Target Selection Workshop Report

1. Target Selection Workshop Report Nick Mostek BigBOSS Science Telecon Dec 6, 2010

2. Target Selection Overview • Highest mass bias objects will be LRGs from 0.6<z<1.0, complementing BOSS survey • Largest volume coverage will be ELGs from 0.7<z<1.7, lower mass bias than LRGs • Ly- QSOs will round out the sample at the high redshift end (z>2), low mass bias in Ly- forest • Samples are intended to complement each other in redshift coverage, volume density, and mass bias

3. BigBOSS LRG Selection WISE Anticipated Coverage WISE passes • LRG selection will use optical photometry + WISE infrared photometry • WISE should reach a 5 limit of mAB<18.9 in the worst case, mAB<19.4 in the confusion limit • Selection is based on the 1.6m restframe ‘bump’, accessed through r-[3.6], r-i color plane • Tests done with CFHT LS ri photometry,Spitzer IRAC imaging, and DEEP2 redshifts

4. BigBOSS LRG Selection • Proposal goal was to deliver 350 LRG targets / deg2. • Minimum LRG selection requires magnitude limits of i<21.5 or r<22.5 in the worst case of WISE imaging depth. • Selection should deliver more LRGs than required, downsample the distribution or sculpt the target selection if necessary

5. Proposed BigBOSS ELG Selection • ELG selection will use PanSTARRS-1 (PS1) gri photometry and/or Palomar Transient Factory (PTF) GR • Selection is similar to DEEP2, simple cut on galaxies with blue restframe colors • PS1 co-added depths are just about perfect for this selection…BUT could use 0.5 mag more! 2.4x10-4 (Mpc/h)-3 1.0x10-4 (Mpc/h)-3 R<23.4

6. ELG Selection Improvements • Can we remove overlap in the LRG and ELG distributions? • Can we increase the number of ELGs out to higher redshifts? (nP=1? nP=0.6?) • Can we improve the targeting efficiency? • Function of [OII] line flux limit, photometric limits, and desired redshift range. • BigBOSS survey restricted by sky density (~2800 targets) and [OII] line flux

7. ELG Selection Improvements • The color-color plan separation seems to work well for [OII] galaxies of about z>0.9 (green) • Attempt to select the bluest galaxies below the green line • A magnitude limit of 23<F1<23.8 was used to produce the appropriate sky density of ~2800 galaxies per deg2 with F([OII])>8x10-16 ergs/s/cm2 • Bluest band should be best correlated with [OII] line strength

8. ELG Selection Improvements • Including errors, low redshift cut (z<1.0) becomes smeared as objects randomly scatter into the cut • High redshift still delivers improved dn/dz over BB proposal while maintaining reasonable target density • Magnitude limits are ~24 in F1 and F2, ~23.5 in F3. FoM improves from 64.1 to 73.3! - P. McDonald

9. QSO Selection Schmidt et. al, 2010 Palanque-Delabrouille et al., in prep SDSS Stripe 82 data • Time-domain photometry will help select QSOs from variability structure function. Selection can be done from multiple bands or one deeper band • Goal is to achieve high Ly- QSO densities through a wide color selection and ~90% completeness, requires a target sample density ~250 deg2 • Redshifts of Ly- QSO candidates identified in first tile pass in survey, cut to 2<z<3.5 for subsequent observations

10. How Many Quasars - z > 2.2 over 14000deg2 in millions [number per deg2] Adam Myers

11. How Many Quasars - 1 < z < 2 over 14000deg2 in millions[number per deg2] Adam Myers

12. Simulation of PTF and Pan-STARRS • ”Fast simulation” of PTF using Stripe 82 data to simulate the other fields: • - SDSS anchor point: 1 point at random in SDSS in years 1 through n-3 • PTF 3-year data: 1 band -4 points in SDSS year n (rescaled errors) • - PS1 3-year data: 4 bands -4 points in SDSS year n (rescaled errors) SDSS original data PTF simulations u g r i z Simulated PTF data (shifted by 0.3 mag) Christophe Yeche

13. Extrapolation for BigBOSS • Our study was BOSS-oriented, i.e. g<22 • Extrapolation to g<23 PS1 5-year like survey Star sample taken as all objects in Stripe 82, with correction for estimated quasar density in sample • Point source object g<23 : 3000 deg-2 • QSOs g<23: 1<z<2 120 deg-2 2<z<5 120 deg-2 • Variability selection only: Star rejection 96% QSO completeness 90% 120(stars)+200(QSOs) deg-2 • By applying a pre-selection based on color, we can reduce by the stars to 40 with a 10% cost for QSO !!!!

