J/MNRAS/372/425 2dF-SDSS Luminous Red Galaxy Survey, 2SLAQ (Cannon+, 2006)
The 2dF-SDSS LRG and QSO (2SLAQ) Luminous Red Galaxy Survey.
Cannon R., Drinkwater M., Edge A., Eisenstein D., Nichol R., Outram P.,
Pimbblet K., De Propris R., Roseboom I., Wake D., Allen P.,
Bland-Hawthorn J., Bridges T., Carson D., Chiu K., Colless M., Couch W.,
Croom S., Driver S., Fine S., Hewett P., Loveday J., Ross N., Sadler E.M.,
Shanks T., Sharp R., Smith J.A., Stoughton C., Weilbacher P., Brunner R.J.,
Meiksin A., Schneider D.P.
<Mon. Not. R. Astron. Soc., 372, 425-442 (2006)>
=2006MNRAS.372..425C 2006MNRAS.372..425C
ADC_Keywords: Surveys ; Galaxies, photometry
Keywords: catalogues - surveys - galaxies: high redshift -
cosmology: observations
Abstract:
We present a spectroscopic survey of almost 15000 candidate
intermediate-redshift luminous red galaxies (LRGs) brighter than
i=19.8, observed with 2dF on the Anglo-Australian Telescope. The
targets were selected photometrically from the Sloan Digital Sky
Survey (SDSS) and lie along two narrow equatorial strips covering
180deg2. Reliable redshifts were obtained for 92 per cent of the
targets and the selection is very efficient: over 90 per cent have
0.45<z<0.8. More than 80 per cent of the ∼11000 red galaxies have pure
absorption-line spectra consistent with a passively evolving old
stellar population. The redshift, photometric and spatial
distributions of the LRGs are described. The 2SLAQ data will be
released publicly from mid-2006, providing a powerful resource for
observational cosmology and the study of galaxy evolution.
Description:
This version of the catalogue was created as v5.1 on 01 Feb 2006 by
Russell Cannon. Essentially the same data were used in the other 2SLAQ
LRG papers written in 2006.
There is one line for each object observed, sorted by RA. The best
available redshift, i.e. the one with the highest reliability
parameter Q (or the higher S/N in the case of a tie), is given for
objects with two or more observations. Another version of the listing,
including repeats, is available from the UQ web site at
http://lrg.physics.uq.edu.au.
The first 27 columns come from the AAO redshifting code (i.e. the
concatenated *z.rz output lists from RDC's version of Will
Sutherland's original Zcode). Columns 28 to 35 are from the SDSS input
target lists prepared by Daniel Eisenstein. Column 36 contains any
notes made during the redshifting or subsequent analysis.
The first 34 columns are present for all targets, in a fixed format
with leading zeroes where appropriate so that they can be easily read
in free format. Column 35 gives the original SDSS run_camcol object
names for the 2003 2dF data only and is blank otherwise.
