February 2024
Editor: Manasvee Saraf
Foreword
MANASVEE SARAF
Welcome to the February 2024 edition of the WALLABY newsletter! As I begin the 20th edition of this newsletter, I would like to thank all the previous contributors and editors. The past six months have been very rewarding, marked by various publications based on the pilot survey! While challenges with the super-computing facilities persist, the ongoing full survey observations have enriched our dataset with over 1700 new detections. The excitement builds as WALLABY unfolds its potential with each new observation of swiftly becoming the largest HI survey.
In this issue the PIs introduce new working-group chairs within the current working group structure and encourage members to register for the upcoming IAU General Assembly. The project manager offers insights into the full survey progress and highlights recent WALLABY-based publications. The project scientist shines light on the updated continuum image validation workflow, highlighting upcoming collaborations with the EMU survey. We welcome 11 new members who have joined us since August 2023. Updates from Xuchen Lin, Nathan Deg, Bi-Qing For and Tamsyn O’Beirne spotlight their recently published or accepted papers. Chandrashekar Murugeshan provides a glimpse into the advancements in the public data release 2, showcasing some high-resolution images. Jeremy Mould and Benne Holwerda present a preview of their upcoming work, while technical working groups (TWG) 1, 4, and 7 share their latest developments.
Happy reading !
Message from the PIs
LISTER STAVELEY-SMITH & BARBARA CATINELLA
The main update from the management team since the last newsletter is the minor restructuring of the WALLABY science working groups, to better meet our needs for the full survey phase. Briefly, SWG 2 & SWG 3 have been merged because of their substantial overlap in both scope and membership, and SWG 5 (“Multi-wavelength & ASKAP Survey Synergies”) has been moved to TWG 2. We welcome the new WG chairs and warmly thank the retiring ones (Bi-Qing For, Ivy Wong, Se-Heon Oh, Cullan Howlett, Adam Stevens and Tristan Reynolds) for their tremendous service and contributions to the project. The updated list of WG chairs is included below. A complete list of WG memberships can be found at https://wallaby-survey.org/working-groups/.
We are pleased to see that the WALLABY team continues growing and welcome several new members onboard. You can read about their interests below.
We also invite all WALLABY members that are actively engaged with the survey science to please submit WALLABY-related abstracts for the upcoming IAU General Assembly in Cape Town, South Africa (in particular for the IAUS 392: Neutral Hydrogen in and around Galaxies in the SKA Era, taking place in the second week of the General Assembly, 13-15 August, 2024) – the deadline is March 1st! On this note, we would greatly appreciate if you could let the PIs know if you’re planning on submitting an abstract to present WALLABY science.
| SWG 1: Milky Way & High-Velocity Clouds | Chairs: Helga Dénes, Mary Putman |
| SWG 3: The Local Universe | Chairs: Marco Grossi, Jing Wang |
| SWG 4: Cosmology & Statistical Studies | Chairs: Matthew Colless, Khaled Said |
| TWG 1: Numerical Simulations & Mock Surveys | Chairs: Connor Bottrell, Kyle Oman |
| TWG 2: Multi-wavelength & ASKAP Survey Synergies | Chairs: Luca Cortese, Li Shao |
| TWG 3: Data Processing, Imaging & Quality Control | Chairs: Karen Lee-Waddell, Jonghwan Rhee |
| TWG 4: Source Finding & Cataloguing | Chairs: Tobias Westmeier |
| TWG 5: Kinematics Pipeline | Chairs: Federico Lelli, Kristine Spekkens |
| TWG 6: Data Visualisation | Chairs: Marcin Glowacki |
| TWG 7: WALLABYcat | Chairs: Nathan Deg, Austin Shen |
Message from the Project Manager
TOBIAS WESTMEIER & BI-QING FOR
After a promising start, WALLABY observations have unfortunately slowed down again as a result of renewed issues with the Setonix supercomputer at the Pawsey Centre, which is being used for processing and imaging ASKAP data. Nevertheless, 19 footprints have been successfully captured so far, and more than 1700 HI detections from these single 8-hour footprints have already been released to the team. This is still only a small fraction of the 2 × 552 footprints that make up the full 5-year survey area, but we will hopefully see a substantial improvement in observing efficiency over the course of this year as Setonix is becoming more stable again.
