An Optical Counterpart to the SPT

1
An Optical Counterpart to the SPT

• A Wide Area Imaging Survey?
• Constraints
• Possibilities

Jim Annis Fermilab Josh Frieman
Fermilab/U Chicago Joe Mohr U Illinois
A1576 z0.30 Stefano Zibetti/SDSS
2
The SPT

• 4000 sq-degrees SZ survey
• gt 20,000 clusters w/o redshifts
• 80 at z lt 1
• How does one followup?

3
Example color cluster images from the SDSS
4
Finding clusters in SDSS data

• Early type galaxies label groups and clusters
• Very uniform old stellar populations colors
• Widefield multicolor CCD data has revitalized
  optical cluster finding
• Cluster members are the reddest galaxies at each
  redshift
• Clusters in position-color space
• Need location, richness, size

Z0.165
SDSS image of Abell 1553
5
Finding red sequence clusters

• Clustering in position-color space essentially
  eliminates contamination by projection
• Gladders Yee (2000), Goto et al. (2001), Annis
  et al. (2003)
• E/SO ridgeline provides extremely accurate
  (?z?0.01) photometric redshift
• Red sequence in place throughout SDSS volume and
  beyond, to zgt1.

E/SO ridgeline
Red sequence galaxies at z1.27 (van Dokkum et
al, 2000)
6
Elliptical Galaxy Spectrum
g
r
i
7
The maxBCG sample redshift
8
The maxBCG sample detection and richness

• Likelihood based on BCG fit and presence of E/SO
  ridgeline
• Cluster center defined by BCG galaxy
• Richness estimated by Ngalsgt0.4L (also Ltot,
  etc)
• Redshift estimated by photoz techniques
• Outputs include cluster info and member list

• Observed richness distribution gt3x105 over 2100
  ??

9
(No Transcript)
10
An Optical Survey CounterpartTo SPT

• One follows up by a 4000 square degree imaging
  survey, in 4 bandpasses, to i24. This allows
• Photometric redshifts for 25,000 SZ clusters
• Optically selected sample of clusters
• redshift and mass estimates
• Weak lensing mass estimates of these clusters
• Weak lensing cosmic shear measurements
• with photo-z tomography
• Galaxy clustering on large scales to z 1
• Galaxy-galaxy lensing
• and much more.

11
Sketch of a Project

• Back of the envelopes should convince you this is
  a doable.
• Simple things first, before complicated
• these are the times before early days

12
Existing Instruments

• SDSS not deep enough
• z 0.3 0.5
• CFHT Legacy Survey
• 20 N declination (2 airmass _at_ -40 dec, meridian)
• PanStarrs
• 20 N declination (2 airmass _at_ -40 dec, meridian)
• Mosaic Camera on Blanco 4m
• FOV too small.
• Otherwise ok (1.5 airmasses at 75 dec,
  meridian)
• LSST
• 2013 (?)

13
CTIO Blanco 4m

• Collecting area10 m2
• Prime focus
• f/2.87
• 15 micron pixels gt 0.267/pixel
• Field of view (diameter)
• Current 0.8 degree
• Need 1.8 degree
• NOAO Long Range Plan
• SOAR high resolution imaging
• Gemini South deep imaging
• Blanco 4m wide field imaging

14
How Much Time

• Assume ¼ time of big telescope, 50 useful
• 3 years to finish survey
• 10 hours 3 good nights 10 months 3 years
• 1000 hours
• 4000 sq-degree and 1000 hours 15 min/sq-degree
• Conservative- perhaps a factor of 2 more, from
  75 useful time and 5 years to completion

15
Depth

• 0.5 L at z 1 in i 24 AB
• z 23, sky brighter
• Factor of 40 times SDSS depths
• i 20.25 (10-sigma) at z0.35,
• gt90 completeness and efficiency
• i 24 (10-sigma) at z 1
• Collecting area 4m gt 2.5m x2
• Seeing 0.8 lt 1.2 x2
• Integration 540sec gt 55sec x10 x40
• 4m per filter/sq-degree
• Imager is 2.25 sq-degrees

16
Imager

• Assume 0.25/pixel
• Assume 1.5 degee per side focal plane
• gt 2.25 sq-degree
• gt 20k x 20k pixels
• Big, but state of the art last January
  Megacam is 16k x 16k
• Recall, we dream two years out, 4 years to light

Megacam, at CFHT
17
Large format cameras
Megacam, at CFHT 36 4k x 2k 300 Megapix 2003
CFH12k 12 4k x 2k 100 Megapix 2000
SDSS 30 2k x 2k 120 Megapix 1998
Megacam at MMT 36 4k x 2k 300 Megapix 2003
18
CDFs Silicon Vertex Detector
19
Elements of a Survey
Science case! for proposals

• Wide field corrector
• Camera
• CCDs/detectors
• Electronics
• Readout
• Control
• Mechanical
• Vacuum systems
• Cooling systems
• Data acquisition system

• Survey obs strategy
• Standard star strategy
• Science Software
• Calibration pipeline
• Coadd pipeline
• Galaxy measurement pipeline
• Cluster finding pipeline
• Data production
• Data distribution
• Science analysis

20
End Thoughts

• 4000 sq-degrees to i24 in 4 filters is possible
  (!)
• All clusters at z lt 1 given redshifts to lt 0.02
• Full utilization of SPT observations
• Cosmology from the optical/weak lensing cluster
  surveys

• What to do next
• Form a collaboration
• Begin working with CTIO
• Work towards proposals to NSF and DOE
• Spend 2 years raising money and designing survey
• maybe in 2005 start building?
• in 2010, work the SPT and optical catalogs.

21
(No Transcript)