Thesis Topic: Dust in the Crab Nebula Supernova Remnant
Thesis Supervisor: Jeremy R. Walsh
Supernovae from massive stars (core collapse supernovae, or SN Types Ib, Ic and II) have long been considered to be a production source for interstellar dust. The observational detection of dust from supernovae is usually done by mid-infrared photometry and spectroscopy. Dust is detected in QSOs and galaxies formed within the first billion years after the Big Bang and it is assumed that the primary source of this dust is supernovae, but there is little proof.
The Crab Nebula supernova remnant, NGC 1952, is the remains of a massive star that underwent a supernova explosion in AD 1054 (see the HST image). It is one the closest (distance about 2 kpc) and most recent supernova remnants and provides a laboratory for a wealth of processes such as pulsar physics, synchrotron emission, shocked gas interactions and the role of magnetic fields. Dust features are observed in the Crab Nebula as absorption against the background emission nebula. If these features are formed from dust ejected from the supernova, then they can provide data to study dust production in a SN.
A thesis topic to study in detail the properties of the dust features in the Crab Nebula is outlined. There is a wealth of archival HST imaging in both emission lines and continuum, including linear polarimetry data, which awaits quantitative investigation. Outcomes of this study are expected to be: properties of the Crab Nebula dust (size distribution, shape, also composition); origin of the dust — ejected by the supernova explosion or swept-up interstellar (or circumstellar) dust; alignment mechanisms of dust grains; interaction of dust and magnetic fields.
As well as study of the dust, detailed analysis of the HST imaging and polarization data can bring new insights into a range of topics from the structure of the remnant (expansion and asymmetry), shock physics of ionized-neutral interfaces and magnetohydrodynamics. Follow-on observations with optical integral field spectrographs (ionized gas kinematics), polarizers (measurement of magnetic field strengths and detection of circular polarization from aligned dust grains) and infrared spectroscopy (H2 and dust emission) are an expected evolution of this project.