Despite the slow progress with observations the WALLABY team continues to be scientifically productive, and 9 peer-reviewed science papers based on WALLABY data have been published in 2023. Among these is a paper on the discovery of two polar ring galaxies candidates led by Nathan Deg, which was the subject of a media release in September 2023. This was picked up by almost 60 news outlets from around the world. Progress has also been made with the generation of high-resolution images of selected nearby galaxies from phase 2 of the pilot survey; these are expected to be released to the public together with the rest of the phase 2 pilot data later this year.
The WALLABY team held its annual virtual science meeting on 19 October 2023. Each session was attended by 20–30 team members from all over the world. The meeting was a great opportunity to catch up on the diverse range of science projects that WALLABY members are working on.
Lastly, WALLABY members are reminded that all of our official policies have been updated to reflect various changes that have occurred over the past few years. We have also released a new project policy which sets out the rules for science projects using full survey data. Copies of all policy documents are available from our public website.
Message from the Project Scientist
KAREN LEE-WADDELL
Although there have been many hurdles with respect to recent WALLABY observations, we are still trying to squeeze out as much science as possible.
We are currently testing a modified validation workflow. If the WALLABY spectral line data is determined to be unsuitable for science (i.e. quality = “bad”), the continuum images are further checked and validated by the ASKAP operations team. Since the continuum images are less affected by certain processing/imaging artefacts, we are able to release validated continuum images and visibilities (with quality = “good” or “uncertain”) from the WALLABY observations. The affected target field is then returned to the pool so it can be re-observed. As such, we do not lose out on the spectral line side of things and eventually benefit from twice the amount of continuum data.
To further increase the science efficiency of the WALLABY, especially with the “extra” continuum data products, we are starting a new joint survey working group (WG). This WG would be for WALLABY and EMU members to discuss areas of overlapping science interests, project ideas, and any ongoing work. We hope this will foster increased collaboration and avoid potential conflicts between the teams. The co-leads for the WG are starting discussions about how they plan to proceed, so keep an eye out for an invite to join the joint WG.
New Member Profiles
Chao-Wei Tsai
Chao-Wei Tsai is a staff research scientist in the Radio Astronomy Division of the National Astronomical Observatories, Chinese Academy of Sciences (NAOC).
His research interests span from optical to radio multi-wavelength observations to investigate the evolution of supermassive black hole growth in dusty environments, examine the properties of the interstellar medium in nearby galaxies, study the formation of massive star clusters, and explore the characteristics of cold dust and neutral hydrogen in dwarf galaxies. His expertise lies in analyzing radio morphology and gas dynamics, conducting optical and near-IR spectroscopy, and performing spectral energy distribution (SED) analysis.
As a new member of the WALLABY collaboration, he will dedicate his efforts to studying nearby galaxies and local dwarf galaxies by leveraging the synergies between the WALLABY and FAST HI surveys.
Connor Bottrell
Connor is a Forrest Fellow at the University of Western Australia (UWA) who specialises in galaxy astronomy and machine learning. He obtained his PhD from the University of Victoria in his home country of Canada. Before moving to ICRAR/UWA in 2023, he was formerly a Kavli Fellow at Kavli IPMU in Tokyo.
Connor’s interests are broad, but he is particularly interested in the competition between galaxy mergers and gas accretion in shaping the structures and star formation histories of galaxies in the local Universe. He is also very keen on the dark matter science that a one-of-a-kind radio survey like WALLABY stands to enable.
