ENVIRONMENTAL EFFECTS ON STAR FORMATION ACTIVITY AT z ∼ 0.9 IN THE COSMOS FIELD

• Published in: The Astrophysical journal 2013-05, Vol.768 (1), p.1-13
• Main Authors: KAJISAWA, M, Shioya, Y, Aida, Y, IDEUE, Y, Taniguchi, Y, Nagao, T, Murayama, T, Matsubayashi, K, RIGUCCINI, L
• Format: Article
• Language: English
• Subjects: ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; Constants; Cosmos; DENSITY; Emitters; ENVIRONMENTAL EFFECTS; Galaxies; MILKY WAY; Narrowband; RED SHIFT; SPACE; Star formation; STARS; TELESCOPES; UNIVERSE
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1088/0004-637X/768/1/51

We investigated the fraction of [OII] emitters in galaxies at z ~ 0.9 as a function of the local galaxy density in the Hubble Space Telescope (HST) COSMOS 2 deg super(2) field. [OII] emitters are selected by the narrowband excess technique with the NB711-band imaging data taken with Suprime-Cam on the Subaru telescope. We carefully selected 614 photo-z-selected galaxies with MU3500 on < -19.31 at z = 0.901 - 0.920, which includes 195 [OII] emitters, to directly compare the results with our previous study at z ~ 1.2. We found that the fraction is almost constant at 0.3 Mpc super(-2) < capital sigma sub(10th) < 10 Mpc super(-2). We also checked the fraction of galaxies with blue rest-frame colors of NUV - R < 2 in our photo-z-selected sample, and found that the fraction of blue galaxies does not significantly depend on the local density. On the other hand, the semi-analytic model of galaxy formation predicted that the fraction of star-forming galaxies at z ~ 0.9 decreases with increasing projected galaxy density even if the effects of the projection and the photo-z error in our analysis were taken into account. The fraction of [OII] emitters decreases from ~60% at z ~ 1.2 to ~30% at z ~ 0.9 independent of galaxy environment. The decrease of the [OII] emitter fraction could be explained mainly by the rapid decrease of star formation activity in the universe from z ~ 1.2 to z ~ 0.9.