Galaxy and Mass Assembly (GAMA): The environmental dependence of the galaxy main sequence

¹ SRON Netherlands Institute for Space Research, Landleven 12, 9747 AD, Groningen, The Netherlands
e-mail: l.wang@sron.nl
² Kapteyn Astronomical Institute, University of Groningen, Postbus 800, 9700 AV, Groningen, The Netherlands
³ ICC & CEA, Department of Physics, Durham University, Durham, DH1 3LE UK
⁴ School of Physics, University of New South Wales, NSW 2052 Australia
⁵ School of Physics and Astronomy, Monash University, VIC 3800, Australia
⁶ Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT 2611, Australia
⁷ International Centre for Radio Astronomy Research (ICRAR), University of Western Australia, Crawley, WA 6009, Australia
⁸ Department of Physics and Astronomy, 102 Natural Science Building, University of Louisville, Louisville, KY 40292 USA
⁹ Australian Astronomical Observatory, 105 Delhi Rd, North Ryde, NSW 2113, Australia
¹⁰ Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen, Denmark
¹¹ Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany
¹² Astronomy Centre, University of Sussex, Falmer, Brighton BN1 9QH, UK
¹³ Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
¹⁴ ESA/ESTEC SCI-S, Keplerlaan 1, 2201 AZ, Noordwijk, The Netherlands
¹⁵ Jeremiah Horrocks Institute, University of Central Lancashire, Preston PR1 2HE, UK
¹⁶ The Astronomical Institute of the Romanian Academy, Str. Cutitul de Argint 5, Bucharest, Romania
¹⁷ Argelander-Institut für Astronomie, Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany

Received: 24 January 2018
Accepted: 22 February 2018

Abstract

Aims: We aim to investigate if the environment (characterised by the host dark matter halo mass) plays any role in shaping the galaxy star formation main sequence (MS).

Methods: The Galaxy and Mass Assembly project (GAMA) combines a spectroscopic survey with photometric information in 21 bands from the far-ultraviolet (FUV) to the far-infrared (FIR). Stellar masses and dust-corrected star-formation rates (SFR) are derived from spectral energy distribution (SED) modelling using MAGPHYS. We use the GAMA galaxy group catalogue to examine the variation of the fraction of star-forming galaxies (SFG) and properties of the MS with respect to the environment.

Results: We examine the environmental dependence for stellar mass selected samples without preselecting star-forming galaxies and study any dependence on the host halo mass separately for centrals and satellites out to z ∼ 0.3. We find the SFR distribution at fixed stellar mass can be described by the combination of two Gaussians (referred to as the star-forming Gaussian and the quiescent Gaussian). Using the observed bimodality to define SFG, we investigate how the fraction of SFG F(SFG) and properties of the MS change with environment. For centrals, the position of the MS is similar to the field but with a larger scatter. No significant dependence on halo mass is observed. For satellites, the position of the MS is almost always lower (by ∼0.2 dex) compared to the field and the width is almost always larger. F(SFG) is similar between centrals (in different halo mass bins) and field galaxies. However, for satellites F(SFG) decreases with increasing halo mass and this dependence is stronger towards lower redshift.