Discovery of the two "wings" of the Kookaburra complex in VHE γ-rays with HESS

Aims. Search for Very High Energy gamma-ray emission in the Kookaburra complex through observations with the HESS array. Methods. Stereoscopic imaging of Cherenkov light emission of the gamma-ray showers in the atmosphere is used for the reconstruction and selection of the events to search for gamma-ray signals. Their spectrum is derived by a forward-folding maximum likelihood fit. Results. Two extended gamma-ray sources with an angular (68%) radius of 3.3-3.4' are discovered at high (> 13 sigma) statistical significance: HESS J1420-607 and HESS J1418-609. They exhibit a flux above 1 TeV of (2.97 +/- 0.18(stat) +/- 0.60(sys)) x 10(-12) and (2.17 +/- 0.17d(stat) +/- 0.43(sys)) x 10(-12) cm(-2) s(-1), respectively, and similar hard photon indices similar to 2.2. Multi-wavelength comparisons show spatial coincidence with the wings of the Kookaburra. Two pulsar wind nebul ae candidates, K3/PSR J1420-6048 and the Rabbit, lie on the edge of the HESS sources. Conclusions. The two new sources confirm the non-thermal nature of at least parts of the two radio wings which overlap with the gamma-ray emission and establish their connection with the two X-ray pulsar wind nebul ae candidates. Given the large point spread function of EGRET, the unidentified source(s) 3EG J1420-6038/GeV J1417-6100 could possibly be related to either or both HESS sources. The most likely explanation for the Very High Energy gamma-rays discovered by HESS is inverse Compton emission of accelerated electrons on the CosmicMicrowave Background near the two candidate pulsar wind nebul ae, K3/PSR J1420-6048 and the Rabbit. Two scenarios which could lead to the observed large (similar to 10 pc) offset-nebula type morphologies are briefly discussed.