耀变体发出的伽马射线揭示的低水平星系际背景光。

A low level of extragalactic background light as revealed by gamma-rays from blazars.

作者信息

Aharonian F, Akhperjanian A G, Bazer-Bachi A R, Beilicke M, Benbow W, Berge D, Bernlöhr K, Boisson C, Bolz O, Borrel V, Braun I, Breitling F, Brown A M, Chadwick P M, Chounet L-M, Cornils R, Costamante L, Degrange B, Dickinson H J, Djannati-Ataï A, Drury L O'C, Dubus G, Emmanoulopoulos D, Espigat P, Feinstein F, Fontaine G, Fuchs Y, Funk S, Gallant Y A, Giebels B, Gillessen S, Glicenstein J F, Goret P, Hadjichristidis C, Hauser D, Hauser M, Heinzelmann G, Henri G, Hermann G, Hinton J A, Hofmann W, Holleran M, Horns D, Jacholkowska A, de Jager O C, Khélifi B, Klages S, Komin Nu, Konopelko A, Latham I J, Le Gallou R, Lemière A, Lemoine-Goumard M, Leroy N, Lohse T, Martin J M, Martineau-Huynh O, Marcowith A, Masterson C, McComb T J L, de Naurois M, Nolan S J, Noutsos A, Orford K J, Osborne J L, Ouchrif M, Panter M, Pelletier G, Pita S, Pühlhofer G, Punch M, Raubenheimer B C, Raue M, Raux J, Rayner S M, Reimer A, Reimer O, Ripken J, Rob L, Rolland L, Rowell G, Sahakian V, Saugé L, Schlenker S, Schlickeiser R, Schuster C, Schwanke U, Siewert M, Sol H, Spangler D, Steenkamp R, Stegmann C, Tavernet J-P, Terrier R, Théoret C G, Tluczykont M, van Eldik C, Vasileiadis G, Venter C, Vincent P, Völk H J, Wagner S J

机构信息

Max-Planck-Institut für Kernphysik, PO Box 103980, D 69029 Heidelberg, Germany.

出版信息

Nature. 2006 Apr 20;440(7087):1018-21. doi: 10.1038/nature04680.

DOI:10.1038/nature04680

PMID:16625189

Abstract

The diffuse extragalactic background light consists of the sum of the starlight emitted by galaxies through the history of the Universe, and it could also have an important contribution from the 'first stars', which may have formed before galaxy formation began. Direct measurements are difficult and not yet conclusive, owing to the large uncertainties caused by the bright foreground emission associated with zodiacal light. An alternative approach is to study the absorption features imprinted on the gamma-ray spectra of distant extragalactic objects by interactions of those photons with the background light photons. Here we report the discovery of gamma-ray emission from the blazars H 2356 - 309 and 1ES 1101 - 232, at redshifts z = 0.165 and z = 0.186, respectively. Their unexpectedly hard spectra provide an upper limit on the background light at optical/near-infrared wavelengths that appears to be very close to the lower limit given by the integrated light of resolved galaxies. The background flux at these wavelengths accordingly seems to be strongly dominated by the direct starlight from galaxies, thus excluding a large contribution from other sources-in particular from the first stars formed. This result also indicates that intergalactic space is more transparent to gamma-rays than previously thought.

摘要

弥漫的河外背景光由宇宙历史中星系发出的星光总和构成，它也可能有来自“第一代恒星”的重要贡献，第一代恒星可能在星系形成开始之前就已形成。由于与黄道光相关的明亮前景发射造成的巨大不确定性，直接测量很困难且尚无定论。一种替代方法是研究那些光子与背景光光子相互作用在遥远河外天体的伽马射线光谱上留下的吸收特征。在此，我们报告分别在红移z = 0.165和z = 0.186处发现了耀变体H 2356 - 309和1ES 1101 - 232的伽马射线发射。它们出人意料的硬光谱给出了光学/近红外波长背景光的上限，该上限似乎非常接近已分辨星系的积分光给出的下限。因此，这些波长的背景通量似乎主要由星系的直接星光主导，从而排除了其他来源特别是第一代恒星形成的大量贡献。这一结果还表明，星系际空间对伽马射线的透明度比之前认为的更高。