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 21 septembre 2018, 14h00
Salle de l'atelier, Paris
Understanding the structure of molecular clouds: Multi-line wide-field imaging of Orion B
Jan ORKISZ
Iram
résumé :
The new generation of wide-bandwidth high-resolution receivers turns
almost any radio observation into a spectral survey. In the case of
wide-field imaging of the interstellar medium, such a wealth of data
provides new diagnostic tools, but also poses new challenges in terms of
data processing and analysis.

The ORION-B project aims at observing 5 square degrees of the Orion B
molecular cloud, or about half of the cloud's surface, over the entire
3mm band. The emission of tens of molecular tracers have been mapped,
including CO isotopologues, HCO+, CN, HNC, N2H+, methanol, SO, CN...
Machine learning techniques have been applied to these maps, in order to
segment the molecular cloud into typical regions based on their
molecular emission, and to idenfify the most meaningful correlations of
different molecular tracers with each other and with physical quantities
such as density or dust temperature.

The spatial coverage, together with the spatial and spectral resolution,
also allow to characterize statistically the kinematics and dynamics of
the gas. The amount of momentum in the compressive and solenoidal
(rotational) modes of turbulence are retrieved, showing that the cloud
is dominated by solenoidal motions, with the compressive modes being
concentrated in two star-forming regions - which is in line with the
overall very low star formation efficiency of the cloud, and highlights
the role of compressive forcing in the star formation process. The
filamentary network of the molecular cloud also proves to have
particluarly low densities, and is very stable against gravitational
collapse and fragmentation, which also points at a young evolutionary
stage of the filaments.
 
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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