Optical/Near-IR Observations of a Deep Chandra Field
Around the Blazar 1156+295
P.S. Coppi R. Guzman S. Zepf T. Maccarone J.H. Woo H. Krawczynski B. Roscherr (Yale University) D. Garcia (UC Madrid) M. Ruiz-Prieto (Canarias) G. Madesjki (SLAC)
Abstract
We present follow-up observations of a 60 ksec
ACIS-I Chandra exposure centered on the gamma-ray
blazar 1156+295. We have imaged the central 100 square
arc minutes of the field in optical down to
and the central 48 square arc
minutes in K down to
We present and analyze
the X-ray spectra, colors, and population statistics of the
serendipitous sources found in the field. Our results
are largely consistent
with those of Mushotzky et al. (2000) and the Chandra Deep Fields.
However, we find that a somewhat larger fraction (
)
of our X-ray sources have no optical counterparts down to
Several (
)
of the objects
with no optical identification, however, are detected in K at the level
These objects could be very high redshift (z>5)
ojbects, or lower redshift (1<z<3) EROs. The X-ray spectra of
the objects with R-K>5 are typically very hard. The optical
colors for most of the Chandra sources are blue (B-R<1),
indicating some level of unobscured starburst or AGN activity.
At faint X-ray flux levels (
), a new class of optically bright, red sources
appears. Preliminary spectroscopy suggests that these are examples
of the nearby "normal" galaxies found in other fields. The X-ray
spectra of these sources are also typically hard. As an example
of possible cosmic variance, however, we find that the fraction of
optically bright sources with X-ray counterparts is significantly
lower than that found by Barger et al. 2000 (
vs.
).
An accurate determination of the average value of this fraction
is crucial for AGN lifetime and black hole accretion
efficiency arguments.
CATEGORY: EXTRAGALACTIC DIFFUSE EMISSION AND SURVEYS