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J/ApJ/569/689 Distant cluster hunting. II. (Donahue+, 2002)
Distant cluster hunting. II. A comparison of X-ray and optical cluster detection techniques and catalogs from the ROSAT optical X-ray survey. Donahue M., Scharf C.A., Mack J., Lee Y.P., Postman M., Rosati P., Dickinson M., Voit G.M., Stocke J.T. <Astrophys. J. 569, 689 (2002)> =2002ApJ...569..689D
ADC_Keywords: Clusters, galaxy ; X-ray sources Keywords: catalogs - dark matter - galaxies: clusters: general - X-rays: galaxies: clusters Abstract: We present and analyze the optical and X-ray catalogs of moderate-redshift cluster candidates from the ROSAT Optical X-Ray Survey, or ROXS. The survey covers the sky area contained in the fields of view of 23 deep archival ROSAT PSPC pointings, 4.8 square degrees. The cross-correlated cluster catalogs were constructed by comparing two independent catalogs extracted from the optical and X-ray bandpasses, using a matched-filter technique for the optical data and a wavelet technique for the X-ray data. We cross-identified cluster candidates in each catalog. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 87 23 ROSAT Fields table2.dat 249 155 Optical Cluster Candidates table3.dat 108 24 Cross-identifications in V and I table4.dat 105 38 Unmatched Cluster Candidates in V and I table6.dat 152 60 X-ray Clusters of Galaxies table7.dat 72 13 Spectroscopic versus Matched Filter Estimated Redshifts
Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 11 A11 --- RField ROSAT field 13- 32 A20 --- RTarget ROSAT target 34- 38 I5 s Exp ROSAT exposure time 40- 41 I2 h RAh Right ascension (J2000) 43- 44 I2 min RAm Right ascension (J2000) 46- 47 I2 s RAs Right ascension (J2000) 49 A1 --- DE- Declination sign (J2000) 50- 51 I2 deg DEd DEclination (J2000) 53- 54 I2 arcmin DEm DEclination (J2000) 56- 57 I2 arcsec DEs DEclination (J2000) 59- 65 F7.5 deg+2 Area Area of field 67- 76 A10 "YYYY/MM/DD" DateI Iband KPNO observation date 78- 87 A10 "YYYY/MM/DD" DateV Vband KPNO observation date
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 11 A11 --- RField ROSAT field 13 A1 --- --- [-] 15- 37 A23 --- IField Field identification 39- 52 A14 --- [DSM2002] Optical ID 54- 55 I2 h RAh Hour of Right Ascension (J2000) 57- 58 I2 min RAm Minute of Right Ascension (J2000) 60- 64 F5.2 s RAs Second of Right Ascension (J2000) 66 A1 --- DE- Sign of the Declination (J2000) 67- 68 I2 deg DEd Degree of Declination (J2000) 70- 71 I2 arcmin DEm Arcminute of Declination (J2000) 73- 76 F4.1 arcsec DEs Arcsecond of Declination (J2000) 78- 81 F4.2 --- sigma Detection confidence in units of σ 83- 88 F6.2 --- Lambda Effective optical luminosity (G1) 90- 93 F4.2 --- z Estimated redshift (G2) 95- 99 F5.2 mag Imag The average I band magnitude 101-103 I3 arcsec Rad Effective radius (G3) 105-109 F5.2 arcmin Theta ? Location of the optical candidate relative to the center of the original PSPC pointing 111-113 F3.1 10-14mW/m2 FLim ? Estimated 4σ X-ray detection threshold in an r=1' aperture in units of 10-14 erg/cm2/s (4) 115-128 A14 --- RXJ The X-ray match, RXJ designation 129 A1 --- u_RXJ [?] Questionnable X-ray match 131-200 A70 --- Com Comment
Note (4): At the position of the optical candidate in the ROSAT PSPC pointing, taking into account the background surface brightness and the off-axis angle.
Byte-by-byte Description of file: table3.dat
Bytes Format Units Label Explanations
1- 8 A8 --- Target Name of original target (1) 10- 13 I4 --- NgalT Number of galaxies in the optical field used as the parent population sample 15- 34 A20 --- [DSM2002] I-band identification, in the target 35 A1 --- n_[DSM2002] Individual note (2) 37- 41 F5.2 --- LambdaI ? Effective total luminosity from Iband (G1) (3) 43- 46 F4.2 --- z(I) ? Effective redshift from I band 48- 49 I2 h RAh ? Right ascension (J2000) 51- 52 I2 min RAm ? Right ascension (J2000) 54- 58 F5.2 s RAs ? Right ascension (J2000) 60 A1 --- DE- Declination sign (J2000) 61- 62 I2 deg DEd ? DEclination (J2000) 64- 65 I2 arcmin DEm ? DEclination (J2000) 67- 70 F4.1 arcsec DEs ? DEclination (J2000) 72 A1 --- n_sigma [*] * for sigma < 2.9 73- 76 F4.2 --- sigma ? Detection confidence in units of σ 78- 83 F6.2 --- LambdaV ? Effective total luminosity from V band (G1) (3) 85- 88 F4.2 --- z(V) ? Effective redshift from V band 90- 94 F5.2 mag Vmag ? Average V band magnitude 96- 98 I3 arcsec Rad ? Effective radius (G3) 100-101 I2 --- Ngals ? Number of galaxies near the centroid of the optical candidate used for the two-dimensional K-S test. 103-107 E5.3 --- P(KS) [0/1]? KS probability (4) 108 A1 --- n_P(KS) [f] Note on P(KS) (5)
Note (1): The target are cluster candidates with X-ray counterparts (Table 6). Note (2): Individual notes: d: Significance in the I band is 2.94σ, formally below a 3σ threshold. e: The center of the I band candidate was significantly obscured by scattered light in the V-band image, but the matched filter algorithm found a couple of cluster candidates in the unaffected regions of the V image. g: These two cluster candidates overlap at the 3σ contour level, but the centroids differ significantly. These systems, if a true match, are filamentary and unlikely to be virialized. h: Note significant difference in estimated redshifts between the I and V data. Note (3): Note though that Lambda from the I and V bands should be similar. Note (4): KS probability between 0 and 1 that the galaxies were randomly selected from the same parent population as the rest of the galaxies in the same field. Typically ∼2000 galaxies were measured in the same field. Note (5): Note on P(KS): f: The joint photometry for this candidate was significantly distant from the X-ray core because of scattered light limitations.
