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J/ApJ/514/148 ROSAT survey of bright galaxies clusters (De Grandi+, 1999)
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A flux-limited sample of bright clusters of galaxies from the southern part
of the ROSAT all-sky survey: the catalog and log n-log s
De Grandi S., Bohringer H., Guzzo L., Molendi S., Chincarini G.,
Collins C., Cruddace R., Neumann D., Schindler S., Schuecker P., Voges W.
<Astrophys. J. 514, 148 (1999)>
=1999ApJ...514..148D
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ADC_Keywords: Clusters, galaxy ; Surveys ; X-ray sources
Mission_Name: ROSAT
Keywords: galaxies: clusters: general - surveys - X-rays: galaxies
Abstract:
We describe the selection of an X-ray flux-limited sample of bright
clusters of galaxies in the southern hemisphere, based on the first
analysis of the ROSAT All-Sky Survey data (RASS1). The sample is
constructed starting from an identification of candidate clusters in
RASS1, after which their X-ray fluxes are remeasured using the
steepness-ratio technique. This method is better suited than the RASS1
standard algorithm to measuring flux from extended sources. The final
sample is count-rate-limited in the ROSAT hard band (0.5-2.0 keV), so
that as a result of the distribution of N_H_, its effective flux limit
varies between {~}3 and 4x10^-12^ ergs cm^-2^ s^-1^ over the selected
area. This covers the {delta} < 2.5{deg} part of the south Galactic
cap region (b < -20{deg}), excluding patches of low RASS1 exposure
time and of the Magellanic Clouds area, for a total of 8235 deg^2^.
One hundred and thirty candidate sources fulfill our selection
criteria for bona fide clusters of galaxies in this area. Of these,
101 are Abell/ACO clusters, while 29 do not have a counterpart in
these catalogs. Of these clusters, 126 (97%) have a redshift, and for
these we compute an X-ray luminosity. 20% of the cluster redshifts
come from new observations, as part of the ESO Key Program survey of
RASS clusters that is currently under completion. Considering the
intrinsic biases and incompletenesses introduced by the flux selection
and source identification processes, we estimate the overall
completeness to be better than 90%. The observed number count
distribution, log Nlog S, is well fitted by a power law with slope
{alpha} =1.34{+/-}0.15 and normalization A=11.87{+/-}1.04 sr^-1^
(10^-11^ ergs cm^-2^ s^-1^)^{alpha}^, in good agreement with other
measurements.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 134 130 ROSAT cluster catalog
notes.dat 129 42 Notes on single sources in table1.dat
refs.dat 118 31 Redshift references in table1.dat
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See also:
J/ApJ/502/558 : Catalog of ROSAT galaxy clusters (Vikhlinin+ 1998)
IX/10A : ROSAT All-Sky Bright Source Catalogue (1RXS) (Voges+ 1999)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq Sequence number in the catalog
6- 7 I2 h RAh Right Ascension (J2000)
9- 10 I2 min RAm Right Ascension (J2000)
12- 16 F5.2 s RAs Right Ascension (J2000)
18 A1 --- DE- Sign of the Declination (J2000)
19- 20 I2 deg DEd Declination (J2000)
22- 23 I2 arcmin DEm Declination (J2000)
25- 28 F4.1 arcsec DEs Declination (J2000)
30- 34 F5.2 10+20cm-2 ColDen Hydrogen Column density (units of 10^20^
cm^-2^) from Dickey & Lockman
(1990ARA&A..28..215D)
36- 41 F6.1 s Time Vignetting-corrected exposure time
43- 46 F4.2 ct/s Cr5 Count rate within a 5' radius from the
0.5-2.0 KeV energy band
48- 51 F4.2 ct/s e_Cr5 Uncertainty (1{sigma}) in Cr5
53- 56 F4.2 ct/s CrSRT Steepness-ratio technique (SRT) count
rate in the 0.5-2.0 KeV band
59- 62 F4.2 ct/s e_CrSRT Lower limit to CrSRT
65- 68 F4.2 ct/s E_CrSRT Upper limit to CrSRT
71- 77 E7.1 % Prob Probability that the source is pointlike
(Prob < 1% is extended)
79- 82 F4.2 10-11mW/m2 Flux Unabsorbed X-ray flux in the 0.5-2.0 KeV
band (units of 10^-11^ ergs/cm^2^/s)
84- 87 F4.2 10-11mW/m2 e_Flux Uncertainty (1{sigma}) in Flux
89- 93 F5.2 10+37W Lum ? X-ray luminosity in the 0.5-2.0 keV
band (units 10^44^ ergs/s) (1)
95- 98 F4.2 10+37W e_Lum ? Uncertainty (1{sigma}) in Lum
101-115 A15 --- ID Optical identification name
118 A1 --- Class [ABC] Classification (2)
120-125 F6.4 --- z ? Redshift
127-128 I2 --- r_z ? Redshift reference (see refs.dat)
130 A1 --- f_z Indicates an estimated redshift
133-134 I2 --- n_Seq ? Notes on single objects (see notes.dat)
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Note (1): The luminosity has been computed in the rest frame of the source
by assuming a power-law spectrum with energy index 0.4, H_o_ =
50 km/s/Mpc, and q_o_ = 0.5.
Note (2): the classification is:
A = Confirmed clusters of galaxies, i.e., objects for which the
inspection of optical images and spectra allow a certain
identification of the X-ray source with a cluster.
B = Likely clusters, i.e., objects with X-ray and optical properties
consistent with clusters, but lacking firm spectroscopic confirmation.
C = Uncertain identifications, i.e., objects for which we have either
insufficient information to discriminate between two possible
classifications, or no information at all.
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Byte-by-byte Description of file: notes.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq Sequence number of the source in the catalog
6- 7 I2 --- RefNotes Number referenced in n_Seq table1.dat
10-129 A120 --- Text Comments on single sources in table1.dat
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Byte-by-byte Description of file: refs.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- zRef Redshift reference number from r_z in
table1.dat
6- 24 A19 --- BibCode Reference Bibcode
28-127 A100 --- Text Reference or description of data
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History:
From ApJ electronic edition
References:
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(1994A&A...281..355B)
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Garcia, A. M. 1993, A&A, 100, 47 (1993A&A...100...47G)
Gioia, I. M., & Luppino, G. A. 1994, ApJS, 94, 583 (1994ApJS...94..583G)
Maccacaro, T., Gioia, I. M., Wolter, A., Zamorani, G., & Stocke, J. T.
1988, ApJ, 326, 680 (1988ApJ...326..680M)
Maccacaro, T., Wolter, A., McLean, B., Gioia, I. M., Stocke, J. T., Della
Ceca, R., Burg, R., & Faccini, R. 1994, Astrophys. Lett. Comm., 29, 267
Struble, M. F., & Rood, H. J. 1991, ApJ, 374, 395 (1991ApJ...374..395S)
Tucker, W. H., Tananbaum, H., & Remillard, R. A. 1995, AJ, 444, 532
(1995AJ....444..532T)
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(End) Greg Schwarz [AAS] 03-Mar-2000