Rotation and Masses of Galaxies at z $\simeq$ 3.2

Abstract

We present infrared spectra at R {\sime} 3000 around 2.1{μ}mobtained recently with ISAAC at the VLT of a small sample of 5(6)high z galaxies discovered by narrowband infrared imaging and confirmedinitially as emission line objects on the basis of relatively lows/n spectra. The primary aim of the new observations was to obtainimproved velocity dispersions and, ideally, rotation curves in orderto extend dynamical mass estimates to much higher redshifts thanpossible so far using visible spectroscopy. They were therefore conductedin service mode under excellent seeing conditions and with integrationtimes of several hours. In most cases the emission `line' can beunambiguously identified as the [OIII]5007/4959{Å} doublet at z{\sime} 3.2. Measured velocity dispersions are typically {\sime}80 km s^{-1}. Of particular interest is the galaxy observed withthe highest s/n and spatial resolution whose emission line exhibitsa position versus velocity line tilt consistent both with orderedrotation and the velocity dispersion. The remainder exhibit eithersome or no rotation and with maximum velocities smaller than theirvelocity dispersions. This is most probably due to inclination and/orsensitivity effects. The derived masses are only typically {\sime}10^{10} M{\sun} within the central {\sime}5 - 10kpc and could beeven lower if outflows also contribute to the observed gas motions.