Information on Service 'Apertif DR1 - HI spectral cubes'

Further access options are discussed below

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:

form -- allows access via an HTML form
scs.xml -- a standard SCS interface as defined by the IVOA to access catalog-type data; SCS clients use https://vo.astron.nl/apertif_dr1/q/apertif_dr1_spectral_cubes/scs.xml? to access the service

This service is published as follows:

Within the set(s) local with the renderer form
Within the set(s) ivo_managed with the renderer scs.xml
Within the set(s) ivo_managed with the renderer tap

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):

Name	Table Head	Description	Unit	UCD
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.

Name	Table Head	Description	Unit	UCD
_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 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.

Name	Table Head	Description	Unit	UCD	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 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

VOResource XML (that's something exclusively for VO nerds)

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