637 research outputs found
Mapping dust column density in dark clouds by using NIR scattered light : Case of the Lupus 3 dark cloud
We present a method of mapping dust column density in dark clouds by using
near-infrared scattered light. Our observations of the Lupus 3 dark cloud
indicate that there is a well defined relation between (1) the H-Ks color of an
individual star behind the cloud, i.e., dust column density, and (2) the
surface brightness of scattered light toward the star in each of the J, H, and
Ks bands. In the relation, the surface brightnesses increase at low H-Ks
colors, then saturate and decrease with increasing H-Ks. Using a simple
one-dimensional radiation transfer model, we derive empirical equations which
plausibly represent the observed relationship between the surface brightness
and the dust column density. By using the empirical equations, we estimate dust
column density of the cloud for any directions toward which even no background
stars are seen. We obtain a dust column density map with a pixel scale of 2.3 x
2.3 arcsec^2 and a large dynamic range up to Av = 50 mag. Compared to the
previous studies by Juvela et al., this study is the first to use color excess
of the background stars for calibration of the empirical relationship and to
apply the empirical relationship beyond the point where surface brightness
starts to decrease with increasing column density
X-ray Measurements of the Gravitational Potential Profile in the Central Region of the Abell 1060 Cluster of Galaxies
X-ray spectral and imaging data from ASCA and ROSAT were used to measure the
total mass profile in the central region of Abell 1060, a nearby and relatively
poor cluster of galaxies. The ASCA X-ray spectra, after correcting for the
spatial response of the X-ray telescope, show an isothermal distribution of the
intra-cluster medium (ICM) within at least 12' (or kpc;
km sMpc) in radius of the cluster center. The
azimuthally averaged surface brightness profile from the ROSAT PSPC exhibits a
central excess above an isothermal model. The ring-sorted ASCA GIS
spectra and the radial surface brightness distribution from the ROSAT PSPC were
simultaneously utilized to constrain the gravitational potential profile. Some
analytic models of the total mass density profile were examined. The ICM
density profile was also specified by analytic forms. The ICM temperature
distribution was constrained to satisfy the hydrostatic equilibrium, and to be
consistent with the data. Then, the total mass distribution was found to be
described better by the universal dark halo profile proposed by Navarro, Frenk,
and White (1996;1997) than by a King-type model with a flat density core. A
profile with a central cusp together with a logarithmic radial slope of was also consistent with the data. Discussions are made concerning the
estimated dark matter distribution around the cluster center.Comment: 32 pages. Accepted: ApJ 2000, 35 pages, Title was correcte
Omeprazole- and Esomeprazole-associated Hypomagnesaemia: Data Mining of the Public Version of the FDA Adverse Event Reporting System
Objective: Case reports showing that proton-pump inhibitors (PPIs), omeprazole and esomeprazole, can cause hypomagnesaemia have been accumulating since 2006. In this study, the reports submitted to the Adverse Event Reporting System (AERS) of the US Food and Drug Administration (FDA) were evaluated to assess omeprazole and esomeprazole in terms of susceptibility to hypomagnesaemia
Near-infrared circular polarization survey in star-forming regions : Correlations and trends
We have conducted a systematic near-infrared circular polarization (CP) survey in star-forming regions, covering high-mass, intermediate-mass, and low-mass young stellar objects. All the observations were made using the SIRPOL imaging polarimeter on the Infrared Survey Facility 1.4 m telescope at the South African Astronomical Observatory. We present the polarization properties of 10 sub-regions in 6 star-forming regions. The polarization patterns, extents, and maximum degrees of linear and circular polarizations are used to determine the prevalence and origin of CP in the star-forming regions. Our results show that the CP pattern is quadrupolar in general, the CP regions are extensive, up to 0.65 pc, the CP degrees are high, up to 20%, and the CP degrees decrease systematically from high- to low-mass young stellar objects. The results are consistent with dichroic extinction mechanisms generating the high degrees of CP in star-forming regions.Peer reviewe
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