Active collaborative projects

PIs: Gemma Anderson (ICRAR), Arne Rau (MPE)
Australian Collaborators: Paul Hancock, James Miller-Jones
eROSITA Collaborators: Joern Wilms
Australian Surveys/Instruments: AAT, ATCA

Summary: The release of gravitational energy when mass is suddenly dumped onto a black hole powers some of the most explosive phenomena in the Universe. This is the most extreme example of a universal process called accretion, which is responsible for the growth of all astrophysical systems, from stars to galaxies. This project aims to understand how the most rapidly-feeding black holes (accreting in the super-Eddington regime) produce powerful outflows, and to determine under what conditions these jets can be launched. We will perform radio follow-up of short-lived, explosive events to unveil when the jets are formed and how they evolve in real time. These include stellar-mass black holes rapidly consuming material torn off a nearby companion star (known as transient ultraluminous X-ray sources), and supermassive black holes tearing apart unlucky stars that wander too close (known as tidal disruption events). The unrivalled capabilities of the new X-ray telescope eROSITA will allow us to discover thousands of such rapidly-evolving systems. We will follow up many of these with Australian radio telescopes to explore in detail the connection between the infalling matter and the launching of jets in some of the most extreme environments known in the Universe.

PIs: Vanessa Moss (CASS), Mara Salvato (MPE) 
Australian Collaborators: E. Sadler, J. Allison, E. Mahony
eROSITA Collaborators: M. Salvato, A. Merloni, A. Georgakakis, A. Del Moro, J. Buchner, T. Dwelly
Australian Surveys/Instruments: FLASH HI 

Summary: We propose a joint CAASTRO/eROSITA project to investigate the nature of dense gas in the environment surrounding supermassive black holes, using HI absorption from ASKAP‐FLASH to measure the neutral gas and eROSITA to trace the hydrogen content via X‐rays. This project will enable us to shed light on the hidden gaseous regions near accreting black holes, and understand the role that neutral gas plays, alongside its eventual fate, in these active galaxies.

PIs: Manami Sasaki (EPAC), Lister Staveley-Smith (ICRAR)
Australian Collaborators: Lister Staveley-Smith, Miroslav Filipovic, Bärbel Koribalski
eROSITA Collaborators: Frank Haberl, Jürgen Kerp
Australian Surveys/Instruments: ASKAP, ATCA, Parkes, MWA, and AAT 

Summary: The evolution of spiral galaxies is driven by star formation and matter cycle between the stars and the interstellar medium (ISM). Massive OB stars inject energy through their radiation, stellar winds, and finally by supernova (SN) explosions. Supernova remnants (SNRs) also act as recycling centres, returning elements forged in stars to the ISM. These processes are often correlated in space and time, generating superbubbles (SBs) with sizes of typically 100 − 1000 pc. By studying the physics of SNRs and SBs we will better understand the chemical composition and evolution of galaxies.

PIs: Christian Wolf (ANU), Mara Salvato (MPE)
Australian Collaborators: Rachel Webster, Wei Jeat Hon (Uni Melbourne), David Raithel, Dr Chris Onken (ANU)
eROSITA Collaborators: Johannes Buchner (MPE Garching), Jörn Wilms (Sternwarte Uni Erlangen), Mirko Krumpe (AIP Potsdam)
Australian Surveys/Instruments: TAIPAN, 2.3m, SkyMapper​ 

Summary: We have seen over the last few decades that some Seyfert galaxies appear to change their type over a time scale of decades to even months. The dominant observed phenomenon is an appearance or disappearance of the broad-line region and the blue accretion-disk continuum in the nuclear spectra of these galaxies. In recent years it has become clear that this phenomenon, called Changing-Look AGN or CL-AGN, is most prevalent at lowAGN luminosities and affects a surprising fraction of objects.  It is elusive how such dramatic changes in the appearance of a Seyfert nucleus may occur on such a short timescale. The preferred interpretation in the literature is a change in accretion state, although the time scales for the disappearance of Seyfert accretion disks is assumed to be much longer than human lifetimes. This project aims at establishing significant statistics on the phenomenon, as the field is currently dominated by publications of individual discoveries and anecdotal evidence. 

PIs: Natasha Hurley-Walker (ICRAR/Curtin), Werner Becker (MPE)
Australian Collaborators: Anne Green
eROSITA Collaborators: Michael Freyberg, Martin Mayer, Manami Sasaki
Australian Surveys/Instruments: GLEAM-X​ 

Summary: Supernova remnants (SNRs) are important contributors to the thermal, kinetic, and cosmic ray energy budget of the Milky Way, and also chemically enrich and shock the ISM, affecting star formation. Of the 2000 predicted SNRs in our Galaxy, fewer than 300 have been detected and confirmed over multiple wavelengths. Radio observations are responsible for the detection of over 90% of known and candidate SNRs, but full characterisation is only truly possible with X-ray observations,  which give insights into the chemical composition of the shocked ejecta, position of the forward and reverse shocks, and allow ages to be estimated without ancillary data  such as measurements of associated pulsars. Recent low-frequency radio surveys enabled the detection of 27 SNRs (Hurley-Walker et al., 2019). Current X-ray surveys are not sensitive enough to detect these objects, which are low surface-brightness, and often at higherGalactic latitudes. The eROSITA all-sky survey will characterise the X-ray emission from these objects, as well as ~300 proposed candidate SNRs in the literature, bringing us closer to detecting the full complement of SNRs predicted to exist in the Milky Way.  Additionally, the GLEAM-eXtended (GLEAM-X) survey will produce deeper, higher-resolution (1′) low-frequency images of the Galactic Plane, highly synergistic with the upcoming eROSITA observations.

