High Redshift Galaxies in the era of reionization

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High Redshift Galaxies in the era of reionization

• Richard McMahon
• Institute of Astronomy
• University of Cambridge, UK

Pathway to the SKA, Oxford, April 2006
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Why?

• The study of the highest redshift objects give us
  direct observational information of the how
  galaxies form and evolve via masses,
  star-formation rates, star-formation histories.
• Observations of zgt6 quasars and the cosmic
  microwave background indicate that reionization
  occurred at z7-13 AND that this reionization is
  due to galaxies and not quasars.

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How many UV luminous star forming sources to
reionize the Universe?
Overproduction of metals

• Necessary input includes
• TIGM
• SFR( Z, IMF)
• fESC
• ClumpinessIGM
• Uncertainties of ?10 likely!

? Surface density of 7 lt zlt 10 sources
(arcmin-2)
Insufficient UV photons
SFR (M?/yr) ?
After Stiavelli, Fall Panagia (2004)
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The Observational Challenges in surveys for
surveys for high redshift objects

• Experimentally difficult because
• Faint Distant objects are very faint.
• Sky brightness The rest frame UV and optical
  radiation is redshifted to regions where night
  sky spectrum is very bright.
• Rare Foreground objects are much more numerous
  so the experimental selection technique has to be
  efficient at descrimination between high redshift
  and low redshift objects.
• Technology May be undetectable, in a
  reasonable amount of time using current
  technology i.e. may need to wait or develop the
  technological solution.

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The Highest Redshift Object History
Quasars
Galaxies
Increase in redshift is primarily driven by
technology and some ingenuity
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The Highest Redshift Object Timeline
Gamma-Ray Bursts
Quasars
Galaxies
Increase in redshift is primarily driven by
technology and some ingenuity
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Spectroscopically confirmed zgt6.0 galaxies

• Narrow Band Surveys (gt21?)
• Hu, Cowie, McMahon et al. 2002(1), Kodeira et al.
  2003(2), Rhoads et al 2004(1), Taniguchi et al.
  2005(9), Kashikawa et al(8)
• z(max)6.60 all have z6.550.05
• Gamma-ray burst host galaxies(1)
• GRB050904 z6.295(Kawai et al, 2006)
• Other Surveys (gt6?)
• 2 other zgt6 emission line selected galaxies
• Kurk et al, 2004(1) Stern etal, 2005(1)
• Ellis etal, lensed search z6-7 candidate (no
  line emission photo-z)
• i-drops Nagao et al, 2004(1) Stanway etal,
  2004(1)

Quasars Sloan Digital Sky Survey(SDSS)
n(zgt6.0)9 (Fan et al, 2001, 2003, 2004,
2006) z(max)6.43 (Fan et al, 2003)
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Searches techniques for high redshift galaxies

• UV drop-out technique survey technique due to
• Intrinsic or Intervening Lyman limit 912Å due
  to optically thick HI
• Neutral Hyrogen column density N(HI)gt1017 cm-2
• Intervening Lyman- ? forest lines (?lt1216Å)
• Neutral Hydrogen column densityN(HI)10121017
  cm-2
• Emission line searches based on Lyman-? line
  emission(?rest 1216Å)

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Principles of photometric continuum selection of
high redshift objects
Lyman-? in absorption in galaxy rest frame
z3 starforming galaxy

• HI in Intergalactic medium causes absorption
  shortward of Lyman-? (1216Å)
• Shortward of 912A neutral hydrogen in the galaxy
  absorbes radiation
• Technique has been used successfully up to z6
  using redder filters

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High Redshift Lyman-? emission lines
surveysAstrophysical principles for Success