Daniela Carollo
Hi! My name is Daniela Carollo and I am a researcher at the National Institute for Astrophysics (INAF), Observatory of Trieste, Italy. I completed my PhD in Australia and worked at Macquarie University. I was a research professor at the University of Notre Dame in Indiana, USA and a member of the Joint Institute for Nuclear Astrophysics for many years. I performed my research at the Space Telescope Science Institute in the USA, the European Southern Observatory in Garching, at the Zentrum fur Astronomie in Heidelberg, at the Tohoku University in Japan, and at the University Andres Bello in Chile.
I’m an expert in galaxy formation and the properties of galactic building blocks. Over the years, I have worked on Galactic dynamics and the chemical signature of the first stars that formed in the Universe. I’m now focusing my work on the star-forming dwarf galaxies in the Local Universe and beyond, with multi-wavelength observations. I am also a full member of the Euclid Consortium.
Hongming Tang
I am a Shuimu postdoctoral research fellow at the Department of Astronomy, Tsinghua University. My research focus is the application of machine learning on hunting rare radio galaxies, identifying radio galaxies of diverse morphologies and investigating the circumstances under which the astronomical predictions of machine learning algorithms are believable.
I am also a member of the EMU and POSSUM survey collaborations and the SKA continuum working group. I co-lead `Radio Galaxy Zoo: EMU’, a citizen science project in preparation, initiated by the EMU team and designed for survey cataloguing and unusual-object hunting. I am a very keen astrophysics and machine-learning educator, aiming to teach students how these subjects connect with their daily lives and how new technologies facilitate new scientific discoveries.
I am very excited to join the WALLABY team, not only to use data for studying how active galactic nuclei feedback may help quench spiral galaxies, but also to seek opportunities for developing synergy- or citizen-science projects based on EMU, WALLABY and multi-wavelength data 🙂
Li Wang
Greetings! I joined CSIRO Space and Astronomy as a postdoctoral fellow 9 months ago. My role is to apply novel machine learning algorithms to the field of astronomy. I am originally from China and have lived in Australia for six years. I studied computer science and got my PhD degree from the University of Technology Sydney, and I also hold a Telecommunication Engineering degree awarded from the Australian National University.
Over the last few years, I have designed state-of-the-art model compression methods to reduce computational complexity while maintaining the same accuracy of the machine learning algorithm. I have also designed advanced machine learning algorithms for real world applications, e.g., from food freshness assessment to nano-composite membranes design, and from sports science to wearable exoskeletons.
The field of radio astronomy is immensely intriguing, and I anticipate learning more about scientific observations and exploring the Universe.
Mayra E. Lebrón Santos
I am a radio astronomer and professor at the University of Puerto Rico, Río Piedras Campus. I coordinate the astronomy research group, Círculo Astrofísico de Puerto Rico.
Our main research areas are star formation and large-scale structure in the Zone of Avoidance. Most of us were Arecibo Observatory users and have experience with galactic and extragalactic HI observations. We are currently studying the galaxies of the Ophiuchus supercluster in the direction of the Galactic centre using archived mid-IR data. Our galaxy sample will also be observed in HI and WALLABY data will be very useful in many ways for this work.
We have students that could benefit from and contribute to WALLABY. We are looking forward to using and contributing to WALLABY.
Niankun Yu
I am Niankun Yu (余捻坤), a postdoctoral fellow at National Astronomical Observatories, Chinese Academy of Sciences (NAOC). I obtained my PhD at Peking University, China.
My primary science interests focus on galaxy formation and evolution, including the baryon cycle in galaxies (HI → H2 → stars), galaxy kinematics and dynamics, polar ring galaxies, and galaxy interaction. The research facilities I have utilised include Arecibo, FAST, ASKAP, VLA, and ALMA. Specifically, I use FAST to reveal faint atomic gas distribution in the ISM, CGM, and IGM of nearby galaxies.
If you are interested in any related discussion, please feel free to contact me at niankunyu@bao.ac.cn. I sincerely hope that, together, we solve the puzzle of galaxies in the near future.
