VII/226 The 2dF Galaxy Redshift Survey 100k Data Release (2dFGRS Team, 2001)
The 2dF Galaxy Redshift Survey 100k Data Release
Colless M., Dalton G., Maddox S., Sutherland W., Norberg P., Cole S.,
Bland-Hawthorn J., Bridges T., Cannon R., Collins C., Couch W., Cross N.,
Deeley K., de Propris R., Driver S.P., Efstathiou G., Ellis R.S.,
Frenk C.S., Glazebrook K., Jackson C., Lahav O., Lewis I., Lumsden S.,
Madgwick D., Peacock J.A., Peterson B.A., Price I., Seaborne M., Taylor K.
<2dF Galaxy Redshift Survey Team (2001)>
ADC_Keywords: Surveys ; Galaxy catalogs ; Redshifts
Keywords: Surveys, galaxies: clusters: general ;
Galaxies: distances and redshifts ; Cosmology: observations ;
Large-scale structure of Universe
Description:
The 2dF Galaxy Redshift Survey (2dFGRS) is designed to measure
redshifts for approximately 250000 galaxies. The 2dFGRS uses the 2dF
multifibre spectrograph on the Anglo-Australian Telescope, which is
capable of observing 400 objects simultaneously over a 2 degree
diameter field. The source catalogue for the survey is a revised and
extended version of the APM galaxy catalogue, and the targets are
galaxies with extinction-corrected magnitudes brighter than bJ=19.45.
The main survey regions are two declination strips, one in the
southern Galactic hemisphere spanning 80x15degrees around the South
Galactic Pole, and the other in the Northern Galactic hemisphere
spanning 75x10degrees along the celestial equator; in addition, there
are 99 fields spread over the southern Galactic cap. The survey covers
2000 square degrees and has a median depth of z=0.11. Adaptive tiling
is used to give a highly uniform sampling rate of 93% over the whole
survey region. The 100k release contains the 102426 objects observed
up to 31 January 2001.
Redshifts are measured from spectra covering 3600-8000 Angstroms at a
two-pixel resolution of 9.0 Angstrom and a median S/N of 13 per pixel.
All redshift identifications are visually checked and assigned a
quality parameter Q in the range 1-5; Q≥3 redshifts are 98.4%
reliable and have an rms uncertainty of 85 km/s. The overall redshift
completeness for Q≥3 redshifts is 91.8% but this varies with
magnitude from 99% for the brightest galaxies to 90% for objects at
the survey limit.
The 2dFGRS data base is available on the World Wide Web at
http://www.mso.anu.edu.au/2dFGRS.
This catalog was extracted from the 2dF Galaxy Redshift Survey 100k
release CD-ROMs using the included mSQL database. This catalog
comprises the basic spectroscopic information from the best spectrum
of each object, that is contained in the extnum=0 rows of the mSQL
database.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
2df_100k.dat 122 102426 2dF 100k release
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See also:
http://www.mso.anu.edu.au/2dFGRS : The 2dF Galaxy Redshift Survey Home Page
Byte-by-byte Description of file: 2df_100k.dat
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Bytes Format Units Label Explanations
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1- 6 I6 --- Serial 2dFGRS serial number (1)
8- 17 A10 --- Name 2dFGRS name
19- 20 I2 h RAh Right ascension (B1950)
22- 23 I2 min RAm Right ascension (B1950)
25- 29 F5.2 s RAs [0,60.] Right ascension (B1950)
31 A1 --- DE- Declination sign (B1950)
32- 33 I2 deg DEd Declination (B1950)
35- 36 I2 arcmin DEm Declination (B1950)
38- 41 F4.1 arcsec DEs [0,60.] Declination (B1950)
43- 45 I3 --- UKST UKST sky survey field number (2)
47 I1 --- Spec Number of spectra (3)
49- 53 A5 --- ObsRun Observation run year and month
55 -58 I4 --- TDFgg 2dFGRS field number (4)
60 -68 F9.6 --- z observed redshift
70 -78 F9.6 --- zHelio heliocentric redshift
80 I1 --- zType redshift type (5)
82 I1 --- q_z Quality (6)
84 -88 F5.2 mag BJmag b_J mag used in object selection
90 -94 F5.1 deg PA orientation (degrees clockwise from E-W)
96-100 F5.3 --- e Eccentricity (UKST plate image)
102-108 F7.1 --- Area Isophotal are in pixels
110 I1 --- IGAL Galaxy flag (1=galaxy)
113-122 A10 --- FITSfile Name of fits file with image and spectra.
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Note (1): Each object in the survey source catalogue has been given a
unique serial number. The name of the FITS file on the CD-ROM for that
object is this serial number. The serial numbers for objects in the
SGP strip are 1-193550 and 416694-467214, for objects in the NGP strip
193551-332694 and 389714-416693, and for objects in the random fields
332695-389713.
Note (2): UK Schmidt Telescope (UKST) Sky Survey Field number
Note (3): Number of spectra taken for this object. Note that this catalog
contains information only on the best spectrum for each object.
Spectral information for the other spectra and the original data are
availabvle on the 2dFGRS CD-ROM
Note (4): 2dFGRS field number. Positive values indicate objects in the
NGP fields, and negative values indicate objects in the SGP fields.
Note (5): Redshift types: 'absorption' redshifts are obtained by
cross-correlation with template spectra (after clipping emission
lines), and 'emission' redshifts are obtained by finding and fitting
emission lines. These automated redshift estimates are followed by a
visual check and (occasionally, where necessary) a 'manual' redshift
obtained by fitting identified spectral features.
Redshift type:
1=absorption feature
2=emission feature
3=manual
Note (6): Redshift estimate quality.
1: means no redshift could be estimated
2: means a possible, but doubtful, redshift estimate
3: means a 'probable' redshift (notionally 90% confidence
4: means a reliable redshift (notionally 99% confidence
5: means a reliable redshift and a high-quality spectrum
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(End) Mark Allen [CDS] 09-Jun-2003