Bars as seen by Herschel & Sloan

TL;DR

This study investigates how stellar bars influence gas distribution and star formation in galaxies, revealing that bars can either promote gas inflow or deplete gas, affecting star formation activity.

Contribution

It provides observational evidence linking bar morphology with gas and star formation suppression, supporting theories of bar-driven gas inflows and evolution.

Findings

Bars correlate with cold-gas distribution and star formation suppression.

Optical and infrared structures of bars are spatially aligned.

Old bars show depleted gas and star formation in their regions.

Abstract

We present an observational study of the effect of bars on the gas component and on the star formation properties of their host galaxies in a statistically significant sample of resolved objects, the $Herschel$ Reference Sample. The analysis of optical and far--infrared images allows us to identify a clear spatial correlation between stellar bars and the cold-gas distribution mapped by the warm dust emission. We find that the infrared counterparts of optically identified bars are either bar--like structures or dead central regions in which star formation is strongly suppressed. Similar morphologies are found in the distribution of star formation directly traced by H$\alpha$ maps. The sizes of such optical and infrared structures correlate remarkably well, hinting at a causal connection. In the light of previous observations and of theoretical investigations in the literature, we interpret our findings as further evidence of the scenario in which bars drive strong inflows toward their host nuclei: young bars are still in the process of perturbing the gas and star formation clearly delineates the shape of the bars; old bars on the contrary already removed any gas within their extents, carving a dead region of negligible star formation.