Note that this version of the redshift listing uses SDSS DR4
photometry in col. 8 and cols. 31-34 (for all but 10 objects) but
retains the original DR1 SDSS positions (as used by 2dF) in cols. 28
and 29. Earlier listings up to and including v4 (available from RDC)
gave the DR1 photometry used for 2dF target selection; the differences
are very small for >99% of the targets.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
catalog.dat 281 14978 The 2SLAQ redshift catalogue
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See also:
VII/226 : The 2dF Galaxy Redshift Survey 100k Data Release (2dFGRS Team, 2001)
VII/241 : The 2dF QSO Redshift Survey (Croom+ 2004)
http://www.sdss.org : SDSS Home Page
J/MNRAS/377/787 : SDSS Luminous Red Galaxies (Barber+, 2007)
Byte-by-byte Description of file: catalog.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- 2SLAQ Object name, (JHHMMSS.ss+DDMMSS.s)
22- 23 I2 h RAh Right ascension (J2000)
25- 26 I2 min RAm Right ascension (J2000)
28- 32 F5.2 s RAs Right ascension (J2000)
35 A1 --- DE- Declination sign (J2000)
36- 37 I2 deg DEd Declination (J2000)
39- 40 I2 arcmin DEm Declination (J2000)
42- 45 F4.1 arcsec DEs Declination (J2000)
48- 52 F5.2 mag Rmag Expected r-band fibre magnitude (1)
55 I1 --- tSp Template spectrum used for best
cross-correlation redshift (2)
58- 62 F5.2 --- xcor Cross-correlation (rx) parameter (3)
64- 70 F7.4 --- zabs Absorption line redshift from best
cross-correlation
72 I1 --- q_xcor [0/4] Quality of automatic xcorr redshift, as
estimated by Zcode. (4 is best, 0 is useless)
74- 80 F7.4 --- z Redshift finally adopted
(= zabs unless manually modified)
83 I1 --- q_zabs Quality of auto redshift assessed by Zcode,
after checking for emission lines (4)
86 I1 --- q_z Redshift quality adopted (= q_zabs unless
manually modified by observer) (5)
89 I1 --- f_z [0/3] A flag indicating manual intervention (6)
91- 93 A3 --- Field 2dF field number. Format LNN, where L is a
letter a-e for northern (Galactic) fields and
L=s for the southern strip
95- 97 I3 --- Fiber 2dF fibre number (7)
99-104 A6 --- Date 6-character identifier for the 2dF data set
from which the spectrum was taken "YYMMDD" (8)
106 I1 --- CCD [2] Identifier of CCD and 2dF spectrograph.
Always 2 for LRGs (spectrograph 1 was used
for the QSOs)
109 I1 --- 2dF [0/1] Field plate identifier
111-117 I7 um Xpos X position of object within 2dF field,
in microns from the centre of the plate (9)
119-125 I7 um Ypos Y position of object within 2dF field,
in microns from the centre of the plate (9)
127-131 F5.2 --- S/N Average signal-to-noise ratio of spectrum (10)
134-138 F5.2 mag xpmag ?=99.00 Magnitude derived from spectrum (11)
140-144 F5.2 mag Vmag ?=99.00 Spectral magnitude from counts over
range 515-595nm, approximately the
V photometric band (starting at 523nm
for March 2003 data).
146-150 F5.2 mag rmag ?=99.00 Spectral magnitude over range
595-680nm, i.e. ∼ r-band.
154-162 F9.5 deg RAdeg Right ascension, in decimal degrees, from
original (DR1) SDSS input lists (J2000) (12)
164-172 F9.5 deg DEdeg Declination, in decimal degrees, from original
(DR1) SDSS input lists (J2000) (11)
175 I1 --- Pry Priority flag (13)
177-183 F7.4 mag i(dev) SDSS extinction-corrected i-band
'de Vaucouleurs' magnitude (14)
185-191 F7.4 mag g-r SDSS reddening-corrected (g-r) 'ModelMag'
colour index (14)
193-199 F7.4 mag r-i SDSS reddening-corrected (r-i) 'ModelMag'
colour index (14)
202-205 F4.2 mag Ar SDSS absorption in the r-band (14)
208 I1 --- PryO ? Original 2SLAQ priority number
210-227 A18 --- NameOri Original 2SLAQ 18-character object name used
in 2003, blank for later data (15)
229-281 A53 --- Com Comments. Mostly copied from Zcode output.
Most often blank
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Note (1): This is the reddened SDSS r(fiber) magnitude which should
give a reasonable approximation to the 2dF counts, although the
2dF spectra include much of the g-band and part of i, and the 2dF
fibres are 2 arcsec in diameter rather than the Sloan's 3 arcsec.
(Initially, the SDSS i(deV) magnitude was used in semester 2003A
and the r-band magnitude in 2003B, and these values remain in the
original Zcode *z.rz lists for individual fields.)