• Partridge and Peebles, 1967, Are Young Galaxies
  visible? Basic idea has been around a long time
• Minimum Flux limit
• Previous surveys in the early 1990s were based
  on the paradigm of a monolithic collapse.
• expected star formation rates of 50-500 Msol yr-1
  i.e. the SCUBA/FIR population?
• Lets assume SFR detection limits more appropriate
  to a slowly forming disc or sub-galactic units in
  a halo
• i.e. 1-3 Msol yr-1
• 1.0-2.0 ? 10-17erg s-1 cm-2 at z4.5 (Hu and
  McMahon, 1998)
• 2.0-6.0 ? 10-18 erg s-1 cm-2 at z7.5
• Minimum Volume
• search a comoving volume within which you expect
  to find the progenitors of around 10 L galaxies.
  (.i.e. Milky Way mass)
• Local density 1.40.2 ? 10-2 h50 Mpc-3 (e.g.
  Loveday etal, 1992)
• minimum is 1000 Mpc3

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The Night Sky Problem
Broad band sky gets brighter as you go to redder
wavelengths
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Spectrum of night sky and the narrow band solution
9200Å window z6.5
8100Å window z5.7
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Basic experimental principle

• Basic principle is to survey regions where the
  sky sky spectrum is darkest in between the
  intense airglow.
• Gaps in the OH airglow picket fence
• 100angtrom width filters
• Lyman-alpha redshifts of gaps in
  Optical-Silicon CCD regime
• 7400 Å z5.3
• 8120 Å z5.7 used extensively
• 9200 Å z6.6 used extensively
• 9600 Å z6.9 no results yet
• CCDs have poor QE and sky relatively bright

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z5.7 for Lyman-?
z6.6 for Lyman-?
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z6.56 Galaxy Behind A370 Hu, Cowie, McMahon
etal, 2002
NARROW BAND (strong Ly a emission) 9200Ang
(width125Ang)
R BAND (no galaxy detected)
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?(observed Lyman-?)9190Å ?(rest
Lyman-?)1216Å Redshift6.558
1 of night sky emission
Filter profile
Lyman-? emission line
Hu, Cowie, McMahon etal, 2002
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Composite spectrum of galaxies with line emission
in the 8100Å window
z0.6 unresolved and 4959 line
OIII4959
OIII(5007Å)
z1.2 note resolved doublet
OII(3727Å)
z5.7 note asymmetry
n18 galaxies
Lyman-?(1216Å)
Hu, Cowie, Capak, McMahon, Hayashino, Komiyama,
2004, AJ, 127, 563
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z6.597 galaxy (Taniguchi et al, PASJ, 2005)

• Survey
• Subaru 8.2m
• Suprimecam 34 x 27 0.2/pixel
• 132Å filter centred at 9196Å
• Exposure time 54,000 secs (15hrs)
• Flux limit(5?) 2x10-18 erg cm-2 sec-1
• Results
• 58 candidates
• 9 spectroscopically confirmed with z6.6 in
  Taniguchi et al(2005)
• 8 further confirmation in Kashikawa et al(2006)

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Narrow band searches in the near Infrared

• OH lines contribute 95 of sky background in
  1.0-1.7?m range
• i.e. 20 times the continuum emission.
• Filters need to have widths of 10Å or 0.1 to
  avoid OH lines.
• c.f. 100Å in the optical
• NB. Narrower band means you solve a smaller
  redshift range so wide angular field is needed to
  increase the volume searched.
• Some of the technical issues
• Filter design and manufacture e.g. filter width
  of 0.1(10Å) BUT you also want the central
  wavelength to 0.01(1Å)
• Field angle causes an off-axis shift of central
  wavelength
• Out of band blocking

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Infrared OH Sky Observations Mahaira etal, 1993,
PASP
GOOD NEWS The 1.0 to 1.8 micron IR sky is very
dark between the OH lines which contain 95 of
broad band background.
THE NOT SO GOOD NEWS The narrowest gaps are
narrower than in the optical filter widths of
0.1 per cent are needed compared with 1 filters
in optical.
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Simulated sensitivity(8m telescope) and narrow
band filter(1nm) J and H band z7 to 15
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DAZLE Dark Ages Z Lyman Explorer(visiting a
Time when Galaxies were Young) McMahon, Parry,
Horton, Band-Hawthorn(AAO)

