The galaxy counterpart of the high-metallicity and 16 kpc impact parameter DLA towards Q0918+1636 - a challenge to galaxy formation models?

The quasar Q0918+1636 (z=3.07) has an intervening high-metallicity Damped Lyman-alpha Absorber (DLA) along the line of sight, at a redshift of z=2.58. The DLA is located at a large impact parameter of 16.2 kpc, and has an almost solar metallicity. It is shown, that a novel type of cosmological galaxy formation models, invoking a new SNII feedback prescription, the Haardt & Madau (2012) UVB field and explicit treatment of UVB self-shielding, can reproduce the observed characteristics of the DLA. UV radiation from young stellar populations in the galaxy, in particular in the photon energy range 10.36-13.61 eV (relating to Sulfur II abundance), are also considered in the analysis. It is found that a) for L~L* galaxies (at z=2.58), about 10% of the sight-lines through the galaxies at impact parameter 16.2 kpc will display a Sulfur II column density N(SII)$>$ 10$^{15.82}$ cm$^{-2}$ (the observed value for the DLA), and b) considering only cases where a near-solar metallicity will be detected at 16.2 kpc impact parameter, the probability distribution of galaxy SFR peaks near the value observed for the DLA galaxy counterpart of ~27 Msun/yr. It is argued, that the bulk of the alpha-elements, like Sulfur, traced by the high metal column density, b=16.2 kpc absorption lines, were produced by evolving young stars in the inner galaxy, and later transported outward by galactic winds.Comment: 22 pages, 24 figures, MNRAS in pres

On the Key-Uncertainty of Quantum Ciphers and the Computational Security of One-way Quantum Transmission

We consider the scenario where Alice wants to send a secret (classical) $n$-bit message to Bob using a classical key, and where only one-way transmission from Alice to Bob is possible. In this case, quantum communication cannot help to obtain perfect secrecy with key length smaller then $n$. We study the question of whether there might still be fundamental differences between the case where quantum as opposed to classical communication is used. In this direction, we show that there exist ciphers with perfect security producing quantum ciphertext where, even if an adversary knows the plaintext and applies an optimal measurement on the ciphertext, his Shannon uncertainty about the key used is almost maximal. This is in contrast to the classical case where the adversary always learns $n$ bits of information on the key in a known plaintext attack. We also show that there is a limit to how different the classical and quantum cases can be: the most probable key, given matching plain- and ciphertexts, has the same probability in both the quantum and the classical cases. We suggest an application of our results in the case where only a short secret key is available and the message is much longer.Comment: 19 pages, 2 figures. This is a revised version of an earlier version that appeared in the proc. of Eucrocrypt'04:LNCS3027, 200

The Density Profile of Cluster-scale Dark Matter Halos

We measure the average gravitational shear profile of 6 massive clusters (M_vir ~ 10^15 M_sun) at z=0.3 out to a radius ~2h^-1 Mpc. The measurements are fitted to a generalized NFW-like halo model \rho(r) with an arbitrary r -> 0 slope \alpha. The data are well fitted by such a model with a central cusp with \alpha ~ 0.9 - 1.6 (68% confidence interval). For the standard-NFW case \alpha = 1.0, we find a concentration parameter c_vir that is consistent with recent predictions from high-resolution CDM N-body simulations. Our data are also well fitted by an isothermal sphere model with a softened core. For this model, our 1\sigma upper limit for the core radius corresponds to a limit \sigma_star \leq 0.1 cm^2 g^-1 on the elastic collision cross-section in a self-interacting dark matter model.Comment: 4 pages, 3 figures; version accepted for publication by ApJ Letters. Three figures omitted to allow space for new fig. 3 and expanded results and discussion sections, including NSIS model fi

Reconciling the Metallicity Distributions of Gamma-ray Burst, Damped Lyman-alpha, and Lyman-break Galaxies at z=3

We test the hypothesis that the host galaxies of long-duration gamma-ray bursts (GRBs) as well as quasar-selected damped Lyman-alpha (DLA) systems are drawn from the population of UV-selected star-forming, high-z galaxies (generally referred to as Lyman-break galaxies). Specifically, we compare the metallicity distributions of the GRB and DLA populations to simple models where these galaxies are drawn randomly from the distribution of star-forming galaxies according to their star-formation rate and HI cross-section respectively. We find that it is possible to match both observational distributions assuming very simple and constrained relations between luminosity, metallicity and HI sizes. The simple model can be tested by observing the luminosity distribution of GRB host galaxies and by measuring the luminosity and impact parameters of DLA selected galaxies as a function of metallicity. Our results support the expectation that GRB and DLA samples, in contrast to magnitude limited surveys, provide an almost complete census of z=3 star-forming galaxies that are not heavily dust-obscured.Comment: 31 pages, 6 figures. Accepted for publication in Ap

Infertility in a community and clinic-based sample of couples in Moshi, northern Tanzania

Background: Previous research on the aetiology of infertility in sub-Saharan Africa was generally clinic based and it is not known whether findings from this work are representative of the general population. A better understanding of the medical causes of infertility is crucial for reducing the incidence of infertility and for improving the clinical management. Objective: To determine the type and aetiology of infertility in a community and clinicbased sample. Design: Couples identified as infertile in a representative cross-sectional survey from a community-based sample of 2019 women aged 20-44 years and couples seeking care for infertility at a tertiary health facility. Setting: The community-based sample was drawn from Moshi Urban District and the clinic-based sample from patients seeking care at Kilimanjaro Christian Medical Centre (KCMC) in 2002 and 2003.Participants: Sixty six couples identified as infertile in the community-based sample and 112 couples seeking care for infertility. Results: The percentage of primary infertility was 37.1% and secondary infertility was 62.9%. Female only factor infertility was identified in 65.9% of the couples, male only factor in 6.8%, male and female factors in 15.2% and unexplained infertility in 12.1%. Conclusion: The type and aetiology of infertility were the same in the community and clinic-based sample suggesting that the couples seeking infertility health care were representative of the general infertile population. Tubal factor infertility was the commonest cause. East AfricanMedical Journaly Vol. 83(1) 2006: 10-1