Dr Julian Pittard
- Position: Reader in Theoretical Astrophysics
- Areas of expertise: colliding stellar winds; computational fluid dynamics; dynamics of the interstellar medium; physics of shocks and mass-loaded flows; star formation; stellar feedback.
- Email: J.M.Pittard@leeds.ac.uk
- Phone: +44(0)113 343 3805
- Location: 9.82 EC Stoner
- Website: Personal home page | Astrophysics research group | Googlescholar | Researchgate | ORCID
- Postgraduate Research Tutor
My research focuses on the impact that massive stars have on their surrounding environment (stellar feedback), and how this affects the dynamics and structure of the interstellar medium (ISM). Massive stars return most of their mass to the ISM during their lives and final death throes. The expelled material, in the form of stellar winds, eruptions and explosions, sweeps up and compresses interstellar material, and drives turbulence in the ISM. Large groups of massive stars can significantly affect galaxy evolution: in dwarf galaxies starburst-driven galactic winds can completely expel the ISM. On more local scales, stellar feedback has the potential to enhance star formation (via triggering), though perhaps more often disrupts it.
I use advanced computational techniques and numerical codes to simulate many aspects of this stellar feedback. On the smallest scales I simulate the interaction of stellar winds in massive binary star systems. Each wind acts as an in-situ probe of the other, and can reveal fascinating details about the process of mass-loss from high mass stars and the physics of high mach number shocks (e.g. post-shock equilibration, particle acceleration and dust formation). I also study the way that astrophysical flows interact with a clumpy environment. The interstellar and circumstellar gas around stars is far from homogeneous and contains dense clumps of gas embedded in a lower density medium. The details of the interaction have consequences for the evolution of many astrophysical sources, including wind-blown bubbles, supernova remnants, and starburst superwinds. The mixing of material stripped from clumps into the background flow is a key issue which is not well understood at present. I have also used 3D simulations to study the effect that massive star winds and their supernova explosions have on the gaseous material remaining in the stellar nursery in which they form. This work showed that both forms of feedback, and the SN explosion in particular, may couple inefficiently to the surrounding medium. However, we are far from fully understanding this process.
- PhD (Physics), 2000, The University of Birmingham, UK
- BSc (Class I, Hons), Physics with Astrophysics, 1994, The University of Birmingham, UK
- International Astronomical Union