Tidal Disruption Event Host Galaxies in the Context of the Local Galaxy Population

TL;DR

This study analyzes the properties of TDE host galaxies within a large galaxy catalog, revealing they have distinctive features such as higher nuclear stellar density and specific photometric traits, which could aid in identifying future TDEs.

Contribution

The paper demonstrates that TDE host galaxies have unique photometric and structural properties that are not fully explained by selection effects, highlighting their distinct nuclear environments.

Findings

TDE hosts are often in the green valley between star-forming and passive galaxies.

They have bluer bulge colors and higher Sersic indices than similar galaxies.

TDE hosts are more centrally concentrated with higher nuclear stellar densities.

Abstract

We study the properties of tidal disruption event (TDE) host galaxies in the context of a catalog of ~500,000 galaxies from the Sloan Digital Sky Survey. We explore whether selection effects can account for the overrepresentation of TDEs in E+A/post-starburst galaxies by creating matched galaxy samples. Accounting for possible selection effects due to black hole (BH) mass, redshift completeness, strong AGN presence, bulge colors, and surface brightness can reduce the apparent overrepresentation of TDEs in E+A host galaxies by a factor of ~4 (from ~$\times$100-190 to ~$\times$25-48), but cannot fully explain the preference. We find that TDE host galaxies have atypical photometric properties compared to similar, "typical" galaxies. In particular, TDE host galaxies tend to live in or near the "green valley" between star-forming and passive galaxies, and have bluer bulge colors ($\Delta (g-r) \approx 0.3$ mag), lower half-light surface brightnesses (by ~1 mag/arcsec$^2$), higher Sersic indices ($\Delta n_{\rm g} \approx 3$), and higher bulge-to-total-light ratios ($\Delta B/T \approx 0.5$) than galaxies with matched BH masses. We find that TDE host galaxies appear more centrally concentrated and that all have high galaxy Sersic indices and $B/T$ fractions---on average in the top 10% of galaxies of the same BH mass---suggesting a higher nuclear stellar density. We identify a region in Sersic index and BH mass parameter space that contains ~2% of our reference catalog galaxies but $\ge\!60\%$ of TDE host galaxies. The unique photometric properties of TDE host galaxies may be useful for selecting candidate TDEs for spectroscopic follow-up observations in large transient surveys.