Extended Red Emission in High Galactic Latitude Interstellar Clouds

Abstract

We report initial results from an optical imaging survey of optically thin high Galactic latitude clouds, which is designed to study the surface brightness, structure, and spectral energy distribution of these objects. The primary aim of this paper is to study the extended red emission (ERE) that has been reported at high Galactic latitudes in earlier investigations and which is attributed to ultraviolet-excited photoluminescence of an as yet unidentified component of interstellar dust. We conduct this ongoing survey with remotely operated, fast, short focal length (0.5 m) telescopes equipped with absolutely calibrated CCD cameras yielding a field of view of 2 ; 3 . The telescopes are located at New Mexico Skies at 7300 ft (2225 m) altitude near Mayhill, New Mexico. 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 (k1000 8 FWHM ) ERE band with peak emission near 600 nm wavelength and peak intensity of $5 ; 10 À9 ergs cm À2 s À1 8 À1 sr À1 in optically thin clouds. This amounts to about 30% of the total optical surface brightness of these clouds, the remainder being consistent with expectations for dust-scattered light.

On the origin of near-infrared extragalactic background light anisotropy

“…The maps are scaled from 100 μm intensity in MJy sr −1 to near-infrared intensity in nW m −2 sr −1 using the empirical correlation determined from an analysis of the CIBER low resolution spectrometer (LRS; paper in preparation), which yields scalings of 15 nW m −2 sr −1 (MJy sr −1 ) −1 and 8 nW m −2 sr −1 (MJy sr −1 ) −1 at 1.1 μm and 1.6 μm, respectively. Our near-to far-infrared conversion factor is consistent with the upper range of conversion factors in previous measurements (19,(45)(46)(47)(48) which produces a conservative estimate for the DGL foreground. We assume a constant scaling, appropriate for optically thin dust in these high Galactic latitude fields.…”

Photoluminescence of hydrogenated amorphous carbons

“…Witt & Boroson 1990), around 700 nm in the dusty halo of M 82 (Perrin et al 1995), between 700 and 780 nm in planetary nebulae (Furton & Witt 1990 and HII regions (Perrin & Sivan 1992;Sivan & Perrin 1993;Darbon et al 1998Darbon et al , 2000 and seems to be even above 800 nm in the Evil Eye galaxy (Pierini et al 2002). Another ERE observation in high galactic latitude interstellar clouds made by Witt et al (2008) (not plotted in Fig. 13 because no reliable width can be determined) seems to confirm that, in the DISM, the ERE emission peak wavelength lies around 600 nm.…”

“…In the case of high galactic latitude interstellar clouds, where most of the diffuse interstellar medium observations occurred, illuminated by highly nonisotropic interstellar radiation field, this forward-scattering nature of interstellar grains sends most of the scattered light into directions other than the line of sight. Not taking this nonisotropic scattering into account, while the ERE is expected to be emitted isotropically, can give rise to an apparent reduction in the absorbed excitation by dust, and then to an apparent enhancement of the ERE yield in these regions, as outlined by Witt et al (2008).…”

“…In the case of a Gaussian shape: Δq = 0.57 · FWHM. (Perrin & Sivan 1992;Sivan & Perrin 1993;Darbon et al 1998Darbon et al , 2000, diffuse interstellar medium (DISM) (Szomoru & Guhathakurta 1998;Gordon et al 1998;Witt et al 2008), and in external galaxies (Perrin et al 1995;Darbon et al 1998;Pierini et al 2002). ERE is thus a general phenomenon.…”

PAHs in Astronomy - A Review

“…The carriers of the ERE are widespread throughout the diffuse interstellar medium of the Milky Way Galaxy and other galaxies (Rhee et al 2007, Berné et al 2008, Witt et al 2008.…”