If we wish to understand the formation and evolution of galaxies, we must also understand the star formation history of the universe, as summarised in the Madau Plot. Currently the errors in the techniques used to establish this plot are very poorly understood, and are frequently ignored altogether. I will review these observational techniques, and examine the state of art of theoretical modelling of starburst galaxies with particular emphasis on the importance of the gas-phase physics in determining the form of the line and continuum SED. I will show, from a theoretical viewpoint, how reliable the star formation indicators may be, and to what galaxian interstellar physics they are sensitive.
It is widely recognized today that the stellar record contains a great deal of fossil information about the early history of the Galaxy. We examine the prospect of identifying the stars that were born with the Sun -- the Solar Family. If we could identify a statistically useful sample, we would learn a great deal about the Solar Protocloud. Furthermore, in our search for these stars, we will be able to reassemble a vast number of star groups that have long since dissolved into the general disk.
The formation of structure and galaxies throughout the Universe is the driving force behind billion-dollar technological developments such as the Square Kilometer Array, the James Webb Space Telescope, and Extremely Large (ground-based) Telescopes. The underlying computational and theoretical efforts associated with these projects - in which Australia has vested financial interests - are driven primarily (and unfortunately) by our "offshore" colleagues. During the course of this talk, I will highlight a number of the key unanswered scientific questions driving Australia's participation in these (and several other) big international projects. I will then describe the progress that our Computational Cosmology Initiative has made in establishing an Australian presence in this most most marketable of astronomy's disciplines. Included in these highlights will be: simulating the first objects in the universe, the near-field cosmological structure of the Milky Way, alternative theories of gravity, the role of AGN feedback in shaping elliptical galaxies, and cosmic star formation as viewed by the SKA.
Conventional wisdom states that high-redshift QSOs live in protoclusters. We show one z=2.16 QSO for which the reverse seems to be true - there is a marked deficit of both neutral hydrogen and lyman-alpha emitting galaxies within a Mega-parsec of it. We hypothesize that the immense UV luminosity of this QSO is photo-evaporating the gas out of small dark matter halos in its environment.
A new model of a luminous (>10^46 ergs/s) ourburst of a radio jet inside a host galaxy and potential shows a detailed x-ray and radio evolutionary sequence. Distinct phases of development are identified, and a general evolutionary sequence for powerful radio sources is outlined.
Accretion disks are responsible for the generation of radiation and meachanical power output from Active Galaxies and Galactic compact objects. Since the classic paper of Shakura and Sunyaev, and despite the increasing awareness of the importance of magnetic fields (as a result of the work by Balbus, Hawley, Stone and colleagues) little has been done to incorporate magnetic field physics in a systematic way into an analytic description of accretion disks. Zdenka Kuncic and I have recently provided such a description, which shows how a turbulent magnetic field dramatically affects the flow of energy. In particular, we show if the ratio of coronal Alfven speed to Keplerian speed is of order unity, then energetically significant winds and Poynting flux into the corona occur. However, a significant change to the energy budget could occur when this parameter is much less then unity. When a large amount of energy is channeled into the corona and winds, the radiative output of the disk is fundamentally altered. An intriguing result is that the azimuthal-vertical component of the magnetic stress will have an important effct on the energy budget when it is of order 1% of the radial-azimuthal stress, which is usually assumed to be the most important stress in accretion discs.
I will present results of numerical simulations on the evolution of star formation rates and accretion rates on super massive black holes in early-type galaxies (E/S0s) formed by gas-rich galaxy merging. I will discuss (1) evolutionary links between nuclear starbursts and AGN formation, (2) stellar populations of QSO host galaxies, and (3) the growth processes of super massive black holes in E/S0s. ~
The FIR-RC correlation is one of the tightest, but also one of the most puzzling corelations in extragalactic astronomy. Its clearly driven by star-formation but why is it so tight? I will descibe new observations of the related CO-RC correlation based on BIMA & VLA data. These may hint at possible explanations, but they also add new twists. I will discuss (as you might expect) some less conventional possibilities.
