Friday, 7th of July

Location: 21 Wally's Walk Rm 2.300

Zoom link: https://skatelescope.zoom.us/j/8625159169?pwd=MjlFR2FpUWlwRHhsQ0xhc1ZOZkZJUT09 

Facilitators: Jimi Green & Shari Breen

This workshop will provide an opportunity to interact with SKAO Science Operations, hear about in country SKA developments, including photos (and maybe even videos!) and enquire about the processes and avenues for community engagement.

Location: 14SCO Rm 163, ground floor

Zoom link:  https://macquarie.zoom.us/j/87986414345

Facilitator: Paul Hancock

This short course of three sequential and connected workshops will use Google Colaboratory and scikit learn to understand how to "do ML" with some astronomy-relevant data sets. Attendance of all three sessions (one per day) is required.

** This session has reached capacity for in-person attendance. 

Location: Mason theatre, ground floor

Zoom link: https://macquarie.zoom.us/j/82321436522

Slack channel: #asa2023-facilities-surveys-outreach

Chair: Virginia Kilborn, Co-Chair: Kateryna Andrych

11:00am: DREAMS: The Dynamic REd All-sky Monitoring Survey - Jamie Soon*, ANU

With the flying success of an NSF-managed Preliminary Design Review earlier this year, the GMT project has now started negotiations with the NSF on its significant partnership in the GMT project. So this is a timely point to update the Australian community on the progress of the project, and the world-leasing (and in some cases) unique instrumentation (several being built here in Australia) that GMT will make available.

11:15am: First light of the Pyxis interferometer - Jonah Hansen*, ANU

Optical/mid-infrared interferometry from space has been a long discussed and highly anticipated technique in high angular resolution astrophysics, in particular for the detection and characterisation of Earth-like exoplanets. In this paper, we discuss the Pyxis interferometer: an autonomous, three-platform ground-based demonstrator to test formation-flying interferometry from the ground, utilising a precise, three stage metrology system, and currently built at Mt Stromlo Observatory at the Australian National University. It is also the only visible light interferometer in the Southern Hemisphere. We will show the current status and progress of the mechanical and optical systems involved, as well as the first light on-sky results: measuring the diameters and peering into the dust shells of nearby Mira variables using spectro-polarimetric data. We conclude with a look into the future, including which science targets and future upgrades are foreseen for Pyxis, as well a mention of its successor: a set of three CubeSat satellites in Low Earth Orbit that will fully demonstrate the required formation flying control for a future, large class interferometer mission such as the LIFE (Large Interferometer For Exoplanets) initiative.

11:30am: On the road to Dark Energy with DESI and LSST - Rossana Ruggeri, UQ/Swinburne

The Dark Energy Spectroscopic Instrument (DESI) and the Vera Rubin Observatory (LSST) are two cutting-edge astronomical facilities poised to revolutionise our understanding of the universe. DESI, a next-generation spectroscopic instrument, aims to unravel the mystery of dark energy by precisely measuring the redshifts of tens of millions of galaxies and quasars. On the other hand, LSST, a state-of-the-art optical telescope, will conduct a decade-long survey of the entire southern hemisphere of the night sky, generating an unprecedented amount of imaging and spectroscopic data.

In this presentation, I will highlight the synergies between DESI and LSST and how they will collectively contribute to advancing our knowledge of the Universe. Firstly, LSST will benefit from DESI's spectroscopic data, which will provide crucial redshift measurements for galaxies and quasars in the LSST survey. These precise redshift measurements will enable LSST to obtain accurate distance measurements and improve the precision of its cosmological probes, such as weak lensing and galaxy clustering, leading to a deeper understanding of the large-scale structure of the universe.

Furthermore, the synergies between DESI and LSST extend beyond cosmology. The combined datasets from DESI and LSST will enable a wide range of astrophysical studies, including galaxy evolution, black hole physics, and transient events, providing a comprehensive view of the universe across a broad range of cosmic epochs.

11:45am: The Vera C. Rubin Observatory’s Legacy Survey of Space and Time. - Sarah Brough, UNSW

Rubin Observatory is approaching completion in Chile with the goal of compiling the deepest, widest image of the Universe at optical wavelengths. This ten-year survey, the Legacy Survey of Space and Time (LSST), is set to begin in 2024 and will survey the entire southern sky approximately every 3 nights. The LSST aims to explore the nature of dark matter and dark energy, map the structure of our Milky Way and nearby galaxies, catalogue the solar system and search for transient objects. I will introduce the telescope, the survey and give an update on Australia’s engagement with LSST.

