Information on Service 'Apertif DR1 - HI spectral cubes'

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Apertif is a phased-array feed system for the Westerbork Synthesis Radio Telescope (WSRT), providing forty instantaneous beams over 300 MHz of bandwidth. This first data release includes observations in the first year of survey operations, from 1 July 2019 through 30 June 2020. The data release includes all raw observational data for a total of 221 observations of 160 independent target fields, covering approximately one thousand square degrees of sky. A subset of processed data products, meeting specified quality assessment criteria as outlined in Adams et al. (2022), are also released. Images and cubes are released on a per beam basis, and 3374 beams (of 7640 considered) are included in this data release. The processed data products are only available for the upper 150 MHz of the band over the range 1280–1430 MHz. The first 12.5 MHz of data are flagged due to persistent RFI resulting in a nominal bandwidth of 137.5 MHz and central frequency of 1361.25 MHz. The data products are not primary-beam corrected, however the primary-beam images are provided separately that may be used for mosaicking or for correction of individual images. This service queries the spectral line cubes from the first data release of Apertif. Four line cubes are produced over a set of different frequency ranges as follows. Cube 0:  1292.5–1337.1 MHz, Cube 1: 1333.1–1377.7 MHz, Cube 2: 1373.8–1418.4 MHz, Cube 3: 1414.5–1429.3 MHz. Cube 3 is produced at full spectral resolution of 12.2 kHz while other cubes are produced with a 3-channel averaging at 36.6 kHz resolution. The cubes have a spatial extent of 1.1 deg × 1.1 deg (661 × 661 pixels, with 6''/pixel). The median noise for all line cubes, with a spectral resolution of 36.6 kHz, is 1.6 mJy/beam, corresponding to a 3-σ H I column density sensitivity of 1.8 × 10^20 atoms cm^−2 over 20 km s^−1 (for a median angular resolution of 24″ × 15″). The corresponding dirty beam cubes are also released to allow offline cleaning of source emission.

For a list of all services and tables belonging to this service's resource, see Information on resource 'Apertif DR-1'

Overview

You can access this service using:

This service is published as follows:

local means it is listed on our front page, ivo_managed means it has a record in the VO registry.

Other services provided on the underlying data include:

Input Fields

The following fields are available to provide input to the service (with some renderers, some of these fields may be unavailable):

NameTable Head DescriptionUnitUCD
beam_number Beam number Beam number N/A meta.id;instr.beam
DEC Delta (ICRS) Declination (ICRS decimal) deg pos.eq.dec
FORMAT Output format Requested format of the image data N/A N/A
hscs_pos Position/Name Coordinates (as h m s, d m s or decimal degrees), or SIMBAD-resolvable object N/A N/A
hscs_sr Search radius Search radius in arcminutes N/A N/A
INTERSECT Intersection type Relation of image and specified Region of Interest. N/A N/A
MAXREC Match limit Maximum number of records returned. Pass 0 to retrieve service parameters. N/A N/A
obsid ObsId Observation id N/A meta.id
POS Position ICRS Position, RA,DEC decimal degrees (e.g., 234.234,-32.46) deg pos.eq
RA Alpha (ICRS) Right Ascension (ICRS decimal) deg pos.eq.ra
RESPONSEFORMAT Output Format File format requested for output. N/A meta.code.mime
SIZE Field size Size in decimal degrees (e.g., 0.2 or 1,0.1) deg N/A
SR Search Radius Search radius deg N/A
target Field Name Name of the field N/A meta.id
VERB Verbosity Exhaustiveness of column selection. VERB=1 only returns the most important columns, VERB=2 selects the columns deemed useful to the average user, VERB=3 returns a table with all available columns. N/A N/A

Default Output Fields

The following fields are contained in the output by default. More fields may be available for selection; these would be given below in the VOTable output fields.

NameTable Head DescriptionUnitUCD
_r Dist. Distance to cone center deg pos.distance
accref Product key Access key for the data N/A N/A
accsize File size Size of the data in bytes byte VOX:Image_FileSize
bandpassHi Band upper Upper limit of the bandpass (in BandPass_Unit units) m VOX:BandPass_HiLimit
bandpassId Bandpass Freeform name of the bandpass used N/A VOX:BandPass_ID
bandpassLo Band lower Lower limit of the bandpass (in BandPass_Unit units) m VOX:BandPass_LoLimit
bandpassRefval Band Ref. Characteristic quantity for the bandpass of the image m VOX:BandPass_RefValue
bandpassUnit Bandpass unit Unit of bandpass specifications (always m). N/A VOX:BandPass_Unit
beam_number Beam Number of the beam N/A meta.id;instr.beam
centerAlpha Ctr. RA Approximate center of image, RA deg pos.eq.ra;meta.main
centerDelta Ctr. Dec Approximate center of image, Dec deg pos.eq.dec;meta.main
coverage Coverage Field covered by the image deg N/A
cube_key Cube key N/A N/A meta.id
cube_qual Qual. flag Quality flag (G: Good, O: Okay, B: Bad) N/A meta.code.qual
dateObs Obs. date Epoch at midpoint of observation d VOX:Image_MJDateObs
f_ex f_ex Fraction of the total number of pixels with an absolute value > 6.75 sigma N/A stat.value
freqMax max. Frequency Maximum frequency MHz em.freq
freqMin min. Frequency Minimum frequency MHz em.freq
imageTitle Title Synthetic name of the image N/A VOX:Image_Title
instId Instrument Identifier of the originating instrument N/A INST_ID
mime Type MIME type of the file served N/A meta.code.mime
n_channels # channels Number of channels N/A em.bin
nAxes #axes Number of axes in data N/A VOX:Image_Naxes
obsid ObsId Unique id N/A meta.id
p_0pt8 p_0.8 Ratio between the width of the noise histogram at a level of 0.8% of the maximum and rms N/A stat.value
pixelScale Scales The pixel scale on each image axis deg/pix VOX:Image_Scale
pixelSize Axes Lengths Number of pixels along each of the axes pix VOX:Image_Naxis
pixflags P. Flags Flags specifying the processing done (C-original; F-resampled; Z-fluxes valid; X-not resampled; V-for display only N/A VOX:Image_PixFlags
pub_did P. DID Dataset identifier assigned by the publisher N/A meta.id;meta.main
refFrame Ref. Frame Coordinate system reference frame N/A VOX:STC_CoordRefFrame
related_products Related products Link related products for the observation N/A meta.ref.url
sigma Noise rms rms noise in the central velocity channel mJy/beam stat.error
target Field Name of the field N/A meta.id
task_id Task id ID of the task N/A meta.id
valid Passed validation Whether or not the dataset has passed validation N/A meta.code.qual
wcs_cdmatrix CD matrix FITS WCS CDij matrix deg/pix VOX:WCS_CDMatrix
wcs_equinox Equinox Equinox of the given coordinates yr VOX:STC_CoordEquinox
wcs_projection Proj. FITS WCS projection type N/A VOX:WCS_CoordProjection
wcs_refPixel Ref. pixel WCS reference pixel pix VOX:WCS_CoordRefPixel
wcs_refValues Ref. values World coordinates at WCS reference pixel deg VOX:WCS_CoordRefValue

