Discovery of Nuclear X-ray Sources in SINGS Galaxies

TL;DR

This study uses Chandra X-ray data to identify nuclear activity in 62 nearby galaxies, revealing a higher AGN fraction than optical methods and suggesting galaxy mass influences black hole accretion rates.

Contribution

It demonstrates the effectiveness of X-ray observations in detecting hidden AGNs and provides new insights into the relationship between galaxy properties and nuclear activity.

Findings

60% of galaxies host AGNs, higher than optical surveys.

Nuclear X-ray sources are more common in earlier type galaxies.

AGN luminosity correlates with 3.6 micron luminosity, not 24 micron.

Abstract

We present the results of a search for nuclear X-ray activity in nearby galaxies using Chandra archival data in a sample of 62 galaxies from the Spitzer Infrared Nearby Galaxy Survey (SINGS). We detect 37 nuclear X-ray sources; seven of these are new detections. Most of the nuclear X-ray sources are likely to be AGNs. The fraction of galaxies hosting AGNs is thus about 60%, much higher than that found with optical searches, and demonstrates the efficacy of X-ray observations to find hidden AGNs in optically normal galaxies. We find that the nuclear X-ray sources are preferentially present in earlier type galaxies. Unlike what is observed at high redshift, we do not find a strong correlation between the AGN luminosity and the 24 micron luminosity of the host galaxy; we find a strong correlation with the 3.6 micron luminosity instead. This suggests that at the present epoch the accretion rate depends on the total mass of the galaxy, as perhaps does the black hole mass.