2006/10/06 by J. V. Wall, Wall, J. V.
Mathematics · Physics and Astronomy · #Astrophysics (astro-ph) #FOS: Physical sciences #Probability and Statistical Research #Statistical and numerical algorithms #Statistics Education and Methodologies #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/0610216
Presented at 'Statistical Challenges in Modern Astronomy - IV', Penn State, May 2006; to appear in the conference proceedings edited by G. J. Babu and E. D. Feigelson, 2 pages, 2 figures
arxiv created 2006/10/06 · openalex publication_date 2006/10/06 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Astronomers traditionally find steep, open-ended functions difficult: the log N - log S curve for example, or the probability-area-radius relation in making cross-waveband identifications. The debate over the existence of a redshift cutoff for RQSOs (radio-loud QSOs; Jarvis and Rawlings 2000, Wall et al. 2005) is a case in point: an instance in which a second-order effect involving radio-variable QSOs, initially selected by survey from a population with a steep source count, leads to discrepant results from different analyses. A redshift cutoff is present in optically-selected QSOs of the SDSS and in X-ray selected QSOs of XMM, ROSAT and CHANDRA. A similar cutoff for radio-loud QSOs is important to establish, because if present, no known type of obscuration can be responsible. Such a space-density diminution then defines an epoch of creation for galaxy hosts of massive black holes powering AGN, a datum for galaxy formation. I discuss the resolution of the debate: the issue is highly relevant to modern surveys and their follow-up observations.