5/12-5/16

SHAO Astrophysics Colloquia

Title: Gaseous Substructures of Spiral Arms in Disk Galaxies

Speaker: Woong-Tae Kim (Seoul National University)

Time: Thursday, 3:00pm, May 15th

Location: Lecture Hall, 3rd floor

Abstract:

    Spiral arms are abound with secondary structures such as young stellar complexes, giant clouds, and spurs/feathers, all in close geometrical association with shocked dust lanes. Despite observational and theoretical efforts during the past 15 years, what forms these secondary structures has still remained uncertain. In particular, do they require the presence of self-gravity or do they originate from non-gravitating hydrodynamic processes? In this talk, I will review the physical mechanisms proposed so far for the formation of the secondary structures, and report our resent work on the hydrodynamic instability of spiral shocks

Seminar talk  

Title: Asteroseismology for Galactic Archaeology - Bridging two fields
Speaker: Luca Casagrande, Australian National University

Time & Place: Wednesday, 3pm, May 14th, Middle conference room

Abstract:

    Homogeneous and accurate stellar parameters are vital for a number of purposes in stellar and Galactic astronomy. While different photometric and spectroscopic methods exist to translate stellar observables into physical parameters, each one of those comes with its pros and cons. Photometry provides a relatively cheap -yet powerful- way to gauge into those uncertainties. I briefly review different photometric methods and highlight the importance of correctly translate magnitudes into physical fluxes. Further, when photometric stellar parameters are coupled with asteroseismology, new and interesting twists become possible. I present results from the ongoing SAGA survey (Str?mgren for Asteroseismology and Galactic Archaeology), which currently includes photometry for over 20,000 stars in the Kepler field, 1000 of which are red giants with seismic information. Coupling Str?mgren metallicities with the Infrared Flux Method, and the unique asteroseismic determination of stellar masses and radii, powerful new diagnostics for Galactic studies are obtained. Using this sample I discuss the age and metallicity gradients in the Galactic disc and the impact of our results for understanding some of the processes relevant in its formation.

Group seminars

Blackhole accretion theory and High-energy astrophysics Seminar

Location: 1608; Contact: Qixiang Yang < qxyang@shao.ac.cn> 

Visitors  

Name: Luca Casagrande (ANU, Australia)

Dates: 14/05-16/05

Office: 1619

Research Interests: Galactic Archaeology, stellar parameters, Stromgren photometry, asteroseismology