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Register a new userThe GMRT 150 MHz All-sky Radio Survey: First Alternative Data Release TGSS ADR1
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We present the first full release of a survey of the 150 MHz radio sky, observed with the Giant Metrewave Radio Telescope between April 2010 and March 2012 as part of the TGSS project. Aimed at producing a reliable compact source survey, our automated data reduction pipeline efficiently processed more than 2000 hours of observations with minimal human interaction. Through application of innovative techniques such as image-based flagging, direction-dependent calibration of ionospheric phase errors, correcting for systematic offsets in antenna pointing, and improving the primary beam model, we created good quality images for over 95 percent of the 5336 pointings. Our data release covers 36,900 square degrees (or 3.6 pi steradians) of the sky between -53 deg and +90 deg DEC, which is 90 percent of the total sky. The majority of pointing images have a background RMS noise below 5 mJy/beam with an approximate resolution of 25 x 25 (or 25 x 25 / cos (DEC - 19 deg) for pointings south of 19 deg DEC). We have produced a catalog of 0.62 Million radio sources derived from an initial, high reliability source extraction at the 7 sigma level. For the bulk of the survey, the measured overall astrometric accuracy is better than 2 in RA and DEC, while the flux density accuracy is estimated at ~10 percent. Within the scope of the TGSS ADR project, the source catalog as well as 5336 mosaic images (5 deg x 5 deg) and an image cutout service, are made publicly available online as a service to the astronomical community. Next to enabling a wide range of different scientific investigations, we anticipate that these survey products provide a solid reference for various new low-frequency radio aperture array telescopes (LOFAR, LWA, MWA, SKA-low), and can play an important role in characterizing the EoR foreground. The TGSS ADR project aims at continuously improving the quality of the survey data products.
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This Rescaled Subset of the Alternative Data Release 1 to the Tata Institute of Fundamental Physics Giant Metrewave Radio Telescope Sky Survey (TGSS-RSADR1) modifies the initial data release of TGSS-ADR1 (Intema et al. 2017) to bring that catalogue to the same flux scale as the extragalactic catalogue from the GaLactic and Extragalactic All-sky Murchison Widefield Array survey (GLEAM: Wayth et al. 2015; Hurley-Walker et al. 2017). In this paper we motivate the derivation of correct and complementary flux density scales, introduce a methodology for correction based on radial basis functions, apply it to TGSS-ADR1, and create a modified catalogue, TGSS-RSADR1. This catalogue comprises 383,589 TGSS-ADR1 sources with updated flux density and flux density uncertainty values, and covers $mathrm{Declination}leq+30^circ$, $|b|geq10^circ$, a sky area of 18,800 deg$^2$.
The Dark Sky Simulations are an ongoing series of cosmological N-body simulations designed to provide a quantitative and accessible model of the evolution of the large-scale Universe. Such models are essential for many aspects of the study of dark matter and dark energy, since we lack a sufficiently accurate analytic model of non-linear gravitational clustering. In July 2014, we made available to the general community our early data release, consisting of over 55 Terabytes of simulation data products, including our largest simulation to date, which used $1.07 times 10^{12}~(10240^3)$ particles in a volume $8h^{-1}mathrm{Gpc}$ across. Our simulations were performed with 2HOT, a purely tree-based adaptive N-body method, running on 200,000 processors of the Titan supercomputer, with data analysis enabled by yt. We provide an overview of the derived halo catalogs, mass function, power spectra and light cone data. We show self-consistency in the mass function and mass power spectrum at the 1% level over a range of more than 1000 in particle mass. We also present a novel method to distribute and access very large datasets, based on an abstraction of the World Wide Web (WWW) as a file system, remote memory-mapped file access semantics, and a space-filling curve index. This method has been implemented for our data release, and provides a means to not only query stored results such as halo catalogs, but also to design and deploy new analysis techniques on large distributed datasets.
The LOFAR Two-metre Sky Survey (LoTSS) is an ongoing sensitive, high-resolution 120-168MHz survey of the entire northern sky for which observations are now 20% complete. We present our first full-quality public data release. For this data release 424 square degrees, or 2% of the eventual coverage, in the region of the HETDEX Spring Field (right ascension 10h45m00s to 15h30m00s and declination 45$^circ$00$$00$$ to 57$^circ$00$$00$$) were mapped using a fully automated direction-dependent calibration and imaging pipeline that we developed. A total of 325,694 sources are detected with a signal of at least five times the noise, and the source density is a factor of $sim 10$ higher than the most sensitive existing very wide-area radio-continuum surveys. The median sensitivity is S$_{rm 144 MHz} = 71,mu$Jy beam$^{-1}$ and the point-source completeness is 90% at an integrated flux density of 0.45mJy. The resolution of the images is 6$$ and the positional accuracy is within 0.2$$. This data release consists of a catalogue containing location, flux, and shape estimates together with 58 mosaic images that cover the catalogued area. In this paper we provide an overview of the data release with a focus on the processing of the LOFAR data and the characteristics of the resulting images. In two accompanying papers we provide the radio source associations and deblending and, where possible, the optical identifications of the radio sources together with the photometric redshifts and properties of the host galaxies. These data release papers are published together with a further $sim$20 articles that highlight the scientific potential of LoTSS.
Most of the sky has been imaged with NOAOs telescopes from both hemispheres. While the large majority of these data were obtained for PI-led projects and almost all of the images are publicly available, only a small fraction have been released to the community via well-calibrated and easily accessible catalogs. We are remedying this by creating a catalog of sources from most of the public data taken on the CTIO-4m+DECam and the KPNO-4m+Mosaic3. This catalog, called the NOAO Source Catalog (NSC), contains over 2.9 billion unique objects, 34 billion individual source measurements, covers ~30,000 square degrees of the sky, has depths of ~23rd magnitude in most broadband filters with ~1-2% photometric precision, and astrometric accuracy of ~7 mas. In addition, ~2 billion objects and ~21,000 square degrees of sky have photometry in three or more bands. The NSC will be useful for exploring stellar streams, dwarf satellite galaxies, QSOs, high-proper motion stars, variable stars and other transients. The NSC catalog is publicly available via the NOAO Data Lab service.
The Beijing-Arizona Sky Survey (BASS) is a wide and deep imaging survey to cover a 5400 deg$^2$ area in the Northern Galactic Cap with the 2.3m Bok telescope using two filters ($g$ and $r$ bands). The Mosaic $z$-band Legacy Survey (MzLS) covers the same area in $z$ band with the 4m Mayall telescope. These two surveys will be used for spectroscopic targeting of the Dark Energy Spectroscopic Instrument (DESI). The BASS survey observations were completed in 2019 March. This paper describes the third data release (DR3) of BASS, which contains the photometric data from all BASS and MzLS observations between 2015 January and 2019 March. The median astrometric precision relative to {it Gaia} positions is about 17 mas and the median photometric offset relative to the PanSTARRS1 photometry is within 5 mmag. The median $5sigma$ AB magnitude depths for point sources are 24.2, 23.6, and 23.0 mag for $g$, $r$, and $z$ bands, respectively. The photometric depth within the survey area is highly homogeneous, with the difference between the 20% and 80% depth less than 0.3 mag. The DR3 data, including raw data, calibrated single-epoch images, single-epoch photometric catalogs, stacked images, and co-added photometric catalogs, are publicly accessible at url{http://batc.bao.ac.cn/BASS/doku.php?id=datarelease:home}.
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