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HELP: star formation as function of galaxy environmentwith Herschel

Authors :: Duivenvoorden, S.
Oliver, S.
Buat, V.
Darvish, B.
Efstathiou, A.
Farrah, D.
Griffin, M.
Hurley, P. D.
Ibar, E.
Jarvis, M.
Papadopoulos, A.
Sargent, M. T.
Scott, D.
Scudder, J. M.
Symeonidis, M.
Vaccari, M.
Viero, M. P.
Wang, L.
Publication Year :: 2016
Abstract: The Herschel Extragalactic Legacy Project (HELP) brings together a vast range of data from many astronomical observatories. Its main focus is on the Herschel data, which maps dust obscured star formation over 1300 deg$^2$. With this unprecedented combination of data sets, it is possible to investigate how the star formation vs stellar mass relation (main-sequence) of star-forming galaxies depends on environment. In this pilot study we explore this question between 0.1 < z < 3.2 using data in the COSMOS field. We estimate the local environment from a smoothed galaxy density field using the full photometric redshift probability distribution. We estimate star formation rates by stacking the SPIRE data from the Herschel Multi-tiered Extragalactic Survey (HerMES). Our analysis rules out the hypothesis that the main-sequence for star-forming systems is independent of environment at 1.5 < z < 2, while a simple model in which the mean specific star formation rate declines with increasing environmental density gives a better description. However, we cannot exclude a simple hypothesis in which the main-sequence for star-forming systems is independent of environment at z < 1.5 and z > 2. We also estimate the evolution of the star formation rate density in the COSMOS field and our results are consistent with previous measurements at z < 1.5 and z > 2 but we find a $1.4^{+0.3}_{-0.2}$ times higher peak value of the star formation rate density at $z \sim 1.9$.<br />Comment: 14 pages, 7 figures. MNRAS accepted