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.
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.
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
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.
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.
Speaker : Donghui Quan (Zhejiang Laboratory)
Title: Modelling Interstellar Prebiotic Molecules: Hydroxylamine (NH2OH), Cyanamide (NH2CN), and Carbodiimide (HNCNH)
Abstract:
Interstellar molecules, commonly referred to as molecules found in the interstellar medium and circumstellar shells, have had around 300 molecules identified thus far (Müller et al., 2023). Over a third of these molecules are complex organic molecules, also known as COMs, revealing a broad range of complex chemistry found in various astronomical sources. Additionally, some interstellar molecules, particularly organic ones, act as precursors for biological molecules like amino acids and nucleosides, which astrophysicists find fascinating. These molecules are called prebiotic molecules and are primarily detected in star-forming areas, as well as quiescent clouds with nearby shocks.
Our research project utilizes computer-assisted modelling using chemical kinetics rate equations. We focus on hydroxylamine (NH2OH), cyanamide (NH2CN), and carbodiimide (HNCNH) isomers, which are known to act as precursors to amino acids or nucleosides. Our models provide an insight into the physical environments and associated chemical/physical processes of these species and related molecules. We identify primary formation and destruction reactions, optimal physical conditions for detecting these molecules, and related molecules. All these information may help with our understanding of astrochemistry in interstellar space, and enrich our knowledge of the complexity of the universe.
Speaker : Miguel Montarges (Observatoire de Paris)
Title: How do star end their lives ? Challenges, results, and perspectives at high angular resolution
Abstract: Cool evolved stars, namely asymptotic giant branch stars and red supergiant stars, experience an important mass loss (10-7 to 10-4 solar mass per year, while the solar wind represents ~10-14 solar mass per year). This stellar wind is enriched in heavy elements and contributes to the chemical evolution of the Galaxy. For massive stars, it can determine the final fate of the star as a neutron star or black hole. Yet, some of its mechanisms are still unknown: (1) the dust nucleation process is still unclear, (2) for low and intermediate mass stars the processes shaping planetary nebulae are not well constrained, (3) for massive stars we still do not know how the material is lifted from the photosphere. I will present recent high angular resolution results on cool evolved stars using adaptive optics, and optical and millimeter interferometry. I will conclude the presentation with an overview of a promising future thanks to a powerful new instrumentation.
Speaker : Olivier Berne (IRAP)
Title: Observations de la nébuleuse d’Orion avec le télescope spatial James Webb : implications pour la spectroscopie des galaxies de l’univers lointain et la formation planétaire
Abstract: Le télescope spatial James Webb a été lancé le 25 décembre 2021. Depuis l’été dernier, il observe avec succès l’univers local et lointain. Dans le cadre du programme Early Release Science intitulé « PDRs4All » (Berné, Habart, Peeters et al., 2022), notre équipe a pu disposer dès le mois de septembre d’observations de la Nébuleuse d’Orion réalisées avec le télescope Webb. Ces observations révèlent les effets du rayonnement UV lointain (FUV, c’est-à-dire des photons UV avec une énergie inférieure à la limite de Lyman de 13,6 eV) émis par les étoiles massives sur leur environnement, avec un niveau de détail inédit.
L’analyse préliminaire des données permet, d’une part, de caractériser le chauffage du milieu interstellaire par le rayonnement FUV des étoiles massives et le spectre infrarouge qui en découle, établissant ainsi une relation entre les signatures spectroscopiques et les conditions physiques. Cette relation pourra ensuite être utilisée pour interpréter les spectres des galaxies, même les plus lointaines, afin de mieux comprendre leurs propriétés.
D’autre part, les observations d’Orion ont permis de mettre en évidence un disque protoplanétaire irradié par les photons FUV. Cette irradiation crée un vent, entraînant une perte de masse du disque équivalente à environ 1% de la masse de la Terre par an. Cette perte de masse est suffisante pour empêcher la formation de planètes géantes autour d’étoiles de faible masse dans des amas contenant des étoiles massives, comme c’est le cas dans la nébuleuse d’Orion.
Le rayonnement FUV semble également avoir un effet sur la chimie du disque, produisant des hydrides tels que OH et CH+. Certaines signatures spectroscopiques présentes dans nos données, en cours d’identification, semblent correspondre à des espèces chimiques carbonées détéctées pour la première fois dans l’espace. Cette identification permettra, avec le soutien des expériences de laboratoire et la modélisation en physique moléculaire, de lever le voile sur des réseaux inexplorés de formation de molécules organiques.
O. Berné, E. Habart, E. Peeters, et al. (2022) Publications of the Astronomical Society of the Pacific 134 (1035)
Par : Melisse Bonfand (U. Virginia)
Titre: Physico-chemical evolution of high-mass star-forming regions
Abstract:
Stars with masses above 8 Msun are known to play a key role in setting up the physics and chemistry of the interstellar medium. Although these high-mass stars have been the prime targets of numerous observational and theoretical studies, the complex interplay between the physical and chemical processes involved in their formation is still a debated issue. The new capabilities of state-of-the art radio-interferometers, combining high-sensitivity and wide-bandwidth observations, together with the new sophisticated numerical chemical codes, have recently opened a new window on the study of high-mass star formation.
In my presentation I will focus on the hot and dense environment of young high-mass stars, known as hot core, which is an excellent laboratory to investigate the formation of complex organic molecules. I will present the first results obtained using a new gas-grain chemical kinetic code, coupled with a 2D radiative hydrodynamical model of star formation. The time-dependent predictions of the chemical models compared to the results derived from several ALMA observing programs that uncovered a large sample of star-forming sources, at different scales and different evolutionary stages, will allow us to determine up to which point the chemical composition of a source can help us to characterize its properties, nature, and evolutionary stage.