In Search of AGN in Starburst Galaxies with NuSTAR
Abstract
The coeval growth of supermassive black holes (SMBH) and their stellar halo hosts provides evidence that star formation and AGN activity must be closely associated, but it is not clear to what extent they must always be coordinated. A prime test of this coordination is the search for AGN activity in starburst galaxies, which by definition have high star-formation rates but whose SMBH can be illusive due to low luminosities and obscuration. NuSTAR offers a unique opportunity to detect AGN activity in starbursts because of its high-sensitivity X-ray imaging above 10 keV. We present the preliminary results of searching for X-ray emission in the starburst galaxies in the NuSTAR starburst program. To date three starbursts have been observed, Arp 299, M83, and NGC 253. Of these, only the nucleus of the western galaxy in the Arp 299 pair has been detected strongly above 20 keV, suggesting that this is the only galaxy harboring an obscured AGN. Evidence from combined Chandra and NuSTAR monitoring indicate that the SMBH in NGC 253 was nearly dormant in 2012 (L/LEdd < 10^-4); however, Chandra data from 2003 indicates that a low-luminosity AGN may have been more active a decade ago. The AGN in the western nucleus of Arp 299 is marginally Compton-thick (N_H ~ 2 x 10^24 cm^2) and also exhibits neutral Fe-K emission. We will discuss the implications of these results as well as prospects for detecting AGN in the remainder of the NuSTAR starburst sample.
- Publication:
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American Astronomical Society Meeting Abstracts #223
- Pub Date:
- January 2014
- Bibcode:
- 2014AAS...22343816P