LTSA 96 Accepted Proposals

P.I.: Weinberg, D.H.       007-96ltsa
Ohio State University

Co.(s): Katz                   University of Washington

Quasar Absorption in the UV: Probing the Intergalactic Medium

Quasar spectra exhibit UV absorption produced by high redshift HeII and
low redshift HI.  We will use hydrodynamic cosmological simulations to
support the analysis and interpretation of space-based UV absorption
measurements, which probe the evolution of cosmic gas from high redshift
to the present day. Artificial observations of a realistic, simulated
universe are a powerful way to evaluate the statistical uncertainties and
systematic biases of an observational analysis, to develop new techniques
for extracting the physical content of observational data, to test
cosmological models, and to combine information from a wide variety of
observations into a coherent physical picture.  The specific projects
proposed fall into three categories: absorption by intergalactic HeII, the
Lyman- alpha forest at low redshift, and the connection between absorbers
and galaxies.

P.I.: Baron, E.A.       014-96ltsa
University of Oklahoma

Co.(s): Branch                 University of Oklahoma
        Hauschildt             Arizona State University

Multi-Wavelength Studies of Supernovae

We propose to model the atmospheres and spectra of both Type II and Type I
supernovae in detail.  We will calculate realistic, physically
self-consistent, model atmospheres and synthetic spectra.  The latter will
be compared with multi-wavelength observations from the ultraviolet to the
infrared, to determine ejection velocities, abundances, and distances of
supernovae, and to constrain theoretical models for the explosion
mechanisms, the progenitor systems, and the yields of radioactive nickel
and titanium.  We will use the results of our calculations and the
Spectral-fitting Expanding Atmosphere Method that we have developed to
estimate the cosmological parameters: the Hubble constant, the
deceleration parameter, and cosmic peculiar velocities.

P.I.: Latter, W.B.       015-96ltsa
NASA/Ames Research Center

Co.(s): Hora                   Institute for Astronomy, Univ. of Hawaii
        Tielens                NASA/Ames Research Center

Photon-Dominated Circumstellar Gas During Early and Late Stages of Stellar 

Exposure of molecular clouds and circumstellar envelopes to intense UV
radiation results in the formation of regions in which the chemistry and
physics are dominated by the presence of a time-varying UV field. Much of
the important physics of the early and late stages of stellar evolution is
similar, because of the high gas densities and the often dominating
influence of UV photons. This study will determine the physical and
chemical evolution of circumstellar gas in both the early and late stages
of stellar evolution. We propose to 1) develop a model for the processes
that occur in star formation regions and planetary nebulae due to the
presence of an intense UV flux, and 2) incorporate time-dependence into
our study of these evolving systems. Diagnostics will be identified for
the study of processes that are far from equilibrium. The role of high
density regions, clumps, tori, or disks -- including proplyds and the
so-called evaporating gas globules -- will be examined in detail.

P.I.: Silk, J.I.       018-96ltsa
University of California at Berkeley

Cosmological Studies of the Cosmic Microwave Background

Interpretation of microwave background temperature anisotropies requires
extensive modelling of extragalactic foregrounds as well as careful
treatment of systematics in individual experiments. Data from COBE and
other cosmic microwave background experiments at higher angular resolution
will be combined, utilizing a variety of methods, including Wiener
filtering, optimal eigenmode expansion and P(D) analysis, in order to make
simulated sky maps. We will include realistic galactic and extragalactic
foregrounds, in conjunction with the characteristics of proposed satellite
experiments (TOP HAT, BOOMERANG), and complementary studies by
ground-based interferometers (CBI, VSA), in order to simulate sky maps,
and develop and sharpen experimental goals and parameters, such as
frequency coverage, agular resolution and sky coverage. We will ascertain
how well the various cosmological parameters can be determined from both
existing and proposed data sets. We intend to make all relevant results
available through the NSSDC, including fits to the COBE DMR data and
simulated maps of the sky.

