HELP star : star formation as a function of galaxy environment with Herschel

S. Duivenvoorden , S. Oliver , V. Buat (1) , B. Darvish , A. Efstathiou , D. Farrah (2) , M. Griffin (3) , P. D. Hurley , E. Ibar (4) , M. Jarvis , A. Papadopoulos (5) , M. T. Sargent (6) , D. Scott , J. M. Scudder , M. Symeonidis (7) , M. Vaccari (8) , M. P. Viero , L. Wang

1 LAM - Laboratoire d'Astrophysique de Marseille
2 Department of Physics [Blacksburg]
3 School of Physics and Astronomy [Cardiff]
4 AUTRES
5 inconnu
6 AIM (UMR7158 / UMR_E_9005 / UM_112) - Astrophysique Interprétation Modélisation
7 Space Science & Technology Department
8 Sans affiliation

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 versus stellar mass relation (main sequence) of star-forming galaxies depends on environment. In this pilot study, we explore this question within 0.1 \textless z \textless 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. Our analysis rules out the hypothesis that the main sequence for star-forming systems is independent of environment at 1.5 \textless z \textless 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 \textless 1.5 and z \textgreater 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 \textless 1.5 and z \textgreater 2 but we find a 1.4(-0.2)(+0.3) times higher peak value of the star formation rate density at z similar to 1.9.

Domaines: Astrophysique [astro-ph]; Planète et Univers [physics]

S. Duivenvoorden, S. Oliver, V. Buat, B. Darvish, A. Efstathiou, et al.. HELP star : star formation as a function of galaxy environment with Herschel. Monthly Notices of the Royal Astronomical Society, 2016, 462 (1), pp.277--289. ⟨10.1093/mnras/stw1466⟩. ⟨hal-01440709⟩