Antonio Algaze Beato
(Photo by Tony Acevedo)
NAIC/AO Newsletter, July 1997
In January, Paul Castleberg completed his Ph.D., submitting his thesis, entitled Lidar Development with Applications to the Stratosphere-Troposphere Exchange and Tropical Aerosol Detection. Paul's contribution to the development of the lidar systems at Arecibo was substantial on every level. He was deeply involved in the design and construction of the Grease Pit lab that, until now, has been temporary housing for the potassium resonance lidar. He built, from the ground, the potassium resonance system while working on his thesis, in which resonance scatter is merely a sidebar. Much of the software and hardware that future lidar observers will use was developed by Paul.
For his dissertation, Paul became interested in high, thin, and invisible to the eye aerosol layers which had been observed, but generally ignored, in the Rayleigh lidar data. This began with a campaign, conceived by Paul, which used both the lidar and the 430 MHz radar to study aerosols in the tropopause and stratosphere. It coincided with the Space Shuttle LITE experiment in September, 1994. These combined observations, coupled with a review of older data sets in which dust from the Mount Pinatubo volcano eruption in June, 1991 was seen, established a database from which the evolution of the dust in the stratosphere could be studied.
Paul completed his doctorate in Electrical Engineering at Cornell under the supervision of Mike Kelley. Craig Tepley served on Paul's committee
Antonio Algaze Beato
(Photo by Tony Acevedo)
On July 3rd, Antonio Algaze Beato, a former NAIC REU student, successfully defended his Master's thesis, The Neutral Hydrogen Content of Early-type Disk Galaxies, at the University of Puerto Rico - Rio Piedras. The thesis research was an outgrowth of Antonio's summer student project which entailed observing and reducing 21 cm spectra for a sensitive survey of early-type disk galaxies with the Arecibo telescope. The survey revealed many galaxies, classified as S0 in the Uppsala General Catalog (UGC), which have gas contents comparable to the amounts expected for normal Sa or Sb spiral galaxies. If the galaxies contain sufficient densities of gas for the star formation process to proceed, it is difficult to understand the apparent lack of structure which led to their classification as S0's.
As his Master's thesis, Antonio obtained a large number of CCD images of these gas-rich S0 galaxies with the Mount Laguna 40" telescope (operated by San Diego State University). The images taken with a blue filter (sensitive to star formation regions) revealed low-surface brightness structure, including outer rings and spiral arms, in almost all of these, which implied that the gas-rich S0's should be classified as anemic spirals, rather than S0's. He also found that a few of the Sa galaxies in his sample did not show structure and therefore could be called S0 galaxies. The misclassifications on the basis of the first Palomar Sky Survey plates are understandable due to the idiosyncrasies of the photographic process. The expanded linear response of the CCD images provides the range and contrast necessary for identifying the low-surface brightness structure. The findings of this study have important implications for theories of galaxy evolution and morphological segregation.
Algaze's thesis work was supervised by Jo Ann Eder, research associate at Arecibo Observatory, and most of the data reduction and analysis was conducted at the Observatory. We hope that this successful collaboration between the Arecibo Observatory and the University of Puerto Rico Physics Department will become the prototype for future joint efforts involving talented Puerto Rican students.