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T. Miyaji, R.E. Griffiths (Carnegie Mellon U.)
We report the results of the fluctuation analysis on the off-source field from the Deepest Chandra Observations on the Chadra Deep Fields (North and South). The distribution of the counts in cells have been compared with the expectations from the Log N - Log S model to constrain the behavior of source number density down to a factor of several lower than the source-detection limit. Our results show that the number counts in the soft band (0.5-2 [keV]) continues to grow down to Sx=7 x 10-18 [erg s-1 cm-2], while the extrapolation of the AGN luminosity function should turn over at Sx<1 x 10-16 [erg s-1 cm-2]. This suggests the emergence of a new population, which is most likely to be from star-foration activities from galaxies. The faintest source counts indeed agree well with the predicted values from star forming galaxies by Ptak et al. (2001). We could only obtain loose constraints for the hard (2-10 keV) band source count below the detection limit and we found an upper limit of 10000 [srcs deg-2] at Sx= 2 x 10-16 [erg s-1 cm-2].
The author(s) of this abstract have provided an email address for comments about the abstract: miyaji@astro.phys.cmu.edu