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Strong Lensing Studies at Fermilab

Strong Lensing Studies at Fermilab. Elizabeth Buckley-Geer for the Experimental Astrophysics Group Fermilab Center for Particle Astrophysics. Collaborators.

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Strong Lensing Studies at Fermilab

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  1. Strong Lensing Studies at Fermilab Elizabeth Buckley-Geer for the Experimental Astrophysics Group Fermilab Center for Particle Astrophysics DES Collaboration Meeting

  2. Collaborators • Fermilab: H. Lin, D. Kubik, H.T. Diehl, S. Allam, D. Tucker, E. Buckley-Geer, J. Kubo, J. Annis, J. Frieman, D. Finley, J. Estrada, D. McGinnis, V. Scarpine, … Fermilab Cosmology Analysis Group • D. Schneider, M. Oguri, A. Shapley, A. Baker, D. Lutz, J.A. Smith, J. Brinchmann, M. Strauss, M.-S. Shin, C. Kochanek, C. Tremonti, … DES Collaboration Meeting

  3. Outline • SDSS Arc Search • Follow-up Observations • Sample Properties • Lens Modeling for LRG-4-606 • A lens from the BCS data DES Collaboration Meeting

  4. SDSS Arc Search • The candidates come from two different samples. • Potential red galaxy lenses from SDSS DR5 (8000 deg2) • 221,000 luminous red galaxies (LRGs) • 29,000 brightest cluster galaxies (BCGs) from maxBCG cluster sample (J. Annis) • SDSS DR5 CAS database query (D. Kubik) • Blue galaxies (g-r and r-i color cuts) • < 10” from LRG or BCG • 57,000 systems returned with n=1 or more blue objects • Rank systems by number of blue objects n • Visual inspections • Inspect all systems (1081) with n ≥ 3 blue objects • 4 separate inspectors looked at SDSS CAS gri color jpeg images • Follow up 14 candidate systems flagged by 2 or more inspectors • Plus 1 more (“clone”) from single-inspector eye scan of n=2 LRG list • Interacting-merging galaxy sample (S.Allam) • Start with 15,000 isolated galaxies and 38,000 isolated galaxy pairs from SDSS DR5 • Exclude spiral galaxies to avoid false detections of lenses • Apply additional selection cuts. • Yields 17500 objects which after visual examination reduces to 3000 objects. DES Collaboration Meeting

  5. Follow-up Observations • The search identified N candidate systems • Follow-up observing program (Fermilab group) on Apache Point Observatory (APO) 3.5m telescope • Arcs are bright (r ~ 20-22) and high SB (r ~ 23-24 mag/arcsec2) • SPIcam gri imaging (15 min exposures per filter) for deeper images (SDSS discovery images are only 54 seconds on a 2.5m telescope) • DIS spectroscopy (45 min exposures) of brighter targets for source and lens redshifts • We curently have 9 spectroscopically confirmed lensing systems. • 6 with z ≥ 2 • 3 have z ~1.0 • Lenses typically have z ~ 0.4 • We also have HST and Spitzer data for one system (lrg_2_2811) DES Collaboration Meeting

  6. 9 Spectroscopically Confirmed Lensing Systems SSA_1113 zl = 0.35 zs = 0.77 lrg-4-606 zl=0.49 zs = 2.03 lrg-3-817 zl = 0.35 zs = 2.26 8 o’clock arc zl = 0.38 zs = 2.73 lrg-3-227 zl = 0.45 zs = 0.98 lrg-2-2811 zl = 0.42 zs = 2.0 “The Clone” lrg-4-581 zl = 0.43 zs = 0.97 “Cosmic Snowman” lrg-3-757 zl = 0.44 zs = 2.38 “Cosmic Horseshoe” SSA_1343 zl = 0.34 zs = 2.1 DES Collaboration Meeting

  7. Example Spectra DES Collaboration Meeting

  8. Comparison of SDSS, Subaru and HST Data for lrg-2-2811 DES Collaboration Meeting

  9. Spitzer Data for lrg-2-2811 DES Collaboration Meeting

  10. Tangential caustic Tangential Critical curve Lens Modeling Results for lrg-2-2811- ‘The Clone’ • Using LENSVIEW (R. Wayth & R.L. Webster, MNRAS 372 (2006) 1187-1207). • Assume a SIE mass profile • Flat cosmology, Wm=0.3, WL=0.7, H0=100 h km s-1 Mpc-1 • Fit for the Einstein radius θEIN Model Image Source Residuals DES Collaboration Meeting

  11. Modeling for lrg-4-606 • Use GALFIT to model the light profiles of the galaxies and the arcs Input Model i band Combination of Sersic profiles for the galaxies and exponential disks for the arcs 18 objects + sky χ2/dof = 1.4 Residuals DES Collaboration Meeting

  12. GALFIT r-band Residuals Input Model Use i-band parameters for galaxies and allow magnitude and position to vary. Allow all arc parameters to vary. Add small red galaxy that is visible at the top left of the arc (it shows up most clearly in r). DES Collaboration Meeting

  13. GALFIT g-band Residuals Input Model Use i-band parameters for galaxies and allow magnitude and position to vary. Allow all arc parameters to vary. DES Collaboration Meeting

  14. Color-magnitude plot DES Collaboration Meeting

  15. LENSVIEW Input Use g-band image Add small red galaxy at correct location using g-band magnitude estimated from color-magnitude plot DES Collaboration Meeting

  16. First try using Lensview Input Model SIE θEIN = 7.4” Axis ratio = 0.77 PA = 44.7° Source DES Collaboration Meeting

  17. BCS data – Elliot Arc Parameters (using Lensmodel) θEIN = 7.5" Ellipticity = 0.269 PA = -32.8 deg χ2/dof = 1.03 σ = 826 km s-1 REIN = 28.2 h-1 kpc MEIN = 1.4x1013h-1 M A4 A1 A2 A3 This system is included in a recent proposal that we submitted to get HST imaging data. The galaxy cluster surrounding the arc has an Ngals ≥ 71 and a mass of M200 ~ 4x1014 h-1 Mwhich makes it a very rich cluster. GMOS spectra taken with Gemini South in August 2007 give zl = 0.38 and zs = 0.9 DES Collaboration Meeting

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