VOTable Output Fields

The following fields are available in VOTable output. The verbosity level is a number intended to represent the relative importance of the field on a scale of 1 to 30. The services take a VERB argument. A field is included in the output if their verbosity level is less or equal VERB*10.

NameTable Head DescriptionUnitUCD Verb. Level
centerAlpha Ctr. RA Approximate center of image, RA deg pos.eq.ra;meta.main 0
centerDelta Ctr. Dec Approximate center of image, Dec deg pos.eq.dec;meta.main 0
imageTitle Title Synthetic name of the image N/A VOX:Image_Title 0
dateObs Obs. date Epoch at midpoint of observation d VOX:Image_MJDateObs 0
accref Product key Access key for the data N/A N/A 1
target Field Name of the field N/A meta.id 1
related_products Related products Link related products for the observation N/A meta.ref.url 1
_r Dist. Distance to cone center deg pos.distance 10
bandpassId Bandpass Freeform name of the bandpass used N/A VOX:BandPass_ID 10
accsize File size Size of the data in bytes byte VOX:Image_FileSize 11
pixelScale Scales The pixel scale on each image axis deg/pix VOX:Image_Scale 12
instId Instrument Identifier of the originating instrument N/A INST_ID 15
pixelSize Axes Lengths Number of pixels along each of the axes pix VOX:Image_Naxis 15
pub_did P. DID Dataset identifier assigned by the publisher N/A meta.id;meta.main 15
mime Type MIME type of the file served N/A meta.code.mime 20
nAxes #axes Number of axes in data N/A VOX:Image_Naxes 20
refFrame Ref. Frame Coordinate system reference frame N/A VOX:STC_CoordRefFrame 20
wcs_equinox Equinox Equinox of the given coordinates yr VOX:STC_CoordEquinox 20
wcs_projection Proj. FITS WCS projection type N/A VOX:WCS_CoordProjection 20
wcs_refPixel Ref. pixel WCS reference pixel pix VOX:WCS_CoordRefPixel 20
wcs_refValues Ref. values World coordinates at WCS reference pixel deg VOX:WCS_CoordRefValue 20
wcs_cdmatrix CD matrix FITS WCS CDij matrix deg/pix VOX:WCS_CDMatrix 20
bandpassUnit Bandpass unit Unit of bandpass specifications (always m). N/A VOX:BandPass_Unit 20
bandpassRefval Band Ref. Characteristic quantity for the bandpass of the image m VOX:BandPass_RefValue 20
bandpassHi Band upper Upper limit of the bandpass (in BandPass_Unit units) m VOX:BandPass_HiLimit 20
bandpassLo Band lower Lower limit of the bandpass (in BandPass_Unit units) m VOX:BandPass_LoLimit 20
pixflags P. Flags Flags specifying the processing done (C-original; F-resampled; Z-fluxes valid; X-not resampled; V-for display only N/A VOX:Image_PixFlags 20
coverage Coverage Field covered by the image deg N/A 20
obsid ObsId Unique id N/A meta.id 20
valid Passed validation Whether or not the dataset has passed validation N/A meta.code.qual 20
task_id Task id ID of the task N/A meta.id 20
beam_number Beam Number of the beam N/A meta.id;instr.beam 20
freqMin min. Frequency Minimum frequency MHz em.freq 20
freqMax max. Frequency Maximum frequency MHz em.freq 20
n_channels # channels Number of channels N/A em.bin 20
cube_key Cube key N/A N/A meta.id 20
cube_qual Qual. flag Quality flag (G: Good, O: Okay, B: Bad) N/A meta.code.qual 20
sigma Noise rms rms noise in the central velocity channel mJy/beam stat.error 20
f_ex f_ex Fraction of the total number of pixels with an absolute value > 6.75 sigma N/A stat.value 20
p_0pt8 p_0.8 Ratio between the width of the noise histogram at a level of 0.8% of the maximum and rms N/A stat.value 20
owner Owner Owner of the data N/A N/A 25
embargo Embargo ends Date the data will become/became public a N/A 25

Copyright, License, Acknowledgements

If you use this data, cite Adams et al. 2022 (2022A&A...667A..38A). Additionally, you can cite the service reference. The Apertif data release 1 is licensed under the Creative Commons Attribution 3.0 License

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