Astronomy and Astrophysics – Astrophysics
Scientific paper
2005-07-05
Mon.Not.Roy.Astron.Soc.370:1008-1024,2006
Astronomy and Astrophysics
Astrophysics
20 pages, 8 figures, matches MNRAS accepted version (includes updated discussion of systematics, no changes to conclusions)
Scientific paper
10.1111/j.1365-2966.2006.10539.x
We present the results of attempts to detect the ellipticity of dark matter halos using galaxy-galaxy weak lensing with SDSS data. We use 2,020,256 galaxies brighter than r=19 with photometric redshifts (divided into colour and luminosity subsamples) as lenses and 31,697,869 source galaxies. We search for and identify several signal contaminants, which if not removed lead to a spurious detection. These include systematic shear that leads to a slight spurious alignment of lens and source ellipticities, intrinsic alignments (due to contamination of the source sample by physically-associated lens source pairs), and anisotropic magnification bias. We develop methods that allow us to remove these contaminants to the signal. We split the analysis into blue (spiral) and red (elliptical) galaxies. Assuming Gaussian errors as in previous work and a power-law profile, we find f_h=e_h/e_g=0.1+/-0.06 for red galaxies and -0.8+/-0.4 for blue galaxies using 20-300 kpc/h, averaged over luminosity. Inclusion of the more realistic non-Gaussian error distributions and of the NFW density profile (which predicts much smaller ellipticity of the shear for scales above the scale radius) yields 0.60+/-0.38 for ellipticals and -1.4+1.7-2.0 for spirals. While there is no concrete detection of alignment in either case, there is a suggestion in the data of a positive alignment in the brightest lens sample of ellipticals. Our results appear to be mildly inconsistent with a previously reported detection by Hoekstra et al. (2004), but more data and further tests are needed to clarify whether the discrepancy is real or a consequence of differences in the lens galaxy samples used and analysis methods.
Brinkmann Jonathan
Broderick Tamara
Hirata Christopher M.
Mandelbaum Rachel
Seljak Uros
No associations
LandOfFree
Ellipticity of dark matter halos with galaxy-galaxy weak lensing does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Ellipticity of dark matter halos with galaxy-galaxy weak lensing, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ellipticity of dark matter halos with galaxy-galaxy weak lensing will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-59018