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Lensing Biasing of Triaxial Halos

Lensing Biasing of Triaxial Halos. Eduardo Rozo. In collaboration with Jacqueline Chen Andrew Zentner. Fermilab - June 15, 2007. To observer. lensing galaxies. The Basic Idea. galaxies. Lensing galaxies are not randomly oriented in space.

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Lensing Biasing of Triaxial Halos

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  1. Lensing Biasing of Triaxial Halos Eduardo Rozo In collaboration with Jacqueline Chen Andrew Zentner Fermilab - June 15, 2007

  2. To observer lensing galaxies The Basic Idea galaxies Lensing galaxies are not randomly oriented in space. Galaxy properties that depend on LOS will be biased in lensing galaxies.

  3. long axis short axis long axis middle axis Axis Ratio short axis middle axis Einstein Radius The Model Use simplest possible model to get order of magnitude estimates. • Triaxial isothermal profile • Power-law source luminosity function (slope -2).

  4. How Are Lensing Halos Oriented? Distribution of LOS for Triaxial Halos prolate doubles long axis prolate quads short axis Quads and Double lenses have very different LOS distributions! How they are different depends on halo shape. middle axis oblate doubles oblate quads

  5. The distribution in quads is strongly skewed towards highly elliptical objects. q0.75 : Axis ratio such for which 75% of the lenses have q<q0.75. The Distribution of Projected Axis Ratios in Lensing Galaxies

  6. The Distribution of Projected Axis Ratios in Lensing Galaxies q0.75 Differences between doubles, quads, and random galaxies depend on halo shape. 0.05 0.09 0.09 0.13 0.13 0.17

  7. The Distribution of Projected Axis Ratios in Lensing Galaxies 75% Cumulative Fraction quads doubles Isophotal Axis Ratio Current number of lenses too small to differentiate between quad, double, and non-lensing galaxies.

  8. Mean Substructure Mass Fraction (no significant differences) <fsub> for random halos: 0.46% 0.55% 0.40% The Substructure Mass Fraction of Lensing Galaxies A Single Halo Viewed Along Two Different LOS Simulations by Andrey Kravtsov.

  9. Summary and Future Work • Lensing galaxies are not randomly oriented in space. • The bias introduced in any observable due to preferred halo orientations in lensing galaxies is calculable: • Lensing biases can help constrain the shape of galaxy halos. • Ellipticity distributions of lensing and non-lensing galaxies are consistent with each other. Differences should become apparent as number of lens systems increases. • Halo triaxiality does not signifanctly affect the amount of substructure mass fraction one expects in lensing galaxies. Most important effect being neglected: • Current model ignores substructure/correlated galaxies which can significantly affect lensing cross sections (Cohn and Kochanek 2004). • Need to repeat calculations including correlated structures.

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