Found 13 talks width keyword Galactic evolution

Thursday May 20, 2021
Dr. Guillaume Thomas


At present, our understanding of the formation history of the MW is limited due to the complexity of observing the imprints of accretion events and of reproducing them in numerical simulations. Moreover, though being the only galaxy, in which the Galactic potential can be probed in detail, the distribution of mass in the MW, and hence of the dark matter, is poorly constraint, especially at large distances. In addition, the MW is not isolated, and it has recently been suggested that the infall of the LMC can induce a perturbation in the stellar and dark matter distribution of the MW. As a consequence, the details of the formation history of our Galaxy are still unknown, such as the number of accretion events, the mass of the accreted galaxies, and the epoch of these events. Yet this information is crucial to understand our environment and to constrain the theoretical models and simulations that try to reproduce it.

One of the major challenges of the field is that a tremendous number of multi-aspect (astrometric, photometric and spectroscopic) observations at significant depth is required to study the morphology, the kinematics and the chemistry of the outskirts of our Galaxy, where are located the signatures of these events. Hopefully, the advent of recent and incoming complementary large surveys, such as the European Gaia mission, UNIONS (Ultraviolet Near Infrared Optical Northern Survey), Pristine, Pan-STARRS (PS), WEAVE or LSST (Legacy Survey of Space and Time), is offering a new global point of view on our Galaxy’s halo, allowing us to precisely probe the Galactic potential our the MW, and to retrace itsaccretion history.

In this talk I will present recent works that have been conducted to better catarerized our Galaxy and its history with some of the existing surveys mentioned above. In addition, I will present the major improvement that will bring this new generation of large, multi-aspect surveys, to study both our Galactic history, as well as the fundamental nature of the dark matter.

Tuesday November 3, 2020
Drs. Paola Di Matteo
Observatoire de Paris


Reconstructing the past of the Milky Way depends on the study of its metal-poor stars, which either have been formed in the Galaxy itself in the first billion years, or have been accreted through mergers of satellite galaxies over time. These stars are usually found in what is known as the Milky Way halo, a light — in terms of total mass —  stellar component which is usually made of stars whose kinematics significantly deviates from that of the Galactic disc.
In this talk, I will discuss how it has been possible to use the astrometric and spectroscopic data delivered by Gaia and complementary surveys  to shed light on the past of our Galaxy, through the study of its halo. Besides the discovery of the possible last significant merger experienced by the Milky Way, the use of 6D phase space information and chemical abundances allowed to reconstruct the impact this merger had on the early Milky Way disc, and the time it occurred, as well as to discover that some of the most metal-poor stars in the Galaxy possibly formed in a disc.  This last finding would imply that the dissipative collapse that led to the formation of the old Galactic disc must have been extremely fast.


Tuesday July 21, 2020
Dr. Joris Vos
University of Potsdam


Wide hot subdwarf B (sdB) binaries with main-sequence companions are outcomes of stable mass transfer from evolved red giants. The orbits of these binaries show a strong correlation between their orbital periods and mass ratios. The origins of this correlation have, so far, been lacking a conclusive explanation.
We have performed a small but statistically significant binary population synthesis study with the binary stellar evolution code MESA. We have used a standard model for binary mass loss and a standard Galactic metallicity history.  We have achieved an excellent match to the observed period - mass ratio correlation without explicitly fine-tuning any parameters. Furthermore, our models produce a good match to the observed period - metallicity correlation.
We demonstrate, for the first time, how the metallicity history of the Milky Way is imprinted in the properties of the observed post-mass transfer binaries. We show that Galactic chemical evolution is an important factor in binary population studies of interacting systems containing at least one evolved low-mass (Mi < 1.6 Msol) component. Finally, we provide an observationally supported model of mass transfer from low-mass red giants onto main-sequence stars.

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Thursday December 12, 2019
Dr. Marc Pinsonneault
Ohio State university


Time-domain space missions have revolutionized our understanding of stellar physics and stellar populations. Virtually all evolved stars can be detected as oscillators in missions such as Kepler, K2, TESS and PLATO.  Asteroseismology, or the study of stellar oscillations, can be combined with spectroscopy to infer masses, radii and ages for very large samples of stars.  This asteroseismic data can also be used to train machine learning tools to infer ages for even larger stellar population studies, sampling a large fraction of the volume of the Milky Way galaxy. In this talk I demonstrate that asteroseismic radii are in excellent agreement with those inferred using Gaia and spectroscopic data; this demonstrates that the current asteroseismic data is precise and accurate at the 1-2% level.  Major new catalogs for Kepler and K2 data are nearing completion, and I present initial results from both. We find unexpected age patterns in stars though to be chemically old, illustrating the power of age information for Galactic archeology.  Prospects for future progress in the TESS era will also be discussed.

