ESPOIRS : Spectroscopic Study of the Optical Properties of analogues of interstellar grains in the Infrared and Submillimeter
ESPOIRS is developed by researchers belonging to the MICMAC Research Group
Background and Objective:
Interstellar dust plays a key role in the evolution of the interstellar medium (ISM) and of our Galaxy. The most abundant component in terms of mass consists of grains of ~100 nm diameter made up of silicates and oxides. These nano-grains, present in every astrophysical environments, are responsible for the emission of ISM in the wavelength range from 100 µm to 1 mm (FIR/submm) covered by the Herschel and Planck satellites launched in May 2009. The submillimetric emission is important since it allows us to detect pre-stellar clouds before they collapse, and thus to study the earliest stages of star formation and to estimate the mass of dust in interstellar clouds. The understanding of both the emission and the polarization of the dust is also essential for the subtraction of foregrounds required for the study of the cosmic microwave background. A major challenge for the Herschel and Planck space missions is to understand the nature of these dust grains and their evolution in the broader context of the physico-chemical evolution of interstellar matter and to understand the physics of the submillimetric emission process of this dust.
The first results of Herschel and Planck illustrate the wealth of information available in these observations to study dust and ISM in our Galaxy and in external galaxies. But they also highlight the lack of laboratory data on analogues of cosmic dust, which are necessary to interpret the observations and to model the FIR emission of dust.
The experimental device ESPOIRS is dedicated to the study of the optical properties of analogues of grains in the mid-infrared to submillimeter domain (2 - 1000/1500 microns) at low temperature (300 - 4K).
ESPOIRS is composed of a Fourier Transform infrared spectrometer covering the spectral range from near infrared to submillimetric (2-1000 microns) through the combination of several beam splitters (CaF2, CsI, Si), of different radiation sources (Tg lamp, Globar, Hg lamp), and various sensors (-DTGS KBr bolometric detectors cooled at 4 K), and cryostats for cooling the samples over a range of temperature between 4 and 300 K coupled to the spectrometer.
- Vertex 70V spectrometer
- Cryostat at gas exchange sample (300-4K)
- Cryostat at vacuum sample
- 4K Ge Bolometer
- 4K TES Bolometer
- Manual hydraulic press for pellet making
Synthesis and characterization of the analogues:
Nanograins are synthesized by the sol-gel method and characterized by electron microscopy (TEM, SEM, to control the size and the form of the nanograins), X-ray diffraction (XRD, control of the crystal structure, of the degree of amorphization), nuclear magnetic resonance (1H, 13C, 29Si NMR, analysis of the chemical environment of the atoms).
- LPCNO (Laboratoire de Physique et Chimie des Nano Objets, INSA, Toulouse) : Céline Nayral, F. Delpech
- UMET (Unité Matériaux Et Transformation, Université Lille 1, Villeneuve d'Ascq) : Hugues Leroux, C. Depecker
- IAS (Institut d'Astrophysique Spatiale, Université Paris Sud, Orsay): A. Abergel, A. Jones, L. Verstraete, N. Ysard, M. Koehler
ESPOIRS is funded by the CNRS (IRAP, INSU, PN PCMI), the Midi-Pyrénées Observatory (AST Molecules and grains), the ANR (2008-2012 Cold Dust Project, 2012-2015 CIMMES project), Europe (FEDER).