LERMA UMR8112

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



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Terahertz Instrumentation and Remote Sensing

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It includes research activities in three directions :
- Terahertz instrumentation for ground-based and space telescopes
- Earth remote sensing using multiple satellite observations
- data processing and virtual observations

The Instrument group at LERMA is a key international player in milllimeter to THz components and instrumentation, with active participation in space borne missions within international collaborations. Its main goal is to advance basic knowledge in THz devices, and to develop new technologies or circuit concepts in order to be able to propose some instruments as PI or as a key partner. This group has always worked at the frontier of electronics in terms of frequency and sensitivity. It is specialized in millimeter to THz heterodyne components and receivers, which provides unique insight in the physics and chemistry, in particular of the interstellar medium and the atmosphere of planets, including the Earth.

The Software Instrumental activity of this pole focuses on the modeling of the instrumentation, the processing of the data, and the development of Virtual Observation strategies. The data come both from instruments (e.g., ALMA, NOEMA, Planck, SKA) and from numerical simulations. The activity includes all the aspects and problems related to data consolidation, data storage and perpetuation, data diffusion and sharing.

The Earth and Planet Remote Sensing component revolves around the microwave to millimeter wave radiometry from satellites, for the characterization of the Earth atmosphere and surface. Different aspects are covered, including the analysis of satellite observations, the modeling of the radiative transfer, and the development of inversion methods. It is based on collaboration with the instrument group and projects couple science and instrument studies. The group works on both atmospheric and surface analysis, using microwave observations but also exploring the synergies between visible, infrared and microwave observations. We produce geophysical variables (e.g., soil moisture, inundation extent, emissivity) over long time series at a global scale, or for use by the climate and meteorological communities. We are also involved in the analysis of satellite observations of planet, using similar methodologies.

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
Anita ZANELLA
ESO
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
IRAM/LERMA
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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