Tidal Dwarf Galaxies as Laboratories for Understanding the Origins of Star Formation

One of the fundamental challenges of modern astrophysics is understanding the physical mechanisms that trigger and regulate star formation. A key outstanding question is the role and the relative importance of the environment, including gas dynamics and magnetic fields, in this process that transforms gas into stars.

Tidal Dwarf Galaxies are thought to form from gravitationally bound condensations of gas and stars that were torn out from their parent galaxy by tidal forces during galaxy interactions.
This makes them ideal laboratories to study the physics of star formation in extreme environments, fundamental in order to understand how stars formed during the early days of the Universe, where galaxy collisions were more frequent than today.

In year 1 of the PhD we will begin by extending a groundbreaking study ('ALMA Resolves Giant Molecular Clouds in a Tidal Dwarf Galaxy' Querejeta et al. 2021 https://doi.org/10.1051/0004-6361/202038955) of the archetypal TDG J1023+1954 in the interacting system Arp 94. We will use data from the Jansky Very Large Array (from 1.4 to 22 GHz) to search for and image radio continuum emission in this galaxy. This will allow us to trace the history of star formation across the TDG, search for radio signatures of relic star formation, and determine the distribution and magnitude of polarization of the radio emission, to map the magnetic field that may be threaded through the gas.

To process the JVLA dataset using CASA, (Common Astronomy Software Applications) it is expected to visit the Manchester University ALMA node. Due to Covid 19 restrictions, the exact date is not confirmed yet.

In subsequent years we will perform a substantial ALMA survey of dense molecular gas for a sample of 10 further TDGs, which will enable us to put J1023+1954 into a wider context and to compare its properties with larger, Milky Way type spiral galaxies.

Using existing archival ALMA 12 m telescope observations, we will aim to characterize the fraction of diffuse gas in this sample and, in parallel, we will apply to use the ALMA Compact Array to observe its molecular gas. The submission of the proposal to use the Atacama Large Millimeter Array is set in April 2022, for which it is expected winning time will be straightforward.

Professor Carole Mundell will be the primary supervisor in Bath, and Professor Cathryn Mitchell will be the second supervisor. In addition, two external supervisors, Dr Ute Lisenfeld (University of Granada, Spain) and Dr Miguel Querejeta (Observatorio Astronómico Nacional, Madrid) will form part of the project. They are experts in multi-wavelength astronomy and galaxy studies, with particular knowledge of radio interferometry at cm and mm wavebands and the study of the multi-phase gas in galaxies, central topics in this PhD project. There will also be an opportunity to work with a wider collaboration network that includes academics at Max-Planck Institute (Heidelberg, Germany), the European Southern Observatory (Munich, Germany) and the University of Cardiff.