SDSSUNUQSR - Sloan Digital Sky Survey Unusual Quasars Catalog

Overview

Large spectroscopic surveys have discovered very peculiar and hitherto unknown types of active galactic nuclei (AGN). Such rare objects may hold clues to the accretion history of the supermassive black holes at the centres of galaxies. The authors aim to create a sizeable sample of unusual quasars from the unprecedented spectroscopic database of the Sloan Digital Sky Survey (SDSS).

This table contains a catalog of 1005 quasars with unusual spectra in the redshift interval from 0.6 to 4.3. [HEASARC Note: the redshifts in this table actually range from 0.497 to 4.771]. The quasars were selected from the Sloan Digital Sky Survey Data Release 7 (Abazajian et al., 2009, ApJS, 182, 543) by means of Kohonen self-organising maps. The spectra are dominated by either broad absorption lines (42%), unusual red continua (27%), weak emission lines (18%), or conspicuously strong optical and/or UV iron emission (11%). This large sample provides a useful resource for both studying properties and relations of/between different types of unusual quasars and selecting particularly interesting objects, even though the compilation is not aimed at completeness in a quantifiable sense. The spectra are grouped into seven types. The catalogue contains the redshift, the absolute magnitude, the spectral type, the radio loudness parameter, a peculiarity index, and some comments on peculiar spectral features.

Catalog Bibcode

2012A&A...541A..77M

References

Unusual quasars from the Sloan Digital Sky Survey selected
by means of Kohonen Self-Organizing Maps.
    Meusinger H., Schalldach P., Scholz R.-D., in der Au A., Newholm M.,
    de Hoon M., Kaminsky B.
    <Astron. Astrophys. 541, A77 (2012)>
    =2012A&A...541A..77M        (SIMBAD/NED BibCode)

Provenance

This table was created by the HEASARC in May 2012 based on CDS table J/A+A/541/A77 file table3.dat.

Parameters

Source_Number
A sequential identification number for each source in the catalog.

Name
The SDSS source designation of the quasar based on its J2000.0 equatorial coordinates (taken from the spectrum FITS header).

RA
The Right Ascension of the quasar in the selected equinox. This was given in J2000.0 coordinates to a precision of 0.01 seconds of time in the original table.

Dec
The Declination of the quasar in the selected equinox. This was given in J2000.0 coordinates to a precision of 0.1 arcseconds in the original table.

LII
The Galactic Longitude of the quasar.

BII
The Galactic Latitude of the quasar.

QCDR7_Flag
The QCDR7 (Schneider et al. 2010, AJ, 139, 2360, the Sloan Digital Sky Survey Quasar Catalog V (7th Data Release), available as the HEASARC table SDSSQUASAR) flag f_c indicating the quasar's status in that catalog as follows:

             0 = not in QCDR7
             1 = in QCDR7, deviation in redshift <= 10%
             2 = in QCDR7, deviation in redshift >  10%

Redshift
The redshift of the quasar from the present study.

Redshift_Flag
This redshift flag parameter indicates the degree to which the redshift is considered to be uncertain:

             0 = certain
             1 = likely, but not certain
             2 = lack of certainly identifiable redshift indicators
             3 = low signal-to-noise

Imag_0
The SDSS apparent i-band magnitude, corrected for Galactic foreground extinction as derived from the "Galactic Dust Extinction Service" of the NASA/IPAC Infrared Science Archive (IRSA).

Abs_Imag
The absolute i-band magnitude, computed as described by Kennefick and Bursick (2008, AJ, 136, 1799) for a spectral index alpha_nu = -0.5.

FIRST_Det_Flag
The FIRST (Faint Images of the Radio Sky at Twenty cm) radio detection flag for the quasar, where 0 means a non-detection, and 1 means a detection.

FIRST_Flux_20_cm
THe FIRST 1.4-GHz peak flux F_1.4 of the quasar, if detected, in mJy.

Radio_Loudness
The radio loudness parameter R_i of the quasar, computed from F_1.4 and the extinction-corrected SDSS i-band magnitude following Ivezic et al. (2002, AJ, 124, 2364).

Peculiarity_Index
The peculiarity index chi² of the spectrum of the quasar. This is a quantitative measure of the deviation of its spectrum from the SDSS quasar composite spectrum and is described in detail in Section 5.1 of the reference paper.

Highest_Sig_Type
The highest significance type classification T₁ of the quasar as obtained from this study using a numerical format (1=A, 2=B, etc.) for computational reasons. The type values are as follows:

             1 = unusual BAL quasars (mostly LoBAL quasars)
             2 = quasars with strong but common BAL structures (mostly HiBALs)
             3 = quasars where the whole continuum is significantly redder than
                  the SDSS composite
             4 = quasars with strong reddening in the ultraviolet
             5 = weak emission line quasars
             6 = strong iron emitters
             7 = miscellaneous
             0 = no type (only for T2 and T3)

Median_Sig_Type
The second highest significance type classification T₂ of the quasar as obtained from this study using a numerical format (1=A, 2=B, etc.) for computational reasons. The type values are as follows:

             1 = unusual BAL quasars (mostly LoBAL quasars)
             2 = quasars with strong but common BAL structures (mostly HiBALs)
             3 = quasars where the whole continuum is significantly redder than
                  the SDSS composite
             4 = quasars with strong reddening in the ultraviolet
             5 = weak emission line quasars
             6 = strong iron emitters
             7 = miscellaneous
             0 = no type (only for T2 and T3)

Lowest_Sig_Type
The lowest significance type classification T₃ of the quasar as obtained from this study using a numerical format (1=A, 2=B, etc.) for computational reasons. The type values are as follows:

             1 = unusual BAL quasars (mostly LoBAL quasars)
             2 = quasars with strong but common BAL structures (mostly HiBALs)
             3 = quasars where the whole continuum is significantly redder than
                  the SDSS composite
             4 = quasars with strong reddening in the ultraviolet
             5 = weak emission line quasars
             6 = strong iron emitters
             7 = miscellaneous
             0 = no type (only for T2 and T3)

Comments
Comments on spectral peculiarities of the quasar. The following abbrevations may be used:

               abs = absorption
                ao = associated absorption
               bel = blueshifted emission line
                bq = (very) blue quasar
                em = emission
              dlas = damped Lyman alpha absorption system
                fg = foreground
               lst = longward-of-systemic trough
               mnt = many narrow troughs
             myst? = related or possibly related to the two mysterious objects
                     from Hall et al. (2002ApJS, 141, 267)
               nlq = narrow-line quasar
                nt = narrow troughs
                ot = overlapping troughs
            sdvdpc = spatially distinct velocity-dependent partial covering
                     of the continuum source
     see 0810(H02) = see object SDSS J081024.75+480615.5 in Hall et al.
                      (2002, ApJS, 141, 267)
                uc = unusual continuum
               ulp = unusual line profile

Contact Person

Questions regarding the SDSSUNUQSR database table can be addressed to the HEASARC Help Desk.

Page Author: Browse Software Development Team
Last Modified: Monday, 16-Sep-2024 17:34:45 EDT