P.I.: Filippenko, A.V.       019-96ltsa
University of California at Berkeley

Co.(s): Sargent                California Institute of Technology
        Ho                     Harvard/Smithsonian Center for Astrophysics

A Multi-Wavelength Study of a Complete Sample of Nearby Galactic Nuclei

We propose to conduct a multi-wavelength study of the nuclei of the 486
brightest northern galaxies, with emphasis on identifying and determining
the physical nature of activity similar to, but less luminous than, that
seen in quasars and classical AGNs. This sample is the subject of our
existing optical survey. We will investigate the physical conditions in
the nuclei with the capability offered by archival HST and ROSAT data,
together with additional pointed observations, ASCA and AXAF spectra, and
complementary optical and radio data, as well as theoretical calculations.
When finished, this program will constitute by far the most definitive
multi-wavelength study yet of the nuclear regions of bright galaxies. It
will be used to address a collection of fundamental questions concerning
these environments. For example, we plan to quantify the luminosity
function of AGNs at the faint end, predict the contribution of
low-luminosity AGNs to the soft X-ray background, determine the excitation
mechanism of various types of emission-line galaxies, and search for
supermassive black holes in the central regions of nearby AGNs.

P.I.: Sanders, W.T.       027-96ltsa
University of Wisconsin - Madison

Studies of the Hot Interstellar Medium and Halo of our Galaxy: Spatial
Structure and Spectral Characteristics of the Low Energy X-ray Background

We propose to extend our previous studies of the spatial structure and
spectral characteristics of the X-ray background in the energy range ~ 70
- 1000 eV. The soft X-ray background originates from hot phases of the
interstellar medium and the galactic halo. This hot matter is not
uniformly distributed, but shows quite different intensities and spectral
ratios in different directions on the sky. The goals of this program are
to constrain the distances to the various hot interstellar regions, and to
constrain their spectral emission parameters. These are necessary steps
toward understanding the origin and evolution of the hot phases of the
interstellar medium and their role in the evolution of our galaxy. The
program uses data primarily from the ROSAT, DXS, and CUBIC orbiting
missions, and secondarily from the EUVE, ALEXIS, and ASCA missions. In
addition, data are used from University of Wisconsin sounding rocket
flights, and from the ground-based WIYN telescope.

P.I.: Hurley, K.C.       031-96ltsa
University of California

Co.(s): Ziock                  Lawrence Livermore National Laboratory

Adding the Mars '96 Gamma-Ray Burst Experiment to the Third Interplanetary

We propose to add a small gamma-ray burst experiment to the 3rd
Interplanetary Network of burst detectors.  This instrument was developed
and built using discretionary funding from a number of sources external to
NASA, and it has been integrated onto the Russian Mars '96 spacecraft for
launch in November 1996.  This experiment completes the network, which
currently consists only of Ulysses as a distant spacecraft, and a number
of near-Earth missions.  In its current form, the network produces burst
locations consisting of narrow annuli, which are not useful for deep
multiwavelength counterpart searches.  The addition of Mars '96 will
reduce these annuli to error boxes of arcminute size. We anticipate that a
total of approximately 200 bursts will be detected during the nominal 2.5
year Mars '96 lifetime.  We will disseminate the positions of these bursts
as the data are received to a worldwide network of >60 observers who are
prepared to conduct counterpart searches.  This proposal requests only the
funding for Mars '96 data reduction and analysis.

P.I.: Hughes, J.P.       036-96ltsa
Rutgers University

Co.(s): Birkinshaw             University of Bristol

Determining the Hubble Constant Using X-ray, Optical, and Radio
Observations of Clusters of Galaxies

Recent advances in instrumentation in the radio and X-ray bands, plus the
development of sophisticated analysis and modeling techniques, have
brought us to the era when the Sunyaev-Zel'dovich (SZ) effect is a viable
method for determining distances to clusters of galaxies and hence the
Hubble constant. The technique is competitive with those utilizing Cepheid
variable stars and Type Ia supernovae, but the SZ effect has the potential
for accurate application to larger distances, redshifts of 0.5 and beyond.
We have X-ray, optical, and radio data on a sample of distant clusters
that will allow us to determine H_0 to an accuracy of 8%. We propose a
program of research using these and other data that will lead to a clear
understanding of the sensitivity of the SZ effect method for distance
determination, detailed knowledge of the systematic errors associated with
such measurements, and a well- selected sample of clusters in time for
definitive studies with AXAF later in the decade.

