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    ABSTRACT: We present for the first time, an infrared data-cube of the central parsec of our Galaxy in the 2.8 to 4.2 micron range. This spectral band (the L-band) harbors important signatures of the interstellar and circumstellar medium, since the water ice absorption feature at 3 micron traces the dense medium and the hydrocarbon absorption at 3.4 micron is only observed in the diffuse gas.Thanks to a calibrator spectrum of the foreground extinction in the L-band derived in a previous paper, we corrected our data-cube for the line of sight extinction. Our observations performed with ISAAC spectrograph at the VLT-ESO telescope suggest that part of the absorption features takes place in the local environment of the Galactic center. This induces the presence of very low temperatures in the central parsec.
    Journal of Physics Conference Series 07/2012; 372(1).
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    ABSTRACT: The production of a hydrogenated amorphous carbon polymer (a-C:H) via the photolysis of a series of organic molecule precursors at low temperature is described. Such amorphous material is synthesised under interstellar conditions (10 K and Lyman-alpha photons) and represents the best candidate to explain the Diffuse Interstellar Medium absorption observed in our Galaxy and in other galaxies. We perform a series of laboratory analyses (Infrared spectroscopy, muspectroscopy, Raman, Photoluminescence and UV-visible spectroscopy) which allow a full characterisation of such polymers. This allows us to assess the importance of the polymer and possible scenarios for its role in crucial aspects of the lifecycle of dust. Such material has implications for the carbon budget at galactic scales, hydrogen formation, extended red emission, as a PAH precursor, and in explaining the 2175 Å extinction bump.
    Astronomy & Astrophysics - ASTRON ASTROPHYS. 01/2005; 432(3):895-908.
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    ABSTRACT: We report spatially resolved variations in the 3.4-mum hydrocarbon absorption feature and the 3.3-mum polycyclic aromatic hydrocarbon (PAH) emission band in the Circinus galaxy over the central few arcsec. The absorption is measured towards warm emitting dust associated with Coronal line regions to the east and west of the nucleus. There is an absorption optical depth tau3.4mum ~ 0.1 in the core which decreases to the west and increases to the east. This is consistent with increased extinction out to ~40 pc east of the core, supported by the Coronal emission line intensities which are significantly lower to the east than the west. PAH emission is measured to be symmetrically distributed out to +/-4 arcsec, outside the differential extinction region. The asymmetry in the 3.4-mum absorption band reflects that seen in the 9.7-mum silicate absorption band reported by Roche et al., and the ratio of the two absorption depths remains approximately constant across the central regions, with tau3.4mum/tau9.7mum ~ 0.06 +/- 0.01. This indicates well-mixed hydrocarbon and silicate dust populations, with no evidence for significant changes near the nucleus.
    Monthly Notices of the Royal Astronomical Society 04/2009; 394:2043-2049. · 5.23 Impact Factor

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