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 23 octobre 2020, 14h00
téléconférence Zoom,
The role of molecular filaments in the origin of the IMF
Philippe ANDRÉ
CEA, Laboratoire d’Astrophysique AIM Paris-Saclay
résumé :
The origin of the stellar initial mass function (IMF) is one of the most debated
issues in astrophysics. I will discuss new insights into this problem based on a systematic census of prestellar cores and molecular filaments in nearby clouds taken as part of the Herschel Gould Belt survey, as well as higher-resolution observations with APEX/ArTéMiS and ALMA. Our results point to the key role of the quasi-universal filamentary structure pervading molecular clouds. They suggest that the dense cores making up the peak of the prestellar core mass function (CMF) - and indirectly the peak of the IMF - result from gravitational fragmentation of molecular filaments near the critical mass per unit length. The Salpeter power-law tail of the CMF/IMF may be at least partly inherited from the filament line mass function (FLMF), which is observed to follow a Salpeter-like power law in the regime of thermally supercritical filaments.

 
Vendredi 4 décembre 2020, 14h00
via Zoom, Paris
Simulating galaxies at high resolution in their cosmological context with NewHorizon: methods and some key results on galaxy properties and their morphology
Yohan DUBOIS
Institut d'Astrophysique de Paris
résumé :
Hydrodynamical cosmological simulations are increasing their level of realism by considering more physical processes, having more resolution or larger statistics. However, one usually has to either sacrifice the statistical power of such simulations or the resolution reach within galaxies. I will introduce the NewHorizon project where a zoom-in region of ~(16 Mpc)^3, larger than a standard zoom-in region around a single halo, embedded in a larger box is simulated at high resolution. A resolution of up to 34 pc, typical of individual zoom-in state-of-the-art resimulated halos is reached within galaxies, allowing the simulation to capture the multi-phase nature of the interstellar medium and the clumpy nature of the star formation process in galaxies. I will present and discuss several key fundamental properties of galaxies and of their black holes. Due to its exquisite spatial resolution, NewHorizon captures the inefficient process of star formation in galaxies, which evolve over time from being more turbulent, gas-rich and star-bursting at high redshift. These high redshift galaxies are also more compact, and are more elliptical, disturbed and clumpier until the level of internal gas turbulence decays enough to allow for the formation of stable rotating discs. I will show the origin and persistence of the thin and thick disc components, and explain why the settling of discs ``magically’’ occurs at around a stellar mass of 1e10 Msun.

 
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