P.I.: Wood, K.       042-96ltsa
University of Wisconsin

Exploring Asymetries In Circumstellar Environments: Winds, Disks, And
Things That Go Clump In The Light

We propose to use a multi-wavelength multi-technique approach to
investigate the effects of rotation and inhomogeneities on the physical
structure of circumstellar environments.  From the analysis of new and
existing space astrophysics data, using our 3-D radiation transfer
analysis techniques, we shall determine the geometry, density, and
ionization structure of hot star winds and the dusty environments of
pre-main-sequence stars. Among the applications of our 3-D analysis
techniques will be determination of the circumstellar temperature and
ionization structure of Oe/Be stars from analysis of their line-blanketed
UV spectropolarimetry, a more accurate determination of O and B stellar
mass loss rates, the effect of non-spherical densities on the radiation
driving force in Wolf Rayet stellar winds and luminous blue variables, a
search for cometary material from analysis of the disk spectra of Beta
Pictoris-like objects and Herbig Ae/Be stars, and observational testing of
currently favored dynamical models for low mass star formation.

P.I.: Crotts, A.       044-96ltsa
Columbia University

SN 1987A: Formation of a Supernova Remnant

The explosion of SN 1987A near the giant star-forming region 30 Doradus in
the LMC gives us 1) a fleeting opportunity to learn about the starburst
process in unprecedented detail, 2) a unique probe of mass loss in high
mass stars, & 3) a once-in-a-lifetime chance to study the formation
process of supernovae and supernova remnants, with this case being the
first with known initial conditions of the pre-existing circumstellar
environment.  Key elements of these opportunities have yet to be
addressed, and the largely space-based study of these questions is the
goal of my next few years of research.  Even though SN 1987A has faded
temporarily, in the next few years it will flare dramatically, forming SN
Remnant 1987A.  In the process the structures in the circumstellar
environment that we have studied so carefully will begin to interact with
the ejecta from the exploding star. Completing our observations of the
nebula about to be destroyed, and continuing intensive study of SNR 1987A
is the major goal of this proposed research.  We can also measure the UV
radiation from the initial SN shock breakout, and constrain the nature of
dust in the LMC.  This involves approved programs on HST, ISO, IUE and
UIT, plus potential programs on SIRTF and SOFIA.

P.I.: Mighell, K.J.       045-96ltsa
Columbia University

The Star Formation Histories of the Local Group Galaxies

The understanding of the formation and evolution of galaxies is one of the
most important goals of galactic astronomy.  Comparative studies of the
oldest stars and the field stellar populations in the Local Group galaxies
can provide important structural, chemical and kinematic clues to the
evolution of the parent galaxy.  I propose a research program to determine
the star formation histories of the Local Group galaxies.  These star
formation histories will be based principally on Hubble Space Telescope
WFPC2 observations from my own general observer programs or the HST data
archive. I will determine the star formation history of the stellar
populations from a) the location and distribution of stars near the main-
sequence turnoff, b) the luminosities, colors, and metallicities of stars
on the giant branch, c) the relation of horizontal-branch morphology to
stellar ages and metallicities, and d) the stellar luminosity function
near the main-sequence turnoff.  I will also use archival HST WFPC2 data
to directly compare the globular clusters in the Milky Way and nearby
Local Group galaxies.  The age-spread of the oldest stars in the Local
Group provides an important cosmological probe for the investigation of
synchronized galaxy formation.

P.I.: Wills, B.J.       047-96ltsa
University of Texas at Austin

Co.(s): Wills                  University of Texas at Austi

The Parsec-Scale Environment of Luminous AGN: Spectroscopic Clues to
Winds, Jets and Accretion

We have successful, ongoing, interrelated programs using HST, ROSAT, IRAS,
EINSTEIN, and ground-based observatories to probe the unresolved
parsec-scale environments of luminous AGNs' (QSOs') central engines.  This
is an opportune time to consolidate our exciting results using a powerful
combination of new tools to investigate the geometry, physics and chemical
structure of the emitting and absorbing gas: (i) the Doppler-boosting of
radio jets allows us to investigate the dependence of the continuum, line
strengths and profiles on the inclination of the spin axis; (ii) the
unprecedented sensitivity and resolution of ROSAT in soft X-rays allows,
for the first time, a comparison of the photoionizing energy with UV
continuum and emission-line spectra from HST observations, and optical-IR
spectra from the ground, and, together with (iii) state-of-the-art
photoionization codes, will provide new opportunities for solving the
outstanding problem of the energy  budget; and (iv) spectropolarimetry.
Newly-discovered  differences between radio-loud and radio-quiet QSOs
should lead  to understanding the role of the jets. The research is
spawning  projects that will introduce senior undergraduate and graduate

