1. Leiden Observatory, Leiden University, PO Box 9513, NL-2300 RA Leiden, the Netherlands
2. Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences, Konkoly Thege Miklós út 15-17, H-1121 Budapest, Hungary
3. Department of Astronomy, Eötvös Loránd University, Pázmány Péter sétány. 1/A, H-1117 Budapest, Hungary
4. MTA-ELTE Extragalactic Astrophysics Research Group, Pázmány Péter sétány 1/A, H-1117 Budapest, Hungary
5. Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg, Germany