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 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:
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FileName Lrecl Records Explanations
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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 70 13 Spectroscopic versus Matched Filter Estimated
Redshifts
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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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
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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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
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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.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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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)
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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.
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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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
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
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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
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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.
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Byte-by-byte Description of file: table7.dat
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Bytes Format Units Label Explanations
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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
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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.
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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 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 1996AJ....111..615P).
Note (G2): Based on the best-fit luminosity function.
Note (G3): Corresponding to the area of detection equal to π Rad2.
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History:
From electronic version of the journal
References:
Postman et al., Paper I 1996AJ....111..615P 1996AJ....111..615P
(End) Greg Schwarz [AAS], Patricia Bauer [CDS] 25-Jun-2002