RASS6DFGS - ROSAT All-Sky Survey/6dF Galaxy Survey Catalog of X-Ray Selected AGN
The authors detect 918 sources (27%) of the RASS-6dFGS sample in the radio using either the 1.4 GHz NVSS or the 843 MHz Sydney University Molonglo Sky Survey (SUMSS) catalogues and find that the detection rate changes with redshift. At redshifts larger than 1 virtually all of these sources have radio counterparts and with a median flux density of 1.15 Jy, they are much stronger than the median flux density of 28.6 mJy for the full sample. The authors attribute this to the fact that the X-ray flux of these objects is being boosted by a jet component, possibly Doppler boosted, that is only present in radio-loud AGN.
The RASS-6dFGS sample provides a large set of homogeneous optical spectra ideal for future studies of X-ray emitting AGN.
The RASS-6dFGS catalogue: a sample of X-ray selected AGN from the 6dF Galaxy Survey Mahony E.K., Croom S.M., Boyle B.J., Edge A.C., Mauch T., Sadler E.M. <Monthly Notices of the Royal Astronomical Society, Volume 401, Issue 2, pp. 1151-1165 (2010)> =2010MNRAS.401.1151M
The 6dFGS name of the source using the J2000.0 RA and Declination position-based nomenclature as recommended by the CDS Dictionary of Nomenclature of Celestial Objects, viz. '6dFGS JHHMMSSS-DDMMSS'. Notice that this differs from the style in the published paper where a non-standard form '6dFGS gHHMMSSS-DDMMSS' was suggested.
The Right Ascension of the optical source in the selected equinox. This was given in J2000.0 coordinates to a precision of 0.01 seconds of time in the original table.
The Declination of the optical source in the selected equinox. This was given in J2000.0 coordinates to a precision of 0.1 arcseconds in the original table.
The Galactic Longitude of the optical source.
The Galactic Latitude of the optical source.
The b_J magnitude of the optical source from the USNO database.
The R magnitude of the optical source from the USNO database.
The RASS name of the source using the J2000.0 RA and Declination position-based nomenclature as recommended by the CDS Dictionary of Nomenclature of Celestial Objects, viz. '1RXS JHHMMSS.s-DDMMSS'. Notice that this differs from the style in the published paper where a non-standard form 'RHHMMSSS-DDMMSS' was suggested.
This flag parameter is set to 'E' to signify that the X-ray source is considered to be exetended. This is determined if the source extent given in the RASS-BSC is larger than 35 arcseconds.
The RASS 0.1-2.4 keV X-ray count rate, in ct/s.
The uncertainty in the RASS 0.1-2.4 keV X-ray count rate, in ct/s.
The Galactic Hydrogen column density in the direction of the source, in cm-2. This was calculated using the N(H) program in the HEASARC collection which uses data from Dickey and Lockman (1990) and Kalberla et al. (2005).
The unabsorbed 0.1-2.4 keV flux of the RASS source, in erg s-1 cm-2, calculated from the HEASARC PIMMS tool using a fixed photon index of 1.7 and the Galactic Hydrogen column density.
The uncertainty in the unabsorbed 0.1-2.4 keV flux of the RASS source, in erg s-1 cm-2.
The NVSS flux density of the radio counterpart at 20 cm, in mJy.
The SUMSS flux density of the radio counterpart at 36 cm, in mJy.
The redshift of the optical object, taken from the 6dFGS.
The uncertainty in the redshift of the optical object, taken from the 6dFGS.
The redshift quality flag Q from the 6dFGS. Redshifts were measured from the 6dFGS spectra using the runz package and assigned a quality, Q, based on the reliability of the redshift. A quality Q= 1 or 2 denotes an unreliable redshift, Q= 3 signifies a probable redshift and Q= 4 implies a certain redshift. Galactic sources were assigned a quality Q= 6. During the redshifting process, unusual spectra or features were flagged with comments (see Comments parameter).
Qualities Q >= 3 are regarded as reliable and Q=0 means that the source was not observed as part of the 6dFGS. In Table 1 of the reference paper (reproduced below), percentages are given with respect to the full catalog in Column 3 (3405 sources) and with respect to only the sources in the observed sample in Column 4 (2224 sources).
Q No. % full % obs. 0 1181 34.7 --- 1 412 12.1 18.5 2 97 2.8 4.4 3 123 3.6 5.5 4 1354 39.8 60.9 6 238 7.0 10.7
The program identification of the 6dFGS spectrum. (See Section 7.5 of the reference paper). A value of '0' once again signifies that the source was not observed.
The classification of the object taken from the NED database, e.g., 'AbLS' for an absorption-line system, 'G' for galaxy, 'QSO' for quasi-stellar object, or 'UvES' for ultraviolet excess source.
The redshift of the object taken from the NED database.
The coded reference for the NED redshift. The HEASARC has created a parameter bibcode_ned_redshift using a table of the codes and their corresponding ADS bibliographic codes (bibcodes) which was obtained from the MNRAS web site.
The ADS bibcode of the reference from which the NED redshift was taken.
This comments parameter contains a brief note regarding any feature in the 6dFGS spectrum. To prevent these comments from being unnecessarily complicated they are generally self-explanatory, one-word entries as follows (a question mark signifies uncertainty in the comments. These comments were added during the visual inspection of the 6dFGS redshifts and should be used as a guide only):
'broad' - the spectrum features broad emission lines. 'narrow' - the spectrum has narrow emission features. 'abs' - the spectrum exhibits only absorption lines. 'BLLac' - a featureless spectrum with strong continuum. 'active_M-star'- characteristic M-star spectrum with strong Balmer emission at z= 0 . 'WD' - white dwarf star. 'CV' - cataclysmic variable star. 'neb' - spectrum displays z= 0 nebula emission lines. 'bad_splicing' - refers to an error in the data reduction process when the two arms of the spectrum (blue and red) were not matched together correctly in the final spectrum. 'fringing' - fringing occasionally occurs causing strong oscillations in the spectrum. This is due to either a small air pocket or damage in the fibre which causes it to act like a fabry-perot filter. Some redshifts could still be distinguished accurately. 'blue/red_arm_only' - an error with either the red or blue arm during observations resulting in only half of the spectrum being available. 'contamination'- a nearby source (generally a foreground star) dominates the spectrum, masking any optical signature of the RASS source.
The HEASARC Browse object classification of the object. This was based on classification information given in the comments, or, if none were provided, the NED classification.