Nikhil Arora
I am postdoctoral fellow at Queen’s University.
I study formation and evolution of present day galaxies with an emphasis on creating apples-to-apples comparison between cosmological simulations and observations. A comparison like this highlights the interaction between baryonic and dark matter contents of galaxies.
I became interested in the WALLABY team to explore the inclusion of radio properties (and therefore gas properties) of galaxies to compare with cosmological simulations.
Rayssa Guimarães Silva
Olá! I’m Rayssa, a PhD student at Observatório do Valongo, Universidade Federal do Rio de Janeiro (Brazil).
Currently, I am working with Prof. Marco Grossi to analyse the properties of dwarf galaxies in low-density environments. We want to understand how these galaxies evolve by analysing the metallicities, dynamics, and morphology of their neutral and ionised gas. Using WALLABY data, we aim to study the role of gas accretion, through either galaxy interactions or inflows from the intergalactic medium, in the process of mass growth. We already have interesting findings, so keep a look out!
Before the PhD, my research was focused on using the mid-infrared spectra taken with Spitzer to detect active galactic nuclei and investigate its effect on the chemistry of the interstellar medium. Thus, my research interests are very broad as long as galaxies are involved!
Xuchen Lin
I am Xuchen Lin, currently a 2nd-year PhD student at Peking University (Beijing, China).
My main research interest is the role of galactic gas content in star-formation and galaxy evolution and its interaction with multi-scale environments. My first PhD paper separated two ongoing environmental mechanisms in the combined WALLABY and FAST data of the NGC 4636 group.
It is exciting to join the WALLABY team. Given the large sky area that will be covered by WALLABY, I am looking forward to applying our methods to a larger sample and extending them to more environmental mechanisms.
FAST-ASKAP synergy: Quantifying coexistent tidal and ram pressure strippings in the NGC 4636 group
by Xuchen Lin
It has been well established that galaxies evolve at different speeds in different environments, and the HI gas, as the reservoir of star formation, plays an important role. Previous studies usually use parameters like position or local number density to describe the environment, and their targets are often those in very extreme conditions showing clear features. In our recent study (Lin et al. 2023), we set out to describe it from a more physical point of view, and attempt to depict the galaxy evolution in a milder group, NGC 4636, where different mechanisms coexist. Both WALLABY Pilot Survey and FAST have observed the NGC 4636 group in synergy.
We consider two mechanisms:
- Ram-pressure stripping (RPS): when galaxies fall into the group and its velocity relative to the intra-cluster medium causes its cold gas to be stripped away.
- Satellite-satellite tidal interaction (tid): the gravitational interaction between encountering galaxies that disrupts, redistributes or even strips their gas.
We define three parameters to better quantify these two effects:
- strength (S) of ram pressure or tidal interaction at the edge of optical disc
- strippable gas fraction (f), i.e. the ratio of strippable gas to total gas
- stripping timescale (tstr), i.e. the time required for all strippable gas to be removed under current conditions
Figure 1 presents an illustration of these parameters.
We found that SRPS and Stid are independent of each other. By comparing the fRPS and ftid, we divided our sample into RPS-dominated systems and tidal stripping (TS)-dominated systems. We found that the HI disc size and the corresponding S parameter showed a tighter relation for the separated sample as opposed to all galaxies. We also found that the TS-dominated galaxies redden with an increasing Stid, while RPS-dominated galaxies do not show a similar trend with SRPS. These findings indicate that our method of disentangling of these two mechanisms is successful. We find 80% of all galaxies are undergoing at least one stripping mechanism, whereas 41% are undergoing both.
We found our estimates of the timescales of gas stripping to vary across a wide range. At 2R200 the stripping is very inefficient, while within R200, the timescale could reach the free-fall timescale of an HI cloud. Such an efficient stripping at the inner region of the group could be as a result of interplay between both stripping mechanisms. Our work is one of the first steps in breaking the degeneracy between many environmental mechanisms. Our results are based on semi-analytical models and, especially those regarding tstr, could be used to calibrate semi-analytical simulations.
