Calendar

Jan
24
mar
Camille Bergez-Casalou – Simultaneous accretion of giant planets or how giant planets fight for food @ B18N, Salle Univers
Jan 24 @ 10 h 30 min – 12 h 30 min
Séminaire

Speaker : Camille Bergez-Casalou (LESIA)

Title: Simultaneous accretion of giant planets or how giant planets fight for food

Abstract:  Among the thousands of exoplanetary systems observed nowadays, some of them host multiple giant planets, like in our Solar System. These giants are probably formed from the same protoplanetary disc. I’m going to present our recent paper where we investigated, with the help of 2D hydrodynamical simulations, how the gas present in the protoplanetary disc is distributed and accreted by two planetary cores. We start with 20 Me cores undergoing runaway gas accretion and follow the evolution of the planets mass ratio. We find that when the planets accrete from the same disc, they end up with very similar masses, independently on the disc viscosity or the delay in accretion between the planets. We finish by suggesting different formation scenarios in order to explain the observed exoplanets distribution.

Fév
7
mar
Damien Gratadour – Bridging Astronomy, HPC and AI in giant telescopes from the optical to radio frequencies @ B18N, Salle Univers
Fév 7 @ 11 h 00 min – 12 h 30 min
Séminaire

Speaker : Damien Gratadour

Title: Bridging Astronomy, HPC and AI in giant telescopes from the optical to radio frequencies
Abstract:  Frontier computing has become a key enabler for scientific discovery,  at the core of the next generation of extremely large multi-science hubs, such as the SKA Observatory or the European Extremely Large Telescope. I will present current efforts and the future roadmap we are contemplating, bridging astronomy with HPC and AI technologies to contribute to these major scientific infrastructures, in particular through the soon to be established ECLAT joint lab, a collaborative effort between CNRS, Inria and Atos. Beyond technical aspects related to increasing the scientific return of these facilities, I will also cover transverse topics such as energy efficiency and operational cost containment.

Fév
21
mar
Christine Ducourante – Gaia explore l’Univers profond: Galaxies, quasars et lentilles gravitationnelles @ B18N, Salle Univers
Fév 21 @ 11 h 00 min – 12 h 30 min
Séminaire

Speaker : Christine Ducourante (LAB)

Title: Gaia explore l’Univers profond: Galaxies, quasars et lentilles gravitationnelles

Abstract: 

Le satellite Gaia est en activité depuis 2013 et scanne sans relâche la voute céleste, mesurant tous les objets en deçà de ses limites de détections. Il mesure ainsi avec une incroyable résolution plusieurs millions de galaxies, certaines abritant des quasars et détecte même des lentilles gravitationnelles. Plusieurs groupes de travail du Data Processing and analysis Consortium (DPAC) Gaia se dédient à caractériser ces objets en les classant, mesurant leur redshift, ou leur morphologie. L’ensemble de ces travaux a été présenté pour la première fois dans la 3eme version du catalogue Gaia en Juin 2022. Par ailleurs, l’analyse du contenu du catalogue  Gaia permet d’identifier parmi 1.8 milliards de sources les « objets » rares et tant recherchés que sont les quasar multi-imagés par phénomène de lentille gravitationnelle. Je présenterai durant cet exposé l’ensemble des analyses et des propriétés de cet univers extragalactique de Gaia.
 
The Gaia satellite has been in operation since 2013 and tirelessly scans the celestial vault, measuring all objects below its detection limits. It thus measures with incredible resolution several million galaxies, some of which harbor quasars, and even detects gravitational lenses. Several working groups of the Gaia Data Processing and Analysis Consortium (DPAC) are dedicated to characterizing these objects by classifying them, measuring their redshift, or their morphology. These results were presented for the first time in the 3rd version of the Gaia catalog in June 2022. In addition, the analysis of the content of the Gaia catalog makes it possible to identify among 1.8 billion sources the rare and highly sought multi-imaged quasars by gravitational lensing. During this presentation, I will present all the analyzes and properties of this extragalactic universe of Gaia.
Fév
22
mer
Lars Bonne – Probing the assembly and dispersal of molecular clouds with the [CII] fine structure line @ B18N, Salle Univers
Fév 22 @ 10 h 00 min – 11 h 30 min
Séminaire

Speaker : Lars Bonne (USRA)

Title: Probing the assembly and dispersal of molecular clouds with the [CII] fine structure line
Abstract: 

