Paul S. Smith
Tucson Nighttime Scientific Staff
Areas of Interest
Active Galactic Nuclei, Polarimetry
Recent Research Results
Optical and UV spectropolarimetry has
proven to be one of the most powerful techniques in the investigation
of the structure of Active Galactic Nuclei (AGNs).
This technique has forcefully advanced the notion that the
AGN ionizing flux does not emerge isotropically from the nuclear
region; implying that our viewing perspective is an important factor
in determining the differences observed between various types of AGNs.
An obscuring torus of material prevents direct observation of the
inner nuclear regions if the torus intersects our line of sight.
Smith has been involved in several studies that have extended these ideas
to various luminosity classes of AGNs (e.g., Hines et al. 1995,
Ap. J., 450, L1; Wilkes et al. 1995, Ap. J., 455, L13).
In addition, HST and ground-based spectropolarimetric studies of
Seyfert 1 nuclei have emphasised that there are multiple scattering
regions close to the broad-line region (BLR; Smith et al. 1995, Ap. J.,
444, 146; Smith et al. 1997, Ap. J., 488, 202).
Another successful technique used to probe the innermost structure of AGNs
is to monitor their emission-line and continuum fluxes. A time delay
between the brightening or fading of the ionizing continuum and the
response of the line-emitting gas can be interpreted as the light travel
time from the central ionizing source to the gas, thereby giving an
estimate of the size of the BLR. Smith and his collaborators
completed the first systematic, long-term spectrophotometric
monitoring program of a well-defined sample of quasars. This project
succeeded in detecting correlated variations between the continuum and
emission-line fluxes and produced the first reliable observational
estimates of the size of the BLR in quasars; extending previous studies
of Seyfert nuclei to higher luminosity (Maoz et al. 1994, Ap. J., 421, 34;
Kaspi et al. 1996, Ap. J., 471, L75). Results from this program
suggests that the size of the BLR roughly scales with the square root
of the continuum luminosity of the AGN as expected from photoionization
models. Smith collaborated with G. Schmidt and J. Liebert (U. of Arizona)
in an HST project to resolve the remarkable
double-degenerate binary LB 11146 (Schmidt, Liebert, &
Smith, 1998, Ap. J., in press). One of the white dwarfs is highly
magnetic with a field strength of around 700 million Gauss and the other
is a non-magnetic (B < 30,000 Gauss), apparently normal DA white dwarf.
This system presents important implications related to models for stellar
formation and/or common envelope evolution. The HST observations do not
resolve the binary and give an upper limit of 0.025" for the separation of the
stellar components which implies a 90% likelihood that the white dwarfs
are separated by < 2.3 AU which makes it likely that there was material
exchanged between stars in the past (though a true common envelope stage
is not required).
Future Research Plans
Smith continues various observational projects that investigate the
blazar class of AGNs. Programs include simultaneous VLBI radio and
optical polarimetry of BL Lacertae objects to find correlations
between their radio and optical synchrotron continuum emission.
A polarization survey of a new sample of BL Lacs is in progress to
study the possibility that radio and X-ray selected BL Lacs have the
same parent population. A nearby AGN will be imaged using HST in
an attempt to resolve the scattering regions around the nucleus.
This particular object, Mrk 231, exhibits many properties similar to
broad absorption-line quasars, and presents an opportunity to resolve
some of the nuclear structures that may be present in
higher-redshift objects. Smith will continue a long-term project
with M. Corbin (Univ. of Arizona) to monitor the emission-line profiles
of quasars with exceptionally broad emission lines.
Service
Smith's primary service activity has been to manage the KPNO telescope
operators. These nine individuals are responsible for the nighttime
operation of the 4m, 2.1m, and WIYN telescopes and as such are the
primary representatives of the observatory to visiting astronomers
during their observing sessions. Smith's duties include hiring,
scheduling, and coordinating training of the operators. Another
major task he undertook during 1998 was to help convert the
compensation method for the operators from an hourly wage to an
annual salary. This conversion is intended to assist in retaining
operators and give them a career path within the observatory.
Smith also assisted in executing the WIYN Queue
Observing Experiment. This experiment is designed to test observing
strategies that most effectively match TAC-approved WIYN
observing projects to observing conditions. About 60 programs per
year are serviced in this manner by NOAO under the policy that
the highest-ranked proposals are given the highest priority within
the WIYN Queue. The flexible schedule of the Queue allows for
synoptic programs to be pursued and the ability to dynamically match image
quality requirements of programs with observing conditions.
Smith's duties include observing for the WIYN Queue program, maintenance
of the program's public Web pages, and some general administration
associated with the experiment. Roughly 120 nights are allocated to
the Queue annually. In addition, Smith is the instrument scientist
for the Hydra Multi-Object Spectrograph. Hydra is one of the two main
instruments permanently mounted on the WIYN telescope.
Go to: [ NOAO Scientific Staff ]
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NOAO is operated by the Association of Universities for Research in Astronomy
(AURA), Inc. under cooperative agreement with the
National Science Foundation
Posted: 28April1998