409 research outputs found
The Molecular Gas Environment around Two Herbig Ae/Be Stars: Resolving the Outflows of LkHa 198 and LkHa 225S
Observations of outflows associated with pre-main-sequence stars reveal
details about morphology, binarity and evolutionary states of young stellar
objects. We present molecular line data from the Berkeley-Illinois-Maryland
Association array and Five Colleges Radio Astronomical Observatory toward the
regions containing the Herbig Ae/Be stars LkHa 198 and LkHa 225S. Single dish
observations of 12CO 1-0, 13CO 1-0, N2H+ 1-0 and CS 2-1 were made over a field
of 4.3' x 4.3' for each species. 12CO data from FCRAO were combined with high
resolution BIMA array data to achieve a naturally-weighted synthesized beam of
6.75'' x 5.5'' toward LkHa 198 and 5.7'' x 3.95'' toward LkHa 225S,
representing resolution improvements of factors of approximately 10 and 5 over
existing data. By using uniform weighting, we achieved another factor of two
improvement. The outflow around LkHa 198 resolves into at least four outflows,
none of which are centered on LkHa 198-IR, but even at our resolution, we
cannot exclude the possibility of an outflow associated with this source. In
the LkHa 225S region, we find evidence for two outflows associated with LkHa
225S itself and a third outflow is likely driven by this source. Identification
of the driving sources is still resolution-limited and is also complicated by
the presence of three clouds along the line of sight toward the Cygnus
molecular cloud. 13CO is present in the environments of both stars along with
cold, dense gas as traced by CS and (in LkHa 225S) N2H+. No 2.6 mm continuum is
detected in either region in relatively shallow maps compared to existing
continuum observations.Comment: 14 pages, 10 figures (5 color), accepted for publication in Ap
Probing dust grain evolution in IM Lupi's circumstellar disc. Multi-wavelength observations and modelling of the dust disc
We present a panchromatic study, involving a multiple technique approach, of
the circumstellar disc surrounding the T Tauri star IM Lupi (Sz 82). We have
undertaken a comprehensive observational study of IM Lupi using photometry,
spectroscopy, millimetre interferometry and multi-wavelength imaging. For the
first time, the disc is resolved from optical and near-infrared wavelengths in
scattered light, to the millimetre regime in thermal emission. Our data-set, in
conjunction with existing photometric data, provides an extensive coverage of
the spectral energy distribution, including a detailed spectrum of the silicate
emission bands. We have performed a simultaneous modelling of the various
observations, using the radiative transfer code MCFOST, and analysed a grid of
models over a large fraction of the parameter space via Bayesian inference. We
have constructed a model that can reproduce all of the observations of the
disc. Our analysis illustrates the importance of combining a wide range of
observations in order to fully constrain the disc model, with each observation
providing a strong constraint only on some aspects of the disc structure and
dust content. Quantitative evidence of dust evolution in the disc is obtained:
grain growth up to millimetre-sized particles, vertical stratification of dust
grains with micrometric grains close to the disc surface and larger grains
which have settled towards the disc midplane, and possibly the formation of
fluffy aggregates and/or ice mantles around grains.Comment: 20 pages, 13 figures. Accepted for publication in A&
Improving Photoelectron Counting and Particle Identification in Scintillation Detectors with Bayesian Techniques
Many current and future dark matter and neutrino detectors are designed to
measure scintillation light with a large array of photomultiplier tubes (PMTs).