14. Mean i seeing, Mayall 4m Astrometry • Fiber spectroscopy requires accurate target centering. • Error sources include: Fiber positioner accuracy and precision, Atmospheric dispersion / distortion, Telescope guiding errors, and Target catalog astrometry • Figure shows integrated light profile for a typical ELG with 0.3’’ half light radius (exponential profile) in a 1.5’’ fiber as a function of increasing blur. • Full requirements have yet to be derived, but a good goal in total astrometric error is ~100 mas • Depends on source brightness, so much larger errors are expected for the faintest sources • Requires S/N~10 at the faint end…can probably co-add between bands for increased precision • SDSS to Tycho-UCAC is 30 mas, target catalog to SDSS should have no more than 30mas systematic on bright sources • Need to fix / revist proper motions in SDSS c2 = (re2+psf2) / (S/N)2

15. Requirements • Filter Bands • Minimum of 3 optical bands, similar to gr(i+z) • IR photometry from WISE • u-band surveys not currently required, but would be useful • Depths: • WISE completion with [3.4]<18.9 (LRGs) • Proposal 5depths of gr<23.5, i<23 • Could benefit from +0.5 mag more depth • Sky Coverage / Fill Factor • Need 14k sq. deg for BigBOSS • Goal of >95% fill factor (carry over from SNAP studies) • Epochs • QSO variability needs a minimum 4 epochs • Number densities require g<23 • QSO completeness increases faster with more epochs in multiple bands • Astrometry • Looking for a < 60 mas systematic error on bright sources, with half of that coming from SDSS astrometry • Goal is ~100mas at the faint end (unrealistic??) • Needs more study at faint end (incorporate into n(z) projections)

16. La SillaQUEST/LBL 24 Camera 3512 x 3512 10.5um CCD • 24LBL CCD’s 3512 x 3512 10.5 um pixels • 11 square degrees active area • 0.7 arc sec pixels Unvignetted circle: 2.86o radius, 307 mm dia. QUEST CCD camera aperture: 336.6 mm dia. 10% vignetting: 380 mm dia. 20% vignetting: 430 mm dia. 30% vignetting: 480 mm dia. Charles Baltay

17. QUEST/LBL 36 Camera 3512 x 3512 10.5um CCD • 36 LBL CCD’s 3512 x 3512 10.5 um pixels • 17 square degrees active area • 0.7 arc sec pixels Unvignetted circle: 2.86o radius, 307 mm dia. QUEST CCD camera aperture: 336.6 mm dia. 10% vignetting: 380 mm dia. 20% vignetting: 430 mm dia. 30% vignetting: 480 mm dia. Charles Baltay

18. SNe from LS-Q • g: 60s exposure during dark - 180s during bright • r: 60s exposure during all times • i(z): 180(300)s exposure during all times In 2” seeing delivers S/N=5 at 21.5 magnitude. 1.7” seeing is 30% faster. Average for the three filters is: 120+60+180 + 3*40s readout = 480s In 8 hr night this is 60 pointings. 4500 sq deg is the most extragalactic sky visible in both North and South at secz < 2.0. 3 day cadence covers this in all three filters. 120 days on these fields would let you hit them 40 times, which is a 2 mag improvement in the co-add. Peter Nugent

19. Matt George

20. CFHT Megacam Matt George

21. Action Items • Taking an “All Options are on the Table” approach • Discussing new camera for La Silla / QUEST telescope • Need to study needed filter bands and exposure times • Need to work out resource share • Still need a plan for the North (Post-PTF Palomar?) • CFHT might work for the bluest bands • MegaCam upgrade would help the red bands • Other options: • Hyper Subprime-Cam? 1.5 deg2, 20s overhead, on sky in 2012 • Contribute to PanSTARRS operations? • R&D plans • TS tests should be carried out for each sample using representative photometric sources (such as WISE, PTF, SDSS coadds) • Flesh out plans for pre-survey spectroscopic tests (WIYN Hydra, etc.) • Outstanding issues • PS1 status? Data access? Survey length? • Investigate Astrometry requirements • Resources for observing, data reduction and analysis?

22. Backup Slides

23. ugr Selection Adelberger (2004) • u-band can also provide a redshift color selection, although it works best for z>2 • Synthetic photometry from Ilbert zCOSMOS code shows a selection box is drawn around F[OII] >5E-17 cgs for 1.5<z<2 galaxies and a magnitude limit of r <24 mag Reddening Redshift Reddyr (2006)

24. ELG Bias Sumiyoshi et al., 2008 • Sumiyoshi et. Al (2009) performed a measurement of the mass bias with the Subaru XMM-Newton Deep Field (SXDF) • Found b(0) ~ 0.8 and that the clustering amplitude was roughly constant with redshift in this redshift range. • Agrees with other studies performed in small redshift windows (Blake et al., 2009, Geach et al., 2008) • Clustering bias could be affected by AGN in the emission line sample

25. How Many Quasars Are There? • Assume Variability Selection is 85% complete at all redshifts • Assume Color selection is 95% complete at z < 2.5 and 50% complete at z > 2.5 Hopkins, Richards & Hernquist (2007) Luminosity Function to Mi < -20 Adam Myers

26. How to get more Volume? 0.2<z<1: Luminous Red Galaxies (extended from BOSS footprint) Padmanabhan, 2004 BigBOSS 0.6<z<1.7: Emission line galaxies 2<z<3.5: Ly forest from QSOs (pioneered from BOSS)

27. Exposure Time *Estimate* • Assumed sky spectrum properties used in BBspecsim (BOSS sky brightness, KPNO atmosphere) • Used 1m clear aperture and the throughput of F3 (Assumes SNAP detector+filter, ignores other losses and efficiencies) • Estimate that S/N=5 at F3=23.5 will take ~ 1 hour of integration time.