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Theoretical Studies, Astrophysics, and Cosmology
STOEGER and ARAëJO (Universidade Federal do Rio de
Janeiro) are making progress on setting up the equations in the general
Friedmann-Lematre-Robertson Walker perturbation case in observational
coordinates using the fluid-ray tetrad formalism. Once that is done, they will
study how to solve these equations and apply them to a variety of cases,
including the cosmic microwave background radiation (CMBR).
With ELLIS and DUNSBY (Department of Mathematics,
University of Cape Town), STOEGER has begun studying the evolution of the
density parameter, the radius of curvature, and the distance to the particle
horizon in closed inflationary cosmological models with a non-zero vacuum energy
(cosmological constant). These models have recently become more attractive, as a
result of best-fits to supernova-distance, galaxy-velocity, and CMBR anisotropy
data, which yield a closed model with substantial vacuum energy. Theoretically,
these models possess some interesting peculiarities that may hold the answer to
some cosmological enigmas.
STOEGER and ELLIS are beginning to review the problem of
gravitational lensing and the formation of caustics in cosmology. A great deal
has already been done on this topic, but it is important to see whether all the
effects of such phenomena have been properly taken into account in CMBR
anisotropy analyses and in more traditionally astronomical cosmological
work.
LISZKA (Swedish Institute of Space Science, Sfrs),
PACHOLCZYK (Steward Observatory, University of Arizona), and STOEGER are
pursuing the extraction of energy spectrum information from ROSAT and Chandra
data sets for variable X-ray flux from Active Galactic Nuclei (AGN) to test
their ballistic black hole scenario for these objects. They are also examining
the possible application of this scenario to other astrophysical phenomena
(e.g., gamma-ray bursts) and are improving aspects of the model that relate to
the reprocessing of the original high-energy burst radiation through its
interaction with the surrounding AGN matter and radiation fields.
JUST (Department of Physics, University of Arizona) and
STOEGER are continuing work in quantum field theory on a number of topics
related to fundamental issues. These include the measurement problem with sharp
masses; realistically combinable operations in quantum theory and their
relationship to the consistent histories approach; the spinless components of
the electromagnetic and gravitational fields; and the allowed polarization
states and the small virtual masses of interacting photons and gravitons. They
are also continuing to pursue development of the quantum induction program,
especially by incorporating gravity into it.
WHITMAN continues his work in the universe of geometric
structures. Since the Einstein model for our universe is such a structure, his
work has a direct bearing on the astrophysical studies of this universe. The
possible structures are quite limited, and WHITMAN is trying to find them and
describe their characteristics. At the meeting of the Clavius Group of
Mathematicians he gave the details of a rather exotic geometrical structure,
which has also found much application in quantum mechanics, namely, the spin
representations of the Clifford algebra. In particular, he showed how these
surprising geometric structures could have been discovered.
HELLER, with SASIN (University of Warsaw), continues to
explore noncommutative geometries with special application to our knowledge of
classical singularities and to the unification of quantum theory and general
relativity. Interesting results have been obtained with respect to the emergence
of time from classical singularities.
Extragalactic Research
FUNES and KENNICUTT (Steward Observatory, University of
Arizona) have started a deep H-alpha imaging survey using the Vatican Advanced
Technology Telescope (VATT). The goal of this program is to obtain a better
understanding of star formation in the local universe (galaxies within 11
megaparsecs). One of the major problems in astrophysics is the understanding of
galaxy formation, where the history of the star formation rate in the universe
plays a very important role. Data from the survey will provide information on
the distribution of local star formation in terms of galaxy types, luminosities,
and interstellar environments.
FUNES continues the study of the gaseous kinematics in the
inner regions of disk galaxies. This work has been done in collaboration with
BERTOLA, CAPPELLARI, CORSINI, PIZZELLA, SARZI, and SCARLATA (Department of
Astronomy, University of Padua) and with VEGA BELTRAN (Instituto de Astrofisica
de Canarias). Recent reports show that the supermassive black hole (SMBH) mass
scales with the central stellar velocity dispersion. The relation is very well
defined and has been computed on a sample of 26 galaxies. However, most of the
SMBHs have been detected in elliptical or lenticular galaxies, and therefore it
is not clear whether the relation holds also in the case of disk galaxies. By
studying the bi-dimensional shape of the emission lines obtained from high
spatial resolution, long-slit spectra along the major axes of disk galaxies, it
is possible to put constraints on the mass of the central SMBH. The goal of this
project is to extend demographic studies about SMBHs in disk galaxies to better
define the relation between their mass and those of the spheroidal components of
the host galaxies. This relation offers strong clues to galaxy formation and
evolution.
