Found 12 talks width keyword Gaia
Understanding stellar structure and evolution significantly impacts our understanding of the tight-knit evolution of galaxies and exoplanet systems. However, hidden behind the luminous layers of the stellar atmosphere, the deep interior of a star is eluding from direct measurements. The seismic study of waves propagating the deep interior provides the only way to measure the internal structure, dynamics, and mixing in any given star and compare it to theoretical models.
With the photometric data from space missions, such as the NASA Kepler telescope, a golden age has begun for seismology. In particular, the seismic studies of thousands of solar-like have led to numerous breakthroughs in our understanding of the stellar structure of red-giant stars. Complimentary information on stellar binarity, tidal forces, rotation, and lithium abundance provide additional constraints to characterize the advanced evolution of stars further and provide high-resolution insights into complex internal adjustments. Approaching a sample of ~1000 identified solar-like oscillators in binary systems, provided by the ESA Gaia and NASA TESS missions draws an exciting picture on the interaction of stellar and orbital evolution.
ID de reunión: 892 7515 0368
Código de acceso: 101169
Only recently, thanks to the Gaia, have we been able to directly measure how our own Galaxy was formed since its infancy, by cannibalizing smaller galaxies formed at the core of dark matter subhalos. These accretion events can be seen as kinematic groups and may have brought their own group of globular clusters, some of which are only seen today as their remnant cold stellar streams. Here I will discuss how the main accretion events unveiled by Gaia can be linked to previously known halo substructures, mainly large stellar clouds identified more than a decade ago in large photometric surveys. Additionally I will discuss the Jhelum stellar stream in the light of its interaction with the Sagittarius stream, which can give us insight on the details of this ongoing accretion event. Finally, I will briefly discuss how the new Gaia XP DR3 spectra is aiding in the identification of metal-poor unmixed halo substructures in the solar neighbourhood, highlighting the case of ED-2, a [Fe/H] = -2.5 cold stellar stream in which the Sun is embedded in.
Gaia Data Release 3 (13 June 2022) contains astrophysical parameters for up to 1.5 billion sources derived from the low resolution BP and RP prism spectra, the high resolution RVS spectra, photometry and astrometry.
These include object classifications (star, galaxy, stellar spectral type,...), unresolved galaxies and quasar redshifts (~6 million), outlier objects, interstellar medium characterisation (extinction and DIBs), and spectroscopic and evolutionary parameters (~470 million) for a large variety of stellar types from ultra-cool dwarfs to hot OB stars.
In this talk, I will present an overview of the astrophysical parameter content of Gaia DR3 that was derived using the Astrophysical Parameters Inference System (Apsis) software. I will first give a brief description of the data, models and methods that were employed, and then I will focus on describing what type of parameters you can find in the archive and where to find them among the 30+ new tables. I will then describe the overall performance and present some pre-Gaia DR3 highlights.
Rotation plays an important role in the life of stars and offers a potential diagnostic to infer their ages and that of their planets. This idea is known as gyrochronology, and if properly calibrated, its applications to Galactic, stellar, and exoplanetary astrophysics would be far-reaching. Nevertheless, while potentially fruitful over a wide range of ages and masses, recent results have raised concerns regarding gyrochronology’s applicability. In this talk, I will present the opportunities that the Gaia astrometry has opened to address these issues. First, regarding rotation’s classical calibrators, I will illustrate the impact that removing the non-member contamination has on the rotational sequences of open clusters. Second, I will present a novel method that tests the state-of-the-art gyrochronology relations in under-explore domains using wide binary stars. Finally, I will discuss the prospects for expanding the existing rotational constraints in unprecedented regimes using data from the TESS mission.
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.
The existence of apparently isolated massive stars has been recognized for some time, and various explanations have been proposed to explain these ranging from isolated star formation to variouscluster ejection mechanisms. In this talk I will present recent results from Gaia and Hubble on stellar dynamics within the Tarantula Nebula/30 Doradus region of the Large Magellanic Cloud. I will discuss how these complementary datasets have improved our knowledge of this nearby mini-starburst. The first results indicate the existence of a few stars in the region with masses ~100 solar masses that have been ejected from the central dense cluster R136. Ejection velocities appear torange from a few 10s of km/s to ~100 km/s. Given the extreme youth of R136 it is therefore likely that the mechanism of ejection was via the dynamical interaction channel rather than the binary supernova ejection scenario.
By providing information on distances and proper motions for one billion stars, the Gaia satellite allows us to investigate the major unsolved challenges in galaxy formation: the nature of dark matter, the origin of Galactic spiral activity and its relation to the bar, and more generally the history of the Milky Way.
My research aims to develop a theoretical approach to modeling and exploiting the big data and address problems at the forefront of Galactic Dynamics at various scales. What is the origin of the spiral activity in the Milky Way? How are all of these perturbations to the structure of the Galaxy coupled to each other directly and through the dark-matter halo? I will also present my ongoing work on statistical techniques of big-data analysis and advanced numerical simulations used to interpret the evolution of star clusters and discover streams in the stellar disk of the Milky Way.
Galactic Archeology is today a vibrant field of research. The adoption and launch of the Gaia astrometric satellite by ESA has resulted in many spectroscopic Galactic surveys that aim to complement the Gaia data with information (for the fainter Gaia stars) about stellar elemental abundances, radial velocities, and stellar parameters. This results in multi-dimensional data sets which will allow us to put the Milky Way stellar populations into a much broader galactic context, eg by comparing with models and galaxies at large look-back times. In this talk I will review a selection of recent exciting developments in Galactic Archeaology found via on-going surveys as well as look to the future and see what surveys like 4MOST and WEAVE will bring. The proposed surveys will be put into a wider context of past, on-going and future spectroscopic surveys and how this can all be combined to understand the Milky Way as a galaxy.
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.
« Newer 1 | 2 Older » Last >>
- TBDThursday December 14, 2023 - 10:30 GMT (Aula)
- GESCOPThursday January 18, 2024 - 10:30 GMT (Aula)