WALLABY pilot survey: The potential polar ring galaxies NGC 4632 and NGC 6156
by Nathan Deg
Recently, the first pair of potential polar ring galaxies detected by WALLABY PDR1 were reported in Deg et al. (2023). It was found that the two galaxies, NGC 4632 and NGC 6156, had large reservoirs of gas that are distinct from the main body and are consistent with having polar orientations. In order to determine this possible orientation, T. Jarrett and the IDIA Vislab used virtual reality software to isolate the main body gas from the anomalous ring gas as seen here.
Beyond being beautiful, optical studies of polar ring galaxies had suggested an incidence rate of 1/1000. But, through careful modelling and tests with mock galaxies, Deg et al. (2023) estimated that the incidence rate of these HI polar rings is 1-3%!!! Subsequently, optical studies have found similar incidence rates (Mosenkov et al. 2023).
Led by J. English, a beautiful image (Figure 2) of the polar nature of NGC 4632 was generated. This was a cornerstone of a wide media release coordinated by Queen’s University (linked), the University of Manitoba (linked), and CSIRO ATNF (linked). The discovery of these polar rings is one of the most widely engaged MNRAS papers released last year and it was picked up around the world (Altmetric). See Bärbel Koribalski’s article in The Conversation for more details.
WALLABY pre-pilot survey: Ultra-diffuse galaxies in the Eridanus supergroup
by Bi-Qing For
In our recent paper (For et al. 2023), we search the pre-pilot Eridanus field of WALLABY for HI content in ultra-diffuse galaxy (UDG) candidates of the Systematically Measuring Ultra-diffuse Galaxies survey (SMUDGes). 78 SMUDGes UDG candidates are narrowed down within the maximum radial extent of the Eridanus subgroup. Most of these candidates have effective radii smaller than 1.5 kpc and fail to meet the defining size threshold. Only one HI detection is found and classified as a low-surface-brightness dwarf. Six putative UDGs are HI-free.
We show the overall distribution of SMUDGes UDG candidates on the size-luminosity relation and compare them with low-mass dwarfs on the atomic gas fraction versus stellar mass scaling relation. We find no correlation between gas-richness and colour indicating that colour is not the sole parameter determining their HI content. The evolutionary paths that drive galaxy morphological changes and UDG formation channels are likely the additional factors to affect the HI content of putative UDGs.
The actual numbers of UDGs for the Eridanus and NGC 1332 subgroups are consistent with the predicted abundance of UDGs and the halo virial mass relation, except for the NGC 1407 subgroup, which has a smaller number of UDGs than the predicted number. Different group environments suggest that these putative UDGs are likely formed via the satellite accretion scenario.
There is an interesting UDG, SMDG 0345097−223826, that could have a tidal origin. This UDG appears to be located at the tail end of a stellar stream of 6dFGS J034506.0−223632. There is also a fairly blue spiral galaxy, LEDA 811216, that is located south of 6dFGS J034506.0−223632 and alongside the stellar stream. The location of LEDA 811216 could be a projection effect, or it could in fact be interacting with 6dFGS J034506.0−22363. The slight disruption on the optical morphology of LEDA 811216 suggests that this pair is interacting. We do not find any HI in any of our velocity ranges at their locations. If SMDG 0345097−223826 is associated with 6dFGS J034506.0−223632, we can rule out that it is a member of the Eridanus group. At that redshift distance, SMDG 0345097−223826 would be large in size (reff > 13 kpc). Further spectroscopic observation is needed to confirm the nature and origin of SMDG 0345097−223826.