FUNES, in collaboration with RAFANELLI (Department of
Astronomy, University of Padua) and RICHTER (Astrophysikalisches Institut
Potsdam), continues to investigate the relationship between gravitational
interaction and galactic activity, as described in last year's Annual Report.
Using images obtained with the VATT, they are searching for disturbed
morphologies, such as distortions in the circumnuclear regions and small bars,
double nuclei, faint companions, and faint tidal tails, that can be interpreted
as the effect of gravitational interaction.
OMIZZOLO continues his program on the luminosity function
of X-ray emitting quasars, using a sample of 800 objects selected from the ROSAT
satellite data. In collaboration with CORBALLY and CRISTIANI (Department of
Astronomy, University of Padua), he has obtained addition low-resolution,
red-region spectra of X-ray emitting QSO candidates with the Steward
Observatory's 2.3-m telescope. He has also obtained spectroscopic data from the
European Southern Observatory at La Silla, Chile. Thus far, all but 150 objects
have been observed.
In collaboration with FALOMO and RAFANELLI (Department of
Astronomy, University of Padua), OMIZZOLO has initiated a program to study the
environment of Active Galactic Nuclei in order to understand how the cosmic
ambient has influenced the evolution of these energetic objects.
The Galaxy and Galactic Objects
CORBALLY and GRAY (Appalachian State University, Boone,
North Carolina) finished observing spectra of late B, A, and early F-type stars
in 11 young and intermediate-age open clusters. The MK classifications are
nearly complete, and analysis with a view to investigating peculiar A-type
stars, including lambda Botis stars, is underway.
CORBALLY continues an investigation of heavily reddened
stars in clusters and of peculiar stars continues. These have been selected by
STRAIZYS (Institute of Theoretical Physics and Astronomy, Vilnius, Lithuania)
from photometric classifications in the Vilnius seven-color system. CORBALLY has
classified cluster stars in the area of NGC 1333, IC 348, the Taurus dark
clouds, NGC 1750, and field stars from spectra he obtained with the Steward
Observatory's 2.3-m telescope.
RUEGER (Diocese of Brooklyn) continued to process UBVRI observations of two calibration
fields in the North Galactic Pole. These fields will help provide G-dwarf star
candidates for further spectroscopic investigation by CORBALLY and GARRISON
(David Dunlap Observatory, University of Toronto).
As part of the Nearby Stars (NStars)/Space Interferometry
Mission preparatory science project, CORBALLY, GRAY, and GARRISON have started
to obtain 1.5-4.5 resolution spectra in the blue-violet for all of the
approximately 3600 nearby stars with spectral types earlier than M0 within 40
parsecs of the sun. These spectra will be used for five purposes: (1) to obtain
homogeneous, precision MK spectral types of these stars; (2) in conjunction with
existing Strmgren and Johnson photometry and synthetic spectra and fluxes from
Kurucz ATLAS9 atmosphere models, to derive the basic astrophysical parameters
for these stars, namely Teff, log g, [M/H], and the microturbulent
velocity; (3) to use the Ca II
K-line included in the proposed spectral range (3800-5100 ) to obtain a measure
of the chromospheric activity of these stars; (4) to provide a
medium-resolution, high S/N (> 100) spectrum for each star in the sample,
which will become a permanent part of the NStars database; (5) to provide a list
of suitable candidates for solar analogs and observing lists for extra-solar
planetary systems. These purposes fulfill a number of important goals of the
NStars project and help to provide necessary science data for the Space
Interferometry Mission.
COYNE, with MAG¶LHAES (Istituto Astron¢mico e Geof¡sico,
University of SÆo Paulo), is initiating a new survey of interstellar
polarization in dark clouds to obtain better data for the magnetic field
structure of these clouds.
KAZLAUSKAS and SPERAUSKAS (Institute of Theoretical
Physics and Astronomy, Vilnius, Lithuania), in collaboration with BOYLE, spent
50 nights observing at the 1.5-m, 1-m, 1.54-m, and 2.3-m telescopes of Steward
Observatory, University of Arizona. They observed about 800 stars of various
spectral and luminosity classes, metallicities, and peculiarities for
calibration of the Stromvil medium-band 7-color photometric system in terms of
stellar physical parameters. This work now continues under STRAIZYS (Institute
of Theoretical Physics and Astronomy, Vilnius) with a Chretien International
Research Grant.
