Galaxy and Mass Assembly (GAMA): variation in galaxy structure across the green valley

: Kelvin LS, Bremer MN, Phillipps S, James PA, Davies LJM, De Propris R, Moffett AJ, Percival SM, Baldry IK, Collins CA, Alpaslan M, Bland-Hawthorn J, Brough S, Cluver M, Driver SP, Hashemizadeh A, Holwerda BW, Laine J, Lara-Lopez MA, Liske J, Maciejewski W, Napolitano NR, Penny SJ, Popescu CC, Sansom AE, Sutherland W, Taylor EN, Kampen E, Wang L

Publisher: OXFORD UNIV PRESS

: 2018

Monthly Notices of the Royal Astronomical Society

: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

: MON NOT R ASTRON SOC

: 477

: 3

: 4116

: 4130

: 15

: 0035-8711

: 1365-2966

DOI: https://doi.org/10.1093/mnras/sty933

: https://academic.oup.com/mnras/article/477/3/4116/4970787#116726248

Using a sample of 472 local Universe (z < 0.06) galaxies in the stellar mass range 10.25 < logM(star)/M-circle dot < 10.75, we explore the variation in galaxy structure as a function of morphology and galaxy colour. Our sample of galaxies is subdivided into red, green, and blue colour groups and into elliptical and non-elliptical (disk-type) morphologies. Using Kilo-Degree Survey (KiDS) and Visible and Infrared Survey Telescope for Astronomy (VISTA) Kilo-Degree Infrared Galaxy Survey (VIKING) derived postage stamp images, a group of eight volunteers visually classified bars, rings, morphological lenses, tidal streams, shells, and signs of merger activity for all systems. We find a significant surplus of rings (2.3 sigma) and lenses (2.9 sigma) in disk-type galaxies as they transition across the green valley. Combined, this implies a joint ring/lens green valley surplus significance of 3.3 sigma relative to equivalent disk-types within either the blue cloud or the red sequence. We recover a bar fraction of similar to 44 per cent which remains flat with colour, however, we find that the presence of a bar acts to modulate the incidence of rings and (to a lesser extent) lenses, with rings in barred disk-type galaxies more common by similar to 20-30 percentage points relative to their unbarred counterparts, regardless of colour. Additionally, green valley disk-type galaxies with a bar exhibit a significant 3.0 sigma surplus of lenses relative to their blue/red analogues. The existence of such structures rules out violent transformative events as the primary end-of-life evolutionary mechanism, with a more passive scenario the favoured candidate for the majority of galaxies rapidly transitioning across the green valley.