12:00pm: MAVIS: An Australian-led facility instrument for the ESO Very Large Telescope  - Richard McDermid, Macquarie University

MAVIS (MCAO Assisted Visible Imager and Spectrograph) is a new facility instrument for the ESO Very Large Telescope (VLT) being built by an Australian-led international consortium. MAVIS will push the frontier of new astronomical instrument technologies to provide, for the first time, wide-field, diffraction-limited angular resolution at visible wavelengths. In combination with the VLT Adaptive Optics Facility, it will use multi-conjugate adaptive optics (MCAO) to feed a 4k × 4k imager covering 30 ×

30 arcseconds, as well as an Integral Field Spectrograph (IFS). Angular resolution down to 18 milliarcseconds will be achieved at a wavelength of 550 nm (V band). The IFS will provide four spectral modes, with spectral resolutions from 4,000 to over 15,000 between 370-950 nm. This will enable a wide variety of science cases, spanning themes that include the emergence of the Hubble sequence, resolving the contents of nearby galaxies, star clusters over cosmic time, and the birth, life, and death of stars and their planets. Delivering visible images and integral- field spectroscopy at an angular resolution 2-3 times better than that of the Hubble Space Telescope will make MAVIS a powerful complement at visible wavelengths to infrared-optimised facilities like JWST and 30–40-metre-class ground-based telescopes currently under construction. I will present an overview and update on the MAVIS project, and plans for community use of associated Guaranteed Time Observations.

12:15pm: An Update on the Giant Magellan Telescope project - Chris Tinney, UNSW

With the flying success of an NSF-managed Preliminary Design Review earlier this year, the GMT project has now started negotiations with the NSF on its significant partnership in the GMT project. So this is a timely point to update the Australian community on the progress of the project, and the world-leasing (and in some cases) unique instrumentation (several being built here in Australia) that GMT will make available.

Poster sparklers in this session:

P7: Garvit Grover*, Curtin University

P46: Gavin Rowell, Adelaide University

P79: Adam Taras, USyd

P80: Tommy Marshman*, Macquarie University

P84: Kate Chow, CSIRO

Location: Mason theatre, ground floor

Zoom link: https://macquarie.zoom.us/j/81099211834

Slack channel: #asa2023-pulsars

Chair: Stuart Ryder, Co-Chair: Saurav Mishra

11:00am: First results from the MeerKAT Pulsar Timing Array - Matthew Miles*, Swinburne/OzGrav

We may be on the verge of opening a new, nanohertz-frequency, window to the gravitational-wave Universe through timing an array of millisecond pulsars. The gravitational wave spectrum at this frequency is expected to be dominated by a stochastic background produced by binary supermassive black holes. Pulsar timing array experiments in Australia, Europe, and North America have recently detected hints of the background. In order to confirm a detection of the background, the presence of "Hellings-Downs" angular correlations between the pulsars in the array is required. This necessitates either observing the pulsars for a longer duration, observing a larger ensemble of pulsars, or both.

We introduce the MeerKAT Pulsar Timing Array, a pulsar timing array experiment being performed with the Square Kilometre Array (SKA) precursor radio telescope, MeerKAT. This array monitors the largest number of pulsars (90), to the highest precision, and at the highest cadence of all pulsar timing arrays. We present results of the first searches for gravitational waves. We discuss the implications of the searches for the binary supermassive black hole population. We conclude by motivating the science possible with a SKA pulsar timing array.

11:15am: The Parkes Pulsar Timing Array Data Release 3: overview and noise budget for the stochastic gravitational wave background - Andrew Zic, CSIRO

The Parkes Pulsar Timing Array (PPTA) is a major project on the Parkes Radio Telescope (Murriyang), with the primary aim of detecting nanohertz-frequency gravitational waves. In this talk, I will present an overview of the new PPTA Data Release 3 (DR3), which includes high-precision timing observations of a set of 32 millisecond pulsars, spanning up to 18 years in length. For the first time, the DR3 dataset incorporates observations taken with the Murriyang Ultra-Wideband Low receiver, which has more than doubled our frequency coverage, and greatly improved our observing efficiency. I will describe our detailed single-pulsar noise analysis, which employs physically-motivated models to carefully account for variations in pulse times of arrival. We demonstrate that detailed noise modelling is necessary for robust and accurate gravitational-wave inference. I will highlight our noise-modelling results for PSR J1713+0747, which shows no evidence for steep-spectrum achromatic red noise, in contrast to expectations for an isotropic gravitational wave background. I will discuss these results in the context of our latest gravitational wave search efforts.

