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ABELL - Abell Clusters

HEASARC
Archive

Overview

The ABELL database contains information from a catalog of clusters of galaxies, each having at least 30 members within the magnitude range m3 to m3+2 (m3 is the magnitude of the third brightest cluster member) and each with a nominal redshift less than 0.2. The database contains the revised Northern Abell catalog, the Southern Abell catalog, and the Supplementary Southern Abell catalog; the catalogs are published as tables 3, 4 and 5 of Abell, Corwin & Orowin (1989).

Catalog Bibcode

1989ApJS...70....1A

References

"A Catalog of Rich Clusters of Galaxies", Abell, G. O., Corwin, H. G. Jr., and Olowin, R. P. Astrophys. J. Suppl., 1989, vol 70, p1.

Provenance

This database table was created by J. Osborne of Leicester from the STADAT SCAR file abelb.dat. The original SCAR version was created by Diana Parsons on 12 March 1990.

Description

The contents of the ABELL database is identical to tables 3, 4 and 5 of Abell, Corwin & Orowin (1989). For each Abell cluster it gives (among other things) RA & Dec, cluster type, magnitude of first, third and tenth ranked cluster members, galactic coordinates, redshift, and richness and distance classes. Sub-samples have been created for the ABELL database, so that users may easily view the three tables separately. The sub-sample called NORTHERN contains table 3, the "Northern Abell catalog", while the sub-sample SOUTHERN contains table 4, the "Southern Abell catalog", and the sub-sample SUPPL contains table 5, the "Supplementary Southern clusters". Users can view any of these samples, or view the standard TOTAL sample, by typing `csam xxxxx` where `xxxxx` is the sample name. Note that entries from the Northern Abell catalog table do not list `xcen`, `ycen`, `Abell type`, `m1`, `m3`, `m10`, previous listings, or number of plates and observers. The Northern catalog has also had all known errors corrected (Struble and Rood 1987a, Leir 1976 as reported by Struble and Rood 1987a, and Corwin 1972 unpublished).

Parameters

_Count
Number of cluster members

_Field
Southern sky survey field no.

_Table
Entry from Table 3, 4 or 5?

Atype
"Abell Type". Cluster classification in Abell's system: I = irregular, R = regular, IR and RI = intermediate. ":" indicates a mean type with differences between estimates of two steps, or an uncertain type estimate; "?" indicates a mean type with differences between estimates of three steps, or a questionable type estimate.

BII
Galactic latitude of the apparent cluster centers, calculated from the 1950 equatorial coordinates.

Bmtype
Number of cluster members

Class
Source classification

Countcd
Code for number of cluster members. (: = mean, ? = quest)

Dec
Declination of the apparent cluster center (degrees). When the cluster was found in more than one field, a mean position is listed. Abell and Corwin used overlays positioned with respect to SAO stars to estimate the position, while Olowin calculated positions from his measured rectangular coordinates. Thus, Olowin's positions were given double weight when means were taken.

Dec_1950
Declination in 1950 coordinates

Dist
Distance class corresponding to Abell's (1958) criteria. For the northern Abell catalog, this is Abell's original distance class from his m10. For the southern catalog, these are from the m10A's listed in the next column.

LII
Galactic longitude of the apparent cluster centers, calculated from the 1950 equatorial coordinates.

M1
Weighted mean total V magnitude estimate for the first-ranked cluster member. NO GALACTIC EXTINCTION CORRECTION HAS BEEN APPLIED. ":" indicates a mean magnitude with a standard deviation of more than +/-0.5 mag, or an uncertain magnitude estimate. "?" indicates a mean magnitude with a standard deviation of more than +/-1.0 mag, or a questionable magnitude estimate. "*" indicates that the magnitude estimate is for a known or probable foreground object.

M10
Weighted mean total V magnitude estimate for the tenth-ranked cluster member, again UNCORRECTED for galactic extinction. Uncertainty symbols as for M1 and M3.

M10cd
Code for M10 magnitude (: = mean, ? = quest)

M1cd
Code for M1 magnitude (: = mean, ? = quest)

M3
Weighted mean total V magnitude estimate for the third-ranked cluster member, again UNCORRECTED for galactic extinction. Uncertainty symbols as for M1.

M3cd
Code for M3 magnitude (: = mean, ? = quest)

Name
The `name` given is the Abell number, in the format "ABELL1965", for example. The clusters are numbered in order of right ascension for 1855 as listed by Abell (1958) for the northern clusters (1 to 2712), and in order of right ascension for 1950 for the southern clusters (2713 to 4076). The supplementary southern clusters are numbered from 1 to 1174, and are followed by an "s"; for example, "ABELL1174s".

