31 research outputs found
Recent Decisions
Comments on recent decisions by Wilmer A. McLaughlin, Robert C. Enburg, Robert A. Layden, Lenton G. Sculthorp, Joseph T. Helling, John L. Globensky, Maurice J. Moriarty, Robert J. Affeldt, Louis J. Mustico, Donald John Tufts, Sidney Baker, and Edward J. VanTassel
No Excess of RR Lyrae Stars in the Canis Major Overdensity
Our multi-epoch survey of ~20 sq. deg. of the Canis Major overdensity has
detected only 10 RR Lyrae stars (RRLS). We show that this number is consistent
with the number expected from the Galactic halo and thick disk populations
alone, leaving no excess that can be attributed to the dwarf spheroidal (dSph)
galaxy that some authors have proposed as the origin of the CMa overdensity. If
this galaxy resembles the dSph satellites of the Milky Way and of M31 and has
the putative Mv~-14.5, our survey should have detected several tens of RRLS.
Even if Mv10, which is not observed. Either the
old stellar population of this galaxy has unique properties or, as others have
argued before, the CMa overdensity is produced by the thin and thick disk and
spiral arm populations of the Milky Way and not by a collision with a dSph
satellite galaxy.Comment: 35 pages, 9 figures, 5 tables. Accepted for publication at the
Astronomical Journa
The M33 Globular Cluster System with PAndAS Data: The Last Outer Halo Cluster?
We use CFHT/MegaCam data to search for outer halo star clusters in M33 as
part of the Pan-Andromeda Archaeological Survey (PAndAS). This work extends
previous studies out to a projected radius of 50 kpc and covers over 40 square
degrees. We find only one new unambiguous star cluster in addition to the five
previously known in the M33 outer halo (10 kpc <= r <= 50 kpc). Although we
identify 2440 cluster candidates of various degrees of confidence from our
objective image search procedure, almost all of these are likely background
contaminants, mostly faint unresolved galaxies. We measure the luminosity,
color and structural parameters of the new cluster in addition to the five
previously-known outer halo clusters. At a projected radius of 22 kpc, the new
cluster is slightly smaller, fainter and redder than all but one of the other
outer halo clusters, and has g' ~ 19.9, (g'-i') ~ 0.6, concentration parameter
c ~ 1.0, a core radius r_c ~ 3.5 pc, and a half-light radius r_h ~ 5.5 pc. For
M33 to have so few outer halo clusters compared to M31 suggests either tidal
stripping of M33's outer halo clusters by M31, or a very different, much calmer
accretion history of M33.Comment: 37 pages, 9 figures. Accepted by the Astrophysical Journa
The Fermi GBM Gamma-Ray Burst Spectral Catalog: Four Years Of Data
In this catalog we present the updated set of spectral analyses of GRBs
detected by the Fermi Gamma-Ray Burst Monitor (GBM) during its first four years
of operation. It contains two types of spectra, time-integrated spectral fits
and spectral fits at the brightest time bin, from 943 triggered GRBs. Four
different spectral models were fitted to the data, resulting in a compendium of
more than 7500 spectra. The analysis was performed similarly, but not
identically to Goldstein et al. 2012. All 487 GRBs from the first two years
have been re-fitted using the same methodology as that of the 456 GRBs in years
three and four. We describe, in detail, our procedure and criteria for the
analysis, and present the results in the form of parameter distributions both
for the observer-frame and rest-frame quantities. The data files containing the
complete results are available from the High-Energy Astrophysics Science
Archive Research Center (HEASARC).Comment: Accepted for publication in ApJ
BVRI Light Curves for 29 Type Ia Supernovae
BVRI light curves are presented for 27 Type Ia supernovae discovered during
the course of the Calan/Tololo Survey and for two other SNe Ia observed during
the same period. Estimates of the maximum light magnitudes in the B, V, and I
bands and the initial decline rate parameter m15(B) are also given.Comment: 17 pages, figures and tables are not included (contact first author
if needed), to appear in the Astronomical Journa
Influence of aerobic fitness on gastrointestinal barrier integrity and microbial translocation following a fixed-intensity military exertional heat stress test
Purpose: Exertional-heat stress adversely disrupts gastrointestinal (GI) barrier integrity, whereby subsequent microbial translocation (MT) can result in potentially serious health consequences. To date, the influence of aerobic fitness on GI barrier integrity and MT following exertional-heat stress is poorly characterised. Method: Ten untrained (UT; VO2max = 45 ± 3 ml·kg−1·min−1) and ten highly trained (HT; VO2max = 64 ± 4 ml·kg−1·min−1) males completed an ecologically valid (military) 80-min fixed-intensity exertional-heat stress test (EHST). Venous blood was drawn immediately pre- and post-EHST. GI barrier integrity was assessed using the serum dual-sugar absorption test (DSAT) and plasma Intestinal Fatty-Acid Binding Protein (I-FABP). MT was assessed using plasma Bacteroides/total 16S DNA. Results: UT experienced greater thermoregulatory, cardiovascular and perceptual strain (p < 0.05) than HT during the EHST. Serum DSAT responses were similar between the two groups (p = 0.59), although Δ I-FABP was greater (p = 0.04) in the UT (1.14 ± 1.36 ng·ml−1) versus HT (0.20 ± 0.29 ng·ml−1) group. Bacteroides/Total 16S DNA ratio was unchanged (Δ; -0.04 ± 0.18) following the EHST in the HT group, but increased (Δ; 0.19 ± 0.25) in the UT group (p = 0.05). Weekly aerobic training hours had a weak, negative correlation with Δ I-FABP and Bacteroides/total 16S DNA responses. Conclusion: When exercising at the same absolute workload, UT individuals are more susceptible to small intestinal epithelial injury and MT than HT individuals. These responses appear partially attributable to greater thermoregulatory, cardiovascular, and perceptual strain