WALLABY pre-pilot survey: An ‘almost’ dark cloud near the Hydra cluster
by Tamsyn O’Beirne
In O’Beirne et al. 2024, we explore the properties of an ‘almost’ dark HI cloud that we found in the phase 1 WALLABY pilot data (Figure 4). Initially this source was thought to be a dark galaxy candidate, but we have identified an extremely faint optical counterpart in the DESI Legacy Imaging Survey Data Release 10 (DR10), measuring the mean g-band surface brightness to be 27.0 ± 0.3 mag arcsec-2. The WALLABY data revealed the cloud to be closely associated with the interacting group Klemola 13. We found that tidal interactions and ram pressure stripping likely played a significant role in the formation of the cloud and the evolution of the system. The ease of detection of this cloud and intragroup gas is due to the sensitivity, resolution and wide field of view of WALLABY, and showcases the potential of the full WALLABY survey to detect many more examples.
The WALLABY pilot survey phase 2: public data release
by Chandrashekar Murugeshan
The WALLABY management team is happy to report that all Pilot Survey Phase 2 data products and catalogue will be released to the public via WALLABY’s Public Data Release 2 (PDR2). In this release, we present ~ 1800 HI detections (in the default 30 arcsec resolution) from the three Phase 2 fields, the NGC 5044 and NGC 4808 groups and the Vela supercluster, covering a total of 180 deg2 of the sky. The number of detections made in phase 2 is a factor of three more than those made in phase 1 of the pilot survey, highlighting the significant improvement in data quality and source finding. In addition, we are also releasing kinematic models for 126 spatially resolved galaxies in the default 30 arcsec resolution.
A latest addition to PDR2 are the 12 arcsec high-resolution “cut-outs” for over 80 galaxies, including their source catalogue. Figure 5 compares the 30 and 12 arcsec moment 0 maps for four galaxies, showing how the higher resolution brings-out finer details in the HI morphology of the galaxies. The release also includes kinematic models for over 30 galaxies in high-resolution. With this new high-resolution data, WALLABY team members can now study detailed HI morphology and kinematics of nearby galaxies, in addition to probing star formation linked to the high column-density HI gas.
With PDR2, the total number of WALLABY detections is already about half the total number of HIPASS sources (~5000), showcasing the true potential of the survey. A PDR2 paper, highlighting all the new results and observations is currently being circulated internally within the WALLABY team and will be submitted to the journal very soon. We hope that WALLABY team members will use the Phase 2 data widely for their exciting new research.
The Tully Fisher relation in the WALLABY survey
by Jeremy Mould
In Courtois et al. 2023, the WALLABY Tully Fisher relation (TFR) team used redshift independent distances from the TFR to show cosmographic maps, demonstrating that the WALLABY pilot survey fields probe a vast diversity of elements of the cosmic web: intersecting numerous features such as voids, filaments, walls, and the nodes which host the targeted clusters.
Our second paper “WALLABY Pilot Survey Phase 2: the NGC 4808, Vela and NGC 5044 fields” will soon be available for team review. It shows something essential for the main 100,000 galaxy survey: it is possible to obtain a TFR from machine readable optical catalogs without having to look at every galaxy, a task beyond even the most dedicated student. The key is to first match the WALLABY catalog to the lesser known Principal Galaxies Catalog, which has positions accurate to an arcsec. One can then match the output to a couple of i band catalogs or the 4HS J band catalog, a forthcoming Swinburne production. This technique opens the way to statistical cosmological studies, which should yield competitive results on the low redshift growth of structure in the Universe, a goal listed in the WALLABY science case.
HI morphometrics in galaxy groups and the nearest neighbour classification
by Benne Holwerda
As a (distant) WALLABY member, I aimed to enhance the quantification of HI morphology in the pilot data using machine learning, a cost-effective approach as manual classification is expensive in human hours. With their enhanced accessibility in Python, machine learning tools can be used alongside catalogues with pre-existing classifications. In Holwerda et al. 2023, I tested different supervised machine learning algorithms on Boolean labels from Wang et al. 2021, indicating signs of ram-pressure stripping in HI morphology of Hydra cluster galaxies. I found the basic random forests algorithm effective but not ideal.
