Astrophysics Research

The research interests of the group run from X-ray to radio wavebands, and cover galactic, extragalactic, and cosmological subjects.

Galaxies and cosmology

In optical astronomy we are studying galaxy populations and their evolution using surveys of nearby galaxies to look for previously undetected low surface brightness and compact galaxies, and observations of more distant clusters and groups to look for evidence of the evolution of their galaxy content. The Fornax Spectroscopic Survey uses the 2dF multi-object spectrograph on the Anglo-Australian Telescope to measure redshifts for complete samples of objects detected in the direction of the Fornax Cluster, while the Bristol - Anglo-Australian Observatory Virgo Cluster Survey is finding and studying large numbers of very low luminosity galaxies (Phillipps, Huxor, Smith, Robotham, Price, Summers).

Other survey work concentrates on the highest redshift galaxies, thus exploring the first structures that formed in the universe and the `epoch of reionization', the era when photons from the first generations of stars and quasars ionized the universe (Bremer, Stanway, Douglas, Winkworth, Davies).

Active galaxies

A number of group members are involved in the study of active galactic nuclei (AGN), particularly radio galaxies, using radio, infra-red, optical, and X-ray techniques (Worrall, Birkinshaw, Young, Dulwich, Bliss). Interests include the environments and dynamics of radio sources, unified models for both high-power and low-power objects, observation and modelling of jets and the X-ray/radio relationship in radio galaxies and quasars. Instruments used by the group include the VLA, the VLBA, MERLIN, the ATCA, BIMA, ISO, the HST, ROSAT, ASCA, XMM and Chandra.

Active galaxies can also be used as cosmological probes. Powerful radio sources are markers of massive structures (clusters of galaxies); by observing them at high redshift we can find massive structures in the early universe, which allows us to test models of structure formation, a key goal of cosmology. Once these structures are found, multi-waveband observations are being used to determine key parameters such as mass, dynamical state and baryon content. Radio observations (e.g. of the Sunyaev-Zel'dovich effect), optical (peculiar velocities, weak lensing) and X-ray observations (measurement of the hot intracluster plasma properties) all contribute to these studies. (Birkinshaw, Bremer, Worrall, Maughan, Lancaster).

Black holes

Black holes have a profound impact on their environment. Gas falling towards a super-massive black hole can produce tremendous quantities of radiation (often outshining an entire galaxy), and can also produce very high velocity outflows such as relativistic jets. The feedback between inflowing gas and outflowing jets and radiation plays an important role in regulating structure (e.g. galaxy and galaxy cluster) formation and evolution. We study the environment immediately surrounding black holes using space-based X-ray observatories (including Chandra and Suzaku), in addition to observations at other wavelengths. X-ray spectroscopy of gas deep in the potential well of the black hole, where the effects of strong gravity are important, allows us to probe the properties of the black hole itself. (Young).

Microwave background radiation

Studies of the cosmic microwave background radiation revolve about the use of the Sunyaev-Zel'dovich (SZ) effect as a cosmological probe. We are involved with two new SZ experiments: the One Centimetre Receiver Array (OCRA) and the Array for Microwave Background Anisotropy (AMiBA). Both instruments will ultimately perform blind surveys for galaxy clusters and in the interim are observing clusters known from X-ray and optical surveys in order to constrain physical models of the cluster atmospheres. We are also investigating other structures induced on the background radiation by relatively local (within a few Gpc) astrophysical phenomena, such as effects due to the propagation of the CMB through changing gravitational fields. (Birkinshaw, Lancaster, Alareedh, Talaganis).

Cooling flows

Such rich clusters of galaxies often contain cooling flows, in which the high-density hot gas trapped in the centre of the cluster is thought to cool rapidly, allowing slow inflow of material. This gives rise to strong X-ray emission in the centres of clusters which is easily detected. However, evidence for the cooled material in other wavebands has been difficult to find, requiring the use of new instrumentation, larger telescopes and novel techniques. We are carrying out detailed study of this gas in the optical and IR with the new generation of 8-m telescopes. (Bremer).

Plasma processes

Many of the observable properties of active galaxies are related to plasma processes in the sources, and this relates closely to terrestrial fusion plasma physics. Work in the group on particle acceleration and radiation has led to collaborations with the UKAEA fusion physics research group at Culham (Birkinshaw, James, Moon, Newton).

Galactic line emission

Research on the photo-excited component of the interstellar medium, continues through our (Masheder, Phillipps, Morris) involvement with the international southern H-alpha survey of the Galactic plane and some other important Galactic and extragalactic regions, using observations taken with the UK Schmidt Telescope at the Anglo-Australian Observatory, and the northern equivalent, called IPHAS, carried out with the Isaac Newton Telescope on La Palma There is a separate page on H-alpha research here.

Coldrick Observatory

The telescopes of the Coldrick Observatory will be used for research (including studies of masers and AGN) when they are fully commissioned.