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. =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 M_5500_=-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, f_B_, 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: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- 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 -------------------------------------------------------------------------------- See also: II/179 : Southern Spectrophotometric Standards. I + II (Hamuy+ 1992,94) Byte-by-byte Description of file: table?.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 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 m_5500_ (at 5500{AA}) magnitude 52- 56 F5.1 mag M5500 Absolute m_5500_ 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 -------------------------------------------------------------------------------- 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; Hamuy et al., 1994, Cat. ). Effective wavelength of filters: uz: 3500{AA} vz: 4175{AA} bz: 4700{AA} yz: 5500{AA} with 200{AA} width. -------------------------------------------------------------------------------- History: Prepared via OCR at CDS. ================================================================================ (End) James Marcout, Patricia Bauer [CDS] 06-Feb-2003