Turning to a labelled galaxy group from Lin et al. 2023, a closer dataset with more information on morphology (i.e. morphometrics), I faced challenges due to smaller training samples, complex labels and non-orthogonality of the morphometric space. I simplified their labels to “perturbed” or “not”. To maximise the training size of the small labelled sample, I split the sample by a 4:1 ratio for training:test sets multiple times, to assess the average performance and variance of the the k-nearest neighbours (kNN) algorithm. kNN algorithm assesses a data point by averaging the classes of its nearest Euclidean neighbours in a training set, with the number of neighbours (k) being the crucial parameter. Careful `feature engineering’ identified—concentration, asymmetry, Gini, M20, deviation, and Sersic index— as the key metrics for identifying perturbance.
Using these key metrics, applying the kNN to unlabelled groups from Lin et al. 2023 and adding estimates for stellar mass and star-formation (based on WISE fluxes) into their SoFiA catalogues, I explored the log-linear stellar mass to star-formation, HI-stellar mass, and baryonic Tully-Fisher relations for perturbed and unperturbed populations individually (with errors from straightforward bootstrapping). This simple A/B testing would indicate informative morphological differentiation if the two morphologically selected samples differed fundamentally in these three relations. While the star-forming main sequence remained consistent between the two populations, the HI-stellar mass relation showed marginal differences in normalisation, and the Baryonic Tully-Fisher relation exhibited significant variations. However, given the algorithm’s 70% accuracy, the fit parameters are expected to differ by at least a standard deviation, even without considering other uncertainties.
In conclusion, morphological classification using kNN and HI morphometrics is promising for statistically identifying populations of perturbed galaxies but provides probabilities rather than certainties for individual galaxies. Further manual classifications of observed galaxy groups will refine predictions and serve as an extensive training set for the full WALLABY survey.
TWG 1 – Numerical Simulations & Mock Surveys
by Kyle Oman & Connor Bottrell on behalf of TWG 1
Connor & Kyle have recently taken over as co-chairs of TWG 1 from Adam Stevens. We see this working group as a bit unique in the sense that its primary activity could be seen as responding to needs either scientific or technical arising in other working groups. We would very much welcome input from members across the survey about what simulation data products could be beneficial to your work. We’ll also be getting in touch with all current TWG 1 members soon.
TWG 4 – Source Finding & Cataloguing
by Tobias Westmeier on behalf of TWG 4
TWG 4 continues to run the SoFiA source finding pipeline on all of the single 8-hour footprints from WALLABY full survey observations. A total of 1738 HI detections from the 19 successful footprints accepted so far have already been internally released to the team for scientific analysis. It should be noted, though, that this single-footprint catalogue is preliminary and suffers from several limitations, most notably lower sensitivity and significant noise variation across the field, particularly towards the field edges.
Eight of the footprints obtained so far have already be combined into four final 16-hour tiles. Source finding has been completed on the inner 3.9° × 3.9° of each of those four tiles where the noise is roughly constant and full WALLABY sensitivity is achieved. This has resulted in the detection of the first ~500 final WALLABY galaxies which have been internally released to the team, with hopefully more to come in the near future as observations progress.
The total number of galaxies detected during the early science, pilot and full survey phases so far sits at roughly 4200 which is about 2% of the anticipated sample size for the full survey. A overview plot of their HI masses as a function of redshift is presented in Figure 6.
TWG 4 will continue to run SoFiA on new footprints and tiles over the next few years to gradually build up the full WALLABY source catalogue. All new detections will be immediately made available to the team for scientific use through our internal WALLABY source database while public releases are envisaged to occur annually.
We have also been making some progress with improving the SoFiA source finding pipeline. A new feature that allows users to import a mask cube and create a source catalogue based on that mask without rerunning the source finder or linker has been successfully implemented and tested. A new version of SoFiA including that feature will be released in the near future.