PIs: Scott Croom (Usyd), Kirpal Nandra (MPE)
Australian Collaborators: Henry Poetrodjojo, SAMI team
eROSITA Collaborators: Andrea Merloni
Australian Surveys/Instruments: SAMI​​ 

Summary: This project aims to use the combined power of eROSITA and the SAMI integral field galaxy survey to further our understanding of the role of AGN in local galaxies.We will particularly focus on the nature of outflows driven by AGN and the excitation mechanisms in LINERS. To do this we will combine eFEDS eROSITA catalogues in the GAMA G09 region and SAMI emission line maps.

PIs: Nicholas Seymour (ICRAR/CURTIN), Andrea Merloni (MPE)
Australian Collaborators: Jess Broderick, Guillaume Drouart, Natasha Hurley-Walker, Ben Quici, Stas Shabala, Ross Turner, Vanessa Moss, Tim Galvin, Simon Driver, (Anna Kapinska)
eROSITA Collaborators: Mara Salvato, Kirpal Nandra, Andrea Meloni, Teng Liu, Riccardo Arcodia, Adam Malyali, Georg Lamer
Australian Surveys/Instruments: GLEAM Exgal DR1, GLEAM-X, GAMA, SWAG-X  (MWA, ASKAP)​​​ 

Summary: The 140 deg2 eFEDS survey reaches the approximate final depth of the all-sky eROSITA survey and is complemented in the radio by deep phase 2 data from the Murchison Widefield Array (MWA) as well as a dedicated early science survey with the Australian Square Kilometre Array Pathfinder (ASKAP). The federated radio to X-ray data for the eFEDS field makes it an ideal data set with which to study the interaction of radio jets with the cosmic microwave background (CMB) and the connection between accretion and jet processes on supermassive black holes. CMB photons become up scattered to high energies (UV -X-ray) by relativistic electrons from radio jets. We aim to study this process in both low redshift (z<0.3) remnant radio galaxies and also in very high redshift (z>5.5) radio galaxies where the effect is much stronger due to the greater intensity of the CMB. To study the accretion/jet connection in both radiatively efficient and inefficient modes we shall model the jet powers and ages of all identified radio-loud AGN in eFEDS using the broad-band radio data (0.07-1.6 GHz) and compare these with X-ray eROSITA AGN, ~8000 of which will have soon also SDSS spectroscopy. ​

PIs: Ray Norris (WSU/CASS), Thomas Reiprich (Bonn Uni)
Australian Collaborators: Gianni Bernardi, Gianfranco Brunetti, Rossella Cassano, Stefan Duchesne, Chiara Ferrari, Bill Forman, Melanie Johnston-Hollitt, Susannah Keel, Andrew O’Brien, Chris Riseley, Tiziana Venturi, Amanda Wilber
eROSITA Collaborators: Kaustuv Basu, Marcus Brueggen, Esra Bulbul, Klaus Dolag, Dominique Eckert,Thomas Erben, Vittorio Ghirardini, Duy Hoang, Florian Kaefer, Melih Kara, Juergen Kerp, Matthias Klein, Konstantinos Migkas, Naomi Ota, Florian
Australian Surveys/Instruments: ASKAP/EMU​​​​ 

Summary: We propose to carry out a combined radio/X-ray study of the Abell 3391/95 field. This includes, e.g.,(i) the connection between potential shocks identified in hot group and cluster gas and radio relics, (ii) the relation between potential turbulence in group and cluster gas as well as in the bridge of gas between the A3391/95 clusters and the potential co-spatial populations of (re-) accelerated relativistic particles, (iii) the interaction of wide angle tail (WAT) galaxies with warm/hot gas properties and their relative motions.The primary data sets are the eROSITA PV Phase observation as well as the ASKAP/EMUEarly Science observation of this field. ​

PIs: Marcus Brueggen (Hamburg Uni), Thomas Reiprich (Bonn Uni), Ray Norris (WSU)
Australian Collaborators: Larry Rudnick, Melanie Johnston-Hollitt, Bill Forman, Tiziana Venturi, A Hopkins, A Kapinska, B Koribalski, S Duchesne, M Brown, J Marvil
eROSITA Collaborators: Esra Bulbul, Mara Salvato, Jeremy Sanders, Kathrin Bockmann, Duy Hoang, Ang Liu, Florian Pacaud, A Veronica
Australian Surveys/Instruments: ASKAP/EMU​​​​​ 