NumObs
Number of fields in which the cluster was found, and the observer's initial (A = Abell,C = Corwin, O = Olowin).

Previ
Sources of previous listings: * B = Braid and MacGillivray (1978) * D = Duus and Newell (1977) * d = Dressler (1980) * K = Klemola (1969) * O = Olowin (1987) * Q = Quintana and White (1980 and private communication) * Rose (1976) * S = Sersic (1974) * s = Snow (1970)

Even though all questionable cases of cross-identification were checked on the Southern Sky Survey, there remain a few uncertain cases. These are given in the Notes to the Catalog.

RA
Right ascension of the apparent cluster center (degrees). When the cluster was found in more than one field, a mean position is listed. Abell and Corwin used overlays positioned with respect to SAO stars to estimate the position, while Olowin calculated positions from his measured rectangular coordinates. Thus, Olowin's positions were given double weight when means were taken.

RA_1950
Right Ascension in 1950 coordinates

Redshift
Cluster redshift from the lists by Struble and Rood (1987b, northern Abell clusters), Huchra's 1986 collection of published redshifts (Huchra, private communication), Fairall (1985), Corwin (1981; see also Corwin and Emerson 1982), Couch and Newell (1981 and private communication), Noonan (1981), and Spinrad (private communication). The redshift is in parentheses if it is more than 0.3 dex from the expected redshift for the cluster's m10. Redshifts from Huchra's list and from Fairall (1985) were determined by selecting all galaxies with known redshifts within one Abell radius of the cluster center, rejecting discordant redshifts, and averaging the remainder. A redshift value of zero means that there is no measurement.

Rich
Richness class as defined by Abell (1958). For the northern Abell catalog, this is Abell's original richness class.

Vmag
`Vmag` is the magnitude for the tenth-ranked cluster member in Abell's (1958) system, CORRECTED FOR GALACTIC EXTINCTION following Abell's formula. For the northern Abell catalog, this is Abell's original magnitude. For the southern catalog, these were transformed from the m10 on the first line (see text).

Xcen
Rectangular X-center in millimeters of the apparent cluster center, referred to the CENTER of the Southern Sky Survey Field given in the previous column. The field centers are defined by the crosses near the edges of the plates. The positive x direction is to the east (left) and the positive y direction is to the north (top). These are in the same sense as the rectangular coordinates given by Lauberts (1983) in the ESO/Uppsala Catalog, and are listed to facilitate location of the cluster on the 5 x 5-degree ESO 1.0-m Schmidt portion of the Southern Sky Survey. Abell and Corwin measured rectangular coordinates from the left and bottom edges of the plates, so the xcen and ycen from their data are calculated assuming that the plate center is 164 millimeters from the left and bottom crosses on the plates (they also measured the crosses). Olowin referred his rectangular coordinates directly to the plate center as defined by the crosses, so no transformation is necessary for his data.

Xll
Rectangular x-coordinate of the apparent cluster center, referred to the south-east (lower left) edge of the Southern Sky Survey Field given in the first line. The field edges are defined by the crosses near the edges of the plates; thus, it is possible for these coordinates to be negative. For the northern Abell catalog, these coordinates are from Rood and Sastry (1971). Olowin's data were transformed assuming that the plate center is 164 millimeters from the crosses.

Ycen
Rectangular Y-center in millimeters of the apparent cluster center, referred to the CENTER of the Southern Sky Survey Field given in the previous column. The field centers are defined by the crosses near the edges of the plates. The positive x direction is to the east (left) and the positive y direction is to the north (top). These are in the same sense as the rectangular coordinates given by Lauberts (1983) in the ESO/Uppsala Catalog, and are listed to facilitate location of the cluster on the 5 x 5-degree ESO 1.0-m Schmidt portion of the Southern Sky Survey. Abell and Corwin measured rectangular coordinates from the left and bottom edges of the plates, so the xcen and ycen from their data are calculated assuming that the plate center is 164 millimeters from the left and bottom crosses on the plates (they also measured the crosses). Olowin referred his rectangular coordinates directly to the plate center as defined by the crosses, so no transformation is necessary for his data.

Yll
Rectangular y-coordinate of the apparent cluster center, referred to the south-east (lower left) edge of the Southern Sky Survey Field given in the first line. The field edges are defined by the crosses near the edges of the plates; thus, it is possible for these coordinates to be negative. For the northern Abell catalog, these coordinates are from Rood and Sastry (1971). Olowin's data were transformed assuming that the plate center is 164 millimeters from the crosses.


Contact Person

Questions regarding the ABELL database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 8-Nov-2004