Laboratoire d’Études du Rayonnement et de la Matière en Astrophysique et Atmosphères

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Spin, Photons and Ices

par Jean-Hugues Fillion - publié le , mis à jour le

Team Composition

Xavier Michaut (Ass. Prof. – Team leader), Jean-Hugues Fillion (Prof.), Mathieu Bertin (Ass. Prof.), Géraldine Féraud (Ass. Prof.), Laurent Philippe (Ass. Prof.), Pascal Jeseck (Engineer), Thomas Putaud (PhD student), Rémi Dupuy (PhD student)


The colder parts of space presents a high variety of molecules, ranging from the simplest ones ( H2, H2O or CO), to organics of increasing complexity (alcohols, aldehydes, carboxylic acids…). The advent of new earth-based or space radiotelescopes allows for their detection with increasing precision in star or planet-forming regions, as well as the determination of their intrinsic molecular properties such as their nuclear spin state, that may be linked to the thermal history of these species.
In these regions, the extremely low temperatures (10-100 K) imply that the majority of the complex molecules forms or condenses onto dust grains, forming ice mantles that constitute the main molecular reservoir. Sublimation of those ices continuously enriches the gas phase, and therefore determines its composition and abundance ratios, and influences the intrinsic properties of the gaseous molecules. Desorption phenomenon and exchange between gas and solid phases are thus a key step that needs to be considered in order to get a better understanding of the observations in the cold regions of the interstellar medium.

The Team

The group “Spins, Photons and Ices” is an experimental physics team, whose interest lies on adsorption and desorption of astrophysics-relevant molecules, and on their role in the quantum states – in particular nuclear spin states – of desorbed molecules. The experiments performed by the team aim at simulating these processes in laboratory, with the objective to quantitatively understand them at a microscopic scale. For this purpose, spectroscopic methods are used (mass spectrometry, mid and very high resolution infrared spectroscopy, multiphoton laser spectroscopy…), together with vacuum, ultrahigh vacuum and cryogenic techniques to mimic the extreme conditions of the interstellar medium.
The team has at its disposal two complementary experimental setups. The SPICES setup is an ultrahigh vacuum setup (pressure E-10 Torr), in which molecular ices and adsorption and – thermal or photo-induced – desorption processes studies are carried-on. SPICES is designed to be adaptable to several kinds of light sources, for spectroscopy or to simulate the interstellar radiation fields : IR to VUV laser sources, available at the laboratory, or synchrotron light source (DESIRS beamline, SOLEIL synchrotron at St Aubin – France) with which part of the experiments is realized. The second setup, the CoSpiNu setup, is designed for the study of small, astrophysics-relevant molecules, in gas phase, at solid-gas interface or trapped in noble gas matrices at very low temperatures. The setup comprises an in-vacuum, very high resolution Fourier Transform InfraRed (FTIR) spectrometer, able to detect very small amounts of gaseous molecules, and to determine their nuclear spin state and its evolution.

Developed themes & collaborations

  • Adsorption and thermal desorption of atoms and molecules from astrophysics-relevant surfaces – SPICES setup, PhD of M. Doronin, collaborations with Y. Ellinger, A. Markovitz, F. Pauzat (LCT - Paris).
  • UV Photo-induced desorption : quantification and molecular mechanisms – SPICES setup, collaborations with H. Linnartz (Leiden Observatory - NL), K. Öberg (Harvard Smithsonian - USA), V. Baglin (CERN - CHE). Experiments realized partly at the SOLEIL synchrotron (France).
  • Nuclear spin conversion in noble gas matrices and at the solid-gas equilibrium –CoSpiNu setup, collaborations with C. Pardaneau, S. Coussan, C. Martin (PIIM – Marseille), P. Cacciani, M. Khelkhal et J. Cosleou (PhLAM – Lilles), P. Ayotte, P.-A. Turgeon, J. Vermette (Sherbrook University, Canada).
  • Desorption processes and its influence on quantum states of gas phase molecules – SPICES and CoSpiNu setups

Contracts and fundings  : ANR Gasospin (ANR-09-BLAN-0066-01), National Program of CNRS « Physique et Chimie du Milieu Interstellaire » (PCMI), Université Pierre et Marie Curie experimental platform « Astrolab », Université Pierre et Marie Curie Labex « MiChem », Ile-de-France region funding through the program DIM-ACAV (« astrophysique et conditions d’apparition de la vie »).

Séminaires à venir

Vendredi 15 novembre 2019, 14h00
Salle de l'atelier, Paris
Excitation mechanisms in the intracluster filaments around the Brightest Cluster Galaxies
Fiorella POLLES
résumé :
In the center of galaxy clusters lie giant elliptical galaxies, the Brightest Cluster galaxies (BCGs). These galaxies are often surrounded by a system of filaments (e.g. Salomé & Combes 2003) that emit in a wide range of wavelengths, illustrating the multi-phase nature of these streams. Many of these filaments do not have strong on-going star formation and the photoionization by stellar emission cannot reproduce their emission (Johnstone et al. 2007): what is preventing these structures to create stars and what heating mech- anisms are involved, are still open questions. I have investigated cosmic rays and X-rays as likely heating sources, combining multi-wavelength line emission (?23 lines: from optical to far-infrared) with Cloudy models (Polles et al in prep.). I have fully constrained the model of the ionized phase combining for the first time optical-to-infrared emission and self-consistent multi-phase models, pushing the analysis to the molecular phase on three off-nuclear regions of NGC 1275, the central giant elliptical galaxy of the Perseus Cluster. We showed that using X-ray emission as the main heating sources, all of the ionized line emission can be reproduced. We found that to reproduce [OI]63?m line, a small filling factor of the photodissociation phase is necessary. We also showed that adding an additional dense phase or an extra pressure component is required to robustly re- produce the H2 line emission.
Vendredi 29 novembre 2019, 14h00
Salle de l'atelier, Paris
The size of galaxies in the era of ultra-deep imaging
Nushkia CHAMBA
Instituto de Astrofisica de Canarias
résumé :
While the effective radius is a robust parameter, its use to
characterise galaxy sizes has provided a counter-intuitive definition of
what the actual extent of a galaxy is. Current deep imaging therefore
offers a unique opportunity to critically review the convention that the
size of a galaxy is its effective radius and rethink how one best
measures the extent of galaxies using a physically motivated parameter.
We introduce a new definition of galaxy size based on the gas density
threshold for star formation in galaxies. Remarkably, our new size
definition not only captures what the human visual system identifies as
the edge of a galaxy, but also dramatically decreases the scatter in the
stellar mass - size plane by a factor of three. Our size parameter
unifies galaxies spanning five orders of magnitude in stellar mass on a
single mass-size relationship. To demonstrate the implications of our
results, we show that ultra-diffuse galaxies have the same sizes as
regular dwarfs when a size indicator that describes the global structure
of galaxies is used. This work may be extended for larger samples of
galaxies using upcoming wide, deep imaging surveys.
Vendredi 6 décembre 2019, 14h00
Salle de l'atelier, Paris
Is accretion-driven turbulence a key process for galaxy growth ?
Vendredi 13 décembre 2019, 14h00
Salle de l'atelier, Paris
Falsifying the concordance of cosmology with the large-scale structures
Yonsei University, Seoul
Vendredi 24 janvier 2020, 14h00
Salle de l'atelier, Paris
The accretion-ejection connection in planet-forming disks. New perspectives from high angular resolution observations
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