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

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LERMA (Laboratory for Studies of Radiation and Matter in Astrophysics and Atmospheres) is a research entity operated by CNRS and four higher education institutions : Observatoire de Paris (OP), Université Pierre et Marie Curie (UPMC - Paris 6), École normale supérieure (ENS), and Université de Cergy-Pontoise (UCP). These institutions host the various LERMA research groups.

The laboratory is organized in four Research Poles :

  • "Galaxies and Cosmology" : studies of the early universe, inflation, cosmic microwave background ; epoch of reionization ; galaxy clusters ; dynamics of galaxies, dark matter ; galaxy formation and evolution ; black holes, AGN, star formation and feedback in local and high-redshift galaxies.
  • "Dynamics of the Interstellar Medium and Stellar Plasmas" : observational characterization of the ISM cycle ; star and planet formation ; ISM modeling, from diffuse gas to stars and disks, chemical diagnostics of the ISM dynamics ; modeling the transport mechanisms in circumstellar plasmas ; laboratory plasma experiments.
  • "Molecules in the Universe" : studies of gas-phase collisional and reactive processes ; VUV spectroscopy and photophysics, exobiology ; gas-solid interactions and heterogeneous catalysis, laboratory astrophysics.
  • "Instrumentation and Remote Sensing" : development of THz heterodyne instrumentation for large instrumental projects, Herschel/HIFI and JUICE/SWI ; research and development activities : HEB and SIS mixers, Schottky diodes for applications in tunable local oscillators ; Earth and planetary remote sensing, instrument software development.

These research poles are complemented by a transverse structure, dedicated to :
Technology and Research Support

Séminaires à venir

Vendredi 28 septembre 2018, 14h00
Salle de l'atelier, Paris
The [CII] emission line as a molecular gas mass tracer in galaxies at low and high redshift
résumé :
So far the gas conditions in main-sequence galaxies at the peak of the cosmic star formation history have been mainly investigated through the CO emission lines. However, observing the CO transitions at higher redshift becomes challenging, since the lines luminosity weakens as metallicity decreases. A powerful alternative could be the [CII] emission at 158um instead: it is one of the brightest lines in the far IR regime observed in star-forming galaxies and it is the main coolant of the interstellar medium. Local studies show that the [CII] luminosity correlates with the galaxy star formation rate (SFR), although main-sequence sources and starbursts seem to have different behaviours. At higher redshift the picture is even less clear and only samples of starbursts have been analyzed so far. To remedy this situation we have observed with ALMA a sample of 10 main-sequence sources at z ~ 2 and we complemented our sample with literature data at lower and higher redshift. We found that the [CII] luminosity correlates with galaxies' molecular gas mass, independently of their depletion time, metallicity, and redshift. This lays foundations for future explorations of the interstellar medium of starbursts and galaxies at much higher redshift (z > 4).

Vendredi 5 octobre 2018, 14h00
Salle de l'atelier, Paris
Astrochemistry in star forming regions : new modeling approaches
Emeric BRON
résumé :
Star-forming regions present rich infrared and millimeter spectra emitted by the gas exposed to the feedback of young stars. This emission is increasingly used to study the star formation cycle in other galaxies, but results from a complex interplay of physical and chemical processes : chemistry in the gas and on grain surfaces, (de)excitation processes of the atoms and molecules, heating and cooling balance,... Its understanding thus requires detailed astrochemical models that include the couplings between these processes. In this talk, I will present several examples where new modeling approaches of specific processes and their couplings proved crucial to solve persistent observational riddles : from the driving role of UV irradiation in the dynamics of photodissociation regions (PDR) to the efficient reformation of molecular hydrogen in these regions.
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