The energy resolution and particle identification capabilities of these
detectors depend in part on the ability to accurately identify individual
photoelectrons in PMT waveforms despite large variability in pulse amplitudes
and pulse pileup. We describe a Bayesian technique that can identify the times
of individual photoelectrons in a sampled PMT waveform without deconvolution,
even when pileup is present. To demonstrate the technique, we apply it to the
general problem of particle identification in single-phase liquid argon dark
matter detectors. Using the output of the Bayesian photoelectron counting
algorithm described in this paper, we construct several test statistics for
rejection of backgrounds for dark matter searches in argon. Compared to simpler
methods based on either observed charge or peak finding, the photoelectron
counting technique improves both energy resolution and particle identification
of low energy events in calibration data from the DEAP-1 detector and
simulation of the larger MiniCLEAN dark matter detector.Comment: 16 pages, 16 figure
Persistent Long-Term Structural, Functional, and Metabolic Changes After Stress-Induced (Takotsubo) Cardiomyopathy
The HEROIC study was funded by the British Heart Foundation Project Grant no. PG/15/108/31928 (D.K.D.), the Josephine Lansdell British Medical Association 2015 Award (D.K.D.), and the Chief Scientist Office CGA-16-4 Catalytic Grant (D.K.D). D.E.N. is supported by the British Heart Foundation (CH/09/002) and a Wellcome Trust Senior Investigator Award (WT103782AIA).Peer reviewedPublisher PD
UWISH2 -- The UKIRT Widefield Infrared Survey for H2
We present the goals and preliminary results of an unbiased, near-infrared,
narrow-band imaging survey of the First Galactic Quadrant (10deg<l<65deg ;
-1.3deg<b<+1.3deg). This area includes most of the Giant Molecular Clouds and
massive star forming regions in the northern hemisphere. The survey is centred
on the 1-0S(1) ro-vibrational line of H2, a proven tracer of hot, dense
molecular gas in star-forming regions, around evolved stars, and in supernova
remnants. The observations complement existing and upcoming photometric surveys
(Spitzer-GLIMPSE, UKIDSS-GPS, JCMT-JPS, AKARI, Herschel Hi-GAL, etc.), though
we probe a dynamically active component of star formation not covered by these
broad-band surveys. Our narrow-band survey is currently more than 60% complete.
The median seeing in our images is 0.73arcsec. The images have a 5sigma
detection limit of point sources of K=18mag and the surface brightness limit is
10^-19Wm^-2arcsec^-2 when averaged over our typical seeing. Jets and outflows
from both low and high mass Young Stellar Objects are revealed, as are new
Planetary Nebulae and - via a comparison with earlier K-band observations
acquired as part of the UKIDSS GPS - numerous variable stars. With their
superior spatial resolution, the UWISH2 data also have the potential to reveal
the true nature of many of the Extended Green Objects found in the GLIMPSE
survey.Comment: 14pages, 8figures, 2tables, accepted for publication by MNRAS, a
version with higher resolution figures can be found at
http://astro.kent.ac.uk/~df
A Search for Neutrinos from the Solar hep Reaction and the Diffuse Supernova Neutrino Background with the Sudbury Neutrino Observatory
A search has been made for neutrinos from the hep reaction in the Sun and from the diffus
Astrophysical turbulence modeling
The role of turbulence in various astrophysical settings is reviewed. Among
the differences to laboratory and atmospheric turbulence we highlight the
ubiquitous presence of magnetic fields that are generally produced and
maintained by dynamo action. The extreme temperature and density contrasts and
stratifications are emphasized in connection with turbulence in the
interstellar medium and in stars with outer convection zones, respectively. In
many cases turbulence plays an essential role in facilitating enhanced
transport of mass, momentum, energy, and magnetic fields in terms of the
corresponding coarse-grained mean fields. Those transport properties are
usually strongly modified by anisotropies and often completely new effects
emerge in such a description that have no correspondence in terms of the
original (non coarse-grained) fields.Comment: 88 pages, 26 figures, published in Reports on Progress in Physic
Independent measurement of the total active B8 solar neutrino flux using an array of He3 proportional counters at the Sudbury Neutrino Observatory
The Sudbury Neutrino Observatory (SNO) used an array of 3He proportional counters to measure the rate of neutral-current interactions in heavy water and precisely determined the total active (νx) 8B solar neutrino flux. This technique is independent of previous methods employed by SNO. The total flux is found to be 5.54-0.31+0.33(stat)-0.34+0.36(syst)×106 cm-2 s-1, in agreement with previous measurements and standard solar models. A global analysis of solar and reactor neutrino results yields Δm2=7.59-0.21+0.19×10-5 eV2 and θ=34.4-1.2+1.3 degrees. The uncertainty on the mixing angle has been reduced from SNO’s previous results
DMRadio-m: A Search for the QCD Axion Below eV
The QCD axion is one of the most compelling candidates to explain the dark
matter abundance of the universe. With its extremely small mass (), axion dark matter interacts as a classical field rather
than a particle. Its coupling to photons leads to a modification of Maxwell's
equations that can be measured with extremely sensitive readout circuits.
DMRadio-m is a next-generation search for axion dark matter below
eV using a T static magnetic field, a coaxial inductive pickup, a
tunable LC resonator, and a DC-SQUID readout. It is designed to search for QCD
axion dark matter over the range (). The primary
science goal aims to achieve DFSZ sensitivity above neV (30
MHz), with a secondary science goal of probing KSVZ axions down to
(10 MHz).Comment: 8 pages, 4 figures. Updated to fix small errors and correct
acknowledgement
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