Constraining Galaxy Formation and Cosmology with the Conditional Luminosity Function of Galaxies

We use the conditional luminosity function (CLF), which gives the number of galaxies with luminosities in the range [L, L+dL] that reside in a halo of mass M, to link the distribution of galaxies to that of dark matter haloes. We seek the CLF that reproduces the galaxy luminosity function and the luminosity dependence of the galaxy clustering strength and test the models by comparing the resulting mass-to-light ratios (M/L) with constraints from the Tully-Fisher (TF) relation. We obtain a number of stringent constraints on both galaxy formation and cosmology. In particular, this method can break the degeneracy between Omega_0 and the power-spectrum normalization sigma_8, inherent in current weak-lensing and cluster-abundance studies. For flat LCDM cosmogonies with sigma_8 normalized by recent weak lensing observations, the best results are obtained for Omega_0~0.3; Omega_0 < 0.2 leads to too large galaxy correlation lengths, while Omega_0 > 0.4 gives too high M/L. The best-fit model for the LCDM concordance cosmology (Omega_0=0.3) predicts M/L that are slightly too high. We discuss a number of possible effects that might remedy this problem, including small modification of cosmological parameters, warm in stead of cold dark matter, systematic errors in current observational data, and the existence of dark galaxies. Finally we use the CLF to predict several statistics about the distribution of galaxy light in the local Universe.Comment: 25 pages, 10 figures. Submitted for publication in MNRA

Bestimmung des Energiespektrums von atmosphärischen Myonneutrinos mit 3 Jahren Daten des IceCube-Detektors

In dieser Arbeit wird die Messung des Energiespektrums atmosphärischer Myonneutrinos in einem Energiebereich zwischen 125 GeV und 2 PeV mit Daten des IceCube-Detektors vorgestellt. Zur Durchführung der Messung wurde zunächst für die drei untersuchten Messjahre ein Myonneutrinodatensatz erzeugt. Für den Datensatz wurde eine Reinheit von 99.7±0.03% bei einer Ereignisrate von 3.47 mHz erreicht. Die Ereignisrate liegt circa 35% höher als bei vergleichbaren Datensätzen der selben Messjahre. Für die Bestimmung des Spektrum wurde ein etablierter Entfaltungsansatz genutzt, der im Rahmen dieser Arbeit entscheidend weiterentwickelt wurde. Das erste Ergebnis ist eine Entfaltung mit 14 Messpunkten zwischen 125 GeV und 2 PeV in einem Zenitbereich zwischen 86° und 180°. Das Ergebnis zeigt ein mit den aktuellen Messungen des astrophysikalischen Flusses kompatibles Abflachen für Eν > 100 TeV. Zusätzlich wurde das Spektrum mit jeweils 11 Messpunkten zwischen 125 GeV und 250 TeV für 3 disjunkte Zenitbereiche entfaltet.In this work the measurement of the energy spectrum of atmospheric muon neutrinos in an energy range from 125 GeV to 2 PeV with data of the IceCube detector is presented. To perform the measurement a muon neutrino sample was created from three years worth of data. The sample achieved a purity of 99.7±0.03% at an event rate of 3.47 mHz. The event rate is approximately 35% higher compared to similar samples created before from the same data. In the course of this analysis an established unfolding appraoch was significantly improved and applied to determine the energy spectrum. The first result is an unfolding with 14 data points between 125 GeV and 2 PeV in a zenith range between 86° and 180°. The result shows a flattening for Eν > 100 TeV compatible with the most recent measurements of the astrophysical flux. In addition, the spectrum was unfolded with 1 data points up to energies of 250 TeV for 3 disjoint zenith regions

RISE Germany Internship: Application of Data Mining Methods on IceCube Event Reconstructions

In this report the results from a 3-month internship are presented. The goal of the internship was to apply data mining methods to low level IceCube data in order to reconstruct the particle energies. IceCube is a neutrino observatory located at the geographical South Pole, built with the aim of detecting high energy astrophysical neutrinos. The detector consists of 5160 photomultipliers, located 1.5-2.5 kilometers beneath the icecap, which detect Cherenkov light radiated by charged particle propagation through the ice. The reconstruction of detected events directly at the pole is challenging, due to heavy constraints on resources. Due to this, only rudimentary reconstructions are performed on-site. The final results are obtained months later, once the data has been transported from the detector. An effective and prompt reconstruction directly at the pole would open a lot of new possibilities for follow-up studies of detected events. The application of state-of-the-art data mining methods can help to obtain these reconstructions on-site

RISE Germany Internship: Unfolding FACT Data

In this report the results from a 10 week internship are presented. The goal of the internship was to apply different unfolding approaches to conduct measurements of energy spectra from data aquired by FACT, the First G-APD Cherenkov Telescope. FACT is the first operational telescope of its kind, employing a camera equipped with silicon photo multipliers (G-APD aka SiPM) to primarily detect gamma rays. Improving the unfolding method can help with better interpretation of the data and more accurate physics results without the need for new equipment or more observations. The approaches tested during this internship range from simplistic matrix inversion to an improvement over of the previous standard (TRUEE)