Radio galaxies are the most massive and powerful objects at any redshift out to z~5. Observations of these monsters are revealing extensive and massive star formation as revealed by optical, radio, and sub-millimetre telescopes and it is indeed beginning to look like we are probing the formation epoch of their host galaxies; confirming the predictions of astrophysicists some 40 years ago. Very recently, we detected ~10^11 solar masses of molecular gas from the highest redshift radio galaxy known to date at z=5.2. In this talk I will present these results and discuss their significance in the wider context of galaxy formation and evolution scenarios.
The FIR-radio correlation is a global property of galaxies which has been difficult to examine locally within galaxies due to the poor angular resolution of IRAS. The proximity of the Magellanic Clouds make them ideal targets to undertake such a study, and we show some results from an ongoing project to compare LMC images across a range of scales. These include a variety of gas and star formation tracers including IR, H-alpha, HI, CO, and radio continuum. We show that the FIR-radio correlation is remarkably tight even down to scales as small as ~50 pc.
Millisecond pulsars (MSPs) are extremely good clocks. Observations of an array of MSPs widely distributed on the sky can be used to investigate the stability of terrestrial time standards and to detect perturbations of the Earth's motion relative to the predictions of Solar System ephemerides. The principal sources of such perturbations are errors in the ephemerides and gravity waves passing over the Earth. In a collaborative effort with Swinburne University and Caltech, we have commenced a program of regular timing observations of ~15 MSPs using the Parkes 64-m radio telescope. For most of these pulsars we can obtain pulse times of arrival with a precision of better than one microsecond at intervals of 2 - 3 weeks. With a 5-year data span, these observations have the potential to detect the stochastic gravitational-wave background expected from a population of supermassive binary black holes in the cores of galaxies.
Giant ground based laser interferometer gravitational wave (GW) detectors are nearing their design sensitivities. The first space based GW antenna is planned to be launched in about 2011. I will summarise the status of these instruments, what has been achieved to date and what needs to be done to initiate GW astronomy.
I will review the nature and the predicted/conjectured astrophysical sources of gravitational waves. In the second half of the talk, I will show how gravitational waves from rapidly spinning neutron stars, if observed, will provide a unique probe of the neutron-star internal structure.
Binary Pulsar B1913+16 is part of a highly relativistic double neutron star system. I describe the latest results of timing and pulse profile measurements. The general relativistic prediction for orbital decay due to gravitational wave emission is consistent with the observed orbital period change, at the 0.2 percent level. In addition, relativistic spin-orbit coupling has precessed the pulsar beam across the line of sight, revealing the two-dimensional beam structure.
The precision required to detect the stochastic gravitational wave background using pulsar timing pushes the bounds of terrestrial time standards. I will review the state of the art in high-precision time-keeping, and describe how pulse times of arrival are referred to the most accurate clock on Earth. I will then discuss how the rotation of pulsars themselves can be harnessed as the most accurate clock in the Universe.
For years astronomers have known that the centers of giant galaxies, built through the collision and merger of lesser galaxies, appear partially depleted of stars. This absence is thought to be a result of the wrecking ball action of supermassive black holes --- from the progenitor galaxies --- as they sink to the center of the newly formed galaxy. A new analysis of Hubble Space Telescope data not only supports this scenario, but reveals that the galactic merger history of the Universe is some ten times less violent than previously thought.
Intermediate-mass black holes (IMBHs; masses ~ 100 - 1000 solar) have been suggested as a possible explanation for Ultraluminous X-ray sources (ie, point-like accreting sources with X-ray luminosities ~ 10^40 erg/s), recently discovered in many star-forming galaxies. The formation process is still unclear. For the larger galaxies, IMBHs could have come from the accreted nuclei of smaller satellite galaxies. Instead, IMBHs in very late-type disk galaxies (Scd, Sm, Im) would be more likely to have been formed in situ. Nuclear star clusters may be a suitable location for the formation of such IMBHs in late-type, bulgeless galaxies. Determining whether these nuclear clusters contain an IMBH will provide a test for various astrophysical scenarios: for example, it will test the Magorrian/Ferrarese relations between dark matter, galactic bulge and BH mass. In merger scenarios, nuclear star clusters (with or without an IMBH) have also been suggested as progenitors of some peculiar, massive globular clusters (eg Omega Cen).
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Updated Fri Nov 19 2004