Our Lunch Talk of this week will be given by Guangwen Chen(陈广文) at 11:00AM Thursday(May. 9th) in the 19th-floor Observatory Hall (天文台报告厅).

The title of the talk is "Mass-dependent Inside-out Quenching in Nearby Galaxies".

Abstract:

We present a study on the radial gradients of D4000 (∇D4000) of nearby galaxies (0.01 < z < 0.15) using a large sample of ∼ 4000 galaxies and integral field Spectroscopic observations from the Mapping Nearby Galaxies at the Apache Point Observatory (MaNGA) survey. We derive the D4000 gradients on the galaxy disk by linear fitting to the radial profiles and classify the types of star formation into ‘inside- out’, ‘flat’ and ‘outside-in’. We investigate the correlation of D4000 gradients with galaxy stellar mass and find that more massive galaxies own smaller D4000 gradients for a given specific star formation rate (sSFR). The star formation in galaxies systematically evolves from ‘outside-in’ or ‘flat’ star forming into inside-out quenching exhibited on the sSFR-∇D4000 plane. Moreover, the mass-dependent inside-out quenching scenario still holds in different structural properties (i.e., bulge-to-total light ratio (B/T), S ́ersic index and compactness) or environments (i.e., halo mass, local overdensity and tidal strength parameter). We normalize the effects of galaxy stellar mass on the radial gradients of D4000 and find that there is no obvious correlation of D4000 gradients with structural properties and environmental parameters, which implies that galaxy stellar mass dominates the types of star formation quenching. In addition, we find that the scenario still exists even after we minimize the influence of the bulge component. Therefore, the effect of galaxy stellar mass on the inside-out quenching is probably not due to the growth of bulge but correlated to the disk evolution.

Guangwen Chen is a PhD student of our department.