Wayne E. Baggett

Inner-truncated Disks in Galaxies

We present an analysis of the disk brightness profiles of 218 spiral and lenticular galaxies. At least 28% of disk galaxies exhibit inner truncations in these profiles. There are no significant trends of truncation incidence with Hubble type, but the incidence among barred systems is 49%, more than 4 times that for nonbarred galaxies. However, not all barred systems have inner truncations, and not all inner-truncated systems are currently barred. Truncations represent a real dearth of disk stars in the inner regions and are not an artifact of our selection or fitting procedures nor the result of obscuration by dust. Disk surface brightness profiles in the outer regions are well represented by simple exponentials for both truncated and nontruncated disks. However, truncated and nontruncated systems have systematically different slopes and central surface brightness parameters for their disk brightness distributions. Truncation radii do not appear to correlate well with the sizes or brightnesses of the bulges. This suggests that the low angular momentum material apparently missing from the inner disk was not simply consumed in forming the bulge population. Disk parameters and the statistics of bar orientations in our sample indicate that the missing stars of the inner disk have not simply been redistributed azimuthally into bar structures. The sharpness of the brightness truncations and their locations with respect to other galactic structures suggest that resonances associated with disk kinematics, or tidal interactions with the mass of bulge stars, might be responsible for this phenomenon.

In-flight performance of the Faint Object Camera of the Hubble Space Telescope: II

This paper gives an update on the performance of the Faint Object Camera--launched with the Hubble Space Telescope--since the last report two years ago. The primary camera, the f/96 relay, continues to work well, but the f/48 relay has recently developed serious problems. The stability of the f/96 relay has been very good with the only change being a small apparent decrease in UV sensitivity. Preliminary results for the f/48 DQE are presented. In-orbit UV flat fields have been obtained and the f/96 objective prisms and polarizers have been calibrated.

Preparing for JWST wavefront sensing and control operations

The James Webb Space Telescopes segmented primary and deployable secondary mirrors will be actively con- trolled to achieve optical alignment through a complex series of steps that will extend across several months during the observatorys commissioning. This process will require an intricate interplay between individual wavefront sensing and control tasks, instrument-level checkout and commissioning, and observatory-level calibrations, which involves many subsystems across both the observatory and the ground system. Furthermore, commissioning will often exercise observatory capabilities under atypical circumstances, such as fine guiding with unstacked or defocused images, or planning targeted observations in the presence of substantial time-variable offsets to the telescope line of sight. Coordination for this process across the JWST partnership has been conducted through the Wavefront Sensing and Control Operations Working Group. We describe at a high level the activities of this group and the resulting detailed commissioning operations plans, supporting software tools development, and ongoing preparations activities at the Science and Operations Center. For each major step in JWSTs wavefront sensing and control, we also explain the changes and additions that were needed to turn an initial operations concept into a flight-ready plan with proven tools. These efforts are leading to a robust and well-tested process and preparing the team for an efficient and successful commissioning of JWSTs active telescope.

A study of environmental influences on the structure of spiral galaxy disks

The results of photographic surface photometry of late-type spiral galaxies in the clusters Abell 426, Abell 1367, and Abell 2151 are presented. U- and R-band surface brightness profile properties are analyzed in terms of the following environmental parameters : the projected distance from cluster center, the projected distance to the nearest neighbor, and the local projected galaxy density. No significant correlation are found between the structure of the galaxies and the projected distance from cluster center