SDSS IV MaNGA – metallicity and nitrogen abundance gradients in local galaxies

Abstract

We study the gas phase metallicity (O/H) and nitrogen abundance gradients traced by star forming regions in a representative sample of 550 nearby galaxies in the stellar mass range 10 9 − 10 11.5 M with resolved spectroscopic data from the SDSS-IV MaNGA survey. Using strong-line ratio diagnostics (R23 and O3N2 for metallicity and N2O2 for N/O) and referencing to the effective (half-light) radius (R e ), we find that the metallicity gradient steepens with stellar mass, lying roughly flat among galaxies with log(M /M ) = 9.0 but exhibiting slopes as steep as -0.14 dex R −1 e at log(M /M ) = 10.5 (using R23, but equivalent results are obtained using O3N2). At higher masses, these slopes remain typical in the outer regions of our sample (R > 1.5 R e ), but a flattening is observed in the central regions (R < 1 R e ). In the outer regions (R > 2.0 R e ) we detect a mild flattening of the metallicity gradient in stacked profiles, although with low significance. The N/O ratio gradient provides complementary constraints on the average chemical enrichment history. Unlike the oxygen abundance, the average N/O profiles do not flatten out in the central regions of massive galaxies. The metallicity and N/O profiles both depart significantly from an exponential form, suggesting a disconnect between chemical enrichment and stellar mass surface density on local scales. In the context of insideout growth of discs, our findings suggest that central regions of massive galaxies today have evolved to an equilibrium metallicity, while the nitrogen abundance continues to increase as a consequence of delayed secondary nucleosynthetic production.

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).…”

The shape of oxygen abundance profiles explored with MUSE: evidence for widespread deviations from single gradients

“…However, recently it has been found that some spiral galaxies show lower (higher) oxygen abundance val-ues in the inner (outer) regions than that expected according to the observed negative gradients. This results in a nearly flat distribution or even a drop towards the centre (Belley & Roy 1992;Rosales-Ortega et al 2011;Sánchez et al 2012bSánchez et al , 2014Sánchez-Menguiano et al 2016b;Zinchenko et al 2016), and an abundance flattening or even an increase in the outermost parts (Martin & Roy 1995;Vilchez & Esteban 1996;Roy & Walsh 1997;van Zee et al 1998;Rosales-Ortega et al 2011;Bresolin et al 2012;Marino et al 2012;López-Sánchez et al 2015;Sánchez-Menguiano et al 2016b;Belfiore et al 2017).…”

“…Peimbert 1979;Shaver et al 1983;Vila-Costas & Edmunds 1992;Zaritsky et al 1994;Kennicutt et al 2003;Pilyugin et al 2004;Bresolin et al 2009b;Rosales-Ortega et al 2011;Marino et al 2012;Sánchez et al 2012b;Pilyugin et al 2014;Sánchez et al 2014;Sánchez-Menguiano et al 2016b;Zinchenko et al 2016;Belfiore et al 2017). However, recently it has been found that some spiral galaxies show lower (higher) oxygen abundance val-ues in the inner (outer) regions than that expected according to the observed negative gradients.…”

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.…”