221 research outputs found
The Allen Telescope Array Twenty-centimeter Survey -- A 700-Square-Degree, Multi-Epoch Radio Dataset -- II: Individual Epoch Transient Statistics
We present our second paper on the Allen Telescope Array Twenty-centimeter
Survey (ATATS), a multi-epoch, ~700 sq. deg. radio image and catalog at 1.4
GHz. The survey is designed to detect rare, bright transients as well as to
commission the ATA's wide-field survey capabilities. ATATS explores the
challenges of multi-epoch transient and variable source surveys in the domain
of dynamic range limits and changing (u,v) coverage.
Here we present images made using data from the individual epochs, as well as
a revised image combining data from all ATATS epochs. The combined image has
RMS noise 3.96 mJy / beam, with a circular beam of 150 arcsec FWHM. The
catalog, generated using a false detection rate algorithm, contains 4984
sources, and is >90% complete to 37.9 mJy. The catalogs generated from snapshot
images of the individual epochs contain between 1170 and 2019 sources over the
564 sq. deg. area in common to all epochs. The 90% completeness limits of the
single epoch catalogs range from 98.6 to 232 mJy.
We compare the catalog generated from the combined image to those from
individual epochs, and from the NRAO VLA Sky Survey (NVSS), a legacy survey at
the same frequency. We are able to place new constraints on the transient
population: fewer than 6e-4 transients / sq. deg., for transients brighter than
350 mJy with characteristic timescales of minutes to days. This strongly rules
out an astronomical origin for the ~1 Jy sources reported by Matsumura et al.
(2009), based on their stated rate of 3.1e-3 / sq. deg.Comment: 28 pages, 12 figures, ApJ accepte
Commensal observing with the Allen Telescope array: software command and control
The Allen Telescope Array (ATA) is a Large-Number-Small-Diameter radio
telescope array currently with 42 individual antennas and 5 independent
back-end science systems (2 imaging FX correlators and 3 time domain beam
formers) located at the Hat Creek Radio Observatory (HCRO). The goal of the ATA
is to run multiple back-ends simultaneously, supporting multiple science
projects commensally. The primary software control systems are based on a
combination of Java, JRuby and Ruby on Rails. The primary control API is
simplified to provide easy integration with new back-end systems while the
lower layers of the software stack are handled by a master observing system.
Scheduling observations for the ATA is based on finding a union between the
science needs of multiple projects and automatically determining an efficient
path to operating the various sub-components to meet those needs. When
completed, the ATA is expected to be a world-class radio telescope, combining
dedicated SETI projects with numerous radio astronomy science projects.Comment: SPIE Conference Proceedings, Software and Cyberinfrastructure for
Astronomy, Nicole M. Radziwill; Alan Bridger, Editors, 77400Z, Vol 774
An Intensity Mapping Detection of Aggregate CO Line Emission at 3 mm
We present a detection of molecular gas emission at using the
technique of line intensity mapping. We make use of a pair of 3 mm
interferometric data sets, the first from the ALMA Spectroscopic Survey in the
Hubble Ultra Deep Field (ASPECS), and the second from a series of Atacama
Compact Array (ACA) observations conducted between 2016 and 2018, targeting the
COSMOS field. At 100 GHz, we measure non-zero power at 97.8% and 99.9%
confidence in the ACA and ALMA data sets, respectively. In the joint result, we
reject the zero-power hypothesis at 99.99% confidence, finding
.
After accounting for sample variance effects, the estimated spectral shot power
is $\tilde{I}^{2}_{s}(\nu)=1010_{-390}^{+550}\ \mu\textrm{K}^2\ \textrm{Hz}\
\textrm{sr}120_{-40}^{+80}\ \mu\textrm{K}^2\ h^{-3}\,\textrm{Mpc}^{3}200^{+120}_{-70}\ \mu\textrm{K}^2\ h^{-3}\,\textrm{Mpc}^{3}90^{+70}_{-40}\ \mu\textrm{K}^2\ h^{-3}\,\textrm{Mpc}^{3}z=1.3z=2.5z=3.6\alpha_{\rm CO}=3.6\ M_{\odot}\ (\textrm{K}\ \textrm{km}\ \textrm{s}^{-1}\
\textrm{pc}^{2})^{-1}\rho_{\textrm{H}_2}(z)\sim 10^{8}\ M_{\odot}\ \textrm{Mpc}^{-3}z=1-3$.Comment: 25 pages, 12 figures, 6 tables, 2 appendices. Accepted for
publication in Ap
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Dietary epidemiology of essential tremor: meat consumption and meat cooking pactices
Background/Aim: Harmane [1-methyl-9H-pyrido(3,4-b)indole] is a tremor-producing neurotoxin. Blood harmane concentrations are elevated in essential tremor (ET) patients for unclear reasons. Potential mechanisms include increased dietary harmane intake (especially through well-cooked meat) or genetic-metabolic factors. We tested the hypothesis that meat consumption and level of meat doneness are higher in ET cases than in controls. Methods: Detailed data were collected using the Lawrence Livermore National Laboratory Meat Questionnaire. Results: Total current meat consumption was greater in men with than without ET (135.3 ± 71.1 vs. 110.6 ± 80.4 g/day, p = 0.03) but not in women with versus without ET (80.6 ± 50.0 vs. 79.3 ± 51.0 g/day, p = 0.76). In an adjusted logistic regression analysis in males, higher total current meat consumption was associated with ET (OR = 1.006, p = 0.04, i.e., with 10 additional g/day of meat, odds of ET increased by 6%). Male cases had higher odds of being in the highest than lowest quartile of total current meat consumption (adjusted OR = 21.36, p = 0.001). Meat doneness level was similar in cases and controls. Conclusion: This study provides evidence of a dietary difference between male ET cases and male controls. The etiological ramifications of these results warrant additional investigation
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