Rare Populations from the SDSS

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Rare Populations from the SDSS

• Xiaohui Fan (Institute for Advanced Study) for
  the SDSS collaboration

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Selection of Rare Populations

• SDSS spectroscopic target selection modules
• Selected from SDSS multicolor photometry
• Galaxies
• Quasars color selected, obj with non-stellar
  colors
• Stars ? WD, CV, BHB, BD etc
• Serendipity
• Rare populations found in SDSS
• Rare species of quasar/galaxy/star in the main
  sample
• Objects with unusual colors picked up as quasar
  candidates

QSO
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Rare Populations in the Spectroscopic Sample

• Extragalactic
• High-z quasars
• Unusual BAL quasars
• Reddened quasars
• EA galaxies
• Superposition of galaxies
• Supernovae

• Galactic
• L dwarfs
• T dwarfs
• Unusual WDs
• Cool WDs
• DQs
• Magnetic WDs
• WD M pairs
• Very metal poor subdwarfs
• Carbon stars
• CVs

SDSS team Anderson, Bauer, Einsenstein, Fan,
Hall, Harris, Hawley, Knapp, Margon, Richards,
Schlegel, Strauss, Szkody, Vanden Berk, et al.
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Unusual BAL Quasars
Weird 1 z1.30

• Deep troughs from low ionization gas esp. from
  FeII, MgII etc. (Hall, Anderson, Strauss, Fan et
  al.)

z2.11
Weird 2 z2.82 (variable)
z1.46
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Other Extragalactic Examples
Superposition of a z1.8 quasar And a z0.01
emission line gal
Field EA Galaxy at z0.8
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Galactic Examples
Highly peculiar CV
DQ White Dwarf
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Galactic Examples
Cool WD T3000 K
Very low metallicity subdwarf
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Case Study i-dropout Survey
zgt5.5 Quasars and BDs

• Astrophysically most interesting
• Technical Challenges
• Rarest objects on the sky Key to success ?
  efficient elimination of contaminants
• Elimination of faise z-band only detections ?
  improved cosmic ray rejection
• Reliability of faint z photometry ? follow-up
  high S/N z photometry
• Separation of quasar/BD ? J-band photometry
• Results
• 1500 deg2 at zABlt20
• 4 quasars at zgt5.7
• 12 Ts and 100 Ls

Fan et al. 2001
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zgt5.7 Quasars
Fan, Narayanan, Strauss, Becker, White et al.
Sciences

• evolution of quasar LF ?
• constraining quasar formation
• optical/IR spectroscopy ?
• metallcity and chemical enrichment
• evolution of Lyman absorption ?
• constraining reionization epoch

Limitation of Current Survey

• SDSS 20 in 10,000 deg2 ?
• small number statisitcs
• SDSS zlt21 ? need faint objects
• To understand complete picture of
• quasar evolution at high-z
• wide-angle, deep survey
• in far-optical, near-IR wavelengths
• with high-quality spectroscopic follow-up

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Sciences

• spectral classification and
• temperature sequence
• atmosphere physics, dust cloud
• spatial density, luminosity function
• and mass density of BDs

Future

• cooler objects Tlt700 K
• sample larger than 2MASS/SDSS
• required
• large far-optical, near-IR imaging
• survey with IR spectroscopic follow-up

T dwarfs
Geballe, Leggett, Knapp Fan, Gilimoski et al.
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Lessons Learned

• Large area and wide wavelength coverage
• Search for color space outliers ? control the
  number of false positive is the name of the game
  
• Photometric precision crucial
• Comprehensive image processing QA flags
• Need for extensive spectral template database to
  automate the rare object recognition
• After 2000 deg2 ? no real surprises yet, no
  previously unknown class of object found
• SDSS will be a rich database for many kinds of
  rare (and weird) objects, but deep
  imaging/spectroscopic survey needed for the
  rarest classes of objects

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Evolution of Quasar LF from SDSS Sample
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Evolution of Quasar Luminosity Density
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Evolution of Quasar LF

• Low-z SDSS result consistent with 2dF
• The exponentially decline (10-0.5z) from z3 - 6
• Luminous high-z quasar evolves faster than normal
  galaxy population
• Current surveys do not probe the faint end of LF
  at high-z majority of high-z quasars have not
  been observed!
• Little constraint on faint end LF evolution

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Quasar Density at z6

• Based on four luminous quasars from SDSS
• Density declines 20 from z3
• Consistent with extrapolation
• Number density implies that quasars unlikely to
  provide enough UV background if LF similar to at
  low-z
• Luminous high-z quasars provide sensitive test to
  quasar and BH models
• MBH109-10 Msun
• Mhalo 1013 Msun
• Find Faint Ones

Fan et al. 2001
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SDSS Quasar Survey

• Quasar sample
• Color-selected, flux-limited, 105 quasars in 104
  deg2
• For zlt3 i lt 19
• For zgt3 i lt 20
• Survey sensitive to zlt6.5
• AGN sample
• Color-selection includes extended sources at
  low-z
• Radio (FIRST) and X-ray (ROSAT) selected
  subsamples
• gt20000 quasars at 0ltzlt6.3 to date

Z3.5
Z4
Z3
Z3.5
Z2
Z4.5
Z5
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Shape of Quasar LF at High-z

• LF fit by a single power law in luminosity range
  probed
• At z4 quasar luminosity function much FLATTER
  than LF at z2
• Shape of quasar LF evolves with redshift as well
• Even less UV ionizing photon at high-z from
  quasar than previously calculated?

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Correlation FunctionQuasars vs. Galaxies
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Evolution of Quasar Clustering
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Evolution of Quasar Clustering

• At zlt2 r_0 7 Mpc/h
• Slow evolution with redshift
• Might be function of luminosity
• At z4
• Quasars strongly clustered (r_0 20 Mpc/h)
• Stronger than the clustering of low-z quasars or
  high-z LBGs
• Luminous high-z quasars are in massive system and
  represent very rare peaks of the density field
• Quasar correlation consistent with a quasar halo
  mass of 1012 1013 M_solar, and short
  life-time (107-108 years)