Three Distant Quasars Found at the Edge of the Universe

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Three Distant Quasars Found at the Edge of the
Universe

• based on poster New zgt6 Quasars from the Sloan
  Digital Sky Survey
• Xiaohui Fan (Arizona),
• Michael Strauss (Princeton),
• Donald Schneider (Penn State),
• Robert Becker (UC Davis),
• Richard White (STScI) et al.
• for the SDSS collaboration

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Outline

• The Sloan Digital Sky Survey recently found three
  new quasars at zgt6
• The 1st, 3rd and 4th most distant quasars known
• Increases number of known quasars from one to
  four
• These new quasars
• Probe the evolution of the earliest quasars and
  black holes
• Probe the end of the cosmic dark ages and cosmic
  reionization

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Sloan Digital Sky Survey
A Wide-Area, Deep, Multi-Object Imaging
and Spectroscopic Survey in Optical Wavelength

• Main Imaging Survey
• 10,000 square degrees of the North Galactic
  Cap
• ? one quarter of the whole sky
• 100 million 5-band images

• Spectroscopic Survey
• brightest 1 million galaxies
• brightest 100,000 quasars
• ? Redshift survey, 3-D distribution

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How to find the most distant quasars?

• The highest redshift, most distant quasars are
  very red ? looking for the reddest objects on the
  sky
• The highest redshift, most distant quasars are
  extremely rare ? one out of many million objects,
  and could be confused with many kinds of
  contaminants brown dwarfs, cosmic ray hits
  etc. ? needles in the haystack ? complicated,
  multi-step searching technique that involves a
  number of follow-up observation telescopes in
  addition to the SDSS facilities.

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Find the most distant quasarsneedles in a
haystack
Hobby-Eberly (Texas) 9.2m
APO 3.5m
Keck (Hawaii) 10m
Calar Alto (Spain) 3.5m

• SDSS database
• 15 million objects

4. Detailed spectra (3 new quasars at z6.1, 6.2,
6.4)
2..Photometric pre-selection 100 objects
3. Photometric and spectroscopic Identification
(10 objects)
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New zgt6 Quasars from the SDSS
z6.1
z6.2
z6.4
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Spectra of new zgt6 quasars
Lyman alpha emission (from hydrogen)
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Cosmic Evolution of Quasars and Supermassive
Black Holes

• Luminous quasars found by SDSS ? residing in
  supermassive black holes of several billion solar
  masses
• At z6, quasars are much rarer than that at z2 ?
  we are witnessing the first generation quasars
  and the initial growth of the supermassive black
  holes in the universe

z2.5 2.5 billion years after big bang
z6, 800 million years After Big Bang
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Quasars and the End of Cosmic Dark Ages probing
the cosmic reionization

• After the Big Bang cosmic dark ages (no sources
  of light) ? first generation of galaxies and
  quasars turned on, this reionization process
  ended the cosmic dark ages
• The most distant quasars themselves are among the
  first sources of light, and they provide direct
  probes to the cosmic reionization
• Many quasars at zgt6 provide multiple sight-lines
  how reionization happened and how uniform this
  process is did the cosmic dark ages end at the
  same time for different part of the universe?
• SDSS expects to find about 15 quasars at zgt6

Highest redshift quasars