The Chandra deep survey of the Hubble Deep Field-North area. II. Results from the Caltech Faint Field Galaxy Redshift Survey area

A deep X-ray survey of the Hubble Deep Field-North (HDF-N) and its environs is performed using data collected by the Advanced CCD Imaging Spectrometer (ACIS) on board the Chandra X-Ray Observatory. Currently a 221.9 ks exposu re is available, the deepest ever presented, and here we give results on X- ray sources located in the 8.'6 x 8.'7 area covered by the Caltech Faint Fi eld Galaxy Redshift Survey (the "Caltech area"). This area has (1) deep pho tometric coverage in several optical and near-infrared bands; (2) extensive coverage at radio, submillimeter, and mid-infrared wavelengths; and (3) so me of the deepest and most complete spectroscopic coverage ever obtained. I t is also where the X-ray data have the greatest sensitivity; the minimum d etectable fluxes in the 0.5-2 keV (soft) and 2-8 keV (hard) bands are appro ximate to1.3 x 10(-16) and approximate to6.5 x 10(-16) ergs cm(-2) s(-1), r espectively. More than approximate to 80% of the extragalactic X-ray background in the h ard band is resolved. The 82 Chandra sources detected in the Caltech area a re correlated with more than 25 multiwavelength source catalogs, and the re sults of these correlations as well as spectroscopic follow-up results obta ined with the Keck and Hobby-Eberly Telescopes are presented. All but nine of the Chandra sources are detected optically with R less than or similar t o 26.5. Redshifts are available for 39% of the Chandra sources, including 9 6% of the sources with R < 23; the redshift range is 0.1-3.5, with most sou rces having z < 1.5. Eight of the X-ray sources are located in the HDF-N it self, including two not previously reported. A population of X-ray faint, o ptically bright, nearby galaxies emerges at soft-band fluxes of less than o r similar to 3 x 10(-16) ergs cm(-2) s(-1). Our multiwavelength correlations have set the tightest constraints to date on the X-ray emission properties of mu Jy radio sources, mid-infrared sourc es detected by the Infrared Space Observatory (ISO), and very red (R - K-s > 5.0) objects. A total of 16 of the 67 1.4 GHz mu Jy sources in the Caltec h area are detected in the X-ray band, and the detection rates for starburs t-type and AGN-candidate mu Jy sources are comparable. Only two of the 17 r ed, optically faint (I > 25) mu Jy sources are detected in X-rays. While ma ny of the starburst-type mu Jy sources appear to contain obscured active ga lactic nuclei (AGNs), the Chandra data are consistent with the majority of the mu Jy radio sources being powered by star formation. A total of 11 of t he approximate to 100 ISO mid-infrared sources found in and near the HDF-N are detected in X-rays. In the HDF-N itself, where both the infrared covera ge and the X-ray coverage are deepest, it is notable that six of the eight Chandra sources are detected by ISO; most of these are known to be AGNs whe re the X-ray and infrared detections reveal both the direct and indirect ac cretion power being generated. The high X-ray-to-infrared matching rate bod es well for future sensitive infrared observations of faint X-ray sources. Four of the 33 very red objects that have been identified in the Caltech ar ea are detected in X-rays; these four are among our hardest Chandra sources , and we argue that they contain moderately luminous obscured AGNs. Overall , however, the small Chandra detection fraction suggests a relatively small AGN content in the optically selected very red object population. A stacki ng analysis of the very red objects not detected individually by Chandra yi elds a soft-band detection with an average soft-band X-ray flux of approxim ate to1.9 x 10(-17) ergs cm(-2) s(-1); the observed emission may be associa ted with the hot interstellar media of moderate-redshift elliptical galaxie s. Constraints on AGN candidates, extended X-ray sources, and Galactic objects in the Caltech area are also presented.