98,041 research outputs found
Large Surveys in Cosmology: The Changing Sociology
Galaxy redshift surveys and Cosmic Microwave Background experiments are
undertaken with larger and larger teams, in a fashion reminiscent of particle
physics experiments and the human genome projects. We discuss the role of young
researchers, the issue of multiple authorship, and ways to communicate
effectively in teams of tens to hundreds of collaborators.Comment: Invited article for "Organizations and Strategies in Astronomy II",
ed. A. Heck, Kluwer Acad. Publ., in press (7 pages, no figures
Science Pipelines for the Square Kilometre Array
The Square Kilometre Array (SKA) will be both the largest radio telescope
ever constructed and the largest Big Data project in the known Universe. The
first phase of the project will generate on the order of 5 zettabytes of data
per year. A critical task for the SKA will be its ability to process data for
science, which will need to be conducted by science pipelines. Together with
polarization data from the LOFAR Multifrequency Snapshot Sky Survey (MSSS), we
have been developing a realistic SKA-like science pipeline that can handle the
large data volumes generated by LOFAR at 150 MHz. The pipeline uses task-based
parallelism to image, detect sources, and perform Faraday Tomography across the
entire LOFAR sky. The project thereby provides a unique opportunity to
contribute to the technological development of the SKA telescope, while
simultaneously enabling cutting-edge scientific results. In this paper, we
provide an update on current efforts to develop a science pipeline that can
enable tight constraints on the magnetised large-scale structure of the
Universe.Comment: Published in Galaxies, as part of a Special Issue on The Power of
Faraday Tomograph
Probing Primordial Gravitational Waves: Ali CMB Polarization Telescope
In this paper, we will give a general introduction to the project of Ali CMB
Polarization Telescope (AliCPT), which is a Sino-US joint project led by the
Institute of High Energy Physics (IHEP) and has involved many different
institutes in China. It is the first ground-based Cosmic Microwave Background
(CMB) polarization experiment in China and an integral part of China's
Gravitational Waves Program. The main scientific goal of AliCPT project is to
probe the primordial gravitational waves (PGWs) originated from the very early
Universe.
The AliCPT project includes two stages. The first stage referred to as
AliCPT-1, is to build a telescope in the Ali region of Tibet with an altitude
of 5,250 meters. Once completed, it will be the worldwide highest ground-based
CMB observatory and open a new window for probing PGWs in northern hemisphere.
AliCPT-1 telescope is designed to have about 7,000 TES detectors at 90GHz and
150GHz. The second stage is to have a more sensitive telescope (AliCPT-2) with
the number of detectors more than 20,000.
Our simulations show that AliCPT will improve the current constraint on the
tensor-to-scalar ratio by one order of magnitude with 3 years' observation.
Besides the PGWs, the AliCPT will also enable a precise measurement on the CMB
rotation angle and provide a precise test on the CPT symmetry. We show 3 years'
observation will improve the current limit by two order of magnitude.Comment: 11 pages, 7 figures, 2 table
Astronomical Surveys and Big Data
Recent all-sky and large-area astronomical surveys and their catalogued data
over the whole range of electromagnetic spectrum are reviewed, from Gamma-ray
to radio, such as Fermi-GLAST and INTEGRAL in Gamma-ray, ROSAT, XMM and Chandra
in X-ray, GALEX in UV, SDSS and several POSS I and II based catalogues (APM,
MAPS, USNO, GSC) in optical range, 2MASS in NIR, WISE and AKARI IRC in MIR,
IRAS and AKARI FIS in FIR, NVSS and FIRST in radio and many others, as well as
most important surveys giving optical images (DSS I and II, SDSS, etc.), proper
motions (Tycho, USNO, Gaia), variability (GCVS, NSVS, ASAS, Catalina,
Pan-STARRS) and spectroscopic data (FBS, SBS, Case, HQS, HES, SDSS, CALIFA,
GAMA). An overall understanding of the coverage along the whole wavelength
range and comparisons between various surveys are given: galaxy redshift
surveys, QSO/AGN, radio, Galactic structure, and Dark Energy surveys. Astronomy
has entered the Big Data era. Astrophysical Virtual Observatories and
Computational Astrophysics play an important role in using and analysis of big
data for new discoveries.Comment: 14 pages, 6 figures, 3 tables, 51 references. Presented at EAAS XII
General Meeting, submitted to Baltic Astronom
Report by the ESA-ESO Working Group on Fundamental Cosmology
ESO and ESA agreed to establish a number of Working Groups to explore
possible synergies between these two major European astronomical institutions.
This Working Group's mandate was to concentrate on fundamental questions in
cosmology, and the scope for tackling these in Europe over the next ~15 years.
One major resulting recommendation concerns the provision of new generations of
imaging survey, where the image quality and near-IR sensitivity that can be
attained only in space are naturally matched by ground-based imaging and
spectroscopy to yield massive datasets with well-understood photometric
redshifts (photo-z's). Such information is essential for a range of new
cosmological tests using gravitational lensing, large-scale structure, clusters
of galaxies, and supernovae. Great scope in future cosmology also exists for
ELT studies of the intergalactic medium and space-based studies of the CMB and
gravitational waves; here the synergy is less direct, but these areas will
remain of the highest mutual interest to the agencies. All these recommended
facilities will produce vast datasets of general applicability, which will have
a tremendous impact on broad areas of astronomy.Comment: ESA-ESO Working Groups Report No. 3, 125 pages, 28 figures. A PDF
version including the cover is available from
http://www.stecf.org/coordination/esa_eso/cosmology/report_cover.pdf and a
printed version (A5 booklet) is available in limited numbers from the Space
Telescope-European Coordinating Facility (ST-ECF): [email protected]
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