TWG 7 – WALLABYcat
by Nathan Deg
The archive working group is continuing to prepare for the upcoming Pilot Data Release 2. We have completed most of the data engineering necessary for the data products, including the addition of more extensive provenance documentation. Early tests on CADC and CASDA have been successful. We are now finalising the value added information in the catalogues and awaiting some final data quality checks. We have also been working to incorporate all this information directly into AusSRC pipelines for the full pipeline.
Upcoming Meetings & Workshops
Note: WALLABY team members can download PDF copies of several WALLABY-related presentations at international meetings from the Redmine wiki under “WALLABY-related presentations and material”.
| When | What | Where |
| 2024 Mar 21 | Monthly WALLABY Science Meeting | Online (8:00 UTC) |
| 2024 Apr 18 | Monthly WALLABY Science Meeting | Online (1:00 UTC) |
| 2024 May 13-15 | ACAMAR 10 Workshop | Guangzhou, China |
| 2024 May 16 | Monthly WALLABY Science Meeting | Online (8:00 UTC) |
| 2024 May 19-24 | 4th URSI Atlantic Radio Science Meeting | Gran Canaria, Spain |
| 2024 May 27-31 | The physical processes shaping the stellar and gaseous histories of galaxies | Pisa, Italy |
| 2024 Jun 20 | Monthly WALLABY Science Meeting | Online (1:00 UTC) |
| 2024 Jun 24-28 | Astronomical Society of Australia Annual Scientific Meeting | Online |
| 2024 Jul 18 | Monthly WALLABY Science Meeting | Online (8:00 UTC) |
| 2024 Jul 18-12 | International Conference on Machine Learning for Astrophysics | Catania, Italy |
| 2024 Jul 29-Aug 2 | Small Galaxies, Cosmic Questions – II | Durham, UK |
| 2024 Aug 15 | Monthly WALLABY Science Meeting | Online (1:00 UTC) |
| 2024 Aug 13-15 | IAU Symposium 392: Neutral Hydrogen in and around galaxies in the SKA era | Cape Town, South Africa |
| 2024 Sep 19 | Monthly WALLABY Science Meeting | Online (8:00 UTC) |
| 2024 Oct 14-18 | RFI 2024 | Bariloche, Argentina |
| 2024 Oct 17 | Monthly WALLABY Science Meeting | Online (1:00 UTC) |
| 2024 Nov 21 | Monthly WALLABY Science Meeting | Online (8:00 UTC) |
| 2024 Dec 19 | Monthly WALLABY Science Meeting | Online (1:00 UTC) |
WALLABY Publications
Aug 2023 – Feb 2024:
- Lin X., Wang J., Kilborn V., Peng E.~W., Cortese L., Boselli A., Liang Z.-Z., et al., 2023, FAST-ASKAP Synergy: Quantifying Coexistent Tidal and Ram Pressure Strippings in the NGC 4636 Group, ApJ, 956, 148. doi:10.3847/1538-4357/accea2
- Deg N., Palleske R., Spekkens K., Wang J., Jarrett T., English J., Lin X., et al., 2023, WALLABY pilot survey: the potential polar ring galaxies NGC 4632 and NGC 6156, MNRAS, 525, 4663. doi:10.1093/mnras/stad2312
- For B.-Q., Spekkens K., Staveley-Smith L., Bekki K., Karunakaran A., Catinella B., Koribalski B.~S., et al., 2023, WALLABY pre-pilot survey: ultra-diffuse galaxies in the Eridanus supergroup, MNRAS, 526, 3130. doi:10.1093/mnras/stad2921
- O’Beirne T., Staveley-Smith L., Wong O.~I., Westmeier T., Batten G., Kilborn V.~A., Lee-Waddell K., et al., 2024, WALLABY pilot survey: An ‘Almost’ dark cloud near the hydra cluster, MNRAS.tmp. doi:10.1093/mnras/stae215
A complete list of WALLABY ADS libraries can be found at https://wallaby-survey.org/papers
