Santi Cassisi (INAF-Teramo), Scilla Degl'Innocenti (Università di Pisa/INFN)
9/18/17, 9:15 AM
Sebastian L. Hidalgo (Observatoire de la Côte d'Azur)
9/18/17, 9:30 AM
We present an overview of the Local Group dwarfs and specifically, about the satellites of the Milky Way (MW) and the role played on its formation. Although there is observational evidence that the MW has affected the evolution of some dwarf galaxies, the role played by dwarf galaxies on the built of the MW's halo and disk is still on debate. The star formation histories and chemical...
Vanessa Hill (Université de la Côte d'Azur)
9/18/17, 10:00 AM
We report on the abundance of 31 neutron-capture elements (including Thorium and Uranium) in the highly r-process-enhanced metal-poor giant CS~29497-004 (Hill et al. 2016, arXiv:1608.07463). Combining the various elemental chronometer pairs that are available for this star, and different theoretical yields for the r-process (Waiting-Point approximation, High Entropy Wind models), we derive...
Aaron Dotter (Harvard-Smithsonian Center for Astrophysics)
9/18/17, 11:00 AM
The early formation history of the Milky Way is preserved in its old, metal-poor stellar populations. The detailed chemical compositions of these stars differ considerably from the solar abundance pattern and, indeed, vary depending on the environment in which the stars formed. I will describe our efforts to understand which chemical elements are most important from the point of view of...
Giampaolo Piotto (Università di Padova)
9/18/17, 11:30 AM
Alessandro Savino (Kapteyn Institute - RUG)
9/18/17, 12:00 PM
I will present a new method that uses the horizontal branch morphology to determine the ancient star formation history of nearby resolved galaxies. Horizontal branch stars are bright and ancient, and their photometric properties depend on age and metallicity. The reason why the horizontal branch is usually neglected in the star formation history determinations of resolved galaxies is the...
Andrea Bellini (STScI)
9/18/17, 12:15 PM
We take advantage of the exquisite quality of the Hubble Space Telescope to distill the main sequence of omega Cen into its constituent populations. To this end, we restrict ourselves to the five most useful filters: the magic “trio” of F275W, F336W, and F438W, along with F606W and F814W. We develop a strategy for identifying color systems where different populations stand out most...
Elena Valenti (ESO)
9/18/17, 12:30 PM
An accurate dating of bulge and halo field populations allows to gauge at which lookback (i.e., at which redshift) one should look for possible analogs of the Milky Way, when their bulge and halo formation process were about to start, well on their way, or even already concluded. However, dating field stellar populations is a very complicated task, generally challenged by the uncertainties in...
Gilles Fontaine (Université de Montréal)
9/18/17, 1:00 PM
White dwarf cosmochronology has yet to reach its full potential due to recurrent uncertainties associated with the constitutive physics of warm dense matter. For instance, radiative opacities still need to be extrapolated in cool white dwarf models. In addition, cooling ages depend sensitively on the internal chemical stratification which is shaped, over time, by the still uncertain rate of...
72. Sub-Gyr Ages of Globular Cluster using Infrared Photometry: New Breakthroughs and Future Prospects
Matteo Correnti (STScI)
9/18/17, 4:00 PM
Recently, a new feature has been observed in several HST WFC3-IR color-magnitude diagrams (CMDs) of nearby Globular Clusters (GCs). At low stellar masses, the stellar main sequence in an infrared (IR) CMD exhibits a sharp "kink" (due to opacity effects in M dwarfs), such that lower mass and cooler dwarfs become bluer in the F110W - F160W color baseline and not redder. In this context, I will...
Sergio Ortolani (University of Padova)
9/18/17, 4:15 PM
We present an updated isochrone age determination of a sub-sample of stars among the halo field stars nearest to the Sun. We use revised parallaxes and reddening estimations based on a detailed study of the local interstellar dust and confirmed by independent diagnostics. The age determination is based on isochrone fitting with a standard technique already used for halo globular clusters....
Saskia Hekker (Max Planck Institute for Solar system research)
9/18/17, 4:30 PM
Age estimates from isochrone fitting of spectroscopic parameters (effective temperature, surface gravity and metallicity) of field stars can be very uncertain (order of 50%). These large uncertainties inhibit the use of stellar ages in for instance galactic archaeology studies. The parallaxes provided by Gaia can significantly improve age estimates from isochrones. Here we present results from...