Tuesday February 25, 2014
Dr. Carmela Lardo
INAF-Osservatorio Astronomico di Bologna


In this talk I present an overview of the structure, activity and goals
of the Gaia-ESO survey, a large public spectroscopic survey aimed at investigating
the origin and formation history of our Galaxy by collecting high quality spectroscopy
of representative samples (about 105 Milky Way stars) of all Galactic stellar populations,
in the field and in clusters. Briefly, I discuss the most relevant results obtained so far.
In particular, I present our study on the internal kinematics of Galactic globular clusters based on the radial estimates obtained from the survey complemented with ESO archive data.

Thursday February 6, 2014
Dr. Elena Pancino
INAF - Osservatorio Astronomico di Bologna


Gaia - the ESA cornerstone astrometric mission - was launched in December 2013, with the goal of censing the Milky Way population in a 6D space (positions and velocity) of 10^9 point-like obects, with errors
100-1000 times smaller than Hipparcos, with three color magnitudes and spectra as well. The scientific impact of its data will be large in many fields of astrophysics, from Galactic science, to Solar system objects, to stellar astrophysics, to galaxies and Quasars; from the distance ladder revision to fundamental physics. I will describe the mission concept, the scientific goals, and the present status of the mission, with special attention to the flux calibration of Gaia data.

Tuesday October 8, 2013
Dr. Heidi Lietzen


Galaxies in different environments have different properties. In dense environments galaxies are more likely to be red, passive ellipticals than in less dense environments. This difference can be detected both on small and large-scale environments. In this talk, I will present results on galaxy populations in different environments on two scales: the group scale and the supercluster scale. The goal of our project is to find out if there are differences between massive galaxies in similar groups, but different large-scale environments. The results will tell if the evolution of galaxies is fully determined by the mass of their dark matter halo, or if the large-scale environment also play a role. 

Thursday April 25, 2013
Dr. Ismael Pérez Fournón


How do the first galaxies form and evolve? Optical and near-infrared deep surveys are now finding galaxies at very high redshifts. However, they are typically small, not massive and present some but not very high star formation. But now the Herschel Multi-tiered Extragalactic Survey (HerMES), the largest project that has being carried out with the Herschel Space Observatory, in collaboration with other groups, has discovered a massive, maximum-starburst galaxy at a redshift of 6.34. The presence of galaxies like HFLS3 in the early Universe challenges current theories of galaxy fomation and evolution. I will describe the method we have developed to find these galaxies, the follow-up observations with different facilities and the main physical properties of this extreme object.

Tuesday September 27, 2011
Dr. Ignacio Trujillo
Instituto de Astrofísica de Canarias, Spain


In the last few years there has been cumulative evidence showing that massive galaxies have dramatically grown in size since z~3. This result has remained very controversial as it seems at odd with our previous knowledge based on the detailed analysis of the stellar populations of nearby massive spheroids which shows that their stars were form very early on and over a short time interval. In addition to this, there is growing observational support for a significant evolution of the morphologies of these galaxies with cosmic time. In this talk, I will summarize what we have learned since the discovery of the strong evolution of the morphological properties of the massive galaxies, the mechanisms proposed to explain their origin and size increase, and the pending questions still to solve.

Thursday July 14, 2011
Dr. Anna Pasquali
Astronomisches Rechen-Institut, Heidelberg, Germany


It has been thirty years since the seminal work of Alan Dressler on the density-morphology relation, which established environment as a driving mechanism for galaxy formation and evolution. In the following three decades, we have learned that both the intrinsic processes (nature) and environment (nurture) contribute towards shaping the galaxy populations, and the connection between these two still remains an open question. I will summarize recent results on the interplay between environment and galaxy evolution, obtained from the SDSS DR4 galaxy groups catalogue (Yang et al. 2007) by comparing the properties of central and satellite galaxies as a function of their stellar mass and the dark matter mass of their
host halos.

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