BOYLE and PHILIP (Union College and Institute for Space
Observations, Schenectady, New York) are using the Stromvil standard stars to
calibrate their VATT CCD star-field observations. Their collaborators SMRIGLIO
and DASGUPTA (University of Rome) are doing the same for CCD observations made
at the Loiano Telescope of the University of Bologna. JANUSZ (Krakow, Poland)
and RUEGER (Diocese of Brooklyn) are collaborating with data processing and
software development.
In October, the European Space Agency (ESA) selected the
GAIA space mission to be Cornerstone 6 of its Science Program. It is likely that
ESA will choose the Stromvil Photometric System for this mission to chart the
billion brightest objects in our Galaxy to learn its composition, formation, and
evolution.
Planetary Sciences
Meteorites
CONSOLMAGNO continued research on the structure of
meteorites, including measurements of meteorite density and porosity and
electron microscope imagery of meteorite fabric. In addition, he developed
several theories to try to account for the observed lithification state of
ordinary chondrite meteorites.
Over the past five years, BRITT (University of Tennessee)
and CONSOLMAGNO have collaborated on efforts to provide a systematic measurement
of meteorite density and porosity, including measurements of meteorite types
previously undersampled. BRITT has received a grant from the NASA Office of
Geology and Geochemistry –with
CONSOLMAGNO, FLYNN (State University of New York, Plattsburgh), and ROBINSON
(Northwestern University) as nonfunded co-investigators–to
carry out this research. The helium pycnometer apparatus used in this work and
described in previous Annual Reports has now been delivered to the Field Museum,
Chicago, where measurements by WILKINSON (Northwestern University) and WADWA
(Field Museum) are being made on samples from the museum's extensive collection.
CONSOLMAGNO has continued the mapping of porosity in
meteorite thin sections. He produced an extensive Scanning Electron Microscope
(SEM) image of a thin section of the ordinary chondrite Ochansk at the London Museum of Natural
History (MNH), with the collaboration of RUSSELL (MNH). This meteorite is known
to have uniform porosity measured at 11% in hand samples from the Vatican
meteorite collection. This SEM image and others will be analyzed quantitatively
by STRAIT (Alma College, California) during 2001. It is clear even from a
preliminary examination of the thin section that on a scale of 100 mm,
the porosity varies significantly across this sample. More importantly, the
porosity visible in these images continues to confirm the idea proposed earlier
by CONSOLMAGNO and colleagues that the porosity measured in hand samples can be
accounted for by post-lithification shock cracks. This means that the
lithification of meteorites in space compacted them to near-zero porosity in the
apparent absence of water, heat, or pressure normally associated with such
lithification in terrestrial rocks.
How and where this lithification occurred remains a
mystery. At the annual meeting of the Meteoritical Society, CONSOLMAGNO
presented one speculative possibility: that some meteorites might come from deep
inside originally ice-rich bodies comparable to the current population of the
Kuiper Belt. But he concluded that many other possibilities need to be explored.
Discussions on this point continued with the collaborators listed above, as well
as with VELBEL (Michigan State University), whose background includes extensive
work in both carbonaceous chondrites and in terrestrial sedimentary rocks; with
BLAND (Open University, Milton Keynes, England), an expert in meteorite
weathering; and with WEIDENSCHILLING (Planetary Science Institute, Tucson), who
has extensively modeled the impact and accretion environment of the early solar
system.
Meteorites from the Vatican collection continue to be made
available to other researchers. DURANTI and MENCHETTI (University of Florence)
separated crystal fragments of melilite from small fragments of the CV-class
meteorites Vigarano and Lanc taken from the Vatican collection.
These minerals were analyzed with an automated single-crystal diffractometer and
an electron microprobe, revealing a peculiar chemical composition compared with
other extraterrestrial melilites in the literature. The tiny samples used are
now exhibited on permanent loan at the Mineralogical Museum of the University of
Florence, which had previously lacked carbonaceous chondrites in its collection.
BRUCATO (Capodimonte Observatory, Naples) made spectral
measurements in the UV-IR
range of the meteorites Renazzo and
Ornans from the Vatican collection.
These meteorites are the type specimens of the CR and CO classes, respectively,
of carbonaceous chondrites. Such measurements are useful for comparison with
data expected from the NASA Stardust and ESA Rosetta missions to comet nuclei.
