© First ASKAP antenna on-site in Western Australia.

WALLABY - the ASKAP HI All-Sky Survey

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© Wallaby in the Wild.
(Photo credit: T. Westmeier)

Welcome

WALLABY is the "ASKAP HI All-Sky Survey" (Koribalski et al. 2020, ApSS 365, 118), a precursor for future, much deeper SKA neutral hydrogen (HI) surveys. Originally, we had proposed an integration time of about two years (or ~16 hours per pointing, based on Tsys/Aeff = 70 K) and a sky coverage from DEC = -90 degr to DEC = +30 degr with to redshifts out to z = 0.26.

Using our best source-finding algorithms - now available as part of SoFiA (Serra et al. 2015; see also the PASA Special Issue 2012 - ed. Koribalski) - we estimate that in the survey volume around 600 000 galaxies are individually detectable in the 21-cm line of neutral atomic hydrogen (Johnston et al. 2008; WALLABY proposal - Koribalski et al. 2009; Duffy et al. 2012; and Koribalski 2012).

We are measuring the HI properties of each galaxy and derive its distance, HI mass, total mass and dark matter content. Most galaxies are also detected in the 20-cm radio continuum, allowing us to derive their star-formation rates. The 30 arcsec angular resolution of WALLABY will allow us to identify likely optical and/or infrared galaxy counterparts. High-resolution HI postage stamps of pre-selected galaxies - like those shown below for NGC 3137 in the Hydra cluster - would further enhance our science.

ASKAP-36 Pilot Surveys Phase 1 and Phase 2 were completed in 2022.

ASKAP-36 full surveys started in Nov 2022. So far, 10 Wallaby fields have been observed (8h each), processing is under way. Over the holiday period over 30 EMU fields were observed (10h each). Each field size is ~30 square degrees.

ASKAP-36 integrated HI column density maps of the nearby spiral galaxy NGC 3137 from WALLABY pilot observations of the Hydra cluster. The data was processed using ASKAPsoft, achieving angular resolutions of 30 arcsec (left), 20 arcsec (middle) and 10 arcsec (right). This illustrates the desirability of high-resolution WALLABY ‘postage stamps’ for the detailed study of galaxy morphology. - See Figure 10 in Koribalski et al. (2020). ASKAP data products and catalogs are available in CASDA.

NEWS

• WALLABY - An SKA Pathfinder HI Survey
  by Koribalski, B.S., et al. 2020, ApSS 365, 118 (arXiv:2002.07311)
  

• WALLABY Early Science V. - The galaxy group LGG 351
  by For et al. 2019, MNRAS 489, 5723

• WALLABY Early Science IV. - The spiral galaxy IC 5201
  by Kleiner, Koribalski et al. 2019, MNRAS 488, 5352

• WALLABY Early Science III. - The spiral galaxy NGC 1566
  by Elagali et al. 2019, MNRAS 487, 2797

April 2019 NEWS

• The full ASKAP-36 array is now operational; pilot surveys are set to commence in May 2019.

• The Eridanus Group has been observed with ASKAP-36 using all 36 PAF beams and 288 MHz of bandwidth. Data processing is on-going.

Jan 2019 NEWS

• Commissioning of the ASKAP-28 array continues.

• WALLABY Early Science II. - The NGC 7232 galaxy group
  by Lee-Waddell, Koribalski et al. 2019, MNRAS 487, 2061

• WALLABY Early Science I. - The NGC 7162 galaxy group
  by Reynolds et al. 2019, MNRAS 482, 3591

May 2018 NEWS

• The WALLABY data processing "busy week" was held at CASS in Sydney on May 21 - 25. Thank you to the great work done by all participants; it is great to see so many papers close to submission.

• The WALLABY Newsletter No 9 has just been distributed and our new webpages are ready at https://wallaby-survey.org. Enjoy :)

• The Australian Government has provided $70m to the Pawsey Supercomputing Centre for a much needed new supercomputer (replacing the Galaxy and Magnus Crays).

• The Local Volume HI Survey (LVHIS) overview paper (Koribalski et al. 2018) is published and the LVHIS database is ready. LVHIS galaxies are essential for WALLABY verification and qualityu checks.

Jan 2018 NEWS

• WALLABY data processing - a successful "busy week" was held at UWA in Perth from Jan 29 to Feb 2, attended by a dedicated group of team members.

• WALLABY Early Science - a visual summary thanks to my postdoc Karen Lee-Waddell.
  
  
  

Dec 2017 NEWS

• All 36 Phased-Array Feeds (PAFs) are now installed on ASKAP.

• ASKAP is currently operating with an array of 16 PAF-equipped antennas and 240 MHz of bandwidth.

• WALLABY has nearly completed four Early Science fields to full depth; the remaining observations are hopefully taken before start of 2018.

