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 Å break (Dn(4000)), Hδ absorption (EW(HδA)), and Hα emission (EW(Hα)) 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(HδA), and EW(Hα). 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(HδA) and EW(Hα) 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.
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C.L. acknowledges the support of the 100 Talents Program of Chinese Academy of Sciences (CAS). This work is supported by NSFC (11173045,11233005,11325314,11320101002), by the Strategic Priority Research Program "The Emergence of Cosmological Structures" of CAS (grant No. XDB09000000), and by World Premier International Research Center Initiative (WPI Initiative), MEXT, Japan. . . . Funding for SDSS-III and SDSS-IV has been provided by the Alfred P. Sloan Foundation and Participating Institutions. Additional funding for SDSS-III comes from the National Science Foundation and the U.S. Department of Energy Office of Science. Further information about both projects is available at www.sdss3.org.
SDSS is managed by the Astrophysical Research Consortium for the Participating Institutions in both collaborations. In SDSS-III these include the University of Arizona, the Brazilian Participation Group, Brookhaven National Laboratory, Carnegie Mellon University, University of Florida, the French Participation Group, the German Participation Group, Harvard University, the Instituto de Astrofisica de Canarias, the Michigan State/Notre Dame/JINA Participation Group, Johns Hopkins University, Lawrence Berkeley National Laboratory, Max Planck Institute for Astrophysics, Max Planck Institute for Extraterrestrial Physics, New Mexico State University, New York University, Ohio State University, Pennsylvania State University, University of Portsmouth, Princeton University, the Spanish Participation Group, University of Tokyo, University of Utah, Vanderbilt University, University of Virginia, University of Washington, and Yale University.
The Participating Institutions in SDSS-IV are Carnegie Mellon University, Colorado University, Boulder, Harvard-Smithsonian Center for Astrophysics Participation Group, Johns Hopkins University, Kavli Institute for the Physics and Mathematics of the universe, Max-Planck-Institut fuer Astrophysik (MPA Garching), Max-Planck-Institut fuer Extraterrestrische Physik (MPE), Max-Planck-Institut fuer Astronomie (MPIA Heidelberg), National Astronomical Observatory of China, New Mexico State University, New York University, The Ohio State University, Penn State University, Shanghai Astronomical Observatory, United Kingdom Participation Group, University of Portsmouth, University of Utah, University of Wisconsin, and Yale University.
We have made use of data from HyperLeda for our work.
Li, Cheng; Wang, Enci; Lin, Lin; Bershady, Matthew A.; Bundy, Kevin; Tremonti, Christy A.; Xiao, Ting; Yan, Renbin; Bizyaev, Dmitry; Blanton, Michael; Cales, Sabrina; Cherinka, Brian; Cheung, Edmond; Drory, Niv; Emsellem, Eric; Fu, Hai; Gelfand, Joseph; Law, David R.; Lin, Lahwai; MacDonald, Nick; Maraston, Claudia; Masters, Karen L.; Merrifield, Michael R.; Pan, Kaike; Sánchez, S. F.; Schneider, Donald P.; Thomas, Daniel; Wake, David; Wang, Lixin; Weijmans, Anne-Marie; Wilkinson, David; Yoachim, Peter; Zhang, Kai; and Zheng, Tiantian, "P-MaNGA: Gradients in Recent Star Formation Histories as Diagnostics for Galaxy Growth and Death" (2015). Physics and Astronomy Faculty Publications. 333.