I will present high spectral resolution observations of the ionized carbon fine structure line at 158 μm ([CII]) from the SOFIA FEEDBACK legacy survey. [CII] is a unique tracer of the CO-dark molecular gas and photodissociation regions (PDRs) at the surface of molecular clouds. The FEEDBACK survey maps the [CII] line in 11 Galactic high-mass star forming regions. First, I will present the [CII] observations of the DR21 ridge in Cygnus-X. There, [CII] unveils that the assembly of this massive star forming ridge is the result of a high-velocity (~20 km/s) colliding flow. This collision also curves the magnetic field around the ridge and thus sets the cloud geometry. Further investigating the molecular cloud dynamics with IRAM 30m observations shows that this rapid mass accumulation initiates gravitational collapse of the full molecular cloud. Then, I will present studies focusing on regions that experience the effect of stellar feedback from high-mass stars. In these regions, [CII] unveils high-velocity mass ejection from the clouds that is not seen in CO. Quantifying the mass ejection rate shows that stellar feedback can disperse these star forming clouds in a few Myr. These results point to a consistent scenario for molecular cloud evolution and star formation on relatively short timescales. Far-infrared fine structure lines are thus important tools to pin down the physical processes that drive the evolution of the interstellar medium (ISM).

Fév
23
jeu
Denis Burgarella – Reunion d’information sur PRIMA @ B18N, Salle Chandon (306)
Fév 23 @ 10 h 00 min – 11 h 30 min
Séminaire

Speaker : Denis Burgarella (LAM)

Reunion d’information sur l’instrument infrarouge PRIMA

Fév
28
mar
Pamela Freeman – The Carbon-based Molecules of High Mass Star Forming Regions AFGL 2591 and IRAS 20126 @ B18N, Salle Univers
Fév 28 @ 11 h 00 min – 12 h 30 min
Séminaire

Speaker : Pamela Freeman

Title: The Carbon-based Molecules of High Mass Star Forming Regions AFGL 2591 and IRAS 20126

Abstract: 

There is a diverse chemical inventory in protostellar regions that has led to the classification of two extreme types of systems: hot corinos, for the hot and dense low-mass systems that contain complex organic molecules, and warm carbon chain chemistry sources, for the warm and dense regions near a protostar containing unsaturated carbon chain molecules. Since these definitions were presented by Ceccarelli et al. (2004) and Sakai et al. (2008), respectively, there has been a growing field to detect these sources and determine if these classes of molecules can co-exist. There have been few studies surveying these molecules in high mass star forming regions—places of significance as the birthplace of most stars. To address this, I have conducted spectral surveys in two high-mass star forming regions in Cygnus X—AFGL 2591 and IRAS 20126—with the Green Bank Telescope and the IRAM 30m Telescope. In these observations, I detect several lines of formaldehyde, H2CO, and methanol, CH3OH, as tracers of hot core chemistry, and several lines of propyne, CH3CCH, and cyclopropenylidene, c-C3H2, as tracers of carbon chain chemistry. With a local thermodynamic equilibrium model, I use the observed molecular spectra to determine the physical conditions of these regions, producing maps of the gas temperatures, column densities, and velocities. These results illuminate the possible physical and dynamical environments of complex organic and carbon chain molecules, and are an initial step in investigating the chemical evolution of carbon-based molecules in star forming regions. The chemical makeup of star forming clouds and protostellar systems leads directly into that of stellar and planetary systems; observing the chemical complexity of star formation and modeling its environment provides an invaluable link between these systems.

 

Avr
4
mar
Marcel Agueros – Studying Low-Mass Stars in the Era of Surveys: Data, Models, and Surprises @ B18N, Salle Univers
Avr 4 @ 10 h 30 min – 12 h 30 min
Séminaire

Speaker : Marcel Agueros (Univ. de Columbia)

Title: Studying Low-Mass Stars in the Era of Surveys: Data, Models, and Surprises

Abstract:  Stellar ages are notoriously difficult to measure accurately for main-sequence low-mass stars, which limits our ability to address questions ranging from the evolutionary state of exoplanets to the chemical history of the Galaxy. Gyrochronology, which uses stellar rotation as a proxy for age, is a promising solution to this quandary. Unfortunately, however, empirical and theoretical models of the age-rotation relation have been hampered by a lack of rotational measurements for large numbers of low-mass stars with a wide range of well-known ages. We are still far from being able to describe fully the evolution of rotation for low-mass stars, or from being able to use rotation measurements to estimate accurately the ages of isolated field stars. I will summarize recent ground-based and space-based work to characterize the rotational behavior of G, K, and M dwarfs in open clusters ranging in age from 125 Myr (the Pleiades) to 3 Gyr (Ruprecht 147), and then compare these data to each other and to models for stellar spin-down to appraise our current understanding of the age-rotation relation. I will also touch on an on-going survey targeting newly discovered single-aged stellar populations to address the broader age-rotation-activity relation.

