Black hole hunters tackle a cosmic conundrum Apr 20, 2015 Please Register or Log in to view the hidden image! A Hubble Space Telescope image shows the Henize 2-10 galaxy, with a hidden supermassive black hole at its center. Credit: NASA Dartmouth astrophysicists and their colleagues have not only proven that a supermassive black hole exists in a place where it isn't supposed to be, but in doing so have opened a new door to what things were like in the early universe. Henize 2-10 is a small irregular galaxy that is not too far away in astronomical terms—30 million light-years. "This is a dwarf starburst galaxy—a small galaxy with regions of very rapid star formation—about 10 percent of the size of our own Milky Way," says co-author Ryan Hickox, an assistant professor in Dartmouth's Department of Physics and Astronomy. "If you look at it, it's a blob, but it surprisingly harbors a central black hole." Read more at: http://phys.org/news/2015-04-black-hole-hunters-tackle-cosmic.html#jCp
http://arxiv.org/pdf/1504.03331v1.pdf ABSTRACT : We present an analysis of the X-ray spectrum and long-term variability of the nearby dwarf starburst galaxy Henize 2–10. Recent observations suggest that this galaxy hosts an actively accreting black hole with mass ˜106 M. The presence of an AGN in a low-mass starburst galaxy marks a new environment for active galactic nuclei (AGNs), with implications for the processes by which “seed” black holes may form in the early Universe. In this paper, we analyze four epochs of X-ray observations of Henize 2–10, to characterize the long-term behavior of its hard nuclear emission. We analyze observations with Chandra from 2001 and XMM-Newton from 2004 and 2011, as well as an earlier, less sensitive observation with ASCA from 1997. Based on detailed analysis of the source and background, we find that the hard (2–10 keV) flux of the putative AGN has decreased by approximately an order of magnitude between the 2001 Chandra observation and exposures with XMMNewton in 2004 and 2011. The observed variability confirms that the emission is due to a single source. It is unlikely that the variable flux is due to a supernova or ultraluminous X-ray source, based on the observed long-term behavior of the X-ray and radio emission, while the observed X-ray variability is consistent with the behavior of well-studied AGNs. Subject headings: galaxies: active — galaxies: dwarf — galaxies: evolution — galaxies: individual (Henize 2–10) — X-rays: galaxies
