Archives Séminaires 2020-2021

Séminaire IPAG de Olivier Poch (IPAG), jeudi 3 septembre 2020, 11h00, IPAG seminar room

The surfaces of Solar System objects are extensively observed at visible and infrared wavelengths by ground-based and space instruments, in order to understand their origins and evolutions.
These surfaces are made of various constituents (ices, salts, minerals, organic molecules) mixed and structured in very peculiar ways, making the interpretation of their observations difficult.
In order to correctly prepare, guide and interpret these observations, I develop experimental simulations (…)

Séminaire IPAG de Michal Was (LAPP), jeudi 24 septembre 2020, 11h00, IPAG seminar room

Since their first observation in 2015 gravitational waves have opened a new astronomical observational window. After introducing gravitational waves and their detector I will summarize the results from the 2016-2017 observation run as well as the first results from the 2019-2020 observation run.
In 2017 the joint observation of GW170817 and GRB 170817A followed by extensive multi wavelength observations of its remnant have provided a wealth of new information on binary neutron star mergers (…)

Séminaire IPAG de Denis Barkats (CfA/ILL), jeudi 8 octobre 2020, 11h00, IPAG seminar room

The inflationary scenario generically predicts the existence of primordial gravitational waves (GW) over a wide range of amplitudes. Currently the most promising method for constraining, and potentially detecting this inflationary GW background is to search for the imprint of these tensor perturbations in the cosmic microwave background (CMB) B-mode polarization. Detecting this faint B-mode pattern requires making maps of unprecedented sensitivity, while separating the faint polarization (…)

Séminaire IPAG de Tom Ray (DIAS) jeudi 15 octobre 2020, 11h00, IPAG seminar room

Outflows from young stellar objects (YSOs) are one of the most striking phenomena in Astrophysics. Aside from looking dramatic they may also be fundamental to the star formation process itself.
For example it appears they remove angular momentum from protoplanetary disks, thereby allowing accretion to occur.
Outflows can also generate turbulence that limits the efficiency of star formation and they may even affect planet formation.
Both accretion and outflow are thought to be mediated (…)

Séminaire IPAG de Julien Milli (IPAG), jeudi 5 novembre 2020, 11h00, IPAG seminar room

Exo-Kuiper belts are belts of planetesimals orbiting at a few tens of astronomical units around main-sequence stars. Depending on their collisional activity, they can produce copious amount of dust particles that re-emit in the infrared. This thermal emission has been used to track their presence and to show that there are very common, with an occurence rate higher than 20%. Optical and near-infrared images at high-angular resolution reveal the light scattered by the micron-sized dust (…)

Séminaire IPAG de Chris Done (Durham University), jeudi 12 novembre 2020, 11h00, IPAG seminar room, online seminar

I will review both observations of winds from the accretion flow as seen by blueshifted absorption lines in both the black hole binaries and the active galaxies.
I will show how these can be mostly understood from theoretical models for their launch and acceleration, and highlight the challenges remaining in our knowledge which can be addressed with higher resolution.
data from XRISM (NASA/JAXA 2022) and Athena (ESA 2030).

Séminaire IPAG de Antoine Petit (Lund University), jeudi 19 novembre 2020, 11h00, IPAG seminar room

Exoplanet discoveries have unveiled a diversity of systems organization, showing that the Solar System shape is far from being the norm. However, a precise determination of the exoplanet orbital parameters is still impossible for the majority of the systems. Stability analysis is a way to put more stringent constraints on planet masses and orbits. Yet, due to the chaotic nature of the dynamics, numerical studies are too computationally prohibitive to be performed on every systems.
In this (…)

Séminaire IPAG de Pierre Hily-Blant (IPAG), jeudi 26 novembre 2020, 11h00, IPAG seminar room

Because protoplanetary disks provide the primitive material of planets and smaller bodies, their chemical composition and the processes shaping it have become key objectives to understand how and when planetary system bodies form. However, the bulk ratio of nitrogen prevailing in the protosolar nebula (PSN) has never been found in comets. Extremely 15N-rich reservoirs of nitrogen such as found in micron-sized inclusions in chondrites can not be explained by current chemical models. Thus, the (…)

Séminaire IPAG de Benoît Commerçon (CRAL), jeudi 3 décembre 2020, 11h00, IPAG seminar room

The new generation of interferometers provide unprecedented constraints on the protostellar disk formation process. Observations indicate that most protostellar disks have a small extent at the Class 0 stage and that disks grow in size at latter stages. I will present the results of 3D protostellar collapse calculations that cover a wide range of initial mass (from 0.5 to 100 solar mass), as well as different initial rotation and/or turbulence support. The calculations are performed using (…)

Séminaire IPAG de Mélanie Chevance (Universität Heidelberg), jeudi 10 décembre 2020, 11h00, IPAG seminar room

The cycling of matter in galaxies between molecular clouds, stars and feedback is a major driver of galaxy evolution. However, it remains a major challenge to derive a theory of how galaxies turn their gas into stars and how stellar feedback affects the subsequent star formation on the cloud scale, as a function of the galactic environment. Star formation in galaxies is expected to be highly dependent on the galactic structure and dynamics, because it results from a competition between (…)