IGR J13042-1020: a massive black hole in spiral galaxy NGC 4939
INTEGRAL has discovered hundreds of new sources in the hard X-ray
range (>20 keV). Most of these sources have an unknown nature, and
multi-wavelength studies are necessary to try to classify them.
This can be a challenging task since different diagnostics can lead
to different classifications for the source type.
Occasionally, however, the sky is quite cooperative. This image
shows one example of a source discovered in hard X-rays by INTEGRAL,
IGR J13042-1020. Multi-wavelength follow-up observations with the
Swift satellite allowed the X-ray, UV, and optical counterparts to
be identified. The image is a composite of the Swift/UVM2,UVW1,UVW2
observations; the small red circle and the large white circle
represent the Swift/XRT soft X-ray and IBIS/ISGRI hard X-ray position,
respectively. The UV/optical counterpart is the nucleus of the galaxy
NGC 4939 which permits an easy identification of IGR J13042-1020 as an
active galactic nucleus (AGN). The galaxy is located 140 million
light-years away (at a redshift of z~0.01).
Examination of the X-ray spectra further enabled us to designate the
source as a probable Type 2 Seyfert AGN. These objects are powered by
accretion of large amounts of material onto a central supermassive black
hole. One of the characteristics of type 2 AGN is the high absorption that
can shield a significant amount of the soft X-rays, and hinders or prevents
their discovery through scanning. By observing at higher energies that are
unaffected by absorption, INTEGRAL has discovered dozens of such systems.
Related links:
Swift follow-up observations of 13 INTEGRAL sources
J. Rodriguez, J.A. Tomsick, A. Bodaghee
Accepted in A&A, 2010,
arXiv:1003.3741
