AAS 201st Meeting, January, 2003
Session 42. Galaxies and Clusters
Poster, Tuesday, January 7, 2003, 9:20am-6:30pm, Exhibit Hall AB

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[42.07] ACS Grism Observations of Galaxy Clusters Abell 1689 and CL1252-2927

Z.I. Tsvetanov, G.R. Meurer, N. Benitez (JHU), P. Rosati (ESO), M. Postman (STScI), C. Gronwall (PSU), D.R. Ardila (JHU), F. Bartko (Bartko Sci. & Tech.), J.P. Blakeslee (JHU), R. Bouwens (UCO/Lick Obs.), T.J. Broadhurst (Hebrew U.), R.A. Brown (STSsI), C. Burrows (STScI), E. Cheng (GSFC), M. Clampin (STScI), N. Cross, P.D. Feldman, H.C. Ford (JHU), M. Franx (Leiden Obs.), D.A. Golimowski (JHU), G. Hartig (STScI), G.D. Illingworth (UCO/Lick Obs.), L. Infante (Univ. Catolica de Chile), R.A. Kimble (GSFC), J. Krist (STScI), M. Lesser (Steward Obs.), A.R. Martel, F. Menanteau (JHU), G. Miley (Leiden Obs.), M. Sirianni (JHU), W.B. Sparks (STScI), H. D. Tran (JHU), R.L. White (STScI), W. Zheng, A.C.S. Science Team (JHU)

We present Advanced Camera for Surveys grism slitless spectroscopy of galaxy clusters CL1252-2927 (z=1.23) and Abell 1689 (z=0.18) obtained as part of the ACS Guaranteed Time Observations program. The observations of Abell 1689 were obtained over three orbits (total exposure time 7100 s) with the Wide Field Camera dithered to close the gap between the CCDs. In the case of CL1252-2927 we covered the cluster with a four-point mosaic pattern with a central overlap area of 1 arcmin2. Each one of the mosaic panels was one orbit deep (2100 s) and the overlap area had an effective total exposure time of 8400 s.

We will present discussion of the ACS grism observations and will compare them with existing ground-based spectroscopy as well as photometric redshift estimates. The Abell 1689 field is very crowded, but the exclusive HST/ACS resolution allow us to spectroscopically confirm the counterpart of a well known gravitationally lensed galaxy at high redshift. For CL1252-2927 we will compare the ACS grism spectra of candidate cluster members identified from the cluster red sequence with those identified spectroscopically from the ground. In the overlapping area we co-add grism spectra from individual mosaic pointings. These allow us to study compact objects with emission line and/or continuum break down to AB magnitude i~26.

ACS was developed under NASA contract NAS 5-32865, and this research is supported by NASA grant NAG5-7697. We are grateful for an equipment grant from the Sun Microsystems, Inc.

The author(s) of this abstract have provided an email address for comments about the abstract: zlatan@pha.jhu.edu

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