Colloquia

Talks given by high profile astronomers and scientists.


Video
Thursday October 9, 2014
Dr. Eva Grebel
Director Astronomisches Rechen-Institut Zentrum für Astronomie der Universität Heidelberg

Abstract

Dwarf galaxies are the most common type of galaxy in the Universe andinclude the most dark-matter-dominated objects known. They offerintriguing insights into evolutionary processes at low halo masses and low metallicities. Moreover, as survivors of a once much more numerous population of building blocks of larger galaxies, they are key to understanding very early star formation processes. The Local Group and particularly the Milky Way's dwarf galaxy entourage offer us the unique possibility to compare in detail dwarf and Galactic populations. This is an important step towards quantifying the magnitude and time scales of dwarf contributions to the build-up of the Milky Way and allows us to test predictions of cosmological theories and hierarchical structure formation.


Video
Thursday March 27, 2014
Prof. John Houghton
Univ. of Oxford

Abstract

Because of the carbon dioxide emissions from fossil fuel burning, the Earth's atmosphere and oceans are warming through what is known as the "greenhouse effect". Big changes are on their way which we have not yet seen because of the time taken for the oceans to warm. It is essential that human communities prepare to adapt to these changes e.g. in sea level rise, severe heat waves, and a greater frequency of climate extremes.

The challenge to scientists is to learn enough about the complexities of the world's climate system to be able to project the climate's likely future.

The nations and peoples of the world need to recognise the urgency of the many actions that can - and must be taken.


Video
Thursday June 27, 2013
Dr. Didier Queloz
Geneva Observatory, Astronomy Department, University of Geneva

Abstract

The discovery of new planets beyond our solar system, in particular the detection and characterization of other habitable planets similar to the Earth, is a fascinating intellectual adventure. The completely unexpected characteristics of exoplanets are capturing the imagination and interest of the scientific community and the general public. More recently the large population of Super-Earth planet questions the universality of our Solar System as a typical planetary system. While the quest to find bodies similar to the Earth is still on going, the first spectra of exoplanets have been taken, signaling the shift from an era of discovery to one of physical and chemical characterization. This talk will provide an overview of current outcomes of planet programs as well as its limitation and prospects to move forward.


Video
Thursday February 21, 2013
Prof. Sally Oey
University of Michigan

Abstract

The fate of ionizing radiation from massive stars has fundamental consequences on scales ranging from the physics of circumstellar disks to the ionization state of the entire universe. On galactic scales, the radiative feedback from massive stars is a major driver for the energetics and phase balance of the interstellar medium in star-forming galaxies. While even starburst galaxies appear to be largely optically thick in the Lyman continuum, ionization-parameter mapping shows that significant populations of HII regions within galaxies are optically thin, powering the diffuse, warm ionized medium. I will discuss our multi-faceted work to clarify our understanding of radiative feedback in star-forming galaxies from the Magellanic Clouds to starbursts.


Video
Thursday January 10, 2013
Prof. Eric Priest
St Andrews University

Abstract

This talk will give an overview of our understanding of the Sun in the 1960's, the major discoveries since then, and the main questions that need to be answered in future. It will focus on the role of the magnetic field in the solar interior, the photosphere, prominences, coronal heating and eruptive flares.


Video
Thursday October 25, 2012
Prof. Monica M. Grady
Open University, Milton Keynes, UK

Abstract

Traditionally, astronomers study stars and planets by telescope. But we can also learn about them by using a microscope – through studying meteorites. From meteorites, we can learn about the processes and materials that shaped the Solar System and our planet. Tiny grains within meteorites have come from other stars, giving information about the stellar neighbourhood in which the Sun was born.

Meteorites are fragments of ancient material, natural objects that survive their fall to Earth from space. Some are metallic, but most are made of stone. They are the oldest objects that we have for study. Almost all meteorites are fragments from asteroids, and were formed at the birth of the Solar System, approximately 4570 million years ago. They show a compositional variation that spans a whole range of planetary materials, from completely unmelted and unfractionated stony chondrites to highly fractionated and differentiated iron meteorites. Meteorites, and components within them, carry records of all stages of Solar System history. There are also meteorites from the Moon and from Mars that give us insights to how these bodies have formed and evolved.

In her lecture, Monica will describe how the microscope is another tool that can be employed to trace stellar and planetary processes.


Video
Thursday June 21, 2012
Prof. Françoise Combes
Observatoire de Paris, LERMA. France

Abstract

I will review some recent results about the molecular content of galaxies and its dynamics, obtained from CO lines, dense tracers (HCN,HCO+), or the dust continuum emission. New data to constrain the conversion factor XCO will be discussed. The molecular surface density is essential to determine the star formation efficiency in galaxies, and the resolved Kennicutt-Schmidt law will be presented as a function of surface density and galaxy type. Large progress has been made on galaxy at moderate and high redshifts, allowing to interprete the star formation history and star formation efficiency as a function of gas content, or galaxy evolution. In massive galaxies, the gas fraction was higher in the past, and galaxy disks were more unstable and more turbulent. ALMA observations will allow the study of more normal galaxies at high z with higher spatial resolution and sensitivity.


Video
Thursday April 26, 2012
Prof. Luis C. Ho
The Observatories of the Carnegie Institution for Science, USA

Abstract

Supermassive black holes are ubiquitous in galaxies and play a fundamental role in their life cycle. I will review observational progress in defining and refining the various empirical scaling relations between black hole masses and host galaxy properties. I will emphasize ways in which the intrinsic scatter of the scaling relations can be quantified, and present evidence that the scatter correlates with physical properties. I will describe how the scaling relations can be extended to active galaxies and summarize preliminary efforts to probe the evolution of these scaling relations with redshift. I will present new measurements of the cold ISM content in AGN host galaxies and constraints they place on currently popular models of AGN feedback. Lastly, I will discuss a new class of low-mass black holes in bulgeless and dwarf galaxies that serve as local analogs of seed supermassive black holes.


Video
Thursday February 16, 2012
Dr. Daniel Eisenstein
SLOAN Digital Sky Survey, CfA Harvard, USA

Abstract

I will discuss how the acoustic oscillations that propagate in the photon-baryon fluid during the first million years of the Universe provide a robust method for measuring the cosmological distance scale. The distance that the sound can travel can be computed to high precision and creates a signature in the late-time clustering of matter that serves as a standard ruler. Galaxy clustering results from the Sloan Digital Sky Survey reveal this feature, giving a geometric distance to a redshift of 0.3 and an accurate measurement of Omega_matter. I will review our recent work on the theory and practice of the acoustic oscillation method and our latest cosmology results from SDSS-II. I will then present SDSS-III, which will use the acoustic method to produce 1% distance measurements in order to map the curvature and expansion history of the Universe and measure the evolution of dark energy.


Video
Thursday January 19, 2012
Dr. Stan Owocki
Bartol Research Institute, University of Delaware, USA

Abstract

Massive stars lose mass through powerful, radiatively driven stellar winds. Building on the original "CAK" model for steady, spherical winds driven by line-scattering, this talk will review recent research on the multi-faceted nature of such wind mass loss under varied conditions, for example due to rapid rotation, magnetic channeling, binary interaction, or a luminosity near the Eddington limit. An overall theme is that wind mass loss can in this way lead to a wide variety of astrophysical phenomena, including bipolar nebulae, massive star magnetospheres, colliding winds or compact companion accretion, and luminous blue variable eruption. The discussion here will summarize these with an emphasis on their varied observational signatures.



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