P.I.: Zaritsky, D.F.       049-96ltsa
The Regents of the University of California

A Study of Dust In and Around Galaxies

We propose a comprehensive study of the distribution of dust in galaxies
that is unique in two respects: (1) we will study the global distribution
of dust in the Magellanic Clouds at a level of spatial detail never
attemtped, and (2) we will study the distribution of dust in galactic
halos. The scientific goal of the first portion of this investigation is
to use the three dimensional mapping of dust across an entire galaxy to
learn about the nature of dust, its connection to the stellar populations
and gas, and how best to interpret observations of the integrated
properties (colors and luminosities) of more distant galaxies. The goal of
the second portion of this investigation is to determine whether dust is
present in the halos of galaxies in order to learn about the baryon
component of galactic halos and to understand how observations of the
distant universe may be affected by extinction from galactic halos along
the line-of-sight. UV and IR observations (HST, IRAS, ISO) are the best
way to sample both the absorption and emission properties of dust, and by
doing so sample the range of dust components that may be present in and
around galaxies.

P.I.: Loredo, T.J.       057-96ltsa
Cornell University

Development and Application of New Tools  For Statistical Analysis of
Discrete Astrophysical Data

I propose to develop and apply rigorous statistical methods for the
analysis of a wide variety of discrete astrophysical data based on the
principles of Bayesian inference.  These methods will use discrete
probability distributions (e.g., the Poisson distribution) to model data.
The Bayesian approach specifies how to use these distributions without
relying on questionable approximations that underly many current analyses,
and also eliminates troublingly subjective aspects of current methods.  I
identify three areas that will benefit from development of new methods,
chosen so that the resulting analysis tools will be of interest to a wide
range of investigators, and for the potential scientific dividends that
could result from applying the tools to the specific astrophysical
problems I will study.  These areas are:  (1) Analysis of photon counting
data, with applications to the analysis of gamma ray burst (GRB) spectra
and time histories.  (2) Analysis of arrival time data, with applications
to the analysis of photon arrival times from GRBs and x ray and gamma ray
pulsars.  (3) Analysis of data from multidimensional point processes, with
applications to x ray source detection, gamma ray bursts, and
observational cosmology.

P.I.: Leventhal, M.       058-96ltsa
University of Maryland

Co.(s): David                  University of Maryland   ***SCIENCE PI***

Galactic Black Holes and Positron Annihilation Radiation

I am proposing for funding to continue a number of projects related to
Galactic black holes, Galactic positron-annihilation radiation, and the
role of the former in producing the latter.  The largest projectis one
currently under way with support from the Compton Gamma Ray Observatory
guest investigator program: mapping the annihilation line using data from
BATSE.  In the long term, I hope to combine these results with those from
OSSE. The black hole candidate 1E 1740.7-2942 has been mentioned as a
possible positron source; other projects in this proposal probe the nature
of this source and a similar object, GRS 1758-258, using XTE.  Smaller but
related projects evolve naturally from the data and techniques of the main
projects: a spectral study of Galactic diffuse x-ray emission with the XTE
data and a study of the high-energy variability of Cygnus X-1 and x-ray
novae with the BATSE data.  Finally, the BATSE background-subtraction and
mapping techniques can be adapted to the High Energy Solar Spectroscopic
Imager, which is under second-round consideration for the Medium Class
Explorer program.

P.I.: Carr, J.S.       059-96ltsa
Naval Research Laboratory

Water in Pre-Main-Sequence Accretion Disks

The properties of cool accretion disks around pre-main-sequence T Tauri
stars will be investigated through the analysis and interpretation of new
space-based spectra of water vapor and through theoretical modeling of
accretion disk atmospheres.  This work will be based on HST and ISO
spectra of young stars in the near to far-infrared spectral regions.  The
ISO mission will provide data on the vibrational and rotational bands of
H2O in the mid and far-infrared, and other molecular constituents such as
H2, OH and CO.  Hot water vapor will be studied using sensitive
low-resolution spectra of the near-infrared vibrational bands obtained
with NICMOS and the HST.  As necessary, these data will be supplemented
with ground-based high-resolution spectra of molecules in the near and
mid-infrared.  This database of infrared molecular spectra, combined with
infrared continuum fluxes, will be modeled to provide information on the
structure of the inner regions (< 5 AU) of the circumstellar disk.  New
calculations of accretion disk atmospheres, with updated opacities and
self-consistent treatment of external radiation, will be carried out to
provide physical interpretations of the results.