Summary: We propose to study the radio properties of X-ray selected galaxy clusters. This includes studies of radio haloes, radio relics, tailed radio galaxies, as well as cluster central radio AGN and their correlation with morphological X-ray parameters. The X-ray and radio views of galaxy clusters are highly complementary, tracing the hot thermal and relativistic particle populations, respectively. ​

PIs: Christian Wolf (ANU), Arne Rau (MPE)
eROSITA Collaborators: Adam Malyali, Mara Salvato, Axel Schwope
Australian Surveys/Instruments: SkyMapper​​​​​​ 

Summary: The sensitivity and observing cadence of eROSITA will open a new window in to the X-ray transient and variable sky. One of the main challenges will be the rapid selection of the most interesting sources, e.g. Tidal Disruption Events and Fast X-ray Flares, from among the general population of variable X-ray sources dominated by AGN and stars. To address this, the eROSITA_DE transient follow-up will utilize its proprietary Target of Opportunity access to the GROND imager at the MPG 2.2m telescope at La Silla observatory. This instrument provides simultaneous optical/NIR imaging in 7-bands with a typical a typical delay of 24-48hr after the eROSITA detection.In order to identify and study the optical/NIR counterparts a sufficiently deep reference data set is needed. Here, we propose to use SkyMapper DR3 imaging data and source catalogs in the g,r,i, and z bands as reference sky for the GROND follow-up of eROSITA transients. The source catalog will allow to identify variable or new sources through comparison of the photometric measurements. Imaging data will be utilized for image subtraction, which is particularly important for nuclear transients such as Tidal Disruption Events.

PIs: Scott Croom (USYD), Kirpal Nandra (MPE)
Australian Collaborators: TBC
eROSITA Collaborators: Kirpal Nandra, David Bogensberger
Possible additional participants (eROSITA): Thomas Boller, Johannes Buchner, Tom Dwelly, Mirko Krumpe, Teng Lui, Adam Malyali, Andrea Merloni, Arne Rau, Mara Salvato.
Australian Surveys/Instruments: AAOmega ​​​​​​ 

Summary: We propose to seek spectroscopic monitoring using AAOmega of eROSITA-detected AGN in the South Ecliptic Pole (SEP). This is a unique region of the sky which, due to the eROSITA scan pattern, obtains intensive variability monitoring. The ~1 deg2 region at the pole itself is currently being covered once every four hours, and in principle this should continue throughout the entire 4 year period of the eROSITA All-Sky survey (eRASS). The resulting X-ray variability dataset is unique, but to exploit it fully requires optical spectroscopy for the identification and characterisation of the sources, determination of black hole masses, and joint spectroscopic variability monitoring. AAOmega provides the ideal complement to eROSITA, with its large field of view able to cover the most intensively monitored region in a single shot. Here we propose a joint program of X-ray and optical spectroscopic monitoring to investigate the relationship between the X-ray variability and fundamental parameters such as the black hole mass, accretion rate, and perhaps black hole spin. The eROSITA monitoring dataset will also likely reveal more dramatic variability such as “changing look” events, tidal disruption events (TDEs) and other transients, some of which may reveal new astrophysical phenomena. ​

PIs: Gavin Rowell (Uni Adelaide), Manami Sasaki (Universität Erlangen-Nürnberg​)
Australian Collaborators: Miroslav Filipovic, Sabrina Einecke, Katie Jameson, Sanja Lazarevic, Alison Mitchell
eROSITA Collaborators: Gerd Pühlhofer
Australian Surveys/Instruments: GLEAM ​​​​​​ 

Summary: With recent advances in γ-ray telescopes coupled with new radio and X-ray surveys, it is now finally possible to probe the origin of rare PeV Cosmic Rays (CR). The search for PeV CRs is a major legacy project for HESS and the CTA. To understand the TeV γ-ray images, we need to visualise the interstellar gas in 3D to create the model target material for CR collisions. The 3D picture will be built from the high-resolution surveys with the Mopra radio telescope, SGPS and GASKAP. Then, by modelling the propagation of CRs from their source into this gas and producing model γ-ray maps and spectra to compare with broadband data from radio to X-rays, we can infer the location of the CR accelerator and its age. To confidently identify the accelerator and its properties, we need eROSITA. X-ray results from eROSITA will provide crucial information on the competing γ-rays from electrons via the inverse Compton processes, as the X-rays constrain electrons and magnetic field properties of the accelerator via synchrotron emission.

PIs: Benjamin McKinley (Curtin), Jeremy Sanders (MPE​)
Australian Collaborators: Steven Tingay
eROSITA Collaborators: Thomas Reiprich, Kirpal Nandra
Australian Surveys/Instruments: MWA ​​​​​​ 

Summary: We anticipate that the wide field of view and increased sensitivity of eRosita will allow us to accurately map out the large-scale X-ray emission of Centaurus A. This will allow us to study the properties of the hot halo out to the thermalisation radius observed with the MWA and to more accurately constrain the properties of the AGN wind. Armed with the radio and X-ray properties of Centaurus A we will be able to determine a more accurate picture of the AGN feedback processes at work and compare our findings with observations of AGN at higher redshifts, where the intricate details that are observable in our nearest radio galaxy remain hidden.