Asteroids
With the new data on the structure of asteroid Eros
returned by the NEAR spacecraft, BRITT and CONSOLMAGNO have applied their data
on meteorite and asteroid density to produce models of asteroid structure. Eros
has been shown to have a density of 2.7 g/cm3, appears to be uniform
throughout its interior (judging from its gravity figure), and its surface
features strongly imply a relatively coherent structure. Yet its surface
composition is comparable to L chondrites, a meteorite class that the Vatican
data have shown to be 30% more dense than this asteroid. This raises a number of
questions about how such a scenario is possible.
BRITT and CONSOLMAGNO note that a number of asteroids now
have reasonably reliable density measurements. Mass estimates come from several
sources. The best are spacecraft measurements, such as the NEAR measurements of
Eros and Mathilde, and Mars orbiter measurements of Phobos and Deimos. But
several moons of asteroids have been detected, and the masses of the parent
asteroids can be determined from the moons' orbits by both spacecraft and
adaptive optics, ground-based observations.
Furthermore, measurements to within a kilometer of the
orbital perturbations of Mars have allowed celestial mechanicians to estimate
the masses of several of the larger asteroids and to put limits on the average
densities of the inner (primarily S class) and outer (primarily C class) main
belt asteroids. Volume estimates for these objects are quite difficult, given
their extremely irregular shapes, but reasonable limits on possible densities
can nonetheless be estimated. A pattern begins to emerge by comparing these data
with data on the densities of proposed meteorite analogs measured by CONSOLMAGNO
and coworkers. Not surprisingly, the largest asteroids (Ceres and Vesta) appear
to be well compacted, with densities not very different from the kinds of
meteorites thought to represent their compositions.
Of the smaller asteroids, CONSOLMAGNO and colleagues find
that the relatively high albedo S-class asteroids, like Eros, are thought to be
made up of ordinary chondrite material, and they are systematically 25-35%
less dense than their meteorite analogs. However, their meteorite data show that
most ordinary chondrites are about 10% porous (pore spaces due to mm-size
cracks); subtracting this porosity means that the asteroidal bodies must be
about 15-25%
macro porous, with cracks that are centimeters to meters wide. This sort of
porosity is not all that uncommon in terrestrial sedimentary structures. The
emerging picture suggests that these bodies can be considred "coherent rubble
piles." Though held together by self-gravity alone, with significant cracking
running throughout these bodies, the rubble pieces, nonetheless, fit together
well enough that the body as a whole behaves as a coherent object when subjected
to impacts and faulting. By contrast, the darker C-class asteroids have
densities at least 50% lower than the densities of the dark meteorites thought
to represent their composition. These bodies are clearly loose piles of rubble.
As the severe impact history of Mathilde demonstrates (this asteroid has six
large craters, comparable in size to the radius of the asteroid itself), such a
loosely packed system will respond to geological processes in a very different
manner than does coherent rock, absorbing impact energies that would completely
shatter and disrupt a more coherent body.
The Nomenclature Working Group of the International
Astronomical Union has officially designated asteroid 1983 UA1, discovered by
BUS (Massachusetts Institute of Technology) in 1983, as asteroid 4597
Consolmagno. In support of this designation, the IAU citation from McCoy (Smithsonian Institution)
acknowledged CONSOLMAGNO's work on basaltic achondrites and meteorite density
measurements. Asteroid 4597 Consolmagno is small, about 20 km across, and orbits
at an average distance of 2.6 AU from the Sun.
The Moon
An old link between basaltic achondrite meteorites and the
lunar surface is leading to new insights into the chemical evolution of Earth's
nearest neighbor. In a series of review presentations before the Geochemical
Group of the British Geological Society and at the International Conference on
Earth-Moon Relationships held in Padua, CONSOLMAGNO discussed the group of
basaltic meteorites classified as either howardite, eucrite, or diogenite and
collectively referred to as HED. These meteorites are closely related chemically
and isotopically and almost certainly originate from the same parent asteroid,
which is thought to be asteroid 4 Vesta. CONSOLMAGNO suggested that our
understanding of the relatively simple HED parent body might lead to new
insights into how the early Moon evolved. In particular, he noted that the
purported chilled crust of anorthosite suggested by the magma-ocean model of the
Moon is not a necessary element in successful models of the evolution of Vesta.