P.I.: Lewin, W.H.       061-96ltsa
Massachusetts Institute of Technology

Co.(s): Kouveliotou            University Space Research Association
        van Paradijs           University of Alabama at Huntsville
	  van der Klis           University of Amsterdam

Accreting Black Holes - An All Out Effort

Black holes are fundamental to our understanding of physics. Yet, we do
not know with certainty whether they exist. We only know that objects with
the required large mass/radius ratio nearly certainly exist in more than
half a dozen X-ray binaries and that such objects probably exist at the
center of some galaxies. We propose to study the sites of the best black-
hole candidates namely those in X-ray binaries. Our ultimate goal is to
verify that black holes, with properties as predicted by General
Relativity, actually exist. This goal is distant and perhaps elusive.
However, in view of the fundamental importance for our understanding of
physics, a comprehensive, systematic, and all-out effort on the observable
phenomenology is justified and only possible with long-term support from
the LTSA Research Program.

P.I.: Allamandola, L.J.       072-96ltsa
NASA - Ames Research Center

Co.(s): Sandford               NASA-Ames Research Center
        Salama                 SETI-Institute and NASA-Ames

Interstellar Dust, Ice, and Polycyclic Aromatic Hydrocarbon Composition
Derived from their IR and UV Spectral Properties Measured from Space.

We propose to use our extensive data base of laboratory spectra of
realistic interstellar analog materials to analyze infrared through
ultraviolet spectra obtained from spacecraft such as ISO, IRTS, MSX, and
HST to study the chemical composition and physical state of interstellar
matter.  We expect this data to provide (i) the identification of
important new molecular species in interstellar ices (such as CO2, O3, and
nitriles), (ii) the degree of amorphicity of these ices, (iii) a
determination of the distribution of cosmic deuterium in these ices and in
PAHs, (iv) the identification and evolution of PAH structures in infrared
emitting objects, (v) a test of the suggestion that PAHs are responsible
for the infrared cirrus, and (vi) the identification of specific PAHs and
their charge state in the diffuse ISM. We are in a particularly unique
position to carry out the proposed program since we have direct access to
the data from three of the spacecraft and the investigators have extensive
experience with astronomical data and a very productive laboratory devoted
to studying the spectroscopic and physical properties of interstellar
dust, ices, and PAHs.

P.I.: Sembach, K.R.       082-96ltsa
Smithsonian Astrophysical Observatory

Diffuse Ionized Gas in Galactic Environments_

I propose to use the large amount of spectroscopic and imaging data
obtainable from space missions and their archives to study the diffuse
ionized gas distributions in the Milky Way and other galactic systems.
The project will focus initially upon understanding the ionization,
distribution, and kinematics of ionized gases in the Milky Way disk, low
halo, and outer halo and their relationship with one another.  I will also
conduct studies of high velocity gas behind fast shocks in supernova
remnants to refine models of shocked, radiatively cooling gas. These
studies will further our understanding of how dust is processed by the
supernova explosions that may produce much of the highly ionized gas in
the Galactic halo.  Further analyses of data for high velocity clouds in
the Galactic halo will also be undertaken to understand the origin,
abundances, and ionization of the Milky Way halo gas.  Throughout this
study, I will apply what I learn about ionized gas in the Galaxy to the
gas in the distant galactic halos responsible for quasar absorption line

P.I.: Owocki, S.P.       087-96ltsa
University of Delaware

Co.(s): Cohen                  Department of Astronomny, U. of Wisconsin

Multi-Spectral Diagnostics and Dynamical Modelling of Structured Hot-Star

Extensive observations hot stars in multiple wavebands by several orbiting
observatories have provided strong evidence that the radiatively driven
stellar winds of hot, luminous stars are highly structured at both large
and small scales. This project aims to apply recently developed
time-dependent radiation hydrodynamical models of these structured stellar
winds to fundamental, physical interpretation of these observations. It
will build upon new computational tools, conceptual insights, and
observational datasets developed in the P.I.'s previous LTSA project, with
a new emphasis on exploiting the EUV and X-ray databases and analysis
methods developed from Co-I.'s recent Ph.D. thesis research. Specific
projects include: 1) Reexamination of mass loss from B-stars in light of
their unexpectedly high X-ray emission meaures; 2) Dynamical model
interpretation of observed X-ray scaling laws for hot- stars; 3) 2-D and
3-D models of wind structure and X-ray variability; 4) Extension of our
ongoing program of analysis of UV wind line variability; and 5) Long-term
development of radiation hydrodynamics code to include MHD

