Mathematics – Logic
Scientific paper
Dec 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006aas...209.8606n&link_type=abstract
2007 AAS/AAPT Joint Meeting, American Astronomical Society Meeting 209, #86.06; Bulletin of the American Astronomical Society, V
Mathematics
Logic
1
Scientific paper
Many of the cosmological tests to be performed with LSST will require extremely well-characterized photometric redshift measurements. The true mean redshift of the objects in each photo-z bin must be known to better than 0.002(1+z) if errors in cosmological measurements are not to be degraded. We are addressing this issue in many ways, both observational and theoretical, to ensure that the power of LSST is not limited by redshift calibration errors. We have applied recent photometric redshift algorithms to weak lensing measurements using Deep Lens Survey data, and are obtaining further wide-field photometry in LSST passbands using Subaru/Suprime-Cam to forecast LSST precision. We are also investigating new techniques: (1) One approach relies on extremely deep, multiwavelength photometry over a small fraction of the LSST area. In these regions, photometric redshifts may be calibrated using relatively bright galaxies with spectroscopy, and then applied to fainter galaxies using the many-band photometry. The accurate multiwavelength photometric redshifts obtained for these fainter galaxies can then be used to calibrate the LSST photometric redshift system. (2) A powerful alternative approach is to exploit the clustering of galaxies to test or perform photometric redshift calibrations. The angular cross-correlation between separate photometric redshift bins provides a measure of the degree to which those bins overlap in redshift, allowing photometric redshift outlier fractions to be measured. High precision results may be obtained by measuring the angular cross-correlation between objects in some photometric redshift bin and objects with known spectroscopic redshift, as a function of the spectroscopic z. This allows the true redshift distribution of the photometric sample to be reconstructed in detail, even if it includes objects too faint for spectroscopy or if spectroscopic samples are highly incomplete (like existing samples at high z). With currently planned spectroscopic samples this method can reach LSST calibration goals.
Aihara Hiroaki
Connolly Andrew J.
LSST Collaboration
Margoniner Vera E.
Miyazaki Satoshi
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