Orbital data suggest that the aluminum-rich rocks of the Moon, thought to be
evidence of the primordial chilled crust, may not be as abundant over the
average Moon as once believed. CONSOLMAGNO suggests that a plagioclase/pyroxene
basalt, similar in composition to the eucrites and howardites, might be a better
match for the composition of the average lunar highland crust. Meanwhile,
detailed analysis of the HED suite of basaltic achondrites has led to a fairly
detailed picture of the evolution of their parent body (Vesta).
Small Outer Solar System Objects
Analysis of the broadband colors and light curves of seven
small outer solar system objects observed at the VATT in 1999 by RETTIG
(University of Notre Dame), TEGLER (Northern Arizona University), ROMANISHIN
(University of Oklahoma), and CONSOLMAGNO, and described in last year's Annual
Report, revealed a number of unexpected oddities. While the general trend of
distinct gray and red color populations as first proposed by TEGLER and
ROMANISHIN still appears to hold true, one object in this group (1998 VG44) does
appear to have a color in the transitional region between the two groups. When
this is considered along with data by other observers, it appears that the two
groups might be better understood as two populations each spread about an
average color and with some amount of overlap between groups. More intriguing
are hints of strong variations in brightness for these objects. The most
complete analysis was performed for the odd outer solar system object 1999 TD10.
This body is unusual in that it has a perihelion distance of 12 AU, similar to
Centaurs (comet-like objects that cross the orbit of Saturn but do not reach
Jupiter or the inner solar system). But 1999 TD10's large semi-major axis of,
190 AU, places it during much of its orbit among the variety of trans-Neptunian
bodies known as "scattered disk" objects.
CONSOLMAGNO and colleagues found that 1999 TD10 exhibits
large variations in brightness, with a light curve with an average V magnitude
of 20.20 and a 0.68 magnitude amplitude, which can be fit with a period of 5.8
h. They found an absolute magnitude, H, of 9.07. If one assumes an albedo of
0.04, then 1999 TD10 has a mean diameter of 100 km. If the variation in
brightness is due to the rotation of an object with an irregular shape, then the
ratio of a/b is 1.88, giving the object dimensions of 130 × 70 km. Such an
irregular shape for such a large object would be unusual for a main belt
asteroid. However, the largest Trojan, 624 Hektor, may be larger and even more
irregular in shape, and the largest irregular moon (Hyperion) has a similar a/b
with much larger dimensions (410 × 260 × 220 km). The B-V color of 0.77 ±
0.02 and a V-R color of 0.47 ±
0.01 place 1999 TD10 in the "gray" population of Centaurs and Edgeworth-Kuiper
Belt Objects, comparable to the Trojan asteroids.
Other objects observed in 1999 showed enigmatic hints of
strong light curves, but the data taken at that time were insufficient to
resolve possible ambiguities. As a result, light curves were observed again for
a number of these objects at the VATT in late September 2000. Analysis of these
results may reveal new insights into the shape and collisional histories of
these mysterious outer solar system objects.
History and Philosophy of Science; Interdisciplinary Studies
CARUANA published a book entitled Holism and the Understanding of Science,
in which he presents the research he has been conducting for the last 5 years.
He starts with a detailed philosophical analysis of holism, concentrating on two
complementary aspects-cognitive
holism and social holism. Using these conceptual tools, he investigates the
relevance of holism to science studies. He thus arrives at new perspectives on
how to bridge the gap between the analytical, historical, and sociological
accounts of science within the context of realism.
CORBALLY has studied complexification in the scientific
story of the evolution of life. He finds that it is only through some kind of
faith that the "story" of life becomes the "scheme" of life. What starts as a
natural wonder can then take on Divine dimensions.
COYNE has completed a study of the changing relationship
of the Church to the culture of science during the papacy of John Paul II. He
has investigated the Pope's thought, especially as expressed in the encyclical
Fides et Ratio on the role of the
sciences in the search for ultimate meaning.
STOEGER recently completed work on the interaction between
cosmology and the other natural sciences with eschatology (the theology of
cosmic destiny and human destiny) under the auspices of the Center of
Theological Inquiry in Princeton, New Jersey. He also contributed work on the
epistemological and ontological implications of quantum theory to the meeting on
"Quantum Mechanics and Quantum Field Theory," sponsored by the Vatican
Observatory and the Center for Theology and the Natural Sciences, Berkeley,
California. The meeting held at Castel Gandolfo in late June (see section III).
In addition, STOEGER has been formulating more carefully a description of the
universe that contemporary cosmology claims to study, and he is also working on
related issues in the philosophy of cosmology.
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