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Contact 		First-author publications:
  • Only marginal alignment of disc galaxies; René Andrae & Knud Jahnke; accepted by MNRAS 2011
    Content: We investigate whether the angular momenta of disc galaxies are not randomly oriented but instead aligned to a certain extent. Given the substantial uncertainties in the data, we do not find statistical evidence for this hypothesis. Moreover, we show that ellipticity estimates from second moments are strongly biased by ellipticity gradients from bulge and disc.
  • Quantifying galaxy shapes: Sersiclets and beyond; René Andrae, Peter Melchior & Knud Jahnke; accepted by MNRAS 2011
    Content: We investigate the orthonormalisation of the Sersic profile and the problems of this approach. One of the major results is to show that the Sersic profile is the first-order Taylor expansion of any light profile. This naturally explains why the Sersic profile is such a good empirical fit. Moreover, it is then obvious how to enhance the Sersic profile by higher-order terms. Finally, a future astrophysically motivated light profile can then also be Taylor-expanded, thereby providing an astrophysical interpretation for the Sersic-model parameters.
  • Parametrising arbitrary galaxy morphologies: potentials and pitfalls; René Andrae, Knud Jahnke & Peter Melchior; MNRAS, vol. 411, pp. 385-401, 2011
    Content: We investigate the limitations of different approaches to parametrise galaxy morphologies, namely, CAS, Gini, M20, Sersic profiles, shapelets. Our results (obtained from simulations and comparison to the Zurich Structure and Morphology Catalog) challenge the current paradigm that favours model-independent approaches (e.g. CAS). We argue that elaborate model-based parametrisation schemes are superior such that their additional level of complication is justified.
  • Soft clustering analysis of galaxy morphologies: A worked example with SDSS; René Andrae, Peter Melchior & Matthias Bartelmann; A&A, vol. 522, pp. A21, 2010
    Content: We introduce an algorithm for classifying galaxy morphologies that automatically discovers the ''optimal'' classes in a given data sample. This approach is called ''clustering analysis''. Galaxy morphologies are parametrised in terms of shapelet decompositions. Furthermore, we argue that galaxy morphologies should only be classified probabilistically (soft). We apply the method to real SDSS galaxies and obtain convincing results. This article summarises my master project.
Co-author publications:
  • The impact of galaxy interactions on AGN activity in zCOSMOS; J.D. Silverman, P. Kampczyk, K. Jahnke, René Andrae, et al.; accepted by ApJ, 2011
    Content:In this paper, the AGN activity on kinematical interacting galaxies is compared to non-interacting galaxies. We find that AGN activity is enhanced by a factor of two for interacting pairs. My contribution was the estimation of intrinsic AGN fractions based on a decision tree that accounts for the non-trivial selection effects in the data.
  • The bulk of the black hole growth since z~1 occurs in a secular universe: No merger-AGN connection; Mauricio Cisternas et al.; submitted to ApJ, vol. 726, pp. 57, 2011
    Content:One of the questions this paper asks is whether AGN acticity is triggered by mergers. Comparing the merger rate in a sample of active and inactive galaxies, we come to the conclusion that there is no statistical evidence that merging events are more frequent for active galaxies than for inactives. I performed the Monte-Carlo sampling from the binomial likelihoods and the Bayesian combination of the ten person's classification results.
  • Deconvolution with Shapelets; Peter Melchior, René Andrae, Matteo Maturi & Matthias Bartelmann; A&A, vol. 493, pp. 727-734, 2009
    Content: We explain how to perform convolution and deconvolution (from the point-spread function) in shapelet space. There have been several prior attempts to solve this problem, but our approach is based on the exact analytic solution. We compare our method to the other methods. My contribution to this work was the analytical solution given in the appendix.
Unrefereed arXiv manuscripts and conference articles:
  • Dos and don'ts of reduced chi-squared; René Andrae, Tim Schulze-Hartung & Peter Melchior, 2010
    Content: In this arXiv manuscript, we review the pitfals of using reduced chi-square. In the astrophysical literature, there are many examples where reduced chi-square is used inadequately such that the results obtained have no credibility.
  • Error estimation in astronomy: A guide; René Andrae, 2010
    Content: This arXiv manuscript is an introduction to methods for error estimation that addresses undergraduate and graduate students. I explain the basics of parameter estimation and why error estimation is of vital importance. Then I briefly outline seven methods for error estimation which are applicable in different contexts.
  • Morphological Galaxy Classification with Shapelets; René Andrae & Peter Melchior; AIP Conference Proceedings vol. 1082, pp. 129-133, 2008
    Content: A preliminary version of Soft clustering analysis of galaxy morphologies: A worked example with SDSS written for the classification workshop 2008 at Ringberg castle, Germany.