1. July 5 2007 23rd IAP Colloquium 1 A Search for Strongly-Lensed, High-z LBGs around SDSS LRGs Elizabeth Buckley-Geer Experimental Astrophysics Group Fermilab Center for Particle Astrophysics

2. July 5 2007 23rd IAP Colloquium 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, …

3. July 5 2007 23rd IAP Colloquium 3 Outline  Motivation  SDSS Arc Search  Follow-up Observations  Sample Properties  Lens Modeling  Plans

4. July 5 2007 23rd IAP Colloquium 4 Motivation   cB58 (Yee et al. 1996) – –Discovered serendipitously in CNOC1 cluster redshift survey – –z = 2.72 Lyman break galaxy (LBG) lensed by z = 0.37 brightest cluster galaxy (BCG) – –Bright, blue object (r = 20.4), 6” away from BCG – –Bright enough to be easily seen in SDSS and to have an SDSS spectroscopic redshift!   8 o’clock arc (Allam et al. 2007) – –Discovered serendipitously in inspection of SDSS DR4 interacting galaxy pairs sample – –z = 2.73 LBG lensed by z = 0.38 SDSS luminous red galaxy (LRG) – –Bright, blue arc (total r = 19), ~4” away from LRG – –Easy absorption line redshift in 20 min DIS spectrum on APO 3.5m   Start systematic search for more systems like cB58 and the 8 o’clock arc in the SDSS

5. July 5 2007 23rd IAP Colloquium 5 8 o’clock arc APO 3.5m g- band image and Keck LRIS spectrum z lens = 0.38

6. July 5 2007 23rd IAP Colloquium 6 SDSS Arc Search   Potential red galaxy lenses from SDSS DR5 (8000 deg 2 ) – –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 – –Look for arc-like morphology – –Reject HII regions, spiral arms, merging galaxies, etc. – –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

7. July 5 2007 23rd IAP Colloquium 7 Follow-up Observations   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/arcsec 2 ) – –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   Additional Hobby-Eberly Telescope (HET) spectroscopic follow-up program (PI D. Schneider) of fainter targets   Subaru FOCAS imaging and spectroscopy (M. Oguri) of “Clone” system   APO and HET programs are ongoing

8. July 5 2007 23rd IAP Colloquium 8 15 Candidate Systems

9. July 5 2007 23rd IAP Colloquium 9 2 Systems Rejected by Follow-Up

10. July 5 2007 23rd IAP Colloquium 10 6 Spectroscopically Confirmed Lensing Systems This system also found by V. Belokurov et al. dubbed the “Cosmic Horseshoe” astro-ph/0706.2326 We obtained spectra in Feb/March 2007 compared with May for the published observation

11. July 5 2007 23rd IAP Colloquium 11 7 Remaining Systems Still Need Follow-Up Confirmation

12. July 5 2007 23rd IAP Colloquium 12 Comparison of SDSS Discovery and APO 3.5m Follow-Up Images

13. July 5 2007 23rd IAP Colloquium 13 lrg_2_2811 (“Clone”) Subaru FOCAS V- band image and spectrum (M. Oguri) z lens = 0.42

