Morphology rather than environment drives the SFR-Mass relation in the local universe

TL;DR

This study shows that in the local universe, galaxy morphology and local interactions primarily influence the star formation rate-stellar mass relation more than the large-scale environment.

Contribution

It provides a detailed analysis of how galaxy morphology and various environmental factors affect the SFR-M_star relation in the local universe, highlighting the dominant role of morphology.

Findings

SFR-M_star relation is environment-independent above certain mass and SSFR thresholds.

Galaxies in less dense environments have higher SFR at fixed mass.

Morphological type strongly influences SFR and SSFR at fixed stellar mass.

Abstract

Exploiting a sample of 680 star-forming galaxies from the Padova-Millennium GalaxyGroup Catalog (PM2GC) (Calvi et al. 2011) in the range 0.038<z<0.104, we present a detailed analysis of the Star Formation Rate (SFR)-stellar mass (M_star) and specific SFR(SSFR)-M_star relations as a function of environment. We adopt three different parameterizations of environment, to probe different scales. We consider separately 1) galaxies in groups, binary and single systems, defined in terms of a Friends-of-Friends algorithm, 2) galaxies located at different projected local densities, 3) galaxies in haloes of different mass. Overall, above logM_ast/M_sun>10.25 and SSFR>10^{-12} yr^{-1}, the SFR-M_ast and SSFR-M_ast relations do not depend on environment, when the global environment is used, while when the halo mass is considered, high mass haloes might have a systematically lower (S)SFR-M_ast relation. Finally, when local densities are exploited, at any given mass galaxies in less dense environments have systematically higher values of SFR. All the relations are characterized by a large scatter ({\sigma}~0.6), which is dueto the coexistence of galaxies of different morphological types. Indeed, at any given mass, late-types are characterized by systematically higher values of SFR and SSFR than S0s and ellipticals. Galaxies of the same morphology show similar trends in all the environments, but their incidence strongly depends on environment and on the environmental parametrization adopted, with late-types generally becoming less common in denser environments, contrasted by the increase of ellipticals and/or S0s. Our results suggest that in the local universe morphology and local interactions, probed by the local density parameterization, have dominant roles in driving the characteristics of the SFR-M_ast relation.