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Published February 1, 2016 | Published + Submitted
Journal Article Open

The SPLASH Survey: Quiescent Galaxies Are More Strongly Clustered but Are Not Necessarily Located in High-density Environments


We use the stellar-mass-selected catalog from the Spitzer Large Area Survey with Hyper-Suprime-Cam (SPLASH) in the COSMOS field to study the environments of galaxies via galaxy density and clustering analyses up to z ~ 2.5. The clustering strength of quiescent galaxies exceeds that of star-forming galaxies, implying that quiescent galaxies are preferentially located in more massive halos. When using local density measurement, we find a clear positive quiescent fraction–density relation at z < 1, consistent with earlier results. However, the quiescent fraction–density relation reverses its trend at intermediate redshifts (1 < z < 1.5) with marginal significance (<1.8σ) and is found to be scale dependent (1.6σ). The lower fraction of quiescent galaxies seen in large-scale dense environments, if confirmed to be true, may be associated with the fact that the star formation can be more easily sustained via cold stream accretion in "large-scale" high-density regions, preventing galaxies from permanent quenching. Finally, at z > 1.5, the quiescent fraction depends little on the local density, even though clustering shows that quiescent galaxies are in more massive halos. We argue that at high redshift the typical halo size falls below 10^(13)M⊙, where intrinsically the local density measurements are so varied that they do not trace the halo mass. Our results thus suggest that in the high-redshift universe, halo mass may be the key in quenching the star formation in galaxies, rather than the conventionally measured galaxy density.

Additional Information

© 2016 The American Astronomical Society. Received 2015 February 28; accepted 2015 November 2; published 2016 January 26. We thank the anonymous referee for constructive suggestions that significantly improved the clarity of this paper. We also thank C.-C. Lai for useful discussions. The work is supported by the Ministry of Science and Technology (MoST) in Taiwan under the grant MOST 103-2112-M-001-031-MY3. C.L. is supported by the ILP LABEX (ANR-10-LABX-63 and ANR- 11-IDEX-0004-02). The UltraVISTA data are based on data products from observations made with ESO Telescopes at the La Silla Paranal Observatory under ESO program ID 179.A-2005 and on data products produced by TERAPIX and the Cambridge Astronomy Survey Unit on behalf of the UltraVISTA consortium.

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Published - Lin_2016p97.pdf

Submitted - 1511.03734v2.pdf


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