Alistair Walker
CTIO Scientific Staff
Areas of Interest
Stellar Populations, Magellanic Clouds, Distance Scale, Stellar Photometry
Recent Research Results
Walker, with J. Nemec (York University) has completed an analysis of
extensive photometry of the RR Lyrae variables in the galactic globular
cluster IC 4499. The work allows direct comparisons between the
observational properties of these old, evolved, low-mass stars and
predictions from evolutionary and pulsation theory.
Walker, with H. Smith (Michigan State) and N. Silbermann (IPAC), is
completing the analysis of CCD photometry of a one-degree square field
in the Small Magellanic Cloud, obtained with the Curtis Schmidt
telescope. This field contains many short-period Cepheids, and the
program is aimed particularly at defining the structure of the faint
end of the Cepheid Period-Luminosity relation in the HR diagram.
A photometric investigation into the stellar populations present in the
local group dwarf spheroidal galaxy, Tucana, from ground-based and
Cycle 4 HST observations (P.I., P. Seitzer, U. Michigan) has been
completed. Walker analyzed all the ground-based and the HST PC
observations. The galaxy shows a single, early epoch of star formation
and is metal-poor. Tucana is unique in the Local Group by virtue of its
remoteness from any luminous group member and thus its properties are
important in the evaluating the effect of interactions between LG
members upon their stellar content and evolution.
Future Research Plans
Walker is a member of two teams (one as P.I.) awarded HST WFPC2 time in
Cycles 5 and 6 for stellar population studies in the Magellanic Clouds.
The first program will determine ages and abundances for several old or
probably old clusters in the inner regions of the Large Magellanic
Cloud. The second program will study the oldest Small Magellanic Cloud
cluster and two distant field regions, one in each Cloud. Extensive
ground-based observations with the CTIO 4-m and 1.5-m telescopes are
integral parts of each program. This work will allow the early star
formation history of the Magellanic Clouds to be deciphered, and the
results will bear directly on our ideas on the early formation and
subsequent evolution of galaxies in general. A collaboration led by D.
Terndrup (OSU), with R. Peterson (UCSD), E. Sadler (AAO), and Walker,
is beginning a search in galactic bulge fields (photometry,
spectroscopy) for hot evolved stars in the hope of identifying the
origin of the copious UV flux in old, metal-rich populations in other
galaxies.
Service
Walker is currently responsible for the Blanco 4-m telescope, and in
particular is supervising the on-going program of optical and thermal
tests, together with managing the upgrades work in these areas. These
efforts are now mostly aimed at optimizing image quality at prime
focus, maintaining the now excellent image quality in general, and
improving the understanding of the causes of the present 0.5 arcsec
image quality floor at the f/8 focus.
Walker directs and coordinates CCD operations and upgrades, supervises
the operation of the CCD laboratory, and is responsible for optical
imaging programs on all telescopes. He is responsible for the Schmidt
telescope and has managed the projects that have automated the
wide-field imager at that telescope. He is the CTIO scientist liaison
with NOAO Tucson on the production of the NOAO 8K x 8K imager and is
project scientist for most projects involving production and
implementation of the Arcon CCD controllers. He is organizing the
long-term visits to CTIO of the Bell Labs mosaic imager LACCD, and
possibly the STScI Advanced Camera.
Walker is a member of ACTR (CTIO Advisory Committee for Technical
Resources) and has served as a member of the US Gemini Science Advisory
Committee since 1994. On two occasions he has represented the US on the
Gemini Science Committee and has recently been named as CTIO observer
at the GSC. He is a member of the American Astronomical Society, the
Astronomical Society of the Pacific, and the Society of Photo-Optical
Instrumentation Engineers.
Go to: [ NOAO Scientific Staff ]
[ NOAO ]
[ CTIO ]
[ KPNO ]
[ NSO ]
[ USGP ]
NOAO is operated by the Association of U
niversities for Research in Astronomy
(AURA), Inc. under cooperative agreement with the
National Science Foundation
Posted: 06Dec1996