科研之友
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摘要
We present results for a galaxy-galaxy lensing study based on imaging data from the Canada-France-Hawaii Telescope Legacy Survey Wide. From a 12 million object multicolour catalogue for 124 deg(2) of photometric data in the u* g'r'i'z' filters, we compute photometric redshifts (with a scatter of sigma Delta z/(1 + z) = 0.033 and an outlier rate of eta = 2.0 per cent for i' <= 22.5) and extract galaxy shapes down to i' = 24.0. We select a sample of lenses and sources with 0.05 < z(d) <= 1 and 0.05 < z(s) <= 2. We fit three different galaxy halo profiles to the lensing signal, a singular isothermal sphere (SIS), a truncated isothermal sphere (BBS) and a universal density profile (NFW). We derive velocity dispersions by fitting an SIS out to 100 h(-1) kpc to the excess surface mass density Delta Sigma and perform maximum likelihood analyses out to a maximum scale of 2 h-1Mpc to obtain halo parameters and scaling relations. We find luminosity scaling relations of sigma(red) proportional to L-0.24 +/- 0.03 for the red lens sample, sigma(blue) proportional to L-0.23 +/- 0.03 for blue lenses and sigma proportional to L-0.29 +/- 0.02 for the combined lens sample with zeropoints of s*red = 162 +/- 2 km s(-1), sigma(blue)* = 115 +/- 3 km s(-1) and sigma* = 135 +/- 2 km s(-1) at a chosen reference luminosity L-r'* = 1.6 x 10(10) h(-2) L-r',L-circle dot. The steeper slope for the combined sample is due to the different zero-points of the blue and red lenses and the fact that blue lenses dominate at low luminosities and red lenses at high luminosities. Themean effective redshifts for the lens samples are < z(red)> = 0.28 for red lenses, < z(blue)> = 0.35 for blue lenses and < z > = 0.34 for the combined lens sample. The BBS maximum likelihood analysis yields for the combined sample -2 km s(-1) and a truncation radius of sigma* = 184+ 17 + 14 h-1 kpc, corresponding to a total mass of M-total,M- BBS* = 2.32(0.25)(+0.28) x 10(12) h(-1) M-circle dot and a mass-to-light (M/L) ratio of M-total,M- BBSL* = 178(-19)(+22) h M-circle dot/L-r', (circle dot) at L-r'*. At a given luminosity, both velocity dispersion s and truncation radius s are larger for red galaxies than for blue galaxies. For an NFW profile, we measure at L-r'* a virial radius of r(200)* = 133(-2)(+3) h(-1) kpc and a concentration parameter of c* = 6.4(-0.7)(+0.9), implying a virial mass of M-200* = 7.6(-0.3)(+0.5) x 10(11) h(-1) M-circle dot. At L* for blue galaxies the concentration parameter is slightly higher than for red galaxies and r(200) is significantly lower. For the combined sample, if described as a single power law, the M/L -0.11, the concentration parameter scales as c proportional to L-0.07+0.11-0.11. Analysing the M/L scaling for red and blue galaxies separately, we find that a broken power law (with a flat slope at high luminosities) provides a more appropriate description for red and possibly also for blue galaxies. We measure M-200/M-star for red galaxies over 2.5 decades in stellar mass.
We find a minimum for this ratio at M-star similar to 3-4 x 10(10) h(-2) M-circle dot with a strong increase for lower stellar masses.
- 出版日期2013-6
