Host galaxies of long gamma-ray bursts in the Millennium Simulation

(abridged) In this work, we investigate the nature of the host galaxies of long Gamma-Ray bursts (LGRBs) using a galaxy catalogue constructed from the Millennium Simulation. We developed an LGRB synthetic model based on the hypothesis that these events originate at the end of the life of massive stars following the collapsar model, with the possibility of including a constraint on the metallicity of the progenitor star. A complete observability pipeline was designed to calculate a probability estimation for a galaxy to be observationally identified as a host for LGRBs detected by present observational facilities. This new tool allows us to build an observable host galaxy catalogue which is required to reproduce the current stellar mass distribution of observed hosts. This observability pipeline predicts that the minimum mass for the progenitor stars should be ~75 solar masses in order to be able to reproduce BATSE observations. Systems in our observable catalogue are able to reproduce the observed properties of host galaxies, namely stellar masses, colours, luminosity, star formation activity and metallicities as a function of redshift. At z>2, our model predicts that the observable host galaxies would be very similar to the global galaxy population. We found that ~88 per cent of the observable host galaxies with mean gas metallicity lower than 0.6 solar have stellar masses in the range 10^8.5-10^10.3 solar masses in excellent agreement with observations. Interestingly, in our model observable host galaxies remain mainly within this mass range regardless of redshift, since lower stellar mass systems would have a low probability of being observed while more massive ones would be too metal-rich. Observable host galaxies are predicted to preferentially inhabit dark matter haloes in the range 10^11-10^11.5 solar masses, with a weak dependence on redshift.Comment: 11 pages, 10 figures, accepted for publication in MNRA

Evaluation of vaccination herd immunity effects for anogenital warts in a low coverage setting with human papillomavirus vaccine—an interrupted time series analysis from 2005 to 2010 using health insurance data

Abstract Background Shortly after the human papillomavirus (HPV) vaccine recommendation and hence the reimbursement of vaccination costs for the respective age groups in Germany in 2007, changes in the incidence of anogenital warts (AGWs) were observed, but it was not clear at what level the incidence would stabilize and to what extent herd immunity would be present. Given the relatively low HPV vaccination coverage in Germany, we aimed to assess potential vaccination herd immunity effects in the German setting. Methods A retrospective open cohort study with data from more than nine million statutory health insurance members from 2005 to 2010 was conducted. AGW cases were identified using ICD-10-codes. The incidence of AGWs was estimated by age, sex, and calendar quarter. Age and sex specific incidence rate ratios were estimated comparing the years 2009–2010 (post-vaccination period) with 2005–2007 (pre-vaccination period). Results Incidence rate ratio of AGWs for the post-vaccination period compared to the pre-vaccination period showed a u-shaped decrease among the 14- to 24-year-old females and males which corresponds well with the reported HPV vaccination uptake in 2008. A maximum reduction of up to 60% was observed for the 16- to 20-year-old females and slightly less pronounced (up to 50%) for the 16- and 18-year-old males. Age groups outside of the range 14–24 years demonstrated no decrease. The decrease of incidence occurred in both sexes early after the vaccine recommendation and stabilized at lower levels in 2009–2010. Conclusions A relative reduction of up to 50% among males of approximately similar age groups as that of females receiving the HPV vaccination suggests herd protection resulting from assortative mixing by age. The early decrease among males can be reduced over time due to partner change