# Galaxy And Mass Assembly (GAMA): The Bright Void Galaxy Population in the Optical and Mid-IR

Penny, SJ and Brown, MJI and Pimbblet, KA and Cluver, ME and Croton, DJ and Owers, MS and Lange, R and Alpaslan, M and Baldry, IK and Bland-Hawthorn, J and Brough, S and Driver, SP and Holwerda, BW and Hopkins, AM and Jarrett, TH and Jones, DH and Kelvin, LS and Lara-Lopez, MA and Liske, J and Lopez-Sanchez, AR and Loveday, J and Meyer, M and Norberg, P and Robotham, ASG and Rodrigues, M (2015) Galaxy And Mass Assembly (GAMA): The Bright Void Galaxy Population in the Optical and Mid-IR. Monthly Notices of the Royal Astronomical Society, 453 (4). pp. 3519-3539. ISSN 0035-8711

## Abstract

We examine the properties of galaxies in the Galaxies and Mass Assembly (GAMA) survey located in voids with radii $>10~h^{-1}$ Mpc. Utilising the GAMA equatorial survey, 592 void galaxies are identified out to z~0.1 brighter than $M_{r} = -18.4$, our magnitude completeness limit. Using the $W_{\rm{H\alpha}}$ vs. [NII]/H$\alpha$ (WHAN) line strength diagnostic diagram, we classify their spectra as star forming, AGN, or dominated by old stellar populations. For objects more massive than $5\times10^{9}$ M$_{\odot}$, we identify a sample of 26 void galaxies with old stellar populations classed as passive and retired galaxies in the WHAN diagnostic diagram, else they lack any emission lines in their spectra. When matched to WISE mid-IR photometry, these passive and retired galaxies exhibit a range of mid-IR colour, with a number of void galaxies exhibiting [4.6]-[12] colours inconsistent with completely quenched stellar populations, with a similar spread in colour seen for a randomly drawn non-void comparison sample. We hypothesise that a number of these galaxies host obscured star formation, else they are star forming outside of their central regions targeted for single fibre spectroscopy. When matched to a randomly drawn sample of non-void galaxies, the void and non-void galaxies exhibit similar properties in terms of optical and mid-IR colour, morphology, and star formation activity, suggesting comparable mass assembly and quenching histories. A trend in mid-IR [4.6]-[12] colour is seen, such that both void and non-void galaxies with quenched/passive colours <1.5 typically have masses higher than $10^{10}$ M$_{\odot}$, where internally driven processes play an increasingly important role in galaxy evolution.

Item Type: Article This is a pre-copyedited, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The version of record MNRAS (November 11, 2015) 453 (4): 3519-3539 is available online at: http://dx.doi.org/10.1093/mnras/stv1926 astro-ph.GA; astro-ph.GA Q Science > QB Astronomy Astrophysics Research Institute Oxford University Press Author 26 Oct 2015 12:40 27 Nov 2015 12:54 10.1093/mnras/stv1926 http://researchonline.ljmu.ac.uk/id/eprint/2074