P.I.: Madore, B.       093-96ltsa
Jet Propulsion Laboratory

Optical Depth and Radiative Transfer in Disk Galaxies

We are proposing a program to interpret the multi-wavelength images of
galaxies in the context of the new  radiative transfer models. Unique data
sets from ASTRO, ISO, HST, and from IRAS  are to be combined with a CCD
survey of the LMC/SMC, as well as a new ground- based optical/infrared
imaging database, with special emphasis on our proprietary ASTRO-2 UV
images, pre-selected to cover the entire Hubble sequence. Our
interpretive  models now incorporate realistic physics, spatially resolved
on ~100 parsec scales,and covering wavelengths from the vacuum UV to the
thermal IR. Our immediate goals are (1) to understand the opacity
structure of the nearest galaxies by a detailed  investigation of high-
resolution and multi-wavelength observations (made by ASTRO, IRAS and ISO)
of individual systems, and (2) to provide an understanding and basis for
the interpretation of the correlations and the statistical  properties
galaxies seen at the present epoch in large-sample broad-band color
surveys, and ultimately (3) to place in context the HST (UV restframe)
images of `normal' galaxies seen at high redshift, in comparison with the
serendipitous UV images of nearby galaxies also being collected by HST.

P.I.: Sakai, S.       094-96ltsa
Jet Propulsion Laboratory

The Local Distance Scale: Application of the Tip of the Red Giant Branch
Distance Indicator

A relatively new,yet very robust method of distance determination for
distance determination for resolved galaxies has been developed in the
last few years. The tip of the red giant branch (TRGB) method has been
shown to be as precise as the Cepheid PL relation, but the uniqueness of
the TRGB method is that it is applicable to any galaxy containing a
detectable population of old, metal-poor, low-mass stars. This means that
practically all nearby galaxies, regardless of Hubble type and/or
inclination, can be placed on a common distance scale out to the crowding
and the flux limits of modern detectors and telescopes. This proposal is
designed to accomplish the following goals.(1) The precise distribution
and detailed kinematics of galaxies in the vicinity of our own Local Group
remains uncertain, largely due to lack of precise distance measurements.
We propose to establish consistent distances to all galaxies within 2Mpc
of the Local Group.(2) Pop II secondary distance indicators still lack a
solid calibration. By detecting the RGB in giant elliptical galaxies in
the Virgo and Fornax clusters, we will be able to double the number of
calibrators.(3) We propose to establish a more solid calibration of the
TRGB method that is directly

P.I.: Mulchaey, J.       095-96ltsa
The Observatories of the Carnegie Institution of Washington

The Intragroup Medium

Most galaxies in the universe occur in small groups, so studies of these
environments are important. The recent discovery of extended X-ray
emission in groups has provided new insight into the dynamics and
evolution of such systems. ROSAT studies of the "intragroup medium"
suggest X-ray emitting gas is not found in all groups, but only those
dominated  by early-type (E and S0) galaxies. I propose a five year study
that will combine observations from ASCA, HST, AXAF and ASTRO-E with
existing ground-based data to address three outstanding questions raised
by the ROSAT observations: 1) What are the masses and dark matter
fractions in groups?, 2) What is the origin of the intragroup medium? and
3) Does an intragroup medium exist in spiral-rich groups?

