P-MaNGA: GRADIENTS IN RECENT STAR FORMATION HISTORIES AS DIAGNOSTICS FOR GALAXY GROWTH AND DEATH

Abstract

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 4000Å-break (D n (4000)), Hδ absorption (EW(Hδ A )) 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 D n (4000) measured in the central spaxel of each datacube exceeds 1.6. For each spaxel we generate both 2D maps and radial profiles of D n (4000), EW(Hδ A ) 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 D n (4000) decreases, while both EW(Hδ A ) 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 outwards as it moves to the red sequence.

SDSS IV MaNGA: Dependence of Global and Spatially Resolved SFR–M∗ Relations on Galaxy Properties

“…Such turnover also indicates the inside-out quenching of galaxies. The quenching process is beyond the scope of the present paper, but is of major importance in the context of galaxy evolution (e.g., Li et al 2015;González Delgado et al 2016;Belfiore et al 2017;Lin et al 2017;Spindler et al 2017;Ellison et al 2018).…”

SDSS-IV MaNGA-resolved Star Formation and Molecular Gas Properties of Green Valley Galaxies: A First Look with ALMA and MaNGA

“…If "nature" processes dominate, galaxies would be expected to grow, evolve, and die inside-out (White & Frenk 1991;Mo et al 1998). Recent IFU observations demonstrate that many nearby spiral galaxies show negative gradients in stellar ages and metallicities, supporting this inside-out picture (González Delgado et al 2014;Sánchez-Blázquez et al 2014;Li et al 2015;Belfiore et al 2017;Goddard et al 2017). On the other hand, if "nurture" dominates galaxy evolution, external processes such as ram-pressure stripping (Gunn & Gott 1972), high speed galaxy encounters (Moore et al 1996), galaxy mergers (Mihos & Hernquist 1994), and "strangulation" (Larson et al 1980;Balogh et al 2000;Peng et al 2015) are responsible for quenching.…”

THE DATA REDUCTION PIPELINE FOR THE SDSS-IV MaNGA IFU GALAXY SURVEY

“…As a part of the fourth generation of the Sloan Digital Sky Survey (SDSS-IV), the MaNGA project bundles single fibers from the Baryon Oscillation Spectroscopic Survey (BOSS) spectrograph (Smee et al 2013) into integral-field units (IFUs); over the six-year lifetime of the survey (2014-2020) MaNGA will obtain spatially resolved optical+NIR spectroscopy of 10,000 galaxies at redshifts z∼0.02-0.1. In addition to providing insight into the resolved structure of stellar populations, galactic winds, and dynamical evolution in the local universe (e.g., Belfiore et al 2015;Li et al 2015;Wilkinson et al 2015), the MaNGA data set will be an invaluable legacy product with which to help understand galaxies in the distant universe. As next-generation facilities come online in the final years of the MaNGA survey, IFU spectrographs such as TMT/IRIS Wright et al 2014), James Webb Space Telescope (JWST)/NIRSPEC (Closs et al 2008;Birkmann et al 2014), and JWST/MIRI-MRS (Wells et al 2015) will trace the crucial rest-optical bandpass in galaxies out to redshift z∼10 and beyond.…”