Jacek Guzik

Publications (5)9.8 Total impact

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  Available from: arxiv.org

  Article: Systematic effects in the sound horizon scale measurements

  Jacek Guzik, Gary Bernstein, Robert E. Smith
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  ABSTRACT: We investigate three potential sources of bias in distance estimations made assuming that a very simple estimator of the baryon acoustic oscillation (BAO) scale provides a standard ruler. These are the effects of the non-linear evolution of structure, scale-dependent bias and errors in the survey window function estimation. The simple estimator used is the peak of the smoothed correlation function, which provides a variance in the BAO scale that is close to optimal, if appropriate low-pass filtering is applied to the density field. While maximum-likelihood estimators can eliminate biases if the form of the systematic error is fully modeled, we estimate the potential effects of un- or mis-modelled systematic errors. Non-linear structure growth using the Smith et al. (2003) prescription biases the acoustic scale by <0.3% at z>1 under the correlation-function estimator. The biases due to representative but simplistic models of scale-dependent galaxy bias are below 1% at z>1 for bias behaviour in the realms suggested by halo model calculations, which is expected to be below statistical errors for a 1000 sq.degs. spectroscopic survey. The distance bias due to a survey window function errors is given in a simple closed form and it is shown it has to be kept below 2% not to bias acoustic scale more than 1% at z=1, although the actual tolerance can be larger depending upon galaxy bias. These biases are comparable to statistical errors for ambitious surveys if no correction is made for them. We show that RMS photometric zero-point errors (at limiting magnitude 25 mag) below 0.14 mag and 0.01 mag for redshift z=1 (red galaxies) and z=3 (Lyman-break galaxies), respectively, are required in order to keep the distance estimator bias below 1%.
  06/2006;
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  Available from: arxiv.org

  Article: Systematic errors in weak lensing: application to SDSS galaxy–galaxy weak lensing

  Rachel Mandelbaum, Christopher M. Hirata, Uroš Seljak, Jacek Guzik, Nikhil Padmanabhan, Cullen Blake, Michael R. Blanton, Robert Lupton, Jonathan Brinkmann
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  ABSTRACT: Weak lensing is emerging as a powerful observational tool to constrain cosmological models, but is at present limited by an incomplete understanding of many sources of systematic error. Many of these errors are multiplicative and depend on the population of background galaxies. We show how the commonly cited geometric test, which is rather insensitive to cosmology, can be used as a ratio test of systematics in the lensing signal at the 1 per cent level. We apply this test to the galaxy–galaxy lensing analysis of the Sloan Digital Sky Survey (SDSS), which at present is the sample with the highest weak lensing signal-to-noise ratio and has the additional advantage of spectroscopic redshifts for lenses. This allows one to perform meaningful geometric tests of systematics for different subsamples of galaxies at different mean redshifts, such as brighter galaxies, fainter galaxies and high-redshift luminous red galaxies, both with and without photometric redshift estimates. We use overlapping objects between SDSS and the DEEP2 and 2df-Sloan LRG and Quasar (2SLAQ) spectroscopic surveys to establish accurate calibration of photometric redshifts and to determine the redshift distributions for SDSS. We use these redshift results to compute the projected surface density contrast ΔΣ around 259 609 spectroscopic galaxies in the SDSS; by measuring ΔΣ with different source samples we establish consistency of the results at the 10 per cent level (1σ). We also use the ratio test to constrain shear calibration biases and other systematics in the SDSS survey data to determine the overall galaxy–galaxy weak lensing signal calibration uncertainty. We find no evidence of any inconsistency among many subsamples of the data.
  Monthly Notices of the Royal Astronomical Society 07/2005; 361(4):1287 - 1322. · 4.90 Impact Factor
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  Available from: arxiv.org

  Article: Inhomogeneous systematic signals in cosmic shear observations

  Jacek Guzik, Gary Bernstein
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  ABSTRACT: We calculate the systematic errors in the weak gravitational lensing power spectrum which would be caused by spatially varying calibration (i.e. multiplicative) errors, such as might arise from uncorrected seeing or extinction variations. The systematic error is fully described by the angular two-point correlation function of the systematic in the case of the 2D lensing that we consider here. We investigate three specific cases: Gaussian, ``patchy'' and exponential correlation functions. In order to keep systematic errors below statistical errors in future LSST-like surveys, the spatial variation of calibration should not exceed 3% rms. This conclusion is independently true for all forms of correlation function we consider. The relative size the E- and B-mode power spectrum errors does, however, depend upon the form of the correlation function, indicating that one cannot repair the E-mode power spectrum systematics by means of the B-mode measurements. Comment: 8 pages, 3 figures. Changes reflect PRD published version
  07/2005;
• Source

  Available from: arxiv.org

  Article: Galaxy-galaxy weak lensing in SDSS: intrinsic alignments and shear calibration errors

  Christopher M. Hirata, Rachel Mandelbaum, Uros Seljak, Jacek Guzik, Nikhil Padmanabhan, Cullen Blake, Jonathan Brinkmann, Tamas Budavari, Andrew Connolly, Istvan Csabai, Ryan Scranton, Alexander S. Szalay
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  ABSTRACT: Galaxy-galaxy lensing has emerged as a powerful probe of the dark matter halos of galaxies, but is subject to contamination if intrinsically aligned satellites of the lens galaxy are used as part of the source sample. We present a measurement of this intrinsic shear using 200,747 lens galaxies from the Sloan Digital Sky Survey (SDSS) spectroscopic sample and a sample of satellites selected using photometric redshifts. The mean intrinsic shear at transverse separations of 30--446$h^{-1}$ kpc is constrained to be $-0.0062<\Delta\gamma<+0.0066$ (99.9 per cent confidence, including identified systematics), which limits contamination of the galaxy-galaxy lensing signal to at most $\sim 15$ per cent on these scales. We present these limits as a function of transverse separation and lens luminosity. We furthermore investigate shear calibration biases in the SDSS, which can also affect galaxy-galaxy lensing, and conclude that the shear amplitude is calibrated to better than 18 per cent. This includes noise-induced calibration biases in the ellipticity, which are small for the sample considered here, but which can be more important if low signal-to-noise or poorly resolved source galaxies are used. Comment: 23 pages, 13 figures, matches MNRAS accepted version. This is a preprint of an Article accepted for publication in Monthly Notices of the Royal Astronomical Society. (c)2004 The Royal Astronomical Society
  Monthly Notices of the Royal Astronomical Society 03/2004; · 4.90 Impact Factor
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  Available from: ArXiv

  Article: Lensing effect on polarization in microwave background: extracting convergence power spectrum

  Jacek Guzik, Uros Seljak, Matias Zaldarriaga
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  ABSTRACT: Matter inhomogeneities along the line of sight deflect the cosmic microwave background (CMB) photons originating at the last scattering surface at redshift $z \sim 1100$. These distortions modify the pattern of CMB polarization. We identify specific combinations of Stokes $Q$ and $U$ parameters that correspond to spin 0,$\pm 2$ variables and can be used to reconstruct the projected matter density. We compute the expected signal to noise as a function of detector sensitivity and angular resolution. With Planck satellite the detection would be at a few $\sigma$ level. Several times better detector sensitivity would be needed to measure the projected dark matter power spectrum over a wider range of scales, which could provide an independent confirmation of the projected matter power spectrum as measured from other methods. Comment: 17 pages, 5 figures, accepted for publication in PRD
  12/1999;