star-forming galaxies demands that the quenching of galaxies around and above M* must follow a rate that is statistically proportional to their star formation rates (or closely mimic such a dependence). We then postulate that this simple mass-quenching law in fact holds over a much broader range of stellar mass (2 dex) and cosmic time. We show that the combination of these two quenching processes, plus some additional quenching due to merging naturally produces (1) a quasi-static single Schechter mass function for star-forming galaxies with an exponential cutoff at a value M* that is set uniquely by the constant of proportionality between the star formation and mass quenching rates and (2) a double Schechter function for passive galaxies with two components. The dominant component (at high masses) is produced by mass quenching and has exactly the same M* as the star-forming galaxies but a faint end slope that differs by {Delta}{alpha}{sub s} {approx} 1. The other component is produced by environment effects and has the same M* and {alpha}{sub s} as the star-forming galaxies but an amplitude that is strongly dependent on environment. Subsequent merging of quenched galaxies will modify these predictions somewhat in the denser environments, mildly increasing M* and making {alpha}{sub s} slightly more negative. All of these detailed quantitative inter-relationships between the Schechter parameters of the star-forming and passive galaxies, across a broad range of environments, are indeed se