Spectroscopy of diffuse light in dust clouds. Scattered light and the solar neighbourhood radiation field

Abstract

The optical surface brightness of dark nebulae is mainly due to scattering of integrated starlight by classical dust grains. It contains information on the impinging interstellar radiation field, cloud structure, and grain scattering properties. We have obtained spectra of the scattered light from 3500 to 9000 Angstrom in two globules, the Thumbprint Nebula and DC303.8-14.2. We use observations of the scattered light to study the impinging integrated starlight spectrum as well as the scattered H-alpha and other line emissions from all over the sky. We search also for the presence of other than scattered light in the two globules. We obtained long-slit spectra encompassing the whole globule plus adjacent sky in a one-slit setting, thus enabling efficient elimination of airglow and other foreground sky components. We calculated synthetic integrated starlight spectra for the solar neighbourhood using HIPPARCOS-based stellar distributions and the spectral library of Pickles. Spectra are presented separately for the bright rims and dark cores of the globules. The continuum spectral energy distributions and absorption line spectra can be well modelled with the synthetic integrated starlight spectra. Emission lines of H-alpha + NII, H-beta, and SII are detected and are interpreted in terms of scattered light plus an in situ warm ionized medium component behind the globules. We detected an excess of emission over the wavelength range 5200-8000 Angstrom in DC303.8-14.2 but the nature of this emission remains open.

References in corpus (5)

• On the mass-to-light ratio of the local Galactic disc and the optical luminosity of the Galaxy
• Extended Red Emission in High-Galactic Latitude Interstellar Clouds
• A comparison of density structures of a star forming and a non-star-forming globule. DCld303.8-14.2 and Thumbprint Nebula
• Spectroscopy of diffuse light in dust clouds. Scattered light and the solar neighbourhood radiation field
• Distances to nearby molecular clouds and star forming regions.III. Localizing extinction jumps with a Hipparcos calibration of 2mass photometry

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• Measurements of the Zodiacal Light Absolute Intensity through Fraunhofer Absorption Line Spectroscopy with CIBER
• Extragalactic Background Light: a measurement at 400 nm using dark cloud shadow I. Low surface brightness spectrophotometry in the area of Lynds 1642
• Spectroscopy of diffuse light in dust clouds. Scattered light and the solar neighbourhood radiation field
• Optical and UV surface brightness of translucent dark nebulae: Dust albedo, radiation field and fluorescence emission by H2
• Light and colour of cirrus, translucent and opaque dust in the high-latitude area of LDN 1642
• Modelling of dust emission of a filament in the Taurus molecular cloud
• Measurement of the extragalactic background light at 8600Å using dark cloud shadow and the CaII-triplet lines