High Redshift Galaxies in the era of reionization

Richard McMahonInstitute of Astronomy

University of Cambridge, UK

Pathway to the SKA, Oxford, April 2006

Overproduction of metals

SFR (M/yr)

After Stiavelli, Fall & Panagia (2004)

Insufficient UV photons

Surface density of 7 < z< 10 sources (arcmin-2)

Necessary input includes:

• TIGM

• SFR( Z, IMF)

• fESC

• ClumpinessIGM

Uncertainties of 10 likely!

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

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

GalaxiesQuasars

Increase in redshift is primarily driven by technology and some ingenuity

The Highest Redshift Object Timeline

GalaxiesQuasars

Increase in redshift is primarily driven by technology and some ingenuity

Gamma-Ray Bursts

Spectroscopically confirmed z>6.0 galaxiesNarrow 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)

Lyman- in absorption in galaxy rest frame

Principles of photometric continuum selection of high redshift objects

• 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

z=3 starforming galaxy

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

Vega (mags)

AB (mags)

mJy

B 4400 22.1 22.2 4.8 2.6V 5500 21.3 21.4 9.6 3.5R 6000 20.4 20.8 17.9 3.9I 7500 19.5 20.0 35.2 5.2Z 8900 18.2 18.7 117.2 6.3J 12,500 16.0 16.9 609.3 9.3H 16,500 14.1 15.5 2335.7 12.6K 22,000 13.3 15.2 3020.1 17.1

WavebandCentral

Wavelength

‘Dark’ Sky brightness per arcsec^2 Redshift

Lyman- (1216Å)

Broad band sky gets brighter as you go to redder wavelengths

Spectrum of night sky and the narrow band solution

8100Å windowz=5.7

9200Å windowz=6.5

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 Hu, Cowie, McMahon etal, 2002

NARROW BAND (strong Ly emission)9200Ang (width=125Ang)

R BAND (no galaxy detected)

(observed; Lyman-)=9190Å(rest; Lyman-)=1216Å

Redshift=6.558

Hu, Cowie, McMahon etal, 2002

1% of night sky emission

Filter profile

Lyman- emission line

Composite spectrum of galaxies with line emission in the 8100Å window

z=5.7; note asymmetry

z=1.2; note resolved doublet

z=0.6; unresolved and 4959 line[OIII]4959

Lyman-(1216Å)

[OII](3727Å)

[OIII](5007Å)

n=18 galaxies

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

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 signedJan 2002; Conceptual Design ReviewAugust 2002: Preliminary Design ReviewJanuary-June 2003: Progressive Final Design ReviewOct, 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

DAZLE: Dark Ages “Z” Lyman Explorer

(visiting a Time when Galaxies were Young)

McMahon, Parry, Horton, Band-Hawthorn(AAO)

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 – Dark Age Z Lyman ExplorerDAZLE – Dark Age Z Lyman Explorer

McMahon, Parry, Bland-Hawthorn(AAO), Horton et alMcMahon, 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;

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

GalaxiesQuasars

Increase in redshift is primarily driven by technology

Gamma-Ray Bursts

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 Quasarsz>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 (Kawai et al, Nature,2006)

• 4.500 (Anderson et al,2000)

• 3.418 (Kulkarni et al, Nature,1998)

• z>0 (van Parad, 1997)

The Highest Redshift Object Timeline

GalaxiesQuasars

Increase in redshift is primarily driven by technology

Gamma-Ray Bursts

From Elizabeth Stanway's thesis (2004), updated from review of Stern & Spinrad

(1999) VLA

QSO fi

eld

Kec

k

HST (f

ix)

Sub

aru

G

emini

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 low-

background region between sky lines, and

follow-up spectra