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Published April 20, 2007 | Published
Journal Article Open

Dynamical Evidence for Environmental Evolution of Intermediate-Redshift Spiral Galaxies

Abstract

Combining resolved optical spectroscopy with panoramic HST imaging, we study the dynamical properties of spiral galaxies as a function of position across two intermediate-redshift clusters, and we compare the cluster population to field galaxies in the same redshift range. By modeling the observed rotation curves, we derive maximal rotation velocities for 40 cluster spirals and 37 field spirals, yielding one of the largest matched samples of cluster and field spirals at intermediate redshift. We construct the Tully-Fisher (TF) relation in both V and K_s bands, and find that the cluster Tully-Fisher relation exhibits significantly higher scatter than the field relation, in both V and K_s bands. Under the assumption that this increased scatter is due to an interaction with the cluster environment, we examine several dynamical quantities (dynamical mass, mass-to-light ratio, and central mass density) as a function of cluster environment. We find that the central mass densities of star-forming spirals exhibit a sharp break near the cluster virial radius, with spirals in the cluster outskirts exhibiting significantly lower densities. We argue that the lower density spirals in the cluster outskirts, combined with the high scatter in both K_s- and V-band TF relations, demonstrate that cluster spirals are kinematically disturbed by their environment, even as far as 2R_(vir) from the cluster center. We propose that such disturbances may be due to a combination of galaxy merging and harassment.

Additional Information

© 2007 The American Astronomical Society. Received 2006 July 21; accepted 2007 January 8. We thank Taddy Kodama and the PISCES collaboration for kindly making their Suprime-Cam observations available to us. We thank Daisuke Nagai, Andrew Benson, and Kevin Bundy for valuable discussions. G. P. S. thanks Dan Stark, Dave Thompson, and Chris Conselice for assistance with the observations from Palomar Observatory. Faint-object spectroscopy at Keck Observatory is made possible by the dedicated effort of the instrument teams and support staff. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. G. P. S. acknowledges financial support from a Royal Society University Research Fellowship. The analysis pipeline used to reduce the DEIMOS data was developed at UC Berkeley with support from NSF grant AST 00-71048. We acknowledge support from STScI grants HST-GO-08559.01-A and HST-GO-09836.01-A.

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August 22, 2023
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