P-MaNGA: gradients in recent star formation histories as diagnostics for galaxy growth and death

Li, Cheng and Wang, Enci and Lin, Lin and Bershady, Matthew A. and Bundy, Kevin and Tremonti, Christy and Xiao, Ting and Yan, Renbin and Bizyaev, Dmitry and Blanton, Michael R. and Cales, Sabrina and Cherinka, Brian and Cheung, Edmond and Drory, Niv and Emsellem, Eric and Fu, Hai and Gelfland, Joseph and Law, David R. and Lin, Lihwai and MacDonald, Nick and Maraston, Claudia and Masters, Karen and Merrifield, Michael R. and Pan, Kaike and Sanchez, Sebastian F. and Schneider, Donald P. and Thomas, Daniel and Wake, David A. and Wang, Lixin and Weijmans, Anne-Marie and Wilkinson, David and Yoachim, Peter and Zhang, Kai and Zheng, Tiantian (2015) P-MaNGA: gradients in recent star formation histories as diagnostics for galaxy growth and death. Astrophysical Journal, 804 (2). 125/1-125/19. ISSN 1538-4357

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We present an analysis of the data produced by the MaNGA prototype run (P-MaNGA), aiming to test how the radial gradients in recent star formation histories, as indicated by the 4000 ??break (Dn(4000)), H? absorption (EW(H?A)), and H? emission (EW(H?)) indices, can be useful for understanding disk growth and star formation cessation in local galaxies. We classify 12 galaxies observed on two P-MaNGA plates as either centrally quiescent (CQ) or centrally star-forming (CSF), according to whether Dn(4000) measured in the central spaxel of each datacube exceeds 1.6. For each spaxel we generate both 2D maps and radial profiles of Dn(4000), EW(H?A), and EW(H?). We find that CSF galaxies generally show very weak or no radial variation in these diagnostics. In contrast, CQ galaxies present significant radial gradients, in the sense that Dn(4000) decreases, while both EW(H?A) and EW(H?) increase from the galactic center outward. The outer regions of the galaxies show greater scatter on diagrams relating the three parameters than their central parts. In particular, the clear separation between centrally measured quiescent and star-forming galaxies in these diagnostic planes is largely filled in by the outer parts of galaxies whose global colors place them in the green valley, supporting the idea that the green valley represents a transition between blue-cloud and red-sequence phases, at least in our small sample. These results are consistent with a picture in which the cessation of star formation propagates from the center of a galaxy outward?as it moves to the red sequence.

Item Type: Article
Additional Information: Copyright 2015 The American Astronomical Society
Keywords: Galaxies: evolution, Galaxies: formation, Galaxies: general, Galaxies: stellar content, Methods: observational, Surveys
Schools/Departments: University of Nottingham UK Campus > Faculty of Science > School of Physics and Astronomy
Identification Number: https://doi.org/10.1088/0004-637X/804/2/125
Depositing User: Merrifield, Michael
Date Deposited: 09 Sep 2016 08:47
Last Modified: 21 Sep 2016 02:40
URI: http://eprints.nottingham.ac.uk/id/eprint/36387

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