The HI absorption feature in PKS1830-211 at z=0.19 is observed with the VLA in conjunction with the VLBA antenna at Pie Town (PT). The PT antenna was linked in real time to the VLA correlator through a new experimental state-of-the-art fiber optics link while the observations at 1191MHz accessed the lowest frequencies available in the 20cm band. The VLA-PT baselines allowed us to separate the two bright radio images in the Einstein ring at 1191 MHz, spatially resolving the HI absorption feature. We find similar absorption profiles against the two components, separated by 42 km/s. Each profile has an optical depth of 0.02 which corresponds to an HI column density of 1.2x1020 atoms/cm2 for a spin temperature of 100K. Deconvolved velocity dispersions are 12 km/s for the NE and 7 km/s for the SW component. These properties are typical for a normal galactic HI disk. Besides a red galaxy near the center of the Einstein ring, a recent HST-NICMOS image by Lehár et al (1999) also shows a bluer galaxy (G2) at 6.2 kpc to the south (H0=75 km/s/Mpc, q0=0.5, z=0.19). We identify G2 as the z=0.19 absorber since two other candidate galaxies in the HST image have impact parameters of 32 and 38 kpc at z=0.19. The NIR morphology of G2 suggests a near face-on late type galaxy which implies that the 42 km/s velocity difference hints at a rather massive system.
American Astronomical Society Meeting Abstracts
- Pub Date:
- December 1999