1,455 research outputs found
Power Spectrum Analysis of Polarized Emission from the Canadian Galactic Plane Survey
Angular power spectra are calculated and presented for the entirety of the
Canadian Galactic Plane Survey polarization dataset at 1.4 GHz covering an area
of 1060 deg. The data analyzed are a combination of data from the 100-m
Effelsberg Telescope, the 26-m Telescope at the Dominion Radio Astrophysical
Observatory, and the Synthesis Telescope at the Dominion Radio Astrophysical
Observatory, allowing all scales to be sampled down to arcminute resolution.
The resulting power spectra cover multipoles from to and display both a power-law component at low multipoles and a
flattening at high multipoles from point sources. We fit the power spectrum
with a model that accounts for these components and instrumental effects. The
resulting power-law indices are found to have a mode of 2.3, similar to
previous results. However, there are significant regional variations in the
index, defying attempts to characterize the emission with a single value. The
power-law index is found to increase away from the Galactic plane. A transition
from small-scale to large-scale structure is evident at ,
associated with the disk-halo transition in a 15 region around
. Localized variations in the index are found toward HII regions
and supernova remnants, but the interpretation of these variations is
inconclusive. The power in the polarized emission is anticorrelated with bright
thermal emission (traced by H emission) indicating that the thermal
emission depolarizes background synchrotron emission.Comment: Accepted to ApJ; 17 page
Anomaluos RR Lyrae (V-I)_0 colors in Baade's Window
We compare (V-I)_0-(V-K)_0 color-color and (V-I)_0-log P period-color
diagrams for Baade's Window and local RRab Lyrae stars. We find that for a
fixed log P the Baade's Window RR Lyrae stars are ~0.17 magnitudes redder in
(V-I)_0 than the local RR Lyrae stars. We also show that there is no such
effect observed in (V-K)_0. We argue that an extinction misestimate towards
Baade's Window is not a plausible explanation of the discrepancy. Unlike
Baade's Window RR Lyrae stars, the local ones follow a black-body color-color
relation and are well approximated by theoretical models. We test two
parameters, metallicity and surface gravity, and find that their effects are
too small to explain the (V-I)_0 discrepancy between the two groups of stars.
We do not provide any explanation for the anomalous (V-I)_0 behavior of the
Baade's Window RR Lyrae stars. We note that a similar effect for clump giant
stars has been recently reported by Paczynski and we caution that RR Lyrae
stars and clump giants, often used as standard candles, can be subject to the
same type of systematics.Comment: 10 pages, 7 figures, submitted to Ap
The structured environments of embedded star-forming cores. PACS and SPIRE mapping of the enigmatic outflow source UYSO 1
The intermediate-mass star-forming core UYSO 1 has previously been found to
exhibit intriguing features. While deeply embedded and previously only
identified by means of its (sub-)millimeter emission, it drives two powerful,
dynamically young, molecular outflows. Although the process of star formation
has obviously started, the chemical composition is still pristine. We present
Herschel PACS and SPIRE continuum data of this presumably very young region.
The now complete coverage of the spectral energy peak allows us to precisely
constrain the elevated temperature of 26 - 28 K for the main bulge of gas
associated with UYSO1, which is located at the interface between the hot HII
region Sh 2-297 and the cold dark nebula LDN 1657A. Furthermore, the data
identify cooler compact far-infrared sources of just a few solar masses, hidden
in this neighbouring dark cloud.Comment: accepted contribution for the forthcoming Herschel Special Issue of
A&A, 5 pages (will appear as 4-page letter in the journal), 6 figure file
Dust-temperature of an isolated star-forming cloud: Herschel observations of the Bok globule CB244
We present Herschel observations of the isolated, low-mass star-forming Bok
globule CB244. It contains two cold sources, a low-mass Class 0 protostar and a
starless core, which is likely to be prestellar in nature, separated by 90
arcsec (~ 18000 AU). The Herschel data sample the peak of the Planck spectrum
for these sources, and are therefore ideal for dust-temperature and column
density modeling. With these data and a near-IR extinction map, the MIPS 70
micron mosaic, the SCUBA 850 micron map, and the IRAM 1.3 mm map, we model the
dust-temperature and column density of CB244 and present the first measured
dust-temperature map of an entire star-forming molecular cloud. We find that
the column-averaged dust-temperature near the protostar is ~ 17.7 K, while for
the starless core it is ~ 10.6K, and that the effect of external heating causes