14. July 5 2007 23rd IAP Colloquium 14 lrg_4_606 APO 3.5m SPIcam gri image and DIS spectrum (unfluxed) z lens = 0.49

15. July 5 2007 23rd IAP Colloquium 15 SDSS 2.5m gri image and APO 3.5m DIS spectrum (unfluxed) lrg_3_757 z lens = 0.44

16. July 5 2007 23rd IAP Colloquium 16 lrg_3_817 APO 3.5m SPIcam gri image and DIS spectrum (unfluxed) z lens = 0.35

17. July 5 2007 23rd IAP Colloquium 17 Sample Properties   Current follow-up results for 15 candidate systems – –6 spectroscopically confirmed   4 with z = 2.0-2.4: “BX” galaxies (z~2 Lyman break galaxies)   2 have z = 1.0 and z = 0.4 – –2 rejected, remaining 7 still need follow-up confirmation   Lensed images are bright (r ~ 20-22) and high SB (  r ~ 23-24 mag/arcsec 2 )   Lens galaxies in z ~ 0.2-0.5 range, but most have z ~ 0.4   Einstein radius, mass, and M/L analysis (D. Kubik master’s thesis) – –Estimate Einstein radius by circle fit to lensed images – –Einstein radii 3-10”, or 10-40 h -1 kpc – –Masses within Einstein radii of 10 12 - 10 13 h -1 M  – –“Intermediate” regime: lensing by groups and centers of clusters – –M/L (g-band rest frame) of 10-140 h (M/L)  on scales of 10-40 h -1 kpc   Consistent with trends from dynamical and X-ray M/L measurements for ellipticals on similar scales   Complementary to other strong lensing results on smaller scales, and weak lensing results on larger scales

18. July 5 2007 23rd IAP Colloquium 18 M/L vs. Radius Comparison SDSS Arc Search Sample Weak lensing by CNOC2 groups (Parker et al. 2005) Keeton et al. (1998) lenses SLACS lenses (Treu et al. 2006, Koopmans et al. 2006) Elliptical galaxies: dynamics and X-rays (Bahcall et al. 1995)

19. July 5 2007 23rd IAP Colloquium 19 Lens Modeling  Use lensmodel/gravlens (C. Keeton, astro-ph/0102340)  Image positions from SExtractor  Assume a SIE mass profile  Flat cosmology,  m =0.3,   =0.7, H 0 =100 h km s -1 Mpc -1  Fit for the Einstein radius θ EIN  Determine velocity dispersion and mass contained within θ EIN  Have modeled the “8 o’clock arc” and the “Clone” so far  Used the SPIcam image for the 8 o’clock arc and both the SDSS and Subaru images for the clone. Get consistent results from the two images of the clone. Show results from fit to Subaru data.  Also have started to use LENSVIEW (R. Wayth & R.L. Webster, MNRAS 372 (2006) 1187-1207). Have a preliminary fit for “The Clone” that qualitatively agrees with the lensmodel results.

20. July 5 2007 23rd IAP Colloquium 20 Modeling Results “8 o’clock arc” θ EIN = 3.35”,ε = 0.53, PA = 12.8 deg χ 2 /dof = 1.04 σ = 392 km s -1 R EIN = 12.2 h -1 kpc M EIN = 1.4 x 10 12 h -1 M  M/L (rest frame g-band) = 13.8 h M  /L  Total Magnification = 12.8 “Clone” θ EIN = 3.83”,ε = 0.291, PA = -73.6 deg χ 2 /dof = 0.5 σ = 440 km s -1 R EIN = 14.9 h -1 kpc M EIN = 2.1 x 10 12 h -1 M  Total Magnification = 27

21. July 5 2007 23rd IAP Colloquium 21 LENSVIEW Results for “The Clone” Model Image Input Image Source Tangential Critical curve Tangential caustic

22. July 5 2007 23rd IAP Colloquium 22 Plans   Observations – –Complete follow-up confirmation programs at APO and HET – –HST Cycle 16 and Spitzer Cycle 4: 8 o’clock arc and clone – –Gemini NIRI spectroscopy of 3 confirmed z > 2 systems (2007B) – –IRAM mm CO and continuum observations of z > 2 systems – –Will propose for IRTF near-IR imaging follow-up   Analyses – –More detailed lens models   Constrain lens mass profiles in group/cluster core environments – –Simulations to determine selection effects – –Understand source and lens redshift distributions   More SDSS arc searches – –Inspect existing n ≤2 query search systems – –Search around fainter, higher-z red galaxies, including Stripe 82 coadds – –Increase search radius to get cluster-scale lensing systems – –Implement automated search methods

23. July 5 2007 23rd IAP Colloquium 23 D. Kubik (2007) Masses and Einstein Radii

24. July 5 2007 23rd IAP Colloquium 24 D. Kubik (2007) M/L vs. Radius

25. July 5 2007 23rd IAP Colloquium 25 D. Kubik (2007) M/L vs. Mass