Byte-by-byte Description of file: table4.dat
Bytes Format Units Label Explanations
1- 8 A8 --- Cluster Cluster designation 10 A1 --- Band [IV] Band name 12- 13 I2 h RAh Right ascension (J2000) 15- 16 I2 min RAm Right ascension (J2000) 18- 22 F5.2 s RAs Right ascension (J2000) 24 A1 --- DE- Declination sign (J2000) 25- 26 I2 deg DEd Declination (J2000) 28- 29 I2 arcmin DEm Declination (J2000) 31- 34 F4.1 arcsec DEs Declination (J2000) 36- 39 F4.2 --- DetConf Detection confidence in units of σ 41- 46 F6.2 --- Lambda Effective optical luminosity (G1) 48- 51 F4.2 --- z Estimated redshift (G2) 53- 57 F5.2 mag Vmag Average V band magnitude 59- 61 I3 arcsec Rad Effective radius (G3) 63-105 A43 --- Com Comments
Byte-by-byte Description of file: table6.dat
Bytes Format Units Label Explanations
1- 11 A11 --- RField ROSAT Observation identification 13- 26 A14 --- RXJ The X-ray candidate cluster name 28- 29 I2 h RAh ? Hour of Right Ascension (J2000) 31- 32 I2 min RAm ? Minute of Right Ascension (J2000) 34- 38 F5.2 s RAs ? Second of Right Ascension (J2000) 40 A1 --- DE- Sign of the Declination (J2000) 41- 42 I2 deg DEd ? Degree of Declination (J2000) 44- 45 I2 arcmin DEm ? Arcminute of Declination (J2000) 47- 50 F4.1 arcsec DEs ? Arcsecond of Declination (J2000) 52- 56 F5.1 ct Counts ? Net number of X-ray photons in the source 58- 61 F4.1 arcmin Theta ? Distance from the center of the PSPC pointing 63- 67 F5.1 arcsec FWHM ? Estimated source Full-Width at Half-Maximum 69- 71 F3.1 --- SigExt ? Confidence level of the source extended nature 73- 77 F5.2 10-14mW/m2 FXray ? Source 0.5-2.0keV X-ray flux in units of 10-14erg/cm2/s 79- 83 F5.2 10-14mW/m2 e_FXray ? The 1σ error in FXray 85- 89 F5.3 --- z ? Available spectroscopic redshift 90 A1 --- u_z Uncertainty flag on z 92 A1 --- f_z [2d] Flag on z (1) 94-107 A14 --- Match The optical match, [DSM2002] designation 108 A1 --- u_Match [?] Questionnable match 110 A1 --- f_Match [3] Flag on Match (2) 112-152 A41 --- Com Comments
Note (1): Flag on redshift: d: double X-ray source; 2: The extended X-ray source RXJ1256.9+4720 is likely to be associated with the radio galaxy 3C280, the target of the original observation. The X-rays could be from the galaxy or a cluster surrounding the galaxy. Note (2): Flag on Match: 3: This source (Abell 1455) was obscured by a nearby F3 star in the I-band data, but 3 optical candidates were identified nearby. The matched filter algorithm may have picked up the outskirts of this cluster. The sources OC 1, 4, 5 are OC1 1203+2758, OC4 1204+2805, OC5 1204+2801, respectively.
Byte-by-byte Description of file: table7.dat
Bytes Format Units Label Explanations
2- 15 A14 --- RXJ X-ray source name 17- 29 A13 --- [DSM2002] Optical source designation 31- 35 F5.3 --- z spectroscopic redshift 37- 39 F3.1 --- z2 Estimated redshift 41 A1 --- n_Com [a] Note on Com (1) 43- 72 A30 --- Com Comments
Note (1): Individual note: a: The X-ray cluster was obscured by the diffraction spike of an F3 star; the matched filter algorithm found three candidates in the vicinity, none close enough for an official match.
Global notes: Note (G1): Corresponds to the equivalent number of L* galaxies in the cluster such that the optical cluster luminosity Lambda/L☉=LambdaL*/L☉=Lambda*10-0.4(M☉_-M*)^ where M☉ is the absolute magnitude of the Sun in the appropriate band (Postman et al., 1996AJ....111..615P). The quantity Lambda is relatively insensitive to H0; variations ∼5% were measured if h75=1.33 rather than 1.0. For reference, a richness class 1 cluster at z≤0.7 had Lambda=30-65 in the I-band (Postman et al., 1996AJ....111..615P). Note (G2): Based on the best-fit luminosity function. Note (G3): Corresponding to the area of detection equal to π Rad2.
History: From electronic version of the journal References: Postman et al., Paper I 1996AJ....111..615P
(End) Greg Schwarz [AAS], Patricia Bauer [CDS] 25-Jun-2002
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