Sloan Digital Sky Survey

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SDSS and UKIDSS

• Jon Loveday
• University of Sussex

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Outline

• Sloan Digital Sky Survey status
• UK Infrared Deep Sky Survey overview and status
• K-band luminosity function from matched
  SDSS-UKIDSS sample
• Future prospects

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SDSS1 Survey Goals

• Make definitive map of local universe
• Image quarter-sky in five colours ugriz
• Measure 50 million galaxy images to r22
• Obtain spectra for 1 million galaxies and 100,000
  quasars
• SDSS1 ended June 2005, immediately followed by
  SDSS2

http//www.sdss.org
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SDSS2 - commenced July 2005

• Legacy survey
• complete SDSS1 goals
• SEGUE
• Galactic structure
• Supernovae
• Repeated imaging of southern equatorial stripe

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SDSS Status (March 2006)

• Unique area imaged (sq deg)
• North 7561 essentially completed 30 Jan 2006
• South 739
• 210 million objects detected
• Spectroscopy 1819 plates inc spectra of
• 697,757 galaxies
• 93,083 QSOs
• 253,261 stars

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Data Release 4

• Published July 2005
• Imaging area 6670 deg2
• Photometry of 180 million unique objects
• Spectra of 849,920 objects over 4783 deg2
• 565,715 galaxies 76,483 quasars
  102,714 stars

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Imaging
Spectroscopy
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Data Release 5

• Due summer 2006
• Imaging area 8000 deg2
• Photometry of 215 million unique objects
• Spectra of 1,048,960 objects over 5740 deg2
• 674,749 galaxies 90,611 quasars
  154,925 stars

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Imaging
Spectroscopy
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SDSS Cosmological Highlights

• Highest known redshift quasar (z 6.4)
• Large scale structure cosmological constraints
• Galaxy properties and environment
• Detection of baryon acoustic peak
• More than 1000 publications using SDSS data, with
  29,000 citations

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z6.4 Quasar
Gunn-PetersonTrough
Fan et al 2003
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Cmbgg OmOl
CMB

LSS
WMAP only SDSS
Tegmark et al 2004
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UKIDSS

• UK Infrared Deep Sky Survey
• Consortium of most UK astronomy departments
• UKIRT 3.8m telescope plus WFCAM (4x20482
  Hawaii-II arrays, 0.21 deg2)
• Etendue of 2.38 m2 deg2 largest of any IR camera
  until VISTA
• zYJHK (1 2.5 ?) near-IR filters
• 5 surveys, 3 extragalactic
• Significantly deeper than 2MASS

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UKIDSS (contd)

• Observing started May 2005
• 7 year observing plan (50 of UKIRT time)
• Pipeline processing in Cambridge, archive in
  Edinburgh
• No proprietary data period
• Data immediately available to ESO members once
  verified
• Rest of world 18 months later

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UKIDSS filters
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Why Near-IR?

• 2? light traces mass in evolved stars - provides
  good estimate of stellar mass
• Helps identify cool dwarf stars and high-z
  quasars (optical dropouts)
• Less sensitive than optical light to dust
  reddening and type-dependent K-corrections

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Quasars vs dwarf stars
T6 brown dwarfz 7 quasar
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UKIDSS Surveys
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Comparison with 2MASS
Lawrence et al 2006 in prep
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UKIDSS Status
http//apm14.ast.cam.ac.uk/status/wfcam/
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UKIDSS Early Data Release

• Available to ESO community 2006 Feb 10
• 1 of final sample, comparable to 2MASS

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Data Access

• Via WFCAM Science Archive (Edinburgh)
  http//surveys.roe.ac.uk/wsa
• Need to register with your community contact
• SQL interface will be familiar to SDSS CAS users
• NB EDR data not all of final survey quality

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Early application of SDSS UKIDSS

• K-band luminosity function
• UKIDSS K-band photometry
• SDSS redshifts

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Current estimates
Bell et al 2003Grey Cole et al 2001
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K-band luminosity function

• Use UKIDSS EDR sample includes areas of sky
  with incomplete filter coverage
• Match UKIDSS EDR LAS with SDSS DR5 main sample
  galaxies (r lt 17.7)
• Tolerance 2 arcsec (nearly all matches within 1
  arcsec)
• Use Petrosian magnitudes

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Sky Coverage
EDR inc. areas with incomplete filter coverage
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Sky Coverage
Matched with SDSS DR5 main galaxy target
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Sky Coverage
Has redshift and K-band detection
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K-band Completeness
LAS galaxies 16.0 SDSS matches 14.0
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r-K colours
Completeness of matched sample (K14) limited by
SDSS r limit (17.77) and reddest r-K colour (3.8)
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LF Estimate

• Use complete sample (K lt 14) ? 1287 galaxies
  (fewer than 50)
• K-corrections to z 0.1 from template fit to
  SDSS ugriz using kcorrect v4
• STY, SWML estimators of ?(MK) - independent of
  density inhomogeneities

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Bivariate LF

• Use entire matched sample by estimating SWML
  bivariate ?(Mr, MK) allowing for SDSS r flux
  limit (r lt 17.7)
• Sample size 3249 galaxies, but faintest galaxies
  will now be bluer than average
• Integrate over Mr to obtain ?(MK)
• Fit Schechter function by least squares

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Conclusions/Future Prospects

• UKIDSS-SDSS K-band LF consistent with earlier
  estimates using 2MASS
• Measurements will improve considerably with more
  data
• UKIDSS Data Release 1 (DR1) due mid-2006 will
  have 10 times as much data
• Two year goals
• LAS half complete
• DXS full depth in JK over 3.1 deg2
• UDS K 22.8, J 23.8

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Future Plans

• Investigate type-dependence of K-band LF and its
  evolution
• Comparison with optical distinguishes stellar
  mass accumulation with star formation history
• Evolution to z 0.3 with SDSS redshifts
• Higher-redshift evolution using photometric
  redshifts

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Future Plans (2)

• SDSS Southern stripe co-added data plus UKIDSS
  DXS excellent for photo-z
• Possible volume-limited redshift survey using
  AAOmega
• Clustering evolution of K-limited (stellar mass
  selected) samples
• VISTA

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Websites

• http//www.sdss.org
• http//www.ukidss.org
• http//surveys.roe.ac.uk/wsa