Note (2): Template spectrum code as follows:
1 = T1, mean SDSS LRG spectrum
2 = T2, T2 and T3 are other galaxies used for the 2dFGRS
3 = T3, T2 and T3 are other galaxies used for the 2dFGRS
4 = T4, T4-T8 are stars with spectral types ranging from A to M and
5 = T5, T4-T8 are stars with spectral types ranging from A to M and
6 = T6, T4-T8 are stars with spectral types ranging from A to M and
7 = T7, T4-T8 are stars with spectral types ranging from A to M and
8 = T8, T4-T8 are stars with spectral types ranging from A to M and
9 = T9, composite e(a) spectrum.
Note (3): A measure of the height of the peak relative to the noise in
the cross-correlation. In general, redshifts are reliable if xcorr>4
and very unreliable if xcorr<3.
Note (4): If there are convincing lines consistent with za
(usually only [OII] 3727Å), q_zabs is set to (q_xcor+1).
Note (5): Redshift quality adopted as follows:
1 = no plausible redshift could be derived
2 = a possible redshift but with reliability 50% or lower
3 = z_fin is very likely to be correct (>95% of cases)
4 = redshift with Q=4 or 5 is virtually certain with >99% probability
5 = redshift with Q=4 or 5 is virtually certain with >99% probability
Note (6): Flag as follows:
0 = a redshift which has been accepted after visual inspection
(although the Q value may have been altered)
1 = a switch between absorption- and emission-line redshifts
(extremely rare for the LRGs)
2 = a different redshift is preferred
3 = the automatic redshift has been accepted without visual checking
(usually only spectra with q_zabs<3 are checked visually).
Note (7): This is the fibre number within the spectrograph, normally in
the range 1-200. Taken together with the CCD and Plate in cols 20
and 21, it uniquely identifies the 2dF fibre used. However, this
does not work in the extended 2SLAQ data sets where some fibres were
re-allocated between nights and objects added were given fibre numbers
from 201.
Note (8): i.e. the central part of the 2dfdr NDF filename which has the
format LNNgYYMMDD2.sdf. When the data come from a single night it
is in fact the UT date of observation. For most fields the data were
taken over several nights, in which case DD is either 'fi' or '00'.
A few spectra were taken from special subsets of the data, to avoid
instrumental problems; these are identified by other characters in
the DD columns.
Note (9): Range ± 260000. Note that X is actually in the declination
direction and Y in RA, and both increase in the conventional
direction, i.e. from S-N and W-E respectively.
Note (10): This is derived by the Zcode, using the signal and variance
(error) arrays generated by 2dfdr. It is thus a true S/N ratio,
taking account of the sky and other sources of noise, and gives
the best indication of the quality of each spectrum. It can however
be negative and still give a reliable redshift, since occasionally
fibre calibration errors result in over-subtraction of sky or
scattered light.
Note (11): Based on -2.5*log(total counts) with a zero point that
approximately matches the r(fib) magnitude for typical 2dF data.
Note (12): Primary SDSS object identifier, also used for postage-stamp images.
SDSS DR4 positions are slightly different for some objects.
Note that 2dF works in decimal radians, a possible source of
small rounding-off errors in coordinate transformations.
Note (13): This is actually the `Sample' parameter as set by Daniel Eisenstein.
(Note that the `priority' integer used by 2dF in *.fld configuration
files runs in the opposite sense, with high digits given highest
priority). From mid-2003 onwards `pry' was usually 8 or 9, with Sample
8 being the primary LRG sample, Sample 9 the secondary sample, and
pry=0 denoting extra targets used as `fillers'. For Semester 2003A
`pry' ranged from 3-5, with 3 being the highest priority, and with
pry=6 used to denote a special faint subsample in field d10.
Note (14): Photometric data are all taken from the SDSS DR4, except for
10 objects (noted in col. "Com") for which earlier SDSS data are used.
Note (15): Concatenated from the 5 integers which identify an object by
photometric dataset in the SDSS input lists.
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History:
Copied at http://www.2slaq.info/
(End) Patricia Vannier [CDS] 28-Jun-2007