AAS 203rd Meeting, January 2004
Session 89 Galaxy Clusters at High Redshift
Poster, Wednesday, January 7, 2004, 9:20am-6:30pm, Grand Hall

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[89.05] H\alpha Star-Formation Rates for the z=0.84 Galaxy Cluster CLJ0023+0423B

R. A. Finn (U. Mass), D. Zaritsky, D. W. McCarthy, Jr. (Steward Observatory)

We present H\alpha-derived star-formation rates (SFRs) for the galaxy cluster CL~J0023+0423B at z = 0.845. Our 3\sigma flux limits corresponds to a star-formation rate of 0.24~\rm h100-2~ M\odot ~ yr-1, and our minimum reliable H\alpha~+ [N~II] equivalent width is > 10~Å, demonstrating that near-infrared narrow-band imaging can sample the star-forming galaxy population in distant clusters. Comparison with spectroscopy shows that the number of false detections is low (9 ±6%) and that our H\alpha equivalent widths are correlated with spectroscopically determined [O~II] equivalent widths. A magnitude-limited spectroscopic survey conducted over the same area missed 70% of the star-forming galaxies and 65% of the integrated star formation. Using Hubble Space Telescope Wide Field Planetary Camera 2 Archive images, we fit Sersic profiles to all galaxies with significant narrow-band equivalent widths and find that equivalent width decreases as the steepness of galaxy profile increases. We find no significant population of early type galaxies with ongoing star formation. The integrated SFR per cluster mass of CLJ0023+0423B is a factor of ten higher than that of the three z ~0.2 clusters in the literature with available H\alpha observations. A larger sample of z ~0.8 clusters spanning a range of cluster masses is needed to determine whether this variation is due to a difference in cluster mass or redshift.

RAF acknowledges support from the NASA Graduate Student Researchers Program through NASA Training Grant NGT5-50283 and from an NSF Astronomy and Astrophysics Postdoctoral Fellowship under award AST-0301328. DZ acknowledges support from the David and Lucile Packard Fellowship.

The author(s) of this abstract have provided an email address for comments about the abstract: rfinn@astro.umass.edu

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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.