Extended Red Emission in High-Galactic-Latitude Interstellar Clouds

Type Conference Paper
Names Adolf N. Witt, S. Mandel, P. H. Sell, T. Dixon, K. D. Gordon, U. P. Vijh
Proceedings Title Bulletin of the American Astronomical Society
Conference Name American Astronomical Society, AAS Meeting #210, #19.04
Volume 38
Pages 119
Date May 1, 2007
URL http://adsabs.harvard.edu/abs/2007AAS...210.1904W
Library Catalog NASA ADS
Abstract Nearby, isolated interstellar clouds at high galactic latitudes are ideal objects in which the interaction of interstellar dust with photons from the well-characterized interstellar radiation field can be studied. Scattering and UV-excited photoluminescence at optical wavelengths as well as thermal emission at mid- and far-infrared wavelengths are observable manifestations of such interactions. Here we report initial results from an optical imaging survey of optically thin high-galactic-latitude clouds, which is designed to study the surface brightness and spectral energy distribution (SED) of these objects, with the primary aim of determining the characteristics of extended red emission (ERE) produced by nanoparticles. We conduct the survey with remotely operated, fast, short-focal-length (0.5 m) telescopes equipped with absolutely-calibrated CCD cameras yielding a field of view of 2x3 degrees. The telescopes are located at New Mexico Skies at 7300 ft altitude near Cloudcroft, NM. The optical surface brightness of our objects is typically a few percent of the brightness of the dark night sky, implying that the cloud SEDs must be deduced from differential surface brightness photometry in different filter bands. We find strong evidence for dust emission in the form of a broad ( 200 nm FWHM) ERE band with peak emission near 600 nm wavelength and peak intensity of 5x10^-9 erg cm^-2 s^-1 A^-1 Sr^-1 in optically thin clouds. This amounts to about 30 % of the total observed surface brightness of the clouds, the remainder being consistent with expectations for dust-scattered light. This demonstrates the ubiquitous strong presence of the ERE carrier throughout the diffuse interstellar medium of the Milky Way Galaxy. This research has been supported by grants from the NSF to the University of Toledo as well as by contributions from corporate sponsors AstroDon, RC Optical Systems, Santa Barbara Instrument Group, and Software Bisque, for which we are grateful.
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