SL applications II

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CDM Substructure and Cosmic Telescopes

lecture 3

The dark matter substructure problem

  • Introduction: a fundamental problem with CDM? [10m; RT 10m]
    • MW
    • Open questions: DM or gastrophysics
  • Lensing is fantastic [15m; RT 25m]
    • reaches the parts other probes cannot reach: external galaxies, mass only. Show plot with scales
    • observable signatures:
      • flux ratios
      • astrometric shifts
      • time delay perturbations
    • sources of noise: [10m; RT 35m]
      • structure along the line of sight.
      • microlensing (optical vs MIR vs X-ray).

BREAK #1: LOOK AT PICTURES OF LENSES AND TELL ME WHAT”S “WRONG” (PG 1115 X-ray; B1422; B2045; MG2016; some picture of clusters) [10m; RT 45m]

  • Results to date: [15m; RT 60m]
    • the galaxy lens satellite problem (Dalal & Kochanek; Xu et al; Vegetti et al)
    • satellites in clusters (Natarajan et al. )
  • What’s the solution? problem with sims? problems with baryons? problems with observations? line of sight clumps?

BREAK #2: WHAT EXPERIMENT WOULD YOU LIKE TO CONDUCT TO ADDRESS THIS ISSUE IF YOU HAD INFINITE RESOURCES? [10m; RT 70]

Cosmic Telescopes

  • Motivation: [5m; RT 75]
    • Reionization/Galaxy Formation
  • How to study the faint and distant universe?
    • cosmic telescopes principles. [10m; RT 85]
      • magnification review.
      • tradeoffs: deeper but smaller volume. When do you win?
    • Advantages: the importance of follow-up
    • Advantages: value of multiple imaging in blind search: geometric redshifts.
  • Critical Review of Results: [10m; RT 95]
    • using a pre-calibrated lens (swinbank et al) z=2 galaxies in detail
    • z=7 galaxies detected and measured (kneib, ellis, bradac).

Leave uncertainties for Lecture 4: magnification vs volume vs sample variance (bradac).

HW: TBD


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