Heidelberg 2007 – wissenschaftliches Programm

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T: Fachverband Teilchenphysik

T 402: γ-Astronomie III

T 402.4: Vortrag

Donnerstag, 8. März 2007, 17:30–17:45, INF 308 Kl. HS

TeV absorption due to the extragalactic background light (EBL): Prediction for sources at high redshifts. — •Bagmeet Behera, Stefan Wagner, and Gerd Puehlhofer — Landessternwarte, Koenigstuhl, University of Heidelberg, D 69117 Heidelberg, Germany.

The EBL in the infrared regime (IR-EBL) contains the history of galaxy formation and evolution from the very early universe. Direct measurements of the IR-EBL are difficult due to the strong infrared foreground. However, an indirect measurement can be made using the TeV spectra of Blazars. TeV photons from Blazars interact with the IR-EBL photons in the intergalactic space to produce electron-positron pairs, hence suffer attenuation. With the new generation of Cherenkov telescopes such as HESS, an unprecedented low energy threshold has been achieved. Blazar spectra at various redshifts (z) can now be derived from ~150 GeV to a few tens of TeV. By comparing the absorption-corrected Blazar spectra using different EBL scenarios, and comparing it to our current understanding of Blazar physics, we can constrain the SED (Spectral Energy Distribution) of the EBL. From the spectra of Blazars, 1ES 1101-232 at z = 0.186, and H2356-309 at z = 0.165 (Aharonian et al., Nature 440 (2006) 1018-1021) it is evident that the EBL level is lower than thought earlier. Hence Blazars at higher z should be visible in TeV. We predict the TeV spectra of gamma bright Blazars at larger z.