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PG: Help

PG - PG Catalog of UV-excess objects


Overview

The Palomar-Green Catalog of UV-excess stellar objects provides positions accurate to about 8 arcsec in each coordinate, photographic B-magnitudes accurate to 0.29mag, spectral types, some cross-references, and photoelectric broad-band, multichannel, and Stroemgren colors when available.

Of the 1874 objects in the catalog as published in 1986 (1878 in this version), 1715 comprise a statistically complete sample covering 10714 square degrees from 266 fields taken on the Palomar 18-inch Schmidt telescope. Limiting magnitudes vary from field to field, ranging from 15.49 to 16.67. The overall completeness is estimated to be 84%, but that figure and the relative contributions of magnitude, color, and accidental errors vary depending on the magnitude and color distribution of the spectroscopic subsample.

The dominant population in this catalog is that of the hot, hydrogen-atmosphere subdwarfs, the sdB stars, which comprise nearly 40 per cent of the sample. The hot white dwarfs of spectral types DA, DB, and DO account for 21, 2.8, and 1.0 per cent of the sample, respectively, while cooler DC or DZ white dwarfs add another 1.2 per cent. Cataclysmic variables and composite-spectrum binaries account for 5 per cent, although many other spectra dominated by a hot star showed evidence for a cool companion at red wavelengths. Planetary nebulae central stars account for another 0.5 per cent. Extragalactic objects comprise about 9 per cent of the complete sample, with QSOs representing 5.4 per cent. Only 0.3 per cent (6 objects) remain with totally unsatisfactory or unknown spectral classes. (Notice that all of these percentage estimates are based on the published version of this catalog, and that the values in the current online version may be slightly different, as the latter includes a small number of updates and additions).


Catalog Bibcode

1986ApJS...61..305G

References

The Palomar-Green Catalog of Ultraviolet-Excess Stellar Objects, R.F. Green, M. Schmidt, and J. Liebert, 1986, ApJS, 61, 305.

Provenance

This database was created at the HEASARC in June 1998 based on the ADC/CDS Catalog II/207 which had been last updated on Oct 17 1997.

Parameters

Name
This parameter was not given in the original published tabular version (Table 5 of Green et al. 1986), but did appear in the finding charts. It was constructed in the standard way, based on the IAU nomenclature convention, using the prefix PG and the 1950 RA and Dec sexagesimal coordinates for each entry. For example, the PG object at RA(1950) = 00 00 02.3 and Dec(1950) = +17 10 47 has the name of PG 0000+171.

RA
The right ascension of the object in the selected equinox. The estimated accuracy of this coordinate is about 8 arc seconds.

Dec
The declination of the object in the selected equinox. The estimated accuracy of this coordinate is about 8 arc seconds.

LII
The galactic longitude of the object.

BII
The galactic latitude of the object.

Pmag
The photographic B-magnitude of the object, with an estimated accuracy of 0.29 magnitudes. If the object was found in overlapping fields, the object magnitude (and limiting magnitude) from the the deeper exposure was selected.

Blim
The limiting B-magnitude for the field in which this object was discovered. If the object was found in overlapping fields, the limiting magnitude (and object magnitude) from the the deeper exposure was selected. A value of 0. for this parameter means that the object is not part of the complete statistical sample, which can be due to faintness, or nondetection in the automated scanning process, or its being in a field with an abnormally bright limiting magnitude.

