Linking bar- and interaction-driven molecular gas concentration with centrally-enhanced star formation in EDGE-CALIFA galaxies

TL;DR

This study investigates how bars and interactions in galaxies influence the concentration of molecular gas and central star formation, revealing that bars and mergers significantly enhance central star formation and gas concentration.

Contribution

It provides observational evidence linking bar-driven and interaction-driven gas inflow to centrally enhanced star formation in nearby galaxies, supported by comparison with hydrodynamic simulations.

Findings

Centrally enhanced star formation is prevalent in barred and merging galaxies.

Barred galaxies show similar features to simulated barred galaxy models.

Cold gas inflow via bars or interactions triggers central star formation rejuvenation.

Abstract

We study the spatially resolved star formation history and molecular gas distribution of 58 nearby galaxies, using integral field spectroscopy from the CALIFA survey and CO $J=1\rightarrow 0$ intensity mapping from the CARMA EDGE survey. We use the 4000 \AA\ break (D$_n$4000), the equivalent width of the H$\delta$ absorption line (EW H$\delta_A$), and the equivalent width of the H$\alpha$ emission line (EW H$\alpha$) to measure the recent star formation history (SFH) of these galaxies. We measure radial profiles of the three SFH indicators and molecular gas mass surface density, from which we measure the level of centrally enhanced star formation and the molecular gas concentration. When we separate our galaxies into categories of barred (17 galaxies), unbarred (24 galaxies), and merging/paired (17 galaxies) we find that the galaxies which have centrally-enhanced star formation (19/58) are either barred (13/19) or in mergers/pairs (6/19) with relatively high molecular gas concentrations. A comparison between our barred galaxies and a snapshot of a hydrodynamic $N$-body simulation of a barred galaxy shows that the current theory of bar formation and evolution can qualitatively reproduce the main features of the observed galaxies in our sample, including both the sharp decrease of stellar age in the galactic center and the gradual decrease of age with increasing distance from center. These findings provide substantial evidence for a picture in which cold gas is transported inward by a bar or tidal interaction, which leads to the growth and rejuvenation of star formation in the central region.