ADC/CDS Standard Document for Catalog:/catalogs/7/7042A/
ADC/CDS Standard Document for Catalog:| 1. Use the ADC Data Viewer Suite to visualize the data. |
|
| 2. Get the data files via anonymous FTP. (See Note.) |
|
VII/42A GMP catalogue: galaxies in the Coma cluster (Godwin+ 1983)
================================================================================
The Coma Cluster - I. A catalogue of magnitudes, colours, ellipticities
and position angles for 6724 galaxies in the field of the Coma cluster
Godwin J.G., Metcalfe N., Peach J.V.
<Mon. Not. R. Astron. Soc. 202, 113 (1983)>
=1983MNRAS.202..113G
================================================================================
ADC_Keywords: Clusters, galaxy
Description:
The catalogue contains isophotal magnitudes, radii, intensity profiles,
ellipticities and (b-r) colours for 6724 galaxies with b26.5 < 21.0 mag
in a 26.3 degree square area centered on the Coma cluster.
The sample is essentially complete to b26.5 = 20.0, with rms deviations
in b26.5, r24.75 and (b-r) all about 0.15mag.
The plates used in this investigation were all taken with the Palomar
48-inch Schmidt telescope during good conditions in 1976 May.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
catalog.dat 104 6724 The catalogue of galaxies, published as
Appendix Microfiche MN202/1 and 2
--------------------------------------------------------------------------------
Byte-by-byte Description of file: catalog.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- GMP [1/6724]+ Identification number
5 A1 --- n_GMP [?] "?" indicates a probable galaxy (1)
6- 11 I6 arcsec Xpos [-4900/4900]+= increasing westwards (2)
12- 17 I6 arcsec Ypos [-4900/4900] increasing northwards (2)
19 A1 --- n_b26.5 [*] indicates an overlapped image in b-band
20- 24 F5.2 mag b26.5 b-band integrated magnitude (3)
26- 30 F5.1 arcsec r(b26.5) Isophotal radius in b; rms is 0.5arcsec (4)
32 A1 --- n_r24.75 [*] indicates an overlapped image in r-band
33- 37 F5.2 mag r24.75 ?=99.99 r-band integrated magnitude (5)
39- 43 F5.1 arcsec r(r24.75) ?=999.9 Isophotal radius in r;
rms is 0.7arcsec. (4)
46- 49 F4.2 mag (b-r) ?=9.99 (b-r) color index (6)
51- 54 F4.1 arcsec r(b-r) ?=99.9 Isophotal radius in (b-r) (4)
56- 58 F3.1 --- eps ?=9.9 Ellipticity (7)
60- 62 I3 deg PosAngle ?=999 Position angle of the major axis (8)
64- 68 F5.2 mag/arcsec alpha(b) ?=9.99 Slope parameter in b-band (9)
70- 73 F4.1 mag gamma(b) ?=9.9 Profile indicator (10)
75- 76 I2 --- N(points) ?=99 Number of points used to form
alpha(b) and gamma(b)
78- 80 I3 --- GP [1/923]? Number in Godwin and Peach (1977)
82- 84 I3 --- [RB67] [1/271]? Number in Rood and Baum (1967,1968)
85-104 A20 --- Com Comments (11)
--------------------------------------------------------------------------------
Note (1): Metcalfe and Peach subjectively discriminated between
galaxies and stars by examination of 14270 images brighter than
b26.5 = 21.0. The final list of objects includes 6205 galaxies,
146 double galaxies, and 2 triple galaxies together with 350 probable
galaxies and 21 probable double galaxies for a total of 6724 objects.
An extensive discussion of the completeness and purity of the search
is given in Section 5 of the paper
Note (2): X and Y positions in arc seconds relative to the approximate
center of the cluster, increasing westwards and northwards
respectively. The origin of these coordinates is at
RA=12h57.3 Dec=+28d14.4'(1950.0).
The galaxies are ordered by increasing Xpos.
Note (3): The b-band magnitude integrated within the 26.5b mag/arsec2
isophote. This limiting isophote, about 3 percent over the background
sky brightness, was chosen for optimum signal-to-noise ratio.
The rms deviation in b26.5, based on the repeatability of measurements
using different scans of the same plates, is 0.13 mag for images
brighter than b26.5 = 20, rising to 0.2 mag in the range
20 <= b26.5 < 21. The external errors are likely to be of order
0.15 mag for images brighter than b26.5 = 20.
Note (4): The isophotal radius is defined by
r = sqrt(A/pi)
where A is the area enclosed within the isophote.
Note (5): The r-band magnitude integrated within the 24.75r mag/arcsec2
isophote. This limiting isophote, about 3 percent over the background
sky brightness, was chosen for optimum signal-to-noise ratio.
The limiting isophotes for the r-band and b-band magnitudes are
separated by roughly the mean galaxy color, so that they refer to
roughly equal metric areas in a given galaxy.
The rms deviation in r24.75 is 0.2 mag for images brighter than
r24.75 = 18. The external errors are likely to be of order 0.15 mag
for images brighter than b26.5 = 20.
A value of 99.99 indicates the r-band magnitude was omitted because of
the limited range of surface brightness measurement.
Note (6): The external error in the (b-r) color is likely to be of order
0.15 mag for images brighter than b26.5 = 20.
A value of 9.99 indicates that the color was not determined.
Note (7): The ellipticity is defined by
eps = (1-b/a) , where b/a is the axial ratio of the ellipse best
approximating the 24r mag/arcsec2 isophote, or, in the event of an
overlap, the lowest undisturbed isophote. The typical accuracy is
+/-0.1 for images with isophotal diameter r(r24) >= 5 arcsec.
A value of 9.9 indicates the ellipticity was not determined.
Note (8): The position angle, theta, of the major axis of the ellipse
is measured counter-clockwise on the sky from north. This angle
is measured to within a few degrees for most images.
A value of 999 indicates that the position angle was not determined.
Note (9): The slope parameter is defined as the slope of the logarithmic
brightness residuals of each image against a polynomial representing
the standard stellar profile. Its rms dispersion, based on
measurements from overlapping scan areas, is about 0.05mag/arcsec.
A value of 9.99 indicates the slope parameter was not determined.
Note (10): this parameter specifies the amount by which the central
surface brightness of the b-band image fell short of that which would
have been expected for a stellar image with the same number of points
measured.
A value of 9.9 indicates that this quantity was not determined.
Note (11): in cases where the object is marked as "double" or "triple"
the photometric data refer to the combined image of its components.
--------------------------------------------------------------------------------
References:
Godwin, J. G., Peach, J. V. 1977, MNRAS 181, 711 1977MNRAS.181..323G
Rood, H. J., Baum, W. A. 1967, AJ 72, 398. 1967AJ.....72..398R
Rood, H. J., Baum, W. A. 1968, AJ 73, 442. 1968AJ.....73..442R
Historical Notes:
* A tape version of the catalogue was provided by J.G. Godwin to CDS
(Centre de Donnees de Strasbourg) in June 1983
* Modifications made by Lee E. Brotzman and Robert S. Hill at the
Astronomical Data Center (ADC), Goddard Space Flight Center, in
January 1984: to strip off the CDS number in the first eight
bytes, strip off the last four bytes (which were always blank),
and to insert default values (all nines) into numerical fields
without data. A printed document describing the catalogue
was generated.
* 18-Aug-1995 at CDS: this standardized documentation was done
from Lee E. Brotzman and Robert S. Hill's document.
================================================================================
(End) Francois Ochsenbein [CDS] 18-Aug-1995