RACS-Mid full catalogue and uniform-sensitivity images

November 24th, 2023

The ASKAP observatory team are proud to announce that Rapid ASKAP Continuum Survey mid-band (RACS-mid at 1367.5 MHz) all-sky catalogues are now available through CASDA: https://doi.org/10.25919/p524-xb81.

This data release contains the “all-sky” catalogues as well as the (mostly-)uniform sensitivity images used for source finding. The catalogues/images are described in a paper that was recently accepted for publication in PASA, and is now on arXiv (Duchesne et al. 2023): https://arxiv.org/abs/2311.12369. Note there are a few versions of the catalogue:

  1. The first and primary catalogue features a resolution that varies over the survey, where each uniform-sensitivity image is formed by convolving neighbouring images to a common resolution prior to mosaicking. This retains high sensitivity and resolution and covers the whole survey (declination -90 to +49).
  2. An auxiliary catalogue is available at a fixed 25 arcsec resolution to match the existing RACS-low catalogue. This may be useful in cross-matching to that catalogue, but for general users I would suggest sticking to the higher-resolution and more sensitive primary catalogue. Due to the 25 arcsec constraint the coverage of this auxiliary catalogue is only -90 to +30 declination, similar to RACS-low DR1.
  3. Another auxiliary catalogue is also available (https://doi.org/10.25919/p8ns-da63) which is simply the concatenation of source lists from individual RACS-mid images without any additional convolution or mosaicking. This results in source measurements at specific epochs (and potentially the highest possible resolution). Note this catalogue has duplicate measurements for sources in overlap regions or in duplicate observations and so is intended for time-domain science.

These data supersede the initial release of RACS-Mid data in CASDA (Duchesne et al. 2023 https://doi.org/10.1017/pasa.2023.31) which was of individual tiles. 

The primary uniform sensitivity tiles of this RACS-Mid release are available through our cutout service. https://data.csiro.au/domain/casdaCutoutService

Figure 1: Median-binned HEALPix representation of the root-mean-square noise distributions of the primary catalogue, showing the sensitivity of RACS-Mid.

FAQ

Q. How do I do a cone search against the new RACS-Mid catalogues?

A. To do a cone search for individual RACS catalogue radio sources you can use TOPCAT or Python Astroquery.

TOPCAT TAP query

In TOPCAT click on VO -> TAP Query. Input “casda” into keywords to search for the CASDA TAP service, or put “https://casda.csiro.au/casda_vo_tools/tap” directly into the TAP URL box and press “Use Service”.

Use the following TAP ADQL query as an example:

SELECT * FROM  AS110.racs_mid_components_v01 where 1=CONTAINS(POINT(‘ICRS’, ra, dec),CIRCLE(‘ICRS’,183.475,11.236,0.01))

The above example is for RA = 183.475, Dec = 11.236 and search radius of 0.01 deg of the extragalactic Gaussian component catalogue.

(Note that you can run any generalised ADQL query, e.g. search for sources with RA and Dec range, or flux density constraints, etc. The above is just an example).

Python Astroquery

In Python use the astroquery TAP module to run the TAP ADQL query with:

from astroquery.utils.tap.core import TapPlus

casdatap = TapPlus(url=”https://casda.csiro.au/casda_vo_tools/tap”)

job = casdatap.launch_job_async(“SELECT * FROM  AS110.racs_mid_components_v01 where 1=CONTAINS(POINT(‘ICRS’, ra, dec),CIRCLE(‘ICRS’,183.475,11.236,0.01))”)

r = job.get_results()

Q. How do I use the UI to find these images?

A.  In the CASDA Observation Search web form:

i) To return all primary images: search for “AS110” project and filename “RACS-MID1_???????.fits”. Leave other options blank.

ii) To return all 25 arcsec images: search for “AS110” project and filename “RACS-MID1_*25arcsec.fits. Leave other options blank.

iii) Combine the above with a cone search to return an image of a position of interest.

Q. Why can’t I download the data?

A. Please make sure you login with an OPAL account.

Q. How do I generate scripted cutouts of these RACS-Mid images?

A. For a small number of cutouts you can use the curated cutout service. . https://data.csiro.au/domain/casdaCutoutService

For a large number of cutouts we recommend using astroquery. https://astroquery.readthedocs.io/en/latest/

And please ensure you install the latest version of astroquery for the most up to date CASDA module. 

One can then run scripted cutouts of RACS_mid doing something like modify for your own needs):

from astropy import coordinates, units as u, wcs

from astropy.coordinates import SkyCoord

from astroquery.casda import Casda 

from astroquery.utils.tap.core import TapPlus

from astroquery.utils.tap.core import Tap

import getpass

#set TAP to the CASDA service 

casdatap = TapPlus(url="https://casda.csiro.au/casda_vo_tools/tap")

centre = SkyCoord.from_name('NGC 5128') 

print(centre) 

#need to set the following to the centre coords

ra = 201.36506338

dec= -43.01911251

#Query for RACS-Mid, we know the filename

query = "select * from ivoa.obscore where filename LIKE 'RACS-MID1________.fits' AND 1 = CONTAINS(POINT('ICRS',"+ str(ra) + ","+ str(dec) + "),s_region)"

#do ADQL command on obscore to return list of images

job = casdatap.launch_job_async(query)

r = job.get_results()

username = 'myemail@email.com'

password = getpass.getpass(str("Enter your OPAL password: "))

casda = Casda(username, password)

#make cutout

url_list = casda.cutout(r, coordinates=centre, radius=5*u.arcmin)

#download cutout

filelist = casda.download_files(url_list, savedir='/Users/huy015/tmp')