H-ATLAS/GAMA : quantifying the morphological evolution of the galaxy population using cosmic calorimetry
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Using results from the Herschel Astrophysical Terrahertz Large-Area Survey (H-ATLAS) and the Galaxy and Mass Assembly (GAMA) project, we show that, for galaxy masses above ≃ 108M⊙, 51 per cent of the stellar mass-density in the local Universe is in earlytype galaxies (ETGs; Sérsic n > 2.5) while 89 per cent of the rate of production of stellar mass-density is occurring in late-type galaxies (LTGs; Sérsic n <2.5). From this zeroredshift benchmark, we have used a calorimetric technique to quantify the importance of the morphological transformation of galaxies over the history of the Universe. The extragalactic background radiation contains all the energy generated by nuclear fusion in stars since the big bang. By resolving this background radiation into individual galaxies using the deepest farinfrared survey with the Herschel Space Observatory and a deep near-infrared/optical survey with the Hubble Space Telescope (HST), and using measurements of the Sérsic index of these galaxies derived from the HST images, we estimate that ≃ 83 per cent of the stellarmass-density formed over the history of the Universe occurred in LTGs. The difference between this value and the fraction of the stellar mass-density that is in LTGs today implies there must have been a major transformation of LTGs into ETGs after the formation of most of the stars.
Eales , S , Fullard , A , Allen , M , Smith , M W L , Baldry , I , Bourne , N , Clark , C J R , Driver , S P , Dunne , L , Dye , S , Graham , A W , Ibar , E , Hopkins , A , Ivison , R , Kelvin , L S , Maddox , S , Maraston , C , Robotham , A S G , Smith , D , Taylor , E N , Valiante , E , Van Der Werf , P , Baes , M , Brough , S , Clements , D , Cooray , A , Gomez , H , Loveday , J , Phillipps , S , Scott , D & Serjeant , S 2015 , ' H-ATLAS/GAMA : quantifying the morphological evolution of the galaxy population using cosmic calorimetry ' Monthly Notices of the Royal Astronomical Society , vol 452 , no. 4 , pp. 3489-3507 . DOI: 10.1093/mnras/stv1300
Monthly Notices of the Royal Astronomical Society
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society. © 2015 The Authors, Published by Oxford University Press on behalf of the Royal Astronomical Society
We thank the STFC (UK) and the ARC (Australia) for financial support. LD, RI and SM acknowlege support from the European Research Council (ERC) in the form of the Advanced Investigator Program, 321302, COSMICISM. The H-ATLAS is a project with Herschel, which is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. Date of Acceptance: 09/06/2015