P.I.: Brickhouse, N.S.       099-96ltsa
Smithsonian Astrophysical Observatory

Spectroscopic Determination of the Physical Conditions in Hot, Optically
Thin Sources

The high spectral resolution of current and future missions (EUVE, ASCA,
AXAF, XMM) offers new opportunities to study the physical conditions of
diverse sources. Plasma emission models, such as our new
Brickhouse-Raymond-Liedahl code, are powerful tools for deriving
temperatures, densities, and abundances of optically thin astrophysical
plasmas from high energy spectra. Currently, however, no tools are
available to study the effect of systematic errors in plasma emission
models. We propose to study these systematic errors: (1) Given the dearth
of laboratory measurements, we will test the atomic data with
astrophysical spectra, particularly stellar coronae. (2) We will test the
spectral implications of common simplifying assumptions. (3) We will
include systematic errors in the spectral analysis. Enhanced confidence in
spectroscopically derived parameters for stellar coronae, galaxies,
clusters of galaxies, the interstellar medium, and supernova remnants will
lead to improved models of physical processes, such as cooling flows and
coronal heating.

P.I.: Allard, F.       110-96ltsa
Wichita State University

Co.(s): Alexander              Wichita State Universit

Spectroscopic Properties of (Sub)Stellar Objects

As progressively cooler stellar and substellar objects are discovered, the
presence of first molecules and then condensed particulates greatly
complicates the understanding of their physical properties.  Brown dwarfs
and giant planets emit over 65 % of their radiation in the infrared,  out
of reach of most ground-based telescopes.  A variety of infrared sky
surveys with IRTS, ISO, HST, and WIRE will soon deliver large data bases
of red dwarfs, brown dwarfs and perhaps giant planets, which will
necessitate the best possible theoretical foundation. In this project we
propose to study in four thrust areas the spectroscopic and photometric
properties of cool stellar and substellar objects.  We will (1) improve
existing low temperature opacities by treating the condensation of grains
in more detail. (2) Construct grids of model atmospheres and interiors for
low mass objects. (3) Establishing the atmospheric, spectroscopic and
structural properties of cool brown dwarfs and giant planets.  And (4)
Interpret combined ground-based, HST and infrared space observations of
red dwarfs, metal-poor subdwarfs, brown dwarfs and giant planets.

P.I.: Szalay, A.S.       115-96ltsa
The Johns Hopkins University

Co.(s): Connolly               The Johns Hopkins University

The Evolution and Clustering of Galaxies at z=1 and Beyond

We propose to use several novel techniques to estimate the redshifts of
galaxies in deep HST samples, such as the Hubble Deep Field, and the Groth
Strip, where traditional ways of obtaining spectroscopic redshifts are no
more feasible. We have shown in a pilot project, that broad band
magnitudes of galaxies correlate extremely well with their
spectroscopically measured redshift (Connolly et al 1995). For fainter,
thus more distant galaxies, evolution becomes much more pronounced, and
various other complications arise. Here we describe several new ideas, how
these problems can be circumvented, like using surface brightness as an
additional measure of redshift, or applying the photometric redshift
technique to several components of the galaxies separately (like bulge,
disk, star forming regions). We expect that not only the redshifts of the
objects can be determined with a reasonable accuracy, but their spectral
type as well. Also, several important applications of the technique are
discussed, like evolution of the luminosity function as a function of
spectral type, clustering evolution as a function of color and morphology
at various redshifts. This technique can also provide better constraints
on cluster masses from gravitational lensing.

P.I.: Weaver, K.A.       118-96ltsa
The Johns Hopkins University

A Robust Test of the Unified Model for Seyfert Galaxies, with Implications
for the Starburst Phenomenon

X-ray studies provide a solid test of the "obscuration-plus-viewing-angle"
unified model hypothesis for Seyfert galaxies.  Not only do iron K line
profiles and variability probe accretion disks and molecular tori, but
trends of equivalent width with column density, luminosity, and
inclination give information about geometrical distributions of the gas
and the degree of continuum isotropy.  This proposal outlines a five-year
research effort that entails detailed modeling of X-ray emission.  Central
to this research is my involvement with analysis of ASCA, Rosat, and XTE
data of Seyfert and Starburst galaxies.  I will build on current studies
of Seyfert galaxies to compile a catalog of X-ray spectral properties.
This catalog will then be used to perform a robust test of the unified
model and investigate a possible AGN-Starburst connection. The research
outlined here is timely because ASCA is providing, for the first time, a
large sample of X-ray spectra of optically-detected Seyfert 2 galaxies.
This allows comparisons with Seyfert 1 galaxies that have never before
been possible. In creating an X-ray catalog, I plan to obtain all of the
information possible to guide current theories of Seyferts.  This
information will allow more efficient use of future high- resolution X-ray
missions such as AXAF and Astro-E.