Needles in a haystack Searching for large separation lensed quasars

1. Needles in a haystack Searching for large separation lensed quasars Eran Ofek Caltech

2. Talk Layout Those we know The example of SDSS1004 Motivation (see Keren Sharon’s talk) Identification and confirmation problems USNO-B1 Searches SDSS

3. Those we know SDSS1004+41(Inada et al., Oguri et al.) Multiple imaged galaxies(Sharon, Ofek et al.) Fifth image(Inada et al.) Time delay

4. Those we know SDSS1004+41(Inada et al., Oguri et al.) Multiple imaged galaxies(Sharon, Ofek et al.) Fifth image(Inada et al.) Time delay (Fohlmeister et al. 2006) More candidates

5. Motivation Lensing statistics(J. Hennawi talk) Constraining dark matter distribution 2 ways to remove k-degeneracy Quasar host galaxies Cosmology(?) However, Dalal et al. 2005

6. Motivation - cosmology Collaborators: K. Sharon, D. Maoz, T. Broadhurst, C. Kochanek, M. Oguri, N. Inada, Y. Suto, G. Smith, E. Falco sim Z=3.3 Z=1.7

7. Motivation - cosmology However, … Dalal et al. 2005 predicts ~100% errors maybe possible to reduce errors(?) If lens redshift is high… Time delay + central images remove degeneracy…

8. Identification and confirmation Problem: large number of large separation quasar candidates How to select best candidates? Lensing galaxy/cluster Color similarity & photo-z Geometry

9. Color similarity Usual assumption: lensing is achromatic Lensed Non-lensed

10. Color similarity Moreover, Some known lenses are achromatic (e.g., HE1104-1805) Collaborators: M. Oguri, N. Jackson More – IR excess

11. Quad geometry selection Quads come in 4 configurations Inclined quad Core quad Long axis quad Short axis quad

12. Searching USNO-B1.0 Collaborators: D. Maoz, H.-W. Rix

13. Searching USNO-B1.0 USNO-B1.0 (Monet et al. 2003) based on POSS photographic plates 109 sources photometry accuracy ~0.3 mag color accuracy ~0.5 mag lots of junk (e.g., diffraction spikes)

14. Quad geometry selection

15. Searching USNO-B1.0 Example-2 Magnitudes

16. Searching USNO-B1.0 116 candidates… (after complicated selection process) Follow up observations: no new lenses (recovering SDSS1004+41)

17. Searching SDSS Searching the photometric quasar sample 3x106 photometric QSOs in SDSS-DR5 Selection criteria: Color, photo-z, geometry, lensing galaxy Follow up: Keck + Palomar

18. End

19. Motivation - cosmology

20. Motivation - cosmology Collaborators: K. Sharon, D. Maoz, T. Broadhurst, C. Kochanek, M. Oguri, N. Inada, G. Smith

21. (small separation lenses – IR excess) Collaborators: M. Oguri, N. Jackson

22. New (small separation lenses – IR excess) Collaborators: M. Oguri, N. Jackson Ofek et al. in prep.

23. (small separation lenses – IR excess)

24. Searching USNO-B1.0

25. Searching USNO-B1.0

26. Searching USNO-B1.0

27. What has been done? Past surveys: Kochanek et al. 1995 Maoz et al. 1997 Marlow et al. 1998 Shanks et al. 1999 Phillips et al. 2001a,b Ofek et al. 2001, 2002 Miller et al. 2004 Oguri et al. 2004; 2005 …

28. Those we know Additional candidates… 2dF J1435+00 33’’ Miller et al. 2004 SDSS J1029+26 22.5’’ Inada et al. 2006 SDSS J1116+41 13’’ Sanchez & Rodriguez ’07 RCS2-2327 35’’ D. Gilbank talk