• Background Funded from Oct 2000 under PPARC
  Opportunity Scheme NOW destined for VLT UT3
  visitor focus. (was Gemini)
• Status May 2001 Design Contract with AAO
  signed
• Jan 2002 Conceptual Design Review
• August 2002 Preliminary Design Review
• January-June 2003 Progressive Final Design
  Review
• Oct, 2005 ESO VLT
  compliance criterion passed.
• Currently being re-integrated in Cambridge all
  optical components have been delivered(including
  a replacement for L1 in collimator)
• Current Schedule
• Aug 2006 Ship to ESO, Paranal
• Nov/Dec 2006 Start survey of GOODS/UDF Chandra
  Deep Field South and COSMOS field

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DAZLE Dark Age Z Lyman Explorer McMahon, Parry,
Bland-Hawthorn(AAO), Horton et al
IR narrow band imager with OH discrimination at
R1000 i.e. 0.1 filter FOV 6.9 ? 6.9 arcmin 2048
Rockwell Hawaii-II 0.2/pixel Sensitivity 2.
10-18 erg cm-2 sec-1(5?), 10hrs on VLT i.e. 1
M? yr-1 at z8
Sky emission and absorption spectrum around 1.06
and 1.33 microns showing DAZLE filter pairs for
Lyman ? at z7.7, 9.9 other gaps are at 8.8, 9.2
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DAZLE Digital state

• 3D CAD drawing of DAZLE Final Design on VLT
  UT3(Melipal) Visitor Focus Nasmyth Platform.
• UT3 optical axis is 2.5m above the platform floor
• grey shading shows the DAZLE cold room(-40C)which
  is 2.5m(l) x 1.75m(w) x 3m(h).
• Blue Dewar at top contains the 2048 x 2048 pixel
  IR detector

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Dazle in Cambridge Laboratory
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Synergy of DAZLE and ALMA

• H070 ?m0.3 ??0.7
• DAZLE (in 2006)
• Field of view at 0.20/pixel 6. 8arc min x 6.8
  arc min
• Redshift range per exposure 0.011
• 1500 Mpc3 (co-moving)
• Sensitivity(5?) SFR of 1Msol/yr 10hrs on VLT
• ALMA
• Field of view 15 arc sec x 15 arc sec at 1mm
• Redshift range 5ltzlt15 (dz10)
• 1500 Mpc3 (co-moving)
• Sensitivity(5?) SFR of 1Msol/yr 70hrs

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Current Prospects for searches for galaxies in
the epoch of reionization

• Current z6.5 barrier is technological
• Technology now exists to carry out sensitive
  enough surveys at zgt7.
• Recent Spitzer studies of z5 to 6.5 galaxies
  show that many have stellar populations where the
  star formation rate at zgt7 was gt10Msol/year. In
  some the starformation at this level may have
  begun at z10-20. (Eyles et al, 2005 Chary et al
  2005 Berger et al 2005, Dow-Hygelund et al,2005
  Egami et al, 2005)
• Fact that quasars exist at z6 imply massive host
  galaxies with ages that place their first stars
  at zgt7.
• Theoretical expectations are highly uncertain
  this means any result is useful! Specifically Le
  Delliou et al(2006), predict 0.3 to 3 per DAZLE
  pointing with the main uncertainty coming from
  the Lyman-? escape fraction(0.02 to 0.2). See
  also Dave et al(2006)

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The Highest Redshift Object Timeline
Gamma-Ray Bursts
Quasars
Galaxies
Increase in redshift is primarily driven by
technology
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THE END
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Z6 Cosmology

• For Ho 70, OmegaM 0.30, Omegavac 0.70, z
  6.000
• It is now 13.666 Gyr since the Big Bang.
• The age at redshift z was 0.950 Gyr.
• The light travel time was 12.716 Gyr.
• The comoving radial distance, which goes into
  Hubble's law, is 8421.8 Mpc or 27.468 Gly.
• The comoving volume within redshift z is 2501.925
  Gpc3.
• The angular size distance DA is 1203.0 Mpc or
  3.9238 Gly.
• This gives a scale of 5.833 kpc/".
• The luminosity distance DL is 58949.3 Mpc or
  192.269 Gly.

