Measurement of the extragalactic background light at 8600\r{A} using dark cloud shadow and the CaII-triplet lines

TL;DR

This study measures the near-infrared extragalactic background light at 8600 Å using a dark-cloud shadow method, achieving a tentative detection with a differential spectrum that minimizes foreground contamination.

Contribution

It introduces a novel dark-cloud shadow technique combined with spectral templates to measure the EBL at 8600 Å, reducing foreground interference.

Findings

Estimated EBL intensity: 13.8 ± 6.5 nW m$^{-2}$ sr$^{-1}$

Tentative detection at 2.1 sigma significance

Method effectively minimizes foreground contamination

Abstract

We present results of a measurement of the near infrared Extragalactic Background Light using the dark-cloud method. Long-slit spectra covering the opaque core of the intermediate--latitude globule DC303.8-14.2 and the almost unobscured off area were measured using nodding-along-the-slit measuring technique providing a differential spectrum free of most of the foreground components. A template for the only remaining major foreground component, the scattered integrated starlight dominated by the strong Ca II triplet lines at 8498, 8542, 8664$\r{A}$, from the dark core itself was constructed using the GAIA RVS spectral database. The derived EBL intensity is $1.62\pm 0.76(\sigma_{stat})\, 10^{-9} erg\, cm^{-2} s^{-1}\r{A}^{-1} sr^{-1}$ or $13.8\pm6.5(\sigma_{stat})$nW m$^{-2}$sr$^{-1}$; this represents a tentative detection at $2.1\sigma$, level.