The Rotation Curves of Galaxies at Intermediate Redshift

We have undertaken a pilot project to measure the rotation velocities of spiral galaxies in the redshift range 0.18≤z≤0.4 using high-dispersion long-slit spectroscopy obtained with the Palomar 5 m telescope. One field galaxy and three cluster objects known to have strong emission lines were observed over wavelength ranges covering the redshifted lines of [O II], Ca II K, Hβ, and [O III]. Two of the objects show extended line emission that allows the tracing of the rotation curve in one or more lines. A line width similar to that obtained with single-dish telescopes for the 21 cm H I line observed in lower redshift galaxies can be derived from the observed Hβ, [O II], and [O III] emission by measuring a characteristic width from the velocity histogram