Transcript Oxford Meeting

High Redshift Galaxies
in the era of
reionization
Richard McMahon
Institute of Astronomy
University of Cambridge, UK
Pathway to the SKA, Oxford, April 2006
How many UV luminous star forming sources to
reionize the Universe?
Overproduction
of metals

Surface
density of
7 < z< 10
sources
(arcmin-2)
Necessary input
includes:
• TIGM
• SFR( Z, IMF)
• fESC
Insufficient
UV photons
SFR (M/yr) 
After Stiavelli, Fall & Panagia (2004)
• ClumpinessIGM
Uncertainties of
10 likely!
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.
The Highest Redshift Object History
Quasars
Galaxies
Increase in redshift is primarily driven by technology
and some ingenuity
The Highest Redshift Object Timeline
Gamma-Ray Bursts
Quasars
Galaxies
Increase in redshift is primarily driven by technology
and some ingenuity
Spectroscopically confirmed z>6.0 galaxies
Narrow Band Surveys (>21?)
• 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 z=6.55±0.05]
Gamma-ray burst host galaxies(1)
• GRB050904; z=6.295(Kawai et al, 2006)
Other Surveys (>6?)
• 2 other z>6 emission line selected galaxies
– Kurk et al, 2004(1); Stern etal, 2005(1)
• Ellis etal, lensed search z=6-7 candidate (no line emission; photo-z)
• i-drops Nagao et al, 2004(1); Stanway etal, 2004(1)
Quasars; Sloan Digital Sky Survey(SDSS)
n(z>6.0)=9 (Fan et al, 2001, 2003, 2004, 2006)
z(max)=6.43 (Fan et al, 2003)
Searches techniques for high redshift
galaxies
1. 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)>1017 cm-2
Intervening Lyman-  forest lines (<1216Å)
• Neutral Hydrogen column densityN(HI):1012–1017 cm-2
2. Emission line searches based on Lyman- line
emission(rest =1216Å)
Principles of photometric continuum selection of
high redshift objects
Lyman- in absorption in galaxy rest frame
z=3 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 z~6 using redder filters
High Redshift Lyman- emission lines surveys:
Astrophysical 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 1990’s 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 z=4.5 (Hu and McMahon, 1998)
 2.0-6.0  10-18 erg s-1 cm-2 at z=7.5
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 1.4±0.2  10-2 h50 Mpc-3 (e.g. Loveday etal, 1992)
 minimum is 1000 Mpc3
The Night Sky Problem
Broad band sky gets brighter as you go to redder wavelengths
‘Dark’ Sky brightness per
Redshift
arcsec^2
Central
Lyman-
Waveband
Wavelength
Vega
AB
(1216Å)
Jy
m
(mags)
(mags)
B
V
R
I
Z
J
H
K
4400
5500
6000
7500
8900
12,500
16,500
22,000
22.1
21.3
20.4
19.5
18.2
16.0
14.1
13.3
22.2
21.4
20.8
20.0
18.7
16.9
15.5
15.2
4.8
9.6
17.9
35.2
117.2
609.3
2335.7
3020.1
2.6
3.5
3.9
5.2
6.3
9.3
12.6
17.1
Spectrum of night sky and the narrow band solution
9200Å window
z=6.5
8100Å window
z=5.7
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; z=5.3
8120 Å; z=5.7; used extensively
9200 Å; z=6.6; used extensively
9600 Å; z=6.9; no results yet
• CCDs have poor QE and sky relatively bright
z=5.7 for Lyman-
z=6.6 for Lyman-
z=6.56 Galaxy Behind A370
NARROW BAND (strong Ly  emission)
9200Ang (width=125Ang)
Hu, Cowie, McMahon etal, 2002
R BAND (no galaxy detected)
(observed; Lyman-)=9190Å
(rest; Lyman-)=1216Å
1% of night sky emission
Redshift=6.558
Filter profile
Lyman- emission line
Hu, Cowie, McMahon etal, 2002
Composite spectrum of galaxies with line
emission in the 8100Å window
[OIII]4959
z=0.6; unresolved and 4959 line
[OIII](5007Å)
z=1.2; note resolved doublet
[OII](3727Å)
n=18 galaxies
z=5.7; note asymmetry
Lyman-(1216Å)
Hu, Cowie, Capak, McMahon, Hayashino, Komiyama, 2004, AJ, 127, 563
z=6.597 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
z=6.6 in Taniguchi et al(2005)
• 8 further confirmation in Kashikawa et
al(2006)
Narrow band searches in the near Infrared
• OH lines contribute 95% of sky background in 1.0-1.7mm
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
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.
Simulated sensitivity(8m telescope) and narrow band
filter(1nm): J and H band; z=7 to 15
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;
Jan 2002;
August 2002:
January-June 2003:
Oct, 2005:
Design Contract with AAO signed
Conceptual Design Review
Preliminary Design Review
Progressive Final Design Review
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
DAZLE – Dark Age Z Lyman Explorer
McMahon, Parry, Bland-Hawthorn(AAO), Horton et al
IR narrow band imager with OH
discrimination at R=1000 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 z=8;
Sky emission and absorption
spectrum around 1.06 and 1.33
microns showing DAZLE filter pairs
for Lyman  at z=7.7, 9.9; other gaps
are at 8.8, 9.2
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
Dazle in Cambridge Laboratory
Current Prospects for searches for galaxies
in the epoch of reionization
•
Current z=6.5 barrier is technological
•
Technology now exists to carry out sensitive enough surveys at z>7.
•
Recent Spitzer studies of z=5 to 6.5 galaxies show that many have
stellar populations where the star formation rate at z>7 was
>10Msol/year. In some the star–formation at this level may have begun
at z~10-20. (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 z=6 imply massive host galaxies with ages
that place their first stars at z>7.
•
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)
The Highest Redshift Object Timeline
Gamma-Ray Bursts
Quasars
Galaxies
Increase in redshift is primarily driven by technology
THE END
Z=6 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.
Z=6 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.
Some Future ground based
surveys for higher redshift Galaxies
and Quasars
z>7 galaxies
• Dark Ages ‘Z’ Lyman- Explorer (DAZLE) on the VLT (to start
Nov 2006)
z>7 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)
FINAL SLIDE
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
Oxford Meeting
Spitzer Constraints on the z = 6.56 Galaxy
Lensed by Abell 370
Specific galaxies
•
•
•
•
•
•
Stern etal
Ellis et al
GRB
Eyles etal
Tanaguchi etal
Dow-Hygelund et al
Recent Theoretical Predictions
Recent Evidence for Star formation
at z>7
• HST and Spitzer Observations of the Host
Galaxy of GRB 050904: A Metal-Enriched,
Dusty Starburst at z=6.295 astro-ph
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).
Z=6 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.
GRB redshift records
•
•
•
•
6.295
4.500
3.418
z>0
(Kawai et al, Nature,2006)
(Anderson et al,2000)
(Kulkarni et al, Nature,1998)
(van Parad, 1997)
The Highest Redshift Object Timeline
Gamma-Ray Bursts
Quasars
Galaxies
Increase in redshift is primarily driven by technology
From Elizabeth Stanway's thesis (2004),
updated from review of Stern & Spinrad
(1999)
Kodaira et al.
(2003) z=6.58
Ly-alpha galaxy
(narrow-band)
Also: Hu et al. (2002)
z=6.56, lensed by
Abell 370 cluster
Both use narrow-band
filter in lowbackground region
between sky lines, and
follow-up spectra