Research

Astrophysics

The Plasma Astrophysics group at the NCPST is concerned with two primary areas of research:- star formation and galaxy formation and evolution. We also have some interests in high energy astrophysics.

In the area of star formation we concentrate on the study of outflows from forming stars. These outflows are generally accepted to be critical to the process of star formation. They are thought to drain away angular momentum from the material orbiting the star, thereby allowing gravity to overcome the centrifugal force and pull material onto itself. This ultimately leads to a build up of pressure and density in the core of the star leading to nuclear fusion and the birth of the star. The physics involved in the process of forming the outflows is extremely complex and requires computational simulations. We use supercomputers to perform simulations of these systems to learn more about how the outflows, and hence the stars themselves, are formed.

In the area of galaxy formation and evolution, we are undertaking a project to study massive stars in distant galaxies. The most distant galaxies we can observe are small and very active. They produce stars at a prodigious rate and expel hot gas into the surrounding medium in giant outflows called superwinds. The effect superwinds have on the evolution of galaxies is rather important. With an analysis of the kinematics and dynamics of this outward moving gas observationally, in combination with numerical modeling of the interaction of this gas with neighbouring galactic winds, we aim to answer the question, 'Could gas outflows from galaxies formed in the early universe have had a significant effect on the process of subsequent galaxy evolution' Ultimately, we aim to understand the contribution of galactic outflows on the process of galaxy formation, which is a fundamental problem in Observational Cosmology.

We also work on simulations of the acceleration of particles at shocks. These particles can be of very high energy and some of them can be seen at earth and are referred to as cosmic rays. These cosmic rays are a health risk for astronauts and air crew. While the creation of most cosmic rays is well understood, how the highest energy cosmic rays are produced remains a mystery, although it is thought they may be produced at shocks. We use computer simulations to couple the models for cosmic ray production with the dynamics of shocks in order to see what conditions are necessary to produce the high energy particles.

For further information visit www.astrophysics.dcu.ie

List of projects within programme

Current

Redshift Survey of Lensed Galaxies
JETSET - EU FP6 Network with 11 EU institutions
Cosmo Grid - HEA PTRLI 3 with DIAS, UCD, Grid Ireland, Met Eireann, Armagh Obs
High Energy Astrophysics - Ulysses Grant with CESR Toulouse
The Stability of rotating stellar jets
Gamma Ray Bursts: Echelle spectroscopy and monitoring with the Robotic Eye Mount telescope; - SFI/RFP
Origin of runaway stars
Advanced evolutionary stages of massive stars
Studies of the B[e] phenomenon
High energy population synthesis simulations of starburst regions
Gamma Ray Burst observations with the Swift satellite

Proposed

Primeval Galactic Winds
Stekkar Jet launching - beyond the flux freezing approximation (RFP 06) w/ Brenda Frye
Archival X-ray data analysis of extragalactic sources
Wolf-Rayet galaxies
Gamma Ray Burst progenitors

Technical Outline

During star formation, large scale jets are launched into the surrounding medium. These jets remove angular momentum from the accretion disk surrounding the forming star, allowing material to fall inwards - a process crucial to star formation itself.

As an example of an ongoing project, jet launching is studied using a novel computational method designed for problems of this type recently developed by members of the group and collaborators from UCD. For the first time it will be possible to incorporate multifluid physics known to be critically important to jet launching into large-scale simulations. We will be able to study this process more reliably than heretofore and, consequently, will learn more about how stars form.

One of our most recent projects in observational Cosmology makes use of the Spitzer Space Telescope and investigates the impact of galaxy outflows on over dense regions of the universe and the origin of the intra-cluster medium (ICM). With this programme we are undertaking a systematic investigation of the connection between star formation in star bursting galaxies and the production of the metal enriched ICM by combining archival Hubble Space Telescope Advanced Camera for Surveys (ACS) and Spitzer Space Telescope observations of clusters at redshifts z>0.8 and proto-clusters at z>2.0. Although the metal-enriched ICM is largely in place by z~1, comparison of Spitzer infrared fluxes and colors with ACS images of the highly resolved late-type galaxies in the halos of these clusters will enable us to study in detail the processes that are similar to those that must have occurred at higher redshifts. We will establish the dominant mechanism for mass injection from star forming galaxies by combining evidence for thermal emission from dust with large scale features that could arise from either stripping of a galaxy halo, or, more likely, mass injection via supernova-heated winds. Such galactic-scale winds are unique for enabling in certain cases the efficient transport of dust into the ICM. We will also measure the dust content of the ICM transported by such galactic winds, and establish the viability of using it as a litmus test for galactic wind activity. With this work, we aim to understand the role of star formation feedback and loss by galactic winds in the general case of galaxy evolution, an outstanding problem in observational cosmology.

The educational outputs are manyfold. This research is of direct relevance to the astronomical community, and also to undergraduate and Ph. D. students.