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

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 LRG selection will use optical photometry + WISE infrared photometry WISE should reach a 5  limit of m AB <18.9 in the worst case, m AB <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 WISE Anticipated Coverage WISE passes

4 BigBOSS LRG Selection Proposal goal was to deliver 350 LRG targets / deg 2. 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 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! Proposed BigBOSS ELG Selection 2.4x10 -4 (Mpc/h) x10 -4 (Mpc/h) -3 R<23.4

6 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 ELG Selection Improvements

7 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 8x ergs/s/cm 2 Bluest band should be best correlated with [OII] line strength ELG Selection Improvements

8 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 ELG Selection Improvements

QSO Selection Schmidt et. al, 2010Palanque-Delabrouille et al., in prep 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 deg 2 Redshifts of Ly-  QSO candidates identified in first tile pass in survey, cut to 2<z<3.5 for subsequent observations SDSS Stripe 82 data

10 How Many Quasars - z > 2.2 over deg 2 in millions [number per deg 2 ] i limitPerfect Survey Variability-only Survey Color-only Survey [79]0.94 [68]0.55 [39] [110]1.31 [94]0.77 [55] [148]1.76 [126]1.04 [74] Adam Myers

11 How Many Quasars - 1 < z < 2 over deg 2 in millions [number per deg 2 ] i limit Perfect Survey Variability- only Survey Color-only Survey [114]1.35 [96]1.51[108] [147]1.75 [125]1.95 [139] [186]2.21 [159]2.47 [176] 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) PTF simulations SDSS original data 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 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 Mean i seeing, Mayall 4m  c 2 = (r e 2 +  psf 2 ) / (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 Silla QUEST/LBL 24 Camera 3512 x um CCD Unvignetted circle: 2.86 o radius, 307 mm dia. QUEST CCD camera aperture: mm dia. 10% vignetting: 380 mm dia. 20% vignetting: 430 mm dia. 30% vignetting: 480 mm dia. 24LBL CCD’s 3512 x um pixels 11 square degrees active area 0.7 arc sec pixels Charles Baltay

17 QUEST/LBL 36 Camera 3512 x um CCD Unvignetted circle: 2.86 o radius, 307 mm dia. QUEST CCD camera aperture: mm dia. 10% vignetting: 380 mm dia. 20% vignetting: 430 mm dia. 30% vignetting: 480 mm dia. 36 LBL CCD’s 3512 x um pixels 17 square degrees active area 0.7 arc sec pixels 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: *40s readout = 480s In 8 hr night this is 60 pointings sq deg is the most extragalactic sky visible in both North and South at secz < 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 Matt George CFHT Megacam

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 deg 2, 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 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 ugr Selection Adelberger (2004) Redshift Reddening Reddyr (2006)

24 ELG Bias 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 Sumiyoshi et al., 2008

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

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

27 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. Exposure Time *Estimate*