• Using the ASKAPsoft pipeline we have reached full WALLABY depth in a few beams towards IC5201. The quality is good !

• The next WALLABY "busy week" is at UWA in Perth, starting Jan 29.

• ASKAP is expected to soon operate with 24 PAF-equipped antennas (ASKAP-24), but due to the high data rate will mainly focus on continuum observations.

• ASKAP Early Science is soon ending to allow final preparations for the full 36-antenna array to go ahead.

Jan 2017 NEWS

• Australian telescope project helps unlock history and secrets of the Universe
  (Ministerial Press Release - 16 Jan 2017)
  " ... Astronomers are using these observations to look for hydrogen gas - the raw material for making stars - in and around galaxies. This is the first step in making a census of hydrogen in galaxies far back in the Universe's history. ..."

• The Australian Square Kilometre Array Pathfinder finally hits the big-data highway
  (article in The Conversation, 16 Jan 2017)
  " ... ASKAP sees large pieces of sky with a field of view of 30 square degrees. The WALLABY team will observe 1,200 of these fields. Each field contains about 500 galaxies detectable in neutral hydrogen, giving a total of 600,000 galaxies. ..."

• The WALLABY team has obtained the ~500 hours of ASKAP-12 Early Science data using up to 192 MHz bandwidth towards four 30 sq degr fields. Two fields are complete and two 50% done. Data processing is on-going.

Oct 2016 NEWS

• ASKAP Early Science has started ! The WALLABY team has obtained the first ~100 hours of data on ASKAP-12 using 48 MHz bandwidth. All data sets have been calibrated, and we made HI data cubes for each of the 36 beams. Combination of the data is the next step.

ASKAP HI mapping of the IC 1459 galaxy group

• The first ASKAP science paper (Serra, Koribalski, Kilborn et al. 2015, MNRAS 452, 2680) is based on HI data obtained with the Boolardy Engineering Test Array (BETA), which consists of six PAF-equipped antennas. Three 10h HI data sets were obtained in Sep 2014 with nine beams arranged in a diamond pattern. The ASKAP HI maps reveal the HI disks of at least 10 galaxies in the IC 1459 galaxy group as well as some previously unknown HI clouds. The data have a resolution of about 1' and 4 km/s.

SoFiA paper

• The paper describing our new Source Finding Application (SoFiA), is now published (Serra et al. 2015). The SoFiA source code is available on GitHub.

ASKAP maps HI in Scultpor pair NGC 253 and NGC247

In Aug 2014 the first nine-beam extragalactic ASKAP HI observations were obtained by targeting the starburst galaxy NGC253, its companion NGC247, located about 4 degr to the north of NGC253, and the area in between the two gas-rich galaxies. Much deeper HI observations would be needed to detect the known dwarf galaxy neighbours with BETA.

ASKAP detects NGC 253's extended HI disk

In May 2014 the first extragalactic ASKAP HI observations were attempted with six Mk1 PAFs (ie 15 baselines, 2 pols). In just two hours the target galaxy, NGC 253, was detected in HI emission on the shortest baselines and in HI absorption on the longest baselines. This was followed by a 12 hour ASKAP observation, which revealed the HI disk of NGC 253 - as known from extensive ATCA HI observations. - The ASKAP HI data calibration and imaging is led by Paolo Serra. - We chose NGC 253, located in the nearby Sculptor Group and seen edge-on, because it is an extremely bright and well-known starburst galaxy. Its hydrogen disk spans about 0.5 degr on the sky, resulting in a distinctive HI double-horn profile. NGC 253's radio core is extremely bright, most helpful for the ASKAP data calibration and imaging at this early stage.

Apr 2014: First ASKAP 15 baseline observations

The first observations with the 15 baseline BETA array (ie, six PAF-equipped ASKAP antennas) are rolling in. See the recent image of PKS 1830-211 and high resolution (18.5 kHz) spectra of the associated HI absorption lines.

Feb 2014: First 9-beam image with six ASKAP PAFs

In February 2014 the first 9-beam image was made using the full 304 MHz bandwidth and combining the data from two BETA sub-arrays, each consisting of three PAF-equipped ASKAP antennas. The three bright extragalactic sources in the field are PKS 1610-771, PKS 1549-790 and PKS 1547-795. The associated press release is here.

Oct & Nov 2013: First HI detection with three ASKAP PAFs

On Oct 16, 2013, the first HI detection was made with three ASKAP PAFs. Auto-correlation spectra for a single PAF port were obtained using the hardware correlator; our target was the standard Galactic S9 region located at RA,DEC(J2000) = 17:52:05.4, -34:25:15.4, Bruens et al. 2005).

In Nov 2013 the first HI absorption detection was achieved towards the gravitational lens PKS 1830-211 at z = 0.89 using the cross-correlation data from three BETA antennas. - Further ASKAP HI observations will be carried out soon and will hopefully result in the first ASKAP HI cube.

