X-ray Deep: Studying the Universe in X-rays

Supermassive Black Holes(SMBH)

Our group also studies supermassive black hole accretion (also known as Active Galactic Nuclei or AGN), including highly obscured AGN like the Compton-thick AGN in the galaxy Arp 299 (Ptak et al. 2015) and AGN in galaxy group environments. Identification of such systems and measurement of the conditions of the circumnuclear obscuring material and the intrinsic luminosity of the AGN are important for understanding the growth of supermassive black holes (SMBH), since it is generally believed that this growth often takes place in galaxy mergers and is heavily obscured.

Image from NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) of colliding galaxies Arp 299. Image credit: NASA/JPL-Caltech/GSFC

Due the high energy emission generated by supermassive black hole accretion, by far the best direct diagnostic for strong AGN activity is nuclear X-ray emission. Compared to the optical, the X-ray regime offers the advantage that the nuclear emissions is not diluted by starlight from the host galaxy, while dust obscuration is very signicantly mitigated due to the higher, penetrating power of X-ray radiation.(Tzanavaris et al. 2013)

Different NuSTAR images of Arp 299, the red circles mark the Chandra positions. Note that A and B are the two galaxy nuclei involve in merger(Ptak et al. 2015).