SHAO Astrophysics Colloquia

Title: 3D Observations of Molecular Gas in Galaxies: From Global Dynamics to Supermassive Black Holes

Speaker: Professor Martin Bureau (Oxford)

Time: 3 PM, Apr. 13th (Thursday)

Abstract:

I will first briefly review the molecular gas content of early-type galaxies. I will show not only that they unexpectedly harbour much cold gas, but also that it is the best tracer of the circular

velocity, thus allowing accurate spatially-resolved dynamical mass measurements in galaxies across the Hubble sequence. Second, I will explore the use of molecular gas for studies of the Tully-Fisher (luminosity-rotational velocity) relation of galaxies to high redshifts. I will highlight the work done to establish local (z=0) benchmarks and will discuss the challenges posed by systematic effects when comparing nearby and distant galaxies. Third, I will demonstrate

that CO can be used to easily and accurately measure the mass of the supermassive black holes lurking at galaxy centres. I will discuss substantial ongoing efforts to do this and present many spectacular new ALMA measurements, that open the way to literaly hundreds of measurements across the Hubble sequence with a unique method. I will also hint at how the same data allow to study the spatially-resolved properties of giant molecular cloud populations in non-local galaxies

for the first time, providing a new tool to understand and contrast the star formation efficiency of galaxies on cloud scale.

Seminar talk

Title: How did our Galaxy form?

Speaker: James Binney (University of Oxford)
Time & Place: Tuesday, 3:00pm, April 11th, Lecture Hall, 3rd floor

 Abstract: Galaxies like are have continued through most of cosmic time to form stars in a thin disc that initially orbited in the gravitational field of a dark halo that formed  earlier. A huge amount can be learnt by modelling the accumulation of stars in the plane. Spiral instabilities and giant molecular clouds (GMCs) move stars to less circular orbits. The GMCs are most effective early on when the disc is low in mass and rich in gas. They establish an almost perfectly exponential vertical density profile. At some time a bar usually forms, but the timing of the bar depends on several factors, including the effectiveness of heating by GMCs. If the bar becomes strong, it buckles to form a peanut-bulge. Increasing the density of the dark halo delays/suppresses bar formation. For a halo density near that now measured locally & expected cosmologically, the model has components that closely resemble the thin disc and the bar/bulge. But there is no thick disc. A thick disc like the Galaxy's can be obtained by (i) starting the simulation with a thick stellar component, possibly formed in a major merger at z > 2, or (ii) allowing early stars to form with large random velocities. These models allow us to predict the distribution in phase-space of stars of every age, and the extent to which stars have migrated from their birth locations, which is key information for models of chemical evolution. Early indications are that generic models provide remarkably good fits to observations.

Group meetings

Black hole Accretion and High-energy Astrophysics /Black Hole Feedback and Cosmic Ray Astrophysics Seminar

Location: 1608

Time: 14:00-16:00, Wednesday(April 12th)

Speaker: Doosoo Yoon

Title: Unifying the Micro and Macro Properties of AGN Feeding and Feedback

http://adsabs.harvard.edu/abs/2017ApJ...837..149G

Speaker: Weixiao Wang

Title: Multiphase, non-spherical gas accretion on to a black hole

http://adsabs.harvard.edu/abs/2012MNRAS.424..728B

Visitors

Name: Prof. James Binney

Affiliation: University of Oxford, UK

Dates: 10th-12th April

Host: Martin C. Smith

Office: 1618