J/AJ/124/3061 uz,vz,bz,yz photometry in Coma cluster (Odell+, 2002)
The color-magnitude relation in Coma:
clues to the age and metallicity of cluster populations.
Odell A.P., Schombert J., Rakos K.
<Astron. J. 124, 3061 (2002)>
=2002AJ....124.3061O 2002AJ....124.3061O
ADC_Keywords: Clusters, galaxy ; Photometry, narrow-band ; Abundances, [Fe/H]
Keywords: galaxies: elliptical and lenticular, cD - galaxies: evolution -
galaxies: stellar content
Abstract:
We have observed three fields of the Coma Cluster of galaxies with a
narrowband (modified Stroemgren) filter system. Observed galaxies
include 31 in the vicinity of NGC 4889, 48 near NGC 4874, and 60 near
NGC 4839, complete to M5500=-18 in all three subclusters.
Spectrophotometric classification finds all three subclusters of Coma
to be dominated by red, E-type (elliptical/S0) galaxies with a mean
blue fraction, fB, of 0.10.
Description:
The Coma Cluster (Abell 1656) is roughly 89' in radius, with three
dominant galaxies (NGC 4889, 4874, and 4839) forming the core of three
separate cluster components. The first two of these, only 7' apart,
seem to be the relic central galaxies of previous groups that have
recently merged into the current cluster. An additional subcluster,
centered on the third galaxy, NGC 4839, 40' to the southwest, seems to
be falling into the central region or has just passed through the main
body of the cluster, perhaps triggering new star formation. Each
section of the Coma Cluster was observed with the Kuiper 1.55m
telescope of the Steward Observatory on Mount Bigelow, Arizona. Data
was taken with the LPL Focal Reducer and 2K CCD chip (binned to 1K),
which yielded 0.65"/pix or a field size of 10.8'. We centered one
field on NGC 4889 (2000 April 24) and the other on the central giant
NGC 4874 (2000 May 10-11). Our results are restricted to these central
regions and therefore are not necessarily typical for the whole
cluster. The total April exposure time for the uz filter was 11700s,
the vz filter 9600s, the bz filter 3000s, and the yz filter 3000s.
Each set of exposures was divided in frames of 600-1200s to reduce the
influence of cosmic rays and irregularities of pixels on the chip. For
the May observing run, the total exposure times were 7200s in each of
yz and bz and 9600s in vz. Weather conditions restricted the uz filter
to 2400s, and therefore it is of lower quality. Calibration was
obtained through a number of spectrophotometric standards measured on
each night. The region around NGC 4839 was observed with the 4 m
Mayall telescope of the National Optical Astronomy Observatory (NOAO)
on Kitt Peak, Arizona (2001 June 27-28). The Prime Focus T2KB CCD
camera produces a 14' field with 0.42"/pix. The total exposure of
1800s in each filter consists of three 300s exposures each night.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 73 31 NGC 4889 group
table2.dat 73 48 NGC 4874 group
table3.dat 73 60 NGC 4839 group
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See also:
II/179 : Southern Spectrophotometric Standards. I + II (Hamuy+ 1992,94)
Byte-by-byte Description of file: table?.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- [OSR2002] Galaxy name
6- 14 F9.5 deg RAdeg Right ascension in decimal degrees (J2000.0)
16- 23 F8.5 deg DEdeg Declination in decimal degrees (J2000.0)
25- 28 F4.2 mag uz-vz uz-vz colour index (1)
30- 33 F4.2 mag bz-yz bz-yz colour index (1)
35- 39 F5.2 mag vz-yz vz-yz colour index (1)
41- 45 F5.2 mag mzmag mz (=(vz-bz)-(bz-yz)) magnitude (1)
47- 50 F4.1 mag m5500 m5500 (at 5500Å) magnitude
52- 56 F5.1 mag M5500 Absolute m5500 magnitude
58- 62 F5.2 [Sun] [Fe/H] ? Metallicity
64- 69 F6.3 mag D(bz-yz) ? Age index, Delta(bz-yz) (1)
72- 73 A2 --- Class Resultion galaxy class
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Note (1): The photometric system is based on the theoretical transmission
curves of filters (which can be obtained from the authors) and the
spectra of spectrophotometric standard stars published in the
literature (Massey & Gronwall, 1990ApJ...358..344M 1990ApJ...358..344M; Hamuy et al.,
1994, Cat. II/179).
Effective wavelength of filters:
uz: 3500Å
vz: 4175Å
bz: 4700Å
yz: 5500Å
with 200Å width.
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History:
Prepared via OCR at CDS.
(End) James Marcout, Patricia Bauer [CDS] 06-Feb-2003