11:30am: Search for a stochastic gravitational wave background with the Parkes Pulsar Timing Array - Daniel Reardon, Swinburne

The Parkes Pulsar Timing Array (PPTA) is a major project on the Parkes Radio Telescope (Murriyang), with the primary aim of detecting nanohertz-frequency gravitational waves (GWs).  A background of GWs (GWB) modulates pulsar arrival times and manifests as a stochastic process, common to all pulsars, with a signature spatial correlation. In this talk I describe a search for an isotropic stochastic GWB using the third data release of the PPTA. We recover a noise process with a common spectrum among the pulsars, which exhibits characteristics consistent with that expected of a GWB from supermassive black hole binaries. We also search for the spatial correlations expected from a GWB using a hierarchical inference technique on individual pulsar pairs, which also enables an estimate of the false-alarm rate via scrambling of our pulsar positions. Using this method we estimate the significance of the correlations expected of a GWB associated with our recovered common-spectrum noise. Contrary to expectations for the GWB from a population of inspiralling supermassive black hole binaries, we demonstrate that the apparent signal strength is changing with time. I will discuss these results in the context of recent analyses from other international pulsar timing array collaborations.

11:45am: The Pulsar That Threw A Tantrum - Rami Mandow*, Macquarie University/CSIRO

Millisecond Pulsars (MSPs) exhibit very high stability in their rotation and emission properties, which enable precision timing comparable over the long term to terrestrial atomic clocks. This stability is core to the success of pulsar timing array experiments, which aim to detect nanohertz-frequency gravitational waves. Significant instabilities that arise in MSPs are surprising, and must be carefully accounted for to avoid compromising gravitational wave detection efforts. We investigate the case of one of the most precisely-timed MSPs – PSR J1713+0747 – which in April 2021 underwent a significant change to its pulse profile, a crucial element in measuring pulse times of arrival. We consider potential causes, and demonstrate its impact on pulsar timing measurements taken with the Ultra-Wideband Low receiver on the Parkes radio telescope, as part of the Parkes Pulsar Timing Array project.

12:00pm: Improving pulsar-timing solutions through dynamic pulse fitting - Rowina Nathan*, Monash University

Precision pulsar timing is integral to the detection of the nanohertz stochastic gravitational-wave background as well as understanding the physics of neutron stars. Conventional pulsar timing often uses fixed time and frequency-averaged templates to determine the pulse times of arrival, which can lead to reduced accuracy when the pulse profile evolves over time. We illustrate a dynamic timing method that fits each observing epoch using basis functions. By fitting each epoch separately, we allow for the evolution of the pulse shape epoch to epoch. We apply our method to PSR J1103-5403 and demonstrate that it undergoes mode changing, making it the fourth millisecond pulsar to exhibit such behaviour. Our method, which is able to identify and time a single mode, yields a timing solution with a root-mean-square error of 1.343$\mu$s, a factor of 1.78 improvement over template fitting on both modes. In addition, the white-noise amplitude is reduced 4.3 times, suggesting that fitting the full data set causes the mode changing to be incorrectly classified as white noise. This reduction in white noise boosts the signal-to-noise ratio of a gravitational-wave background signal for this particular pulsar by 32%.

12:15am: Flux density monitoring of 89 millisecond pulsars with MeerKAT - Pratyasha Gitika*, Swinburne

We present a study of the flux density measurements of 89 millisecond pulsars (MSPs) regularly monitored as part of the MeerKAT Pulsar Timing Array (MPTA), using the L-Band receiver with an approximately two week cadence. The mean flux densities, modulation indices and peak-to-median values are presented for three sub-bands centred at 944, 1429 and 1625 MHz as well as spectral indices over the entire frequency. We find strong evidence that the intrinsic radio luminosities of MSPs are stable, and only influenced by the interstellar medium. Using the temporal variation of the flux densities we measured the temporal structure function of all the MSPs and the refractive scintillation timescale for 7 of them. As a population the average modulation indices at 20 cm wavelengths peak near unity at dispersion measures (DMs) of ∼20 pc cm−3 and by a DM of 100 pc cm−3 are closer to 0.2 where the variations are dominated by refractive scintillation. In one observation, PSR J1909–3744 had a flux density a factor of 47 greater than its median value in a sub-band. Our results can be used to help plan and optimise Pulsar Timing Array (PTA) observations, and predict how fast radio burst (FRB) detection rates and flux densities are biased. We find that 20 cm FRB surveys should prioritise highly scintillating mid-high latitude regions of the galactic sky where they will find ∼30% more events and at greater distances than in on-plane regions.

Poster sparklers in this session:

P7: Garvit Grover*, Curtin University

P46: Gavin Rowell, Adelaide University

P79: Adam Taras, USyd

P80: Tommy Marshman*, Macquarie University

P84: Kate Chow, CSIRO