Galaxy And Mass Assembly (GAMA): extended intragroup light in a group at z=0.2 from deep Hyper Suprime-Cam images

Abstract

We present a pilot study to assess the potential of Hyper Suprime-Cam Public Data Release 2 (HSC-PDR2) images for the analysis of extended faint structures within groups of galaxies. We examine the intragroup light (IGL) of the group 400138 (M-dyn = 1.3 +/- 0.5 x 10(13) M-circle dot, z similar to 0.2) from the Galaxy And Mass Assembly (GAMA) survey using Hyper Suprime-Cam Subaru Strategic Program Public Data Release 2 (HSC-SSP PDR2) images in g, r, and i bands. We present the most extended IGL measurement to date, reaching down to mu(lim)(g) = 30.76 mag arcsec(-2) (3 sigma; 10 x 10 arcsec(2)) at a semimajor axis of 275 kpc. The IGL shows mean colour values of g - i = 0.92, g - r = 0.60, and r - i = 0.32 (+/- 0.01). The IGL stellar populations are younger (2-2.5 Gyr) and less metal rich ([Fe/H] similar to -0.4) than those of the host group galaxies. We find a range of IGL fractions as a function of total group luminosity of similar to 2-36 per cent depending on the definition of IGL, with larger fractions the bluer the observation wavelength. The early-type to late-type galaxy ratio suggests that 400138 is a more evolved group, dominated by early-type galaxies, and the IGL fraction agrees with that of other similarly evolved groups. These results are consistent with tidal stripping of the outer parts of Milky Way-like galaxies as the main driver of the IGL build-up. This is supported by the detection of substructure in the IGL towards the galaxy member 1660615 suggesting a recent interaction (<1 Gyr ago) of that galaxy with the core of the group.