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Publisher: New York : Hindawi Publishing Corporation ×

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    The STELLA robotic observatory on tenerife
    (New York : Hindawi Publishing Corporation, 2010) Strassmeier, K.G.; Granzer, T.; Weber, M.; Woche, M.; Popow, E.; Jrvinen, A.; Bartus, J.; Bauer, S.-M.; Dionies, F.; Fechner, T.; Bittner, W.; Paschke, J.
    The Astrophysical Institute Potsdam (AIP) and the Instituto de Astrofísica de Canarias (IAC) inaugurated the robotic telescopes STELLA-I and STELLA-II (STELLar Activity) on Tenerife on May 18, 2006. The observatory is located on the Izaa ridge at an elevation of 2400m near the German Vacuum Tower Telescope. STELLA consists of two 1.2m alt-az telescopes. One telescope fiber feeds a bench-mounted high-resolution echelle spectrograph while the other telescope feeds a wide-field imaging photometer. Both scopes work autonomously by means of artificial intelligence. Not only that the telescopes are automated, but the entire observatory operates like a robot, and does not require any human presence on site. Copyright © 2010 Klaus G. Strassmeier et al.
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    Three years of experience with the STELLA robotic observatory
    (New York : Hindawi Publishing Corporation, 2010) Granzer, T.; Weber, M.; Strassmeier, K.G.
    Since May 2006, the two STELLA robotic telescopes at the Izaa observatory in Tenerife, Spain, delivered an almost uninterrupted stream of scientific data. To achieve such a high level of autonomous operation, the replacement of all troubleshooting skills of a regular observer in software was required. Care must be taken on error handling issues and on robustness of the algorithms used. In the current paper, we summarize the approaches we followed in the STELLA observatory. Copyright © 2010 Thomas Granzer et al.
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    Dwarf galaxies in voids: Dark matter halos and gas cooling
    (New York : Hindawi Publishing Corporation, 2010) Hoeft, M.; Gottlber, S.
    Galaxy surveys have shown that luminous galaxies are mainly distributed in large filaments and galaxy clusters. The remaining large volumes are virtually devoid of luminous galaxies. This is in concordance with the formation of the large-scale structure in the universe as derived from cosmological simulations. However, the numerical results indicate that cosmological voids are abundantly populated with dark matter haloes which may in principle host dwarf galaxies. Observational efforts have in contrast revealed that voids are apparently devoid of dwarf galaxies. We investigate the formation of dwarf galaxies in voids by hydrodynamical cosmological simulations. Due to the cosmic ultraviolet background radiation low-mass haloes show generally a reduced baryon fraction. We determine the characteristic mass below which dwarf galaxies are baryon deficient. We show that the circular velocity below which the accretion of baryons is suppressed is approximately 40km s-1. The suppressed baryon accretion is caused by the photo-heating due to the UV background. We set up a spherical halo model and show that the effective equation of the state of the gas in the periphery of dwarf galaxies determines the characteristic mass. This implies that any process which heats the gas around dwarf galaxies increases the characteristic mass and thus reduces the number of observable dwarf galaxies. Copyright © 2010 M. Hoeft and S. Gottlöber.
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    Bosonic spectral function and the electron-phonon interaction in HTSC cuprates
    (New York : Hindawi Publishing Corporation, 2010) Maksimov, E.G.; Kulić, M.L.; Dolgov, O.V.
    In this paper we discuss experimental evidence related to the structure and origin of the bosonic spectral function α2 F(ω) in high-temperature superconducting (HTSC) cuprates at and near optimal doping. Global properties of α2 F(ω), such as number and positions of peaks, are extracted by combining optics, neutron scattering, ARPES and tunnelling measurements. These methods give evidence for strong electron-phonon interaction (EPI) with 1<λep3.5 in cuprates near optimal doping. We clarify how these results are in favor of the modified Migdal-Eliashberg (ME) theory for HTSC cuprates near optimal doping. In Section 2 we discuss theoretical ingredientssuch as strong EPI, strong correlationswhich are necessary to explain the mechanism of d-wave pairing in optimally doped cuprates. These comprise the ME theory for EPI in strongly correlated systems which give rise to the forward scattering peak. The latter is supported by the long-range part of EPI due to the weakly screened Madelung interaction in the ionic-metallic structure of layered HTSC cuprates. In this approach EPI is responsible for the strength of pairing while the residual Coulomb interaction and spin fluctuations trigger the d-wave pairing. Copyright © 2010 E. G. Maksimov et al.