Avr
25
mar
Jacques Taillard – La nuit gardienne de notre sommeil et de notre santé @ B18N, Salle Univers
Avr 25 @ 11 h 00 min – 12 h 30 min
Séminaire

Speaker : Jacques Taillard

Title: La nuit gardienne de notre sommeil et de notre santé

Abstract:  Le cycle veille sommeil est sous le contrôle des horloges biologiques qui vont imposer la période de sommeil et d’éveil au cours de la journée et donc l’heure de coucher et l’heure de réveil. Grace aux horloges biologiques, ces périodes d’éveil et de sommeil, mais également les processus physiologiques, seront parfaitement en phase (synchronisés) avec le rythme lumière/obscurité et ainsi nos comportements seront en totale harmonie avec notre environnement. L’horloge biologique principale est localisée dans le cerveau. Cette horloge fonctionne avec une périodicité légèrement supérieure à 24hr, elle doit être donc remise à l’heure tous les jours par différents synchroniseurs. C’est surtout le cycle lumière/obscurité, en particulier la lumière solaire ou artificielle, qui va agir sur le fonctionnement de l’horloge biologique. Ainsi, une exposition à la lumière au mauvais moment de la journée, la nuit par exemple, peut désynchroniser l’horloge biologique. Notre mode de vie moderne va également contribuer à une mauvaise synchronisation entre notre temps social et notre temps biologique. La lumière artificielle nocturne et nos comportements contribuent à des dérèglements qui vont agir sur notre sommeil, notre santé et notre bien-être. L’objectif de cette conférence est de vous éclairer sur les bienfaits ou les méfaits de la lumière sur notre santé mais aussi vous donner les bons comportements à adopter pour améliorer votre sommeil.

Jacques Taillard
Ingénieur de recherche CNRS
UMR 6033 SANPSY,  Sommeil, addiction et neuropsychiatrie

Mai
2
mar
Robert Simon – The cycling of matter from the interstellar medium to stars and back: The CCAT-prime Galactic Ecology project @ B18N, Salle Univers
Mai 2 @ 11 h 00 min – 12 h 30 min
Séminaire

Speaker : Robert Simon (I. Physikalisches Institut Köln)

Title: The cycling of matter from the interstellar medium to stars and back: The CCAT-prime Galactic Ecology project
Abstract:  The Fred Young Submillimeter Telescope (FYST) at the CCAT observatory will be a novel 6 m aperture telescope enabling highly sensitive wide field observations at submillimeter wavelengths to address science topics ranging from the formation of molecular clouds and stars, the evolution of the interstellar medium (ISM) in the Milky Way and nearby galaxies, to galaxies in the early universe and cosmology.

The telescope will be deployed near the summit of Cerro Chajnantor at 5600 m altitude in the Chilean Atacama desert and become operational in late 2024. The CCAT-prime Galactic Ecology project (GEco) is one of the key science projects of the observatory designed to study the formation and evolution of molecular clouds in the Milky Way, the Magellanic clouds, and other nearby galaxies through submm spectroscopy. The GEco project will do this with dedicated large scale surveys in spectrally resolved lines of CO (J=4-3 and 7-6) and atomic carbon ([CI] 1-0 and 2-1) that become possible with the novel large format CCAT-prime Heterodyne Array Instrument (CHAI). I will introduce our planned observations and the science that GEco will address.

Mai
9
mar
Sacha Gavino – Shaping the CO snowline in protoplanetary disks @ Zoom
Mai 9 @ 11 h 00 min – 12 h 30 min
Séminaire

Speaker : Sacha Gavino

Title: Shaping the CO snowline in protoplanetary disks

Abstract:  Characterizing the dust thermal structure in protoplanetary disks is a fundamental task as the dust temperature can affect both the disk chemical evolution and planet formation. It is a challenging task, however, since the temperature is strongly dependent on many parameters, including the grain size distribution. We investigate the effects of the radiative interactions between multiple dust populations on the CO distribution using dedicated thermochemical disk models. We find that the interaction of the dust scattered light between at least two dust grain populations can produce a complex temperature structure. In particular, the scattered light is sufficient to significantly raise the temperature of micron-sized grains in the midplane. This results in the splitting of the CO snowline that can strongly reshuffle the distribution of both CO in the gas-phase and on the grain surface.