New Paper Published: Only flat bars are actively forming stars!

Wednesday, May 15, 2019

As part of the CARS survey PhD student Justus Neuman from the Leibniz-Intstitute for Astrophysics in Potsdam systematically studied the star formation along bars in the AGN host galaxies, which has been accepted to be published in the journal A&A. In this work Justus compared the amount of SFR along the bar as traced using the optical Halpha line with morphological properties of the bar as measured through detailed 2D photometric decompositions of the galaxy images. He found that the sample appears bimodal clearly separating into star-forming and non-star-forming bars. In comparison with the surface brightness of the bar, Justus found that only the bars with very flat surface brightness profiles were forming stars. The lack of star formation in less flat bars may be connected also to the presence of inner rings in those galaxies.

Bars are also thought to be one mechanisms through which gas is funneled towards the center of the galaxy to fuel AGN at their centers. However, no correlation between the star formation rate along the bar with AGN bolometric luminosity was found. Whether such a non-correlation is caused by time-scale difference or implies an insignificant link between bars and AGN fueling remains to be understood in the future.

Justus work is the first step in characterizing the star formation properties of AGN host galaxies. More work on AGN outflows and potential impact on the star formation will be studied in future CARS publications in more detail.

Comparison between star formation rate of the bar with the Sersic parameter n which indicates the steepness/flatness of the bars surface brightness profile. The observations show a clear bimodal distribution in SFR and Sersic parameter which highlights that only bars with a very flat surface brightness profile are actively forming stars.