Extragalactic background light : a measurement at 400 nm using dark cloud shadow(*dagger)-I. Low surface brightness spectrophotometry in the area of Lynds 1642

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Mattila , K , Lehtinen , K , Väisänen , P , von Appen-Schnur , G & Leinert , C 2017 , ' Extragalactic background light : a measurement at 400 nm using dark cloud shadow(*dagger)-I. Low surface brightness spectrophotometry in the area of Lynds 1642 ' , Monthly Notices of the Royal Astronomical Society , vol. 470 , no. 2 , pp. 2133-2151 . https://doi.org/10.1093/mnras/stx1295

Title: Extragalactic background light : a measurement at 400 nm using dark cloud shadow(*dagger)-I. Low surface brightness spectrophotometry in the area of Lynds 1642
Author: Mattila, K.; Lehtinen, K.; Väisänen, P.; von Appen-Schnur, G.; Leinert, Ch.
Contributor: University of Helsinki, Department of Physics
University of Helsinki, Department of Physics
Date: 2017-09
Language: eng
Number of pages: 19
Belongs to series: Monthly Notices of the Royal Astronomical Society
ISSN: 0035-8711
URI: http://hdl.handle.net/10138/215213
Abstract: We present the method and observations for the measurement of the Extragalactic Background Light (EBL) utilizing the shadowing effect of a dark cloud. We measure the surface brightness difference between the opaque cloud core and its unobscured surroundings. In the difference the large atmospheric and Zodiacal light components are eliminated and the only remaining foreground component is the scattered starlight from the cloud itself. Although much smaller, its separation is the key problem in the method. For its separation we use spectroscopy. While the scattered starlight has the characteristic Fraunhofer lines and 400 nm discontinuity, the EBL spectrum is smooth and without these features. Medium resolution spectrophotometry at lambda = 380-580 nm was performed with VLT/FORS at ESO of the surface brightness in and around the high-galactic-latitude dark cloud Lynds 1642. Besides the spectrum for the core with AV greater than or similar to 15 mag, further spectra were obtained for intermediate-opacity cloud positions. They are used as proxy for the spectrum of the impinging starlight spectrum and to facilitate the separation of the scattered starlight (cf. Paper II; Mattila et al.). Our spectra reach a precision of less than or similar to 0.5 x 10(-9) erg cm(-2) s(-1) sr(-1) angstrom(-1) as required to measure an EBL intensity in range of similar to 1 to a few times 10(-9) erg cm(-2) s(-1) sr(-1) angstrom(-1). Because all surface brightness components are measured using the same equipment, the method does not require unusually high absolute calibration accuracy, a condition that has been a problem for some previous EBL projects.
Subject: ISM: clouds: Lynds 1642
dust, extinction
solar neighbourhood
diffuse radiation
cosmology: observations
FAR-INFRARED OBSERVATIONS
1ST DETECTIONS
EXPERIMENT SEARCH
SKY BRIGHTNESS
8000 ANGSTROM
DUST CLOUD
GALAXIES
BLAZARS
TEMPERATURE
RADIATION
115 Astronomy, Space science
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