Breaking The Quasar L-z Degeneracy Using PDF-weighted Quasar-galaxy Cross-correlations In Deep, Wide NASA Fields

Details Breaking The Quasar L-z Degeneracy Using PDF-weighted Quasar-galaxy Cross-correlations In Deep, Wide NASA Fields Breaking The Quasar L-z Degeneracy Using PDF-weighted Quasar-galaxy Cross-correlations In Deep, Wide NASA Fields

Jan 2010

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010aas...21540905b&link_type=abstract

American Astronomical Society, AAS Meeting #215, #409.05; Bulletin of the American Astronomical Society, Vol. 42, p.233

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We present a new method for measuring the two-point correlation function, as described by Myers, White, and Ball (2009). The method is an augmentation of previous techniques that use a heterogeneous set of spectroscopic objects to anchor the distance scale, and a well-controlled set of photometric detections to reduce noise. Our new approach weights by the information present in the full photometric redshift probability density function (PDF) to dramatically improve the clustering signal. For instance, an initial test yielded a factor of 5 improvement for quasar clustering in the Sloan Digital Sky Survey. The extra signal arises because we neither express the photometric redshift as a single value nor assign a simplified PDF functional form such as a single Gaussian. Our technique is generally applicable and should be particularly useful where complex spectroscopic data sets (e.g., BOSS) are overlapped by deep photometry (e.g., Pan-STARRS, DES, or LSST).
Our method depends only on photometric detections in a single survey, but additional multi-wavelength data can be used to refine the information in the PDF weighting. This makes our approach also highly suited to regions of the sky where deep, multiwavelength space surveys overlap ground-based spectroscopy (e.g., COSMOS or the Bootes Survey). We assign photometric redshift PDFs to photometrically classified galaxies detected in the optical component of COSMOS, and use PDF weights to cross-correlate them against a spectroscopically confirmed AGN sample. We also report on similar results in the Bootes Survey. The deep spectroscopy and photometry in fields such as COSMOS and Bootes will allow new investigations of how AGN cluster as a function of luminosity and type, potentially breaking the so-called L-z degeneracy. Finally, we address the often computationally intensive requirements of utilizing full PDFs.
This research was funded in part by NASA ADP grant NNX08AJ28G.

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