NOAO >   Observing Info >   Approved Programs >   2001A-0083

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Proposal Information for 2001A-0083


PI: Ilaria Cagnoni, SAO, USA and SISSA, Italy, icagnoni@cfa.harvard.edu
Address: 60 Garden St., Cambridge, MA 02138, USA

CoI: Martin Elvis, SAO, USA
CoI: Dong-Woo Kim, SAO, USA
CoI: Fabrizio Nicastro, SAO, USA
CoI: Annalisa Celotti, SISSA, Italy

Title: Unveiling the mystery of ROSAT blank filed sources

Abstract: The \it ROSAT surveys contain a surprising number of ``blank field sources'' (BFS) i.e. bright X-ray sources (F_X>10^-13 cgs) with no optical counterpart on the Palomar Sky survey (O>21.5). The faintness of any optical counterpart means that BFS have extreme X-ray to optical ratios (F_X/F_V >60), incompatible with any known population. Without further constraints these sources might be: high z cluster of galaxies, isolated old neutron stars, reddened AGNs or `failed clusters'. The R and K band imaging we obtained show red (R-K>5) counterparts for 5 out of 16 BFS and a recent Chandra observation shows an extended nature for one of them. Could they be high redshift clusters of galaxies? Detection of cluster members can be obtained with deep IR imaging while the redshift can be estimated with good accuracy with the photometric redshift technique. Deep optical and IR imaging in needed for this. KPNO SQIID and PF Camera are particularly suited to obtain deep imaging in a reasonable time for the 16 BFS in our sample.


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NOAO >   Observing Info >   Approved Programs >   2001A-0083

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