1,075 research outputs found
4-Dimensional BF Theory as a Topological Quantum Field Theory
Starting from a Lie group G whose Lie algebra is equipped with an invariant
nondegenerate symmetric bilinear form, we show that 4-dimensional BF theory
with cosmological term gives rise to a TQFT satisfying a generalization of
Atiyah's axioms to manifolds equipped with principal G-bundle. The case G =
GL(4,R) is especially interesting because every 4-manifold is then naturally
equipped with a principal G-bundle, namely its frame bundle. In this case, the
partition function of a compact oriented 4-manifold is the exponential of its
signature, and the resulting TQFT is isomorphic to that constructed by Crane
and Yetter using a state sum model, or by Broda using a surgery presentation of
4-manifolds.Comment: 15 pages in LaTe
Magellan/M2FS Spectroscopy of Galaxy Clusters: Stellar Population Model and Application to Abell 267
We report the results of a pilot program to use the Magellan/M2FS
spectrograph to survey the galactic populations and internal kinematics of
galaxy clusters. For this initial study, we present spectroscopic measurements
for quiescent galaxies observed along the line of sight to the galaxy
cluster Abell 267 (). We develop a Bayesian method for modeling the
integrated light from each galaxy as a simple stellar population, with free
parameters that specify redshift () and characteristic age,
metallicity (), alpha-abundance (), and
internal velocity dispersion () for individual galaxies.
Parameter estimates derived from our 1.5-hour observation of A267 have median
random errors of ,
, $\sigma_{\mathrm{[Fe/H]}}=0.11\
\mathrm{dex}\sigma_{[\alpha/\mathrm{Fe}]}=0.07\ \mathrm{dex}\sigma_{\sigma_\mathrm{int}}=20\ \mathrm{km\ s^{-1}}$. In a companion paper,
we use these results to model the structure and internal kinematics of A267.Comment: 16 pages, 11 figures, accepted for publication in The Astronomical
Journa
Low Mass Companions for Five Solar-Type Stars from the Magellan Planet Search Program
We report low mass companions orbiting five Solar-type stars that have
emerged from the Magellan precision Doppler velocity survey, with minimum
(Msini) masses ranging from 1.2 to 25 Mjup. These nearby target stars range
from mildly metal-poor to metal-rich, and appear to have low chromospheric
activity. The companions to the brightest two of these stars have previously
been reported from the CORALIE survey. Four of these companions (HD 48265-b, HD
143361-b, HD 28185-b, HD 111232-b) are low-mass Jupiter-like planets in
eccentric intermediate and long-period orbits. On the other hand, the companion
to HD 43848 appears to be a long period brown dwarf in a very eccentric orbit.Comment: Accepted for publication on ApJ, 26 pages, 10 figures, 7 table
How Lyman Alpha Emission Depends On Galaxy Stellar Mass
In this work, we show how the stellar mass (M) of galaxies affects the
3<z<4.6 Ly-alpha equivalent width (EW) distribution. To this end, we design a
sample of 629 galaxies in the M range 7.6 < logM/Msun < 10.6 from the
3D-HST/CANDELS survey. We perform spectroscopic observations of this sample
using the Michigan/Magellan Fiber System, allowing us to measure Ly-alpha
fluxes and use 3D-HST/CANDELS ancillary data. In order to study the Ly-alpha EW
distribution dependence on M, we split the whole sample in three stellar mass
bins. We find that, in all bins, the distribution is best represented by an
exponential profile of the form dN(M)/dEW= A(M)exp(-EW/W0(M))/W0(M). Through a
Bayesian analysis, we confirm that lower M galaxies have higher Ly-alpha EWs.
We also find that the fraction A of galaxies featuring emission and the
e-folding scale W0 of the distribution anti- correlate with M, recovering
expressions of the forms A(M)= -0.26(.13) logM/Msun+3.01(1.2) and W0(M)=
-15.6(3.5) logM/Msun +166(34). These results are crucial for proper
interpretation of Ly-alpha emission trends reported in the literature that may
be affected by strong M selection biases.Comment: 4 pages, 5 figure
AGB Sodium Abundances in the Globular Cluster 47 Tucanae (NGC 104)
A recent analysis comparing the [Na/Fe] distributions of red giant branch
(RGB) and asymptotic giant branch (AGB) stars in the Galactic globular cluster
NGC 6752 found that the ratio of Na-poor to Na-rich stars changes from 30:70 on
the RGB to 100:0 on the AGB. The surprising paucity of Na-rich stars on the AGB
in NGC 6752 warrants additional investigations to determine if the failure of a
significant fraction of stars to ascend the AGB is an attribute common to all
globular clusters. Therefore, we present radial velocities, [Fe/H], and [Na/Fe]
abundances for 35 AGB stars in the Galactic globular cluster 47 Tucanae (47
Tuc; NGC 104), and compare the AGB [Na/Fe] distribution with a similar RGB
sample published previously. The abundances and velocities were derived from
high resolution spectra obtained with the Michigan/Magellan Fiber System (M2FS)
and MSpec spectrograph on the Magellan-Clay 6.5m telescope. We find the average
heliocentric radial velocity and [Fe/H] values to be =-18.56 km s^-1
(sigma=10.21 km s^-1) and =-0.68 (sigma=0.08), respectively, in
agreement with previous literature estimates. The average [Na/Fe] abundance is
0.12 dex lower in the 47 Tuc AGB sample compared to the RGB sample, and the
ratio of Na-poor to Na-rich stars is 63:37 on the AGB and 45:55 on the RGB.
However, in contrast to NGC 6752, the two 47 Tuc populations have nearly
identical [Na/Fe] dispersion and interquartile range values. The data presented
here suggest that only a small fraction <20% of Na-rich stars in 47 Tuc may
fail to ascend the AGB. Regardless of the cause for the lower average [Na/Fe]
abundance in AGB stars, we find that Na-poor stars and at least some Na-rich
stars in 47 Tuc evolve through the early AGB phase. [abridged]Comment: Accepted for publication in the Astronomical Journal; 15 pages; 8
figures; 4 table
Book Reviews
If there is a living American qualified to prepare material for the student of future interests probably law teachers would agree that Professor Kales is the man. He has written a book on Future Estates in Illinois which has made a distinct impression on the law of that state and is recognized elsewhere as a sound and scholarly treatise. He has taught the course on future interests and illegal restraints at Northwestern University Law School for many years, and last year gave the same course at Harvard
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