SDSS-IV MaNGA: Inside-out versus Outside-in Quenching of Galaxies in Different Local Environments

The large Integral Field Spectroscopy surveys have allowed the classification of ionizing sources of emission lines on sub-kiloparsec scales. In this work, we define two non-parametric parameters, quiescence (F _q ) and its concentration (C _q ), to quantify the strength and the spatial distribution of the quenched areas, respectively, traced by the LI(N)ER regions with low EW(Hα). With these two measurements, we classify MaNGA galaxies into inside-out and outside-in quenching types according to their locations on the F _q versus C _q plane and we measure the fraction of inside-out (outside-in) quenching galaxies as a function of halo mass. We find that the fraction of galaxies showing inside-out quenching increases with halo mass, irrespective of stellar mass or galaxy type (satellites versus centrals). In addition, high-stellar-mass galaxies exhibit a greater fraction of inside-out quenching compared to low-stellar-mass ones in all environments. In contrast, the fraction of outside-in quenching does not depend on halo mass. Our results suggest that morphological quenching may be responsible for the inside-out quenching seen in all environments. On the other hand, the flat dependence of the outside-in quenching on halo mass could be a mixed result of ram pressure stripping and galaxy mergers. Nevertheless, for a given environment and stellar mass, the fraction of inside-out quenching is systematically greater than that of outside-in quenching, suggesting that inside-out quenching is the dominant quenching mode in all environments.