the cloud dust-temperature to rise to ~ 17 K where the hydrogen column density
drops below 10^21 cm^-2. The total hydrogen mass of CB244 (assuming a distance
of 200 pc) is 15 +/- 5 M_sun. The mass of the protostellar core is 1.6 +/- 0.1
M_sun and the mass of the starless core is 5 +/- 2 M_sun, indicating that ~ 45%
of the mass in the globule is participating in the star-formation process.Comment: Accepted for A&A Herschel Special Issue; 5 pages, 2 figure
P19-53 LB. Priming with recombinant BCG expressing HIV-1 Gag or RT and boosting with recombinant MVA induces an effective immune response in mice
Mycobacterium bovis BCG (BCG) has a number of characteristics that give it great potential to act as a vehicle for the delivery of recombinant vaccines. However, its success depends on overcoming the challenges of poor antigen expression levels and genetic instability. Our studies using an optimized mycobacterial shuttle vector which utilizes the Mycobacterium tuberculosis mtrA promoter, induced upon infection of macrophages, and the M. tuberculosis 19 kDa signal sequence may overcome these issues. We have used this system to generate a recombinant BCG (rBCG) expressing HIV-1 subtype C full length Gag or reverse transcriptase (RT)
Recommended from our members
Tritium system test assembly control system cost estimate
The principal objectives of the Tritium Systems Test Assembly (TSTA), which includes the development, demonstration and interfacing of technologies related to the deuterium--tritium fuel cycle for fusion reactor systems, are concisely stated. The various integrated subsystems comprising TSTA and their functions are discussed. Each of the four major subdivisions of TSTA, including the main process system, the environmental and safety systems, supporting systems and the physical plant are briefly discussed. An overview of the Master Data Acquisition and Control System, which will control all functional operation of TSTA, is provided
The Earliest Phases of Star formation (EPoS): Temperature, density, and kinematic structure of the star-forming core CB 17
Context: The initial conditions for the gravitational collapse of molecular
cloud cores and the subsequent birth of stars are still not well constrained.
The characteristic cold temperatures (about 10 K) in such regions require
observations at sub-millimetre and longer wavelengths. The Herschel Space
Observatory and complementary ground-based observations presented in this paper
have the unprecedented potential to reveal the structure and kinematics of a
prototypical core region at the onset of stellar birth.
Aims: This paper aims to determine the density, temperature, and velocity
structure of the star-forming Bok globule CB 17. This isolated region is known
to host (at least) two sources at different evolutionary stages: a dense core,
SMM1, and a Class I protostar, IRS.
Methods: We modeled the cold dust emission maps from 100 micron to 1.2 mm
with both a modified blackbody technique to determine the optical
depth-weighted line-of-sight temperature and column density and a ray-tracing
technique to determine the core temperature and volume density structure.
Furthermore, we analysed the kinematics of CB17 using the high-density gas
tracer N2H+.
Results: From the ray-tracing analysis, we find a temperature in the centre
of SMM1 of 10.6 K, a flat density profile with radius 9500 au, and a central
volume density of n(H) = 2.3x10^5 cm-3. The velocity structure of the N2H+
observations reveal global rotation with a velocity gradient of 4.3 km/s/pc.
Superposed on this rotation signature we find a more complex velocity field,
which may be indicative of differential motions within the dense core.
Conclusions: SMM is a core in an early evolutionary stage at the verge of
being bound, but the question of whether it is a starless or a protostellar
core remains unanswered.Comment: published in A&
Marked influence of the nature of chemical bond on CP-violating signature in molecular ions and
Heavy polar molecules offer a great sensitivity to the electron Electric
Dipole Moment(EDM). To guide emerging searches for EDMs with molecular ions, we
estimate the EDM-induced energy corrections for hydrogen halide ions
and in their respective ground states. We find that the energy corrections due to EDM for the two
ions differ by an unexpectedly large factor of fifteen. We demonstrate that a
major part of this enhancement is due to a dissimilarity in the nature of the
chemical bond for the two ions: the bond that is nearly of ionic character in
exhibits predominantly covalent nature in .
We conclude that because of this enhancement the HI ion may be a
potentially competitive candidate for the EDM search.Comment: This manuscript has been accepted for publication in Physical Review
Letters. The paper is now being prepared for publicatio
- …