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Z6 Cosmology

• For Ho 70, OmegaM 0.30, Omegavac 0.70, z
  6.000
• It is now 13.666 Gyr since the Big Bang.
• The age at redshift z was 0.950 Gyr.
• The light travel time was 12.716 Gyr.
• The comoving radial distance, which goes into
  Hubble's law, is 8421.8 Mpc or 27.468 Gly.
• The comoving volume within redshift z is 2501.925
  Gpc3.
• The angular size distance DA is 1203.0 Mpc or
  3.9238 Gly.
• This gives a scale of 5.833 kpc/".
• The luminosity distance DL is 58949.3 Mpc or
  192.269 Gly.

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Some Future ground based surveys for higher
redshift Galaxies and Quasars

• zgt7 galaxies
• Dark Ages Z Lyman-? Explorer (DAZLE) on the VLT
  (to start Nov 2006)
• zgt7 quasars
• UKIDSS UK Intra-Red Deep Sky Survey (started May
  2005 5 year survey project)
• UKIRT (Hawaii) WFCAM
• ESO members Public Access from late 2005)
  Worldwide 18month
• VISTA Surveys (to start early 2007)

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FINAL SLIDE
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TODO

1. Tran, Lilly paper with the figure
2. Need a sensitivity plot of L v z?
3. Include Fraser diagram in H and K

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Oxford Meeting
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Spitzer Constraints on the z 6.56 Galaxy Lensed
by Abell 370
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Specific galaxies

• Stern etal
• Ellis et al
• GRB
• Eyles etal
• Tanaguchi etal
• Dow-Hygelund et al

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Recent Theoretical Predictions
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Recent Evidence for Star formation at zgt7

• HST and Spitzer Observations of the Host Galaxy
  of GRB 050904 A Metal-Enriched, Dusty Starburst
  at z6.295 astro-ph

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• Fig. 3. Spectral energy distribution of the host
  galaxy of GRB050904 from HST (blue) and Spitzer
  (red) data.
• Three representative SEDs are shown (see 3 for
  details) with model parameters given in the
  figure. The models with
• AV 0.2 . 0.3 mag are based on the extinction
  inferred from the afterglow emission. For
  comparison, the dotted line
• represents the best-fit model to the SED of the z
  6.56 galaxy HCM6A (redshifted to z 6.295)
  with an age of 5 Myr,
• AV 1.0 mag, and M 8.4 108 M? (Chary et al.
  2005).

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Z6 Cosmology

• For Ho 70, OmegaM 0.30, Omegavac 0.70, z
  6.000
• It is now 13.666 Gyr since the Big Bang.
• The age at redshift z was 0.950 Gyr.
• The light travel time was 12.716 Gyr.
• The comoving radial distance, which goes into
  Hubble's law, is 8421.8 Mpc or 27.468 Gly.
• The comoving volume within redshift z is 2501.925
  Gpc3.
• The angular size distance DA is 1203.0 Mpc or
  3.9238 Gly.
• This gives a scale of 5.833 kpc/".
• The luminosity distance DL is 58949.3 Mpc or
  192.269 Gly.

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GRB redshift records

• 6.295 (Kawai et al, Nature,2006)
• 4.500 (Anderson et al,2000)
• 3.418 (Kulkarni et al, Nature,1998)
• zgt0 (van Parad, 1997)

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The Highest Redshift Object Timeline
Gamma-Ray Bursts
Quasars
Galaxies
Increase in redshift is primarily driven by
technology
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VLA QSO field Keck HST
(fix) Subaru
Gemini
From Elizabeth Stanway's thesis (2004), updated
from review of Stern Spinrad (1999)
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Kodaira et al. (2003) z6.58 Ly-alpha galaxy
(narrow-band)
Also Hu et al. (2002) z6.56, lensed by Abell
370 cluster
Both use narrow-band filter in low-background
region between sky lines, and follow-up spectra