Optically dim counterparts of hard X-ray selected AGNs
Abstract
We present near-IR photometry and imaging observations of a small sample of sources identified in the BeppoSAX 5-10 keV survey (HELLAS) which resolves ~ 20-30% of the X-ray background at these energies. The near-IR data are combined with optical spectra and photometry. Only 40% of the sources in our sample have the blue, power law continuum typical of color-selected QSOs. The remaining 60% are dominated by a galactic component which, on the basis of the continuum colors and shape, have ages ranging from 109 to 1010 years. The images show that the blue QSOs are pointlike at our angular resolution, while all the other sources are extended, consistent with their spectral appearance and low redshift. Since down to R = 20 only about two thirds of the HELLAS sources have a counterpart, the preliminary HELLAS census comprises in roughly equal parts: i) blue QSOs (mostly at high redshifts); ii) optically dim, galaxy-dominated active nuclei (mostly at modest redshifts); and iii) empty fields (possibly highly absorbed QSOs at high redshifts). Based on observations made with the Italian Telescopio Nazionale Galileo (TNG) operated on the island of La Palma by the Centro Galileo Galilei of the CNAA (Consorzio Nazionale per l'Astronomia e l'Astrofisica) at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- March 2000
- DOI:
- 10.48550/arXiv.astro-ph/0002447
- arXiv:
- arXiv:astro-ph/0002447
- Bibcode:
- 2000A&A...355L..47M
- Keywords:
-
- X-RAYS: GALAXIES;
- INFRARED: GALAXIES;
- GALAXIES: ACTIVE;
- COSMOLOGY: DIFFUSE RADIATION;
- Astrophysics
- E-Print:
- 5 pages, 2 figures, to appear in A&