7 years of successful INTEGRAL operations will be celebrated
in Otranto (Italy), between 13th-17th October when astronomers
meet to discuss "The Extreme Sky"
http://www.iasf-roma.inaf.it/extremesky2009/ .
During this occasion, the "state-of-the-art" of the high energy
sky will be discussed.
INTEGRAL continues to expand our knowledge of the sky above 10 keV,
and the meeting will see the 4th IBIS/INTEGRAL catalog presented,
which contains 331 new sources when compared to the third catalog.
The image shows the sky distribution of new sources when
superimposed on the delta exposure, ie the increase in exposure
since the third catalog. Of these new sources, around 120 are
associated with extragalactic sources (green circles), while only
about 25 are associated with known Galactic sources, and the
remainder are so far unidentified (red crosses).
The new sources can be seen to be closely following the exposure,
and still comprise a very significant Galactic component. The fact
that most of these are unidentified suggests that the INTEGRAL
observations along the Galactic Plane have reached a level of depth
where previous X-ray observations are no longer always able to provide
associations for the new sources.
When combined with the variability of the Galactic sources, this
indicates that further observations of the Galaxy will continue to
uncover new sources, and prompt follow-up of these new sources is of
critical importance to understand their true nature. However, it's
not quite that simple - many of the new sources found in or near the
Galactic Plane by INTEGRAL have been identified as extragalactic sources,
and INTEGRAL has proved particularly adept at uncovering this obscured
population.