Comments
This parameter contains redshifts for extragalactic sources, spectral types for companions to the blue stars, and/or brief notes about any spectral peculiarities or uncertainties. It contains also cross-identifications of the objects. Notice that the cross-identification of PG 1535+547 with a Zwicky Catalog object has been changed from I Zw 120 to I Zw 121. For complete cross-referencing on white dwarfs, see the McCook & Sion White Dwarf Catalog (1984), ADC/CDS Catalog <III/129>. Lists of previously identified ultraviolet-excess objects include:

       PHL (Palomar-Haro-Luyten, 1962BITon...3...37H), ADC/CDS catalog <III/74>
       EG = Eggen and Greenstein (1965ApJ...141...83E, 1967ApJ...150..927E)
        T = Tonantzintla lists   (1957BOTT....2G...3I, 1959BOTT....2I...3C)
        U = Usher and collaborators (1981ApJS...46..117U, 1982ApJS...48...51U,
               1982ApJS...49...27U, 1984ApJS...56..393H)
        K = Kiso UV survey
       PB = Palomar-Berger (1977A&AS...28..123B)
     L,LB = Luyten lists (Univ. Minnesota)
     G,GD = Giclas Proper Motion Survey (see cats. <I/79>, <I/112>)
        F = Feige (1958ApJ...128..267F)
       HZ = Humason-Zwicky (1947ApJ...105...85H)
     C,CB = Pesch & Sandyuleak (1983ApJS...51..171P, 1984ApJS...55..517S)
  

Pg_Class
A spectral classification full details of which are given in Section IV of the published version of this catalog. A colon in this field denotes uncertainty. The various categories are as follows:

       HBB = Horizontal-branch B star
       SDB = Subdwarf B (sdB) star
     SDB-O = Subdwarf B star with a suggestion of He I 4471 A in absorption
        SD = Presumed subdwarf but spectrum had low signal-to-noise
      SDOA = Subdwarf star with dominant H and pronounced He 4471 absorption
      SDOB = Subdwarf star with dominant He and (generally) H absorption
      SDOC = Hottest type of sdO star with dominant He II absorption
      SDOD = Cooler subdwarf with "pure" He I absorption spectrum
       SDO = Subdwarf O (sdO) star
       DA+ = White dwarf of the DA type, where + is the temperature subtype
       DB+ = White dwarf of the DB type, where + is the temperature subtype
       DAO = White dwarf with an atmosphere of mixed H and He composition
       DAB = White dwarf with an atmosphere of mixed H and He composition
       DBA = White dwarf with an atmosphere of mixed H and He composition
        DO = White dwarf with spectrum dominated by He II absorption
      1159 = Member of the PG 1159-035 spectroscopic class
        DC = White dwarf of the DC type
        DZ = White dwarf of the DZ type
       PNN = Planetary Nebula Nucleus
        CV = Presumed galactic cataclysmic variable
       BIN = Composite spectrum object thought to be non-interacting binary
       DME = M dwarf emission line star probably observed during flare
       QSO = Broad emision line object with absolute B mag brighter than -23
       SEY = Broad emision line object with absolute B mag fainter than -23
       GAL = Galaxy with UV excess and (in most cases) sharp emission lines
       BLL = BL Lacertae-type oject
        ?? = Object of unknown type
  

Spect_Note
A flag that is set to "Y" if there was at least one follow-up spectrum obtained at higher dispersion than the original Palomar spectrum.

Bmag
Photoelectric Johnson B magnitude.

Bmag_Flag
A colon in this field denotes uncertainty.

UB_Color
Photoelectric Johnson (U-B) color index.

UB_Color_Flag
A colon in this field denotes uncertainty.

BV_Color
Photoelectric Johnson (B-V) color index.

Pal_Vmag
The Palomar 5m multichannel spectrophotometric v magnitude. This is one of four "monochromatic" bands defined by Greenstein (1976, ApJ, 207, L119) centered at 2.80 inverse microns (um-1) for u, 2.12 um-1 for g, 1.85 um-1 for v, and 1.44 um-1 for r, and calibrated in the "AB79" system by Oke & Gunn (1983, ApJ, 266, 713).

Pal_Vmag_Flag
A colon in this field denotes uncertainty.

