The exoctic chemical composition of giant stars discovered in the H-band of APOGEE

主讲人 (Speaker): 

Jose Fernandez-Trincado

主讲人单位 (Speaker's Institute): 

智利康塞普西翁大学

邀请人 (Invited by): 

汤柏添

时间 (Time): 

星期三, 2019/01/02 - 15:00 to 16:00

地点 (Location): 

珠海校区海滨红楼17栋107 (Rm 107, Red House 17)

摘要 (Abstract): 

        APOGEE contains more than hundred thousands new giant stars. This enabled us to collected an unprecedented and homogeneous sample of giant stars with light-element abundance variations similar to observed in “second-generation” globular cluster stars. If they are really former members of dissolved globular clusters, stars in these groups should show some of the basic SG-like chemical patterns known for stars currently belonging to the Milky Way globular clusters, such as depletion in C and O together with N and Al enrichments. Here, I will present the results of an updated census of SG-like stars from a near-infrared manual analysis using the Brussels Automatic Stellar Parameter (BACCHUS) code to provide the abundances of C, N, O, Mg, Si, Al, Fe, Ce and Nd for every line of possible cluster member stars, which they migrate to the disk, halo and bulge as unbound stars, and become part of the general stellar population of the Milky Way. By combining wide-field time-series photometry with APOGEE-2S spectroscopy data, we are in a good position to put the big picture together. The VVV survey have produced a large variability dataset towards the Milky Way bulge and disk, including data in the near-IR (J and Ks). These data will allow us to place constraints on the “polluters" that are responsible for the chemical peculiarities, with candidates including TP-AGB stars, binary mass transfer, accretion of material from the winds of AGB stars, etc.  A cross match between VVV sources and APOGEE targets is ongoing.

主讲人简介 (Speaker's CV): 

Research expertise:Galactic dynamics: I developed the galaxy modelling algorithm called GravPot16 (web service: https://gravpot.utinam.cnrs.fr), which is designed to make a new dynamical model of the Milky Way for the orbital interpretation of future releases of the Gaia data. Numerical simulations: I have built particle simulations (~100 million particles) of multiple disk components evolved in a 3-D steady-state potential model of the Milky Way in order to infer the kinematics and orbital properties of the barred Milky Way galaxy, as well as constraining the structural parameters of the rotating-Galactic bar and spiral arms, with an emphasis on the interpretation of data from the European Space Agency’s Gaia mission along with other complimentary spectroscopic survey data like APOGEE. Data mining: Applying statistical methods on large astronomical datasets, creating mock surveys with GravPot16+Besancon galaxy model; Model comparison and structure finding. Stellar abundances: Characterization and discovery of absorptions lines associated with s?process elements (Ce II and Nd II) in H -band spectra (1.51 - 1.69 μm); line-by-line spectrum synthesis calculations for the full set of (atomic and molecular) lines of APOGEE spectra using the Brussels Automatic Stellar Parameter (BACCHUS) code and iSpec (for optical spectra). Further interests: constraints of the astrophysical sources that led to the unusual abundance patterns in the Milky Way field; multiple stellar population in metal-rich stellar clusters; integral- field spectroscopy; chemo-dynamics models of the Milky Way; variable stars as tracers of halo?substructures around globular clusters; understand the origin of the moving groups from dynamical models.