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Published August 1, 2009 | Published
Journal Article Open

Environmental Effects on the Star Formation Activity in Galaxies at z ≃ 1.2 in the COSMOS Field


We investigate the relation between the star formation activity in galaxies and environment at z ≃ 1.2 in the Cosmic Evolution Survey field, using the fraction of [O II] emitters and the local galaxy density. The fraction of [O II] emitters appears to be almost constant over the surface density of galaxies between 0.2 and 10 Mpc^(–2). This trend is different from that seen in the local universe where the star formation activity is weaker in higher density regions. To understand this difference between z ~ 1 and z ~ 0, we study the fraction of non-isolated galaxies as a function of local galaxy density. We find that the fraction of non-isolated galaxies increases with increasing density. Our results suggest that the star formation in galaxies at z ~ 1 is triggered by galaxy interaction and/or mergers.

Additional Information

© 2009. The American Astronomical Society. Print publication: Issue 2 (2009 August 1) Received 2008 December 2; accepted for publication 2009 May 25; published 2009 July 7. We would like to thank both the Subaru and HST staff for their invaluable help and acknowledge the anonymous referee for an extremely useful report. This work was financially supported in part by the Ministry of Education, Culture, Sports, Science, and Technology (nos. 10044052 and 10304013) and by JSPS (nos. 15340059, 17253001, and 19340046).

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