In this data release from the ongoing LOw-Frequency ARray (LOFAR)
Two-metre Sky Survey (LoTSS) we present 120-168 MHz images covering
27% of the northern sky. Our coverage is split into two regions
centred at approximately 12h45m +44°30′ and 1h00m +28°00′ and spanning
4178 and 1457 square degrees respectively. The images were derived
from 3,451 hrs (7.6 PB) of LOFAR High Band Antenna data which were
corrected for the direction-independent instrumental properties as
well as direction-dependent ionospheric distortions during extensive,
but fully automated, data processing. A catalogue of 4,395,448 radio
sources is derived from our total intensity (Stokes I) maps, where the
majority of these have never been detected at radio wavelengths
before. At 6′′ resolution, our full bandwidth Stokes I continuum maps
with a central frequency of 144 MHz have: a median rms sensitivity of
83 μ Jy/beam; a flux density scale accuracy of approximately 10%; an
astrometric accuracy of 0.2′′; and we estimate the point-source
completeness to be 90% at a peak brightness of 0.8 mJy/beam. By
creating three 16 MHz bandwidth images across the band we are able to
measure the in-band spectral index of many sources, albeit the error
on the derived spectral index is > ±0.2 which is a consequence of our
flux-density scale accuracy and small fractional bandwidth. Our
circular polarisation (Stokes V) 20′′ resolution 120-168 MHz continuum
images have a median rms sensitivity of 95 μ Jy/beam, and we estimate
a Stokes I to Stokes V leakage of 0.056%. Our linear polarisation
(Stokes Q and Stokes U) image cubes consist of 480 97.6 kHz wide
planes and have a median rms sensitivity per plane of 10.8mJy/beam at
4′ and 2.2mJy/beam at 20′′; we estimate the Stokes I to Stokes Q/U
leakage to be approximately 0.2%. Here we characterise and publicly
release our Stokes I, Q, U and V images in addition to the calibrated
uv-data to facilitate the thorough scientific exploitation of this
unique dataset. This service queries the Stokes I continuum mosaic
images.
The LOFAR Two Meter Sky Survey LoTSS DR2
(:bibcode:`2022A&A...659A...1S`) obtained radio data from 27% of the
northern sky between 120 and 168 MHz in the year 2014 through 2020. This
service publishes polarization spectra of extragalactic radio sources
(radio galaxies and blazars) and the rotation measures derived from them.
We also give redshifts for all sources. The data has a spatial resolution
of 20 arcsec.
This service queries the catalog of radio sources from the LOFAR
Two-metre Sky Survey First Data Release (LoTSS-DR1). This data release
contains images and catalogs that characterise the low-frequency radio
emission in the region of the HETDEX Spring Field (right ascension
10h45m00s to15h30m00s and declination 45◦00′00′′ to 57◦00′00′′). A
total of 325,694 radio sources are detected in a region covering 424
square degrees. The maps have a median sensitivity of 71 uJy/beam and
a resolution of 6 arcsec. Optical counterparts for 71% of the radio
sources have been identified and where possible photometric redshifts
for these sources have been derived.
The LOFAR Two Meter Sky Survey LoTSS DR2
(:bibcode:`2022A&A...659A...1S`) obtained radio data from 27% of the
northern sky between 120 and 168 MHz in the year 2014 through 2020. This
service publishes polarization spectra of extragalactic radio sources
(radio galaxies and blazars) and the rotation measures derived from them.
We also give redshifts for all sources. The data has a spatial resolution
of 20 arcsec.
In this data release from the ongoing LOw-Frequency ARray (LOFAR)
Two-metre Sky Survey (LoTSS) we present 120-168 MHz images covering
27% of the northern sky. Our coverage is split into two regions
centred at approximately 12h45m +44°30′ and 1h00m +28°00′ and spanning
4178 and 1457 square degrees respectively. The images were derived
from 3,451 hrs (7.6 PB) of LOFAR High Band Antenna data which were
corrected for the direction-independent instrumental properties as
well as direction-dependent ionospheric distortions during extensive,
but fully automated, data processing. A catalogue of 4,395,448 radio
sources is derived from our total intensity (Stokes I) maps, where the
majority of these have never been detected at radio wavelengths
before. At 6′′ resolution, our full bandwidth Stokes I continuum maps
with a central frequency of 144 MHz have: a median rms sensitivity of
83 μ Jy/beam; a flux density scale accuracy of approximately 10%; an
astrometric accuracy of 0.2′′; and we estimate the point-source
completeness to be 90% at a peak brightness of 0.8 mJy/beam. By
creating three 16 MHz bandwidth images across the band we are able to
measure the in-band spectral index of many sources, albeit the error
on the derived spectral index is > ±0.2 which is a consequence of our
flux-density scale accuracy and small fractional bandwidth. Our
circular polarisation (Stokes V) 20′′ resolution 120-168 MHz continuum
images have a median rms sensitivity of 95 μ Jy/beam, and we estimate
a Stokes I to Stokes V leakage of 0.056%. Our linear polarisation
(Stokes Q and Stokes U) image cubes consist of 480 97.6 kHz wide
planes and have a median rms sensitivity per plane of 10.8mJy/beam at
4′ and 2.2mJy/beam at 20′′; we estimate the Stokes I to Stokes Q/U
leakage to be approximately 0.2%. Here we characterise and publicly
release our Stokes I, Q, U and V images in addition to the calibrated
uv-data to facilitate the thorough scientific exploitation of this
unique dataset. This service queries the Stokes I continuum mosaic
source catalogue.
This service queries the catalog of images from the LOFAR HBA Tier-1
preliminary data release (LoTSS-PDR). This data release contains
images and catalogs that characterise the low-frequency radio emission
in the region of the HETDEX Spring Field. In excess of 40,000 sources
are detected in the images that cover an area of over 350 square
degrees, have a resolution of 25 arcsec, and typical noise levels of
less than 0.5 mJy/beam.
This service provides cutouts from the images of the LOFAR HBA Tier-1
preliminary data release (LoTSS-PDR). This data release contains
images and catalogs that characterise the low-frequency radio emission
in the region of the HETDEX Spring Field. In excess of 40,000 sources
are detected in the images that cover an area of over 350 square
degrees, have a resolution of 25 arcsec, and typical noise levels of
less than 0.5 mJy/beam.
A catalogue of E(V-I) extinction values is presented for 3174 (LMC)
and 693 (SMC) fields within the Magellanic Clouds. The extinction
values were computed by determining the (V-I) colour difference of the
red clump from Optical Gravitational Microlensing Experiment (OGLE
III) observations in the V and I bands and theoretical values for
unreddend red clump colours.
The MAGIC project observes the VHE sky (GeV~TeV) through Cherenkov
radiation events. The project is operating since 2004 and with the
support from the Spain-VO team they provide data access through a
VO-SSAP and web services. This service re-publishes the data with
homogeneized in flux units (given here in 'erg/(s.cm2)'). Photon
energy values in are transfomred to frequencies.
