156 research outputs found
Publications of the Jet Propulsion Laboratory, 1984
The Jet Propulsion Laboratory (JPL) bibliography 39-26 describes and indexes by primary author the externally distributed technical reporting, released during calendar year 1984, that resulted from scientific and engineering work performed, or managed, by the Jet Propulsion Laboratory. Three classes of publications are included: (1) JPL Publications (82-, 83-, 84-series, etc.), in which the information is complete for a specific accomplishment; (2) articles from the quarterly Telecommunications and Data Acquisition (TDA) Program Report (42-series); and (3) articles published in the open literature
Scatter broadening of compact radio sources by the ionized intergalacticmedium: prospects for detection with Space VLBI and the SquareKilometre Array
We investigate the feasibility of detecting and probing various components of the ionized intergalactic medium (IGM) and their turbulent properties at radio frequencies through observations of scatter broadening of compact sources. There is a strong case for conducting targeted observations to resolve scatter broadening (where the angular size scales as ~Îœâ2) of compact background sources intersected by foreground galaxy haloes and rich clusters of galaxies to probe the turbulence of the ionized gas in these objects, particularly using Space very long baseline interferometry (VLBI) with baselines of 350 000âkm at frequencies below 800âMHz. The sensitivity of the Square Kilometre Array (SKA) allows multifrequency surveys of interstellar scintillation (ISS) of ~100âÎŒJy sources to detect or place very strong constraints on IGM scatter broadening down to ~1âÎŒas scales at 5âGHz. Scatter broadening in the warmâhot component of the IGM with typical overdensities of ~30 cannot be detected, even with Space VLBI or ISS, and even if the outer scales of turbulence have an unlikely low value of ~1âkpc. None the less, intergalactic scatter broadening can be of the order of ~100âÎŒas at 1âGHz and ~3âÎŒas at 5âGHz for outer scales ~1âkpc, assuming a sufficiently high-source redshift that most sight-lines intersect within a virial radius of at least one galaxy halo (z >~ 0.5 and 1.4 for 10 10 and 10 11âMâ systems, following McQuinn 2014). Both Space VLBI and multiwavelength ISS observations with the SKA can easily test such a scenario, or place strong constraints on the outer scale of the turbulence in such regions
The ALMA2030 Wideband Sensitivity Upgrade
The Wideband Sensitivity Upgrade (WSU) is the top priority initiative for the
ALMA2030 Development Roadmap. The WSU will initially double, and eventually
quadruple, ALMA's system bandwidth and will deliver improved sensitivity by
upgrading the receivers, digital electronics and correlator. The WSU will
afford significant improvements for every future ALMA observation, whether it
is for continuum or spectral line science. The continuum imaging speed will
increase by a factor of 3 for the 2x bandwidth upgrade, plus any gains from
improved receiver temperatures. The spectral line imaging speed will improve by
a factor of 2-3. The improvements provided by the WSU will be most dramatic for
high spectral resolution observations, where the instantaneous bandwidth
correlated at 0.1-0.2 km/s resolution will increase by 1-2 orders of magnitude
in most receiver bands. The improved sensitivity and spectral tuning grasp will
open new avenues of exploration and enable more efficient observations. The
impact will span the vast array of topics that embodies ALMA's motto "In Search
of our Cosmic Origins". The WSU will greatly expand the chemical inventory of
protoplanetary disks, which will have profound implications for how and when
planets form. Observations of the interstellar medium will measure a variety of
molecular species to build large samples of clouds, cores and protostars. The
WSU will also enable efficient surveys of galaxies at high redshift. The first
elements of the WSU will be available later this decade, including a wideband
Band 2 receiver, a wideband upgrade to Band 6, new digitizers and digital
transmission system, and a new correlator. Other upgrades are under study,
including the newly developed ACA spectrometer and upgrades to Bands 9 and 10.
The gains enabled by the WSU will further enhance ALMA as the world leading
facility for millimeter/submillimeter astronomy. [Abridged]Comment: 59 pages, 36 figures; ALMA Memo 621 at
https://library.nrao.edu/alma.shtm
First results from BRASS-p broadband searches for hidden photon dark matter
We discuss first results from hidden photon dark matter searches made with a
prototype of the Broadband Radiometric Axion/ALPs Search Setup (BRASS-p) in the
range of particle mass of 49.63-74.44 eV (frequency range of 12-18 GHz).
The conceptual design of BRASS and a detailed description of its present
prototype, BRASS-p, are given, with a view of the potential application of such
setups to hidden photon, axion, and axion-like particle (ALP) dark matter
searches using heterodyne detectors in the range of particle mass from
40eV to 4000eV (10 GHz to 1 THz). Pioneering measurements made with
BRASS-p achieve the record sensitivity of (0.3--1.0) to the
kinetic mixing between the normal and hidden photons, assuming the dark matter
is made entirely of unpolarized hidden photons. Based on these results, a
discussion of further prospects for dark matter searches using the BRASS-p
apparatus is presented.Comment: 17 pages, 13 figures. Prepared for submission to JCA
Pathway to the Square Kilometre Array - The German White Paper -
The Square Kilometre Array (SKA) is the most ambitious radio telescope ever
planned. With a collecting area of about a square kilometre, the SKA will be
far superior in sensitivity and observing speed to all current radio
facilities. The scientific capability promised by the SKA and its technological
challenges provide an ideal base for interdisciplinary research, technology
transfer, and collaboration between universities, research centres and
industry. The SKA in the radio regime and the European Extreme Large Telescope
(E-ELT) in the optical band are on the roadmap of the European Strategy Forum
for Research Infrastructures (ESFRI) and have been recognised as the essential
facilities for European research in astronomy.
This "White Paper" outlines the German science and R&D interests in the SKA
project and will provide the basis for future funding applications to secure
German involvement in the Square Kilometre Array.Comment: Editors: H. R. Kl\"ockner, M. Kramer, H. Falcke, D.J. Schwarz, A.
Eckart, G. Kauffmann, A. Zensus; 150 pages (low resolution- and colour-scale
images), published in July 2012, language English (including a foreword and
an executive summary in German), the original file is available via the MPIfR
homepag
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