1,613 research outputs found
Dark Matter Constraints from the Sagittarius Dwarf and Tail System
2MASS has provided a three-dimensional map of the >360 degree, wrapped tidal
tails of the Sagittarius (Sgr) dwarf spheroidal galaxy, as traced by M giant
stars. With the inclusion of radial velocity data for stars along these tails,
strong constraints exist for dynamical models of the Milky Way-Sgr interaction.
N-body simulations of Sgr disruption with model parameters spanning a range of
initial conditions (e.g., Sgr mass and orbit, Galactic rotation curve, halo
flattening) are used to find parameterizations that match almost every extant
observational constraint of the Sgr system. We discuss the implications of the
Sgr data and models for the orbit, mass and M/L of the Sgr bound core as well
as the strength, flattening, and lumpiness of the Milky Way potential.Comment: 6 pages, 0 figures. Contribution to proceedings of ``IAU Symposium
220: Dark Matter in Galaxies'', eds. S. Ryder, D.J. Pisano, M. Walker, and K.
Freema
Effect of illicit direct to consumer advertising on use of etanercept, mometasone, and tegaserod in Canada: controlled longitudinal study
Objective To assess the impact of direct to consumer advertising of prescription drugs in the United States on Canadian prescribing rates for three heavily marketed drugsâetanercept, mometasone, and tegaserod
Second generation Robo-AO instruments and systems
The prototype Robo-AO system at the Palomar Observatory 1.5-m telescope is
the world's first fully automated laser adaptive optics instrument. Scientific
operations commenced in June 2012 and more than 12,000 observations have since
been performed at the ~0.12" visible-light diffraction limit. Two new infrared
cameras providing high-speed tip-tilt sensing and a 2' field-of-view will be
integrated in 2014. In addition to a Robo-AO clone for the 2-m IGO and the
natural guide star variant KAPAO at the 1-m Table Mountain telescope, a second
generation of facility-class Robo-AO systems are in development for the 2.2-m
University of Hawai'i and 3-m IRTF telescopes which will provide higher Strehl
ratios, sharper imaging, ~0.07", and correction to {\lambda} = 400 nm.Comment: 11 pages, 4 figures, 3 table
2MASS Studies of Differential Reddening Across Three Massive Globular Clusters
J, H, and K_S band data from the Two Micron All-Sky Survey (2MASS) are used
to study the effects of differential reddening across the three massive
Galactic globular clusters Omega Centauri, NGC 6388, and NGC 6441. Evidence is
found that variable extinction may produce false detections of tidal tails
around Omega Centauri. We also investigate what appears to be relatively strong
differential reddening towards NGC 6388 and NGC 6441, and find that
differential extinction may be exaggerating the need for a metallicity spread
to explain the width of the red giant branches for these two clusters. Finally,
we consider the implications of these results for the connection between
unusual, multipopulation globular clusters and the cores of dwarf spheroidal
galaxies (dSph).Comment: 40 pages, 14 figures. Accepted for publication in Oct. 2003 A
The kinematics of ionized gas in lyman-break analogs at z ~ 0.2
We present results for 19 âLyman-break analogsâ observed with Keck/OSIRIS with an adaptive-optics-assisted
spatial resolution of less than 200 pc. We detect satellites/companions, diffuse emission, and velocity shear, all
with high signal-to-noise ratios. These galaxies present remarkably high velocity dispersion along the line of sight
(~70 km s^(â1)), much higher than standard star-forming spirals in the low-redshift universe. We artificially redshift
our data to z ~ 2.2 to allow for a direct comparison with observations of high-z Lyman-break galaxies and find
striking similarities between both samples. This suggests that either similar physical processes are responsible
for their observed properties, or, alternatively, that it is very difficult to distinguish between different mechanisms
operating in the low- versus high-redshift starburst galaxies based on the available data. The comparison between
morphologies in the UV/optical continuum and our kinemetry analysis often shows that neither is by itself sufficient
to confirm or completely rule out the contribution from recent merger events. We find a correlation between the
kinematic properties and stellar mass, in that more massive galaxies show stronger evidence for a disk-like structure.
This suggests a co-evolutionary process between the stellar mass buildup and the formation of morphological and
dynamical substructure within the galaxy
Exploring Halo Substructure with Giant Stars: Spectroscopy of Stars in the Galactic Anticenter Stellar Structure
To determine the nature of the recently discovered, ring-like stellar
structure at the Galactic anticenter, we have collected spectra of a set of
presumed constituent M giants selected from the 2MASS point source catalog.
Radial velocities have been obtained for stars spanning ~100 degrees,
exhibiting a trend in velocity with Galactic longitude and an estimated
dispersion of 20 +/- 4 km/sec. A mean metallicity [Fe/H] = -0.4 +/- 0.3
measured for these stars combines with previous evidence from the literature to
suggest a population with a significant metallicity spread. In addition, a
curious alignment of at least four globular clusters of lower mean metallicity
is noted to be spatially and kinematically consistent with this stellar
distribution. We interpret the M giant sample position and velocity variation
with Galactic longitude as suggestive of a satellite galaxy currently
undergoing tidal disruption in a non-circular, prograde orbit about the Milky
Way.Comment: (1) University of Virginia, 4 pages, 3 figures, accepted for
publication in The Astrophysical Journal Letter
Effect of 5âČ-methylthioadenosine on gene action during heat shock in Drosophila melanogaster
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