Pal_Uv_Color
The Palomar 5m multichannel spectrophotometric (u-v) index. This system is based on 4 "monochromatic" bands defined by Greenstein (1976, ApJ, 207, L119) centered at 2.80 inverse microns (um-1) for u, 2.12 um-1 for g, 1.85 um-1 for v, and 1.44 um-1 for r, and calibrated in the "AB79" system by Oke & Gunn (1983, ApJ, 266, 713).

Pal_Uv_Color_Flag
A colon in this field denotes uncertainty.

Pal_BV_Color
The Palomar 5m multichannel spectrophotometric (b-v) index. This system is based on 4 "monochromatic" bands defined by Greenstein (1976, ApJ, 207, L119) centered at 2.80 inverse microns (um-1) for u, 2.12 um-1 for g, 1.85 um-1 for v, and 1.44 um-1 for r, and calibrated in the "AB79" system by Oke & Gunn (1983, ApJ, 266, 713).

Pal_GR_Color
The Palomar 5m multichannel spectrophotometric (g-r) index. This system is based on 4 "monochromatic" bands defined by Greenstein (1976, ApJ, 207, L119) centered at 2.80 inverse microns (um-1) for u, 2.12 um-1 for g, 1.85 um-1 for v, and 1.44 um-1 for r, and calibrated in the "AB79" system by Oke & Gunn (1983, ApJ, 266, 713).

Strom_Vmag
The V magnitude in the Stromgren (Stroemgren) system.

Strom_BY_Color
The (b-y) color index in the Stromgren (Stroemgren) system.

Strom_BY_Color_Flag
A colon in this field denotes uncertainty.

Strom_UB_Color
The (u-b) color index in the Stromgren (Stroemgren) system.

Strom_UB_Color_Flag
A colon in this field denotes uncertainty.

Strom_M1_Index
The m1 index in the Stromgren (Stroemgren) system.

Reference
References for the photoelectric photometry and studies of individual objects. Additional broad-band photometry was quoted from Eggen (1968, ApJS< 16, 97). Most of the values without citations are based on the authors' measurements. Those with numbers refer to the following papers:

        1 = Green              =1980ApJ...238..685G
        2 = Graham             =1972AJ.....77..144G
        3 = Greenstein         =1984ApJ...276..602G
        4 = Wegner             =1983AJ.....88..109W
        5 = Liebert & Stockman =1980PASP...92..657L
        6 = Wesemael et al.    =1985ApJS...58..379W
        7 = Bond et al.        =1984ApJ...279..751B
        8 = Ferguson et al.    =1981ApJ...251..205F
        9 = Margon et al.      =1981Natur.293..200M
       10 = Ferguson et al.    =1984ApJ...287..320F
       11 = Green et al.       =1982PASP...94..560G
       12 = Becker et al.      =1982MNRAS.201..265B
       13 = Penning et al.     =1984ApJ...276..233P
       14 = Liebert et al.     =1982ApJ...256..594L
       15 = Liebert et al.     =1984ApJ...277..692L
       16 = Liebert et al.     =1983ApJ...264..262L
       17 = Barker & Cudworth  =1984ApJ...278..610B
       18 = Schmidt & Green    =1983ApJ...269..352S
       19 = Weymann et al.     =1980Natur.285...64W
       20 = Ellis et al.       =1984PASP...96..283E
       21 = Sion et al.        =1985ApJ...292..477S
       22 = Sion et al.        =1985ApJ...292..471S
       23 = Szkody et al.      =1985ApJ...293..321S
       24 = McGraw et al.      =1979IAUCo..53..377M
       25 = Winget et al.      =1984IAUC.3932.....W
       26 = Winget et al.      =1984ApJ...279L..15W
       27 = Nather et al.      =1984IAUC.4021.....N
       28 = Green              =1976PASP...88..665G
  

Class
The HEASARC browse classification for the object, constructed from its PG classification (pg_class).


Contact Person

Questions regarding the PG database table can be addressed to the HEASARC User Hotline.
If you have any problems, please consult the help page or mail ledas-help@star.le.ac.uk
 
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