Issue |
Astron. Astrophys. Suppl. Ser.
Volume 123, Number 1, May II 1997
|
|
---|---|---|
Page(s) | 103 - 114 | |
DOI | https://doi.org/10.1051/aas:1997347 | |
Published online | 15 May 1997 |
Identification of a complete sample of northern ROSAT All-Sky Survey X-ray sources
II. The optical observations
1
Landessternwarte Königstuhl (LSW), D-69117 Heidelberg, Germany
2
Max–Planck–Institut für Extraterrestrische Physik (MPE), Giessenbachstrasse, Postfach 1603, D-85740 Garching, Germany
3
Universitätssternwarte München, Scheinerstr. 1, D-81679 München, Germany
4
Instituto de Astronomia-UNAM, Apdo Postal 70-264, 04510 México D.F., Mexico
5
Instituto Nacional de Astrofisica, Optica y Electronica (INAOE), A. Postal 51 y 216 Z.P., 72000 Puebla, Mexico
6
Observatoire de Strasbourg, 11 rue de l'Université, F-67000 Strasbourg, France
Send offprint request to: F.-J. Zickgraf
Received:
29
August
1996
Accepted:
5
September
1996
We describe a program for the optical identi fication of a
re presen tative sample
of RASS sources contained in six study areas north of ,
with
including one region near the North
Galactic pole (NGP) and one near the North Ecliptic pole (NEP) and
present some pre liminary results.
A full identi fication has been carried out for a count-rate and area-limited
complete sub sample comprising
674 sources. The ratio of "extragalactic” ( e.g. AGN, clusters of
galaxies) to "stellar”
(e.g. coronal emitters, active binaries) counterparts was found
to depend on the galactic neutral hydrogen column density, NH. In the
area near the NGP (low NH)
"extra galactic” counter parts dominate, while in
the area with the highest NH most X-ray sources are identi fied with
stellar counter parts.
Key words: surveys / X-rays: general / X-rays: galaxies / X-rays: stars / galaxies: active / galaxies: cluster: general
© European Southern Observatory (ESO), 1997