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We measure the cross-correlation of Atacama cosmology telescope cosmic microwave background (CMB) lensing convergence maps with quasar maps made from the Sloan Digital Sky Survey DR8 SDSS-XDQSO photometric catalog. The CMB lensing quasar cross-power spectrum is detected for the first time at a significance of 3.8σ, which directly confirms that the quasar distribution traces the mass distribution at high redshifts z>1. Our detection passes a number of null tests and systematic checks. Using this cross-power spectrum, we measure the amplitude of the linear quasar bias assuming a template for its redshift dependence, and find the amplitude to be consistent with an earlier measurement from clustering; at redshift z≈1.4, the peak of the distribution of quasars in our maps, our measurement corresponds to a bias of b=2.5±0.6. With the signal-to-noise ratio on CMB lensing measurements likely to improve by an order of magnitude over the next few years, our results demonstrate the potential of CMB lensing cross-correlations to probe astrophysics at high redshifts.
Sherwin, B. D., Das, S., Hajian, A., Addison, G., Bond, R., Crichton, D., Devlin, M. J., & Reese, E. D. (2012). The Atacama Cosmology Telescope: Cross-Correlation of Cosmic Microwave Background Lensing and Quasars. Retrieved from https://repository.upenn.edu/physics_papers/274
Date Posted: 27 February 2013
This document has been peer reviewed.