Apr 2013: First 3-beam image with three ASKAP PAFs

In August 2012 first fringes between three PAF-equipped ASKAP antennas as well as zero closure phase measurements were obtained towards the radio galaxy Virgo A (M87). In April 2013 the first high-quality multibeam image was obtained with the BETA1 system (928 MHz, 16 x 1 MHz bandwidth, 1 pol, 12h integration time, all with the interim software correlator). The first 9-beam image was recently obtained using three PAFs and the new hardware correlator. Another three Mk1 PAFs are currently being installed on site. Engineering and science commissioning with six PAF-equipped ASKAP antennas - known as BETA - is expected to happen towards the end of 2013.

2012 PASA Special Issue (Vol 29, Issue 3)

The 2012 PASA Special Issue on Source Finding and Visualisation is now complete and all papers are online. I like to thank all authors for their contributions. --- For a brief overview of the WALLABY project see Koribalski (2012).

2012 SKA Site Decision

On May 25, 2012, the SKA Members met and adopted a dual-site implementation for SKA Phase 1 and SKA Phase 2. The SKA Phase 1 implementation will use existing (or currently being built) infrastructure at both sites, including the precursor telescopes, ASKAP in Australia and MeerKAT in South Africa. After demonstrating the power of PAFs on ASKAP (and WSRT), it is planned - as part of SKA Phase 1 - to add an array of 60 PAF-equipped dishes to ASKAP.

2011 Simulations Fest

• Homepage & Registration
• Workshop Program, Abstracts (incl. pdf files of most presentations), and Participants
• Data Visualisation

General Information

ASKAP is the "Australian SKA Pathfinder". See ASKAP Live ! and the ASKAP Webcams for up-to-date information. As ASKAP design and software are progressing rapidly, we have assembled international science teams who will carry out survey design studies, liase with the software team, explore the sky via cosmological simulations and write many excellent papers.

WALLABY - led by B. Koribalski and L. Staveley-Smith - is the top-ranked spectral line survey. It will observe the sky up to declinations of +30 degr over the frequency range of 1130 - 1430 MHz, ie velocity range of -2,000 to +77,000 km/s at approx. 4 km/s resolution. Assuming a Tsys of 50 K we will integrate for 8h (or more) per field. See our survey proposal for details.

• ASKAP Information for Users
• ASKAP Science
• ASKAP Memos
• Virtual Radio Interferometer

ASKAP consists of 36 x 12-m antennas (4072 sq m) with phased array feeds providing a field-of-view of 5.5 deg x 5.5 deg (= 30 sq deg) operating in the range 0.7 - 1.8 GHz, i.e. ideal for large HI line and 20-cm continuum surveys. The inner 30 antennas (3400 sq m) of ASKAP are optimally arranged in a 2-km configuration, delivering an angular resolution of 30". A further six antennas are placed at larger distances (baselines up to 6-km), giving an angular resolution of ~10".

The first ASKAP antenna arrived on site in December 2009. The picture at the top shows the fully assembled antenna on its pad in Western Australia (WA). Phased array feed (PAF) design is on-going with testing under way on the Parkes 12-m test antenna. Recent Tsys results of the PAF Mk2 system are very encouraging (close to Tsys = 50 K across the band). --- Construction of all 36 ASKAP antennas is now complete. PAFs are currently installed on all six BETA antennas (1, 3, 6, 8, 9 and 15). Engineering commissioning is continuing and will soon be including first spectral line observations.

Computing

Funding of the Pawsey Centre and the NBN link between Geraldton and Perth may in future (tbd) provide the computing power needed to process the full spectral line visibilities from all 36 ASKAP antennas with baselines up to 6-km, in contrast to the previous limitation to the inner 30 antennas (baselines < 2 km). This has many implications:

• maximum angular resolution increases from about 30" to 10"
• pixel size has to decrease from 10" to around 3" (i.e., cubes will be 10x larger !)
• increased number of baselines (from 435 to 630)
• increased point source sensitivity (factor ?)
• expanded, but less uniform uv-coverage as compared to that of the inner 30 ASKAP antennas (see image below) => higher sidelobes levels
• high-resolution "postage stamps" will be obsolete

Questions to address:

• the optimum weighting of the ASKAP visibilities needs to be evaluated and tested using simulations
• re-consider WALLABY products: initially we requested one data cube per pointing at 30" resolution, now we may require two or more data cubes per pointing at different angular resolutions (=> to be investigated)
• what angular resolution is required to match with a future WSRT+APERTIF HI survey of the northern sky

  Caption: ASKAP uv-coverage with 30 (red) and 36 (blue) antennas, created with the V.R.I. tool.

IDEAS !

Idea: develop GalaxyZoo for Wallaby :)

Page design and maintenance: B. Koribalski