High Redshift Galaxies in the era of reionization Richard McMahon Institute of Astronomy University of Cambridge, UK Pathway to the SKA, Oxford, April 2006

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 z>6 quasars and the cosmic microwave background indicate that reionization occurred at z~7-13 AND that this reionization is due to galaxies and not quasars.

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: T IGM SFR( Z, IMF) f ESC Clumpiness IGM 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 Galaxies Quasars Increase in redshift is primarily driven by technology and some ingenuity

The Highest Redshift Object Timeline Galaxies Quasars Increase in redshift is primarily driven by technology and some ingenuity Gamma-Ray Bursts

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)>10 17 cm -2 –Intervening Lyman-  forest lines ( <1216Å) Neutral Hydrogen column densityN(HI):10 12 –10 17 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 M sol 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 M sol yr -1   erg s -1 cm -2 at z=4.5 (Hu and McMahon, 1998)   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  h 50 Mpc -3 (e.g. Loveday etal, 1992)  minimum is 1000 Mpc 3

The Night Sky Problem Broad band sky gets brighter as you go to redder wavelengths

Spectrum of night sky and the narrow band solution 8100Å window z= Å window z=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, % 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  ) 2x 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  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

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 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 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 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: 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

Synergy of DAZLE and ALMA H 0 =70;  m =0.3;   =0.7 DAZLE: (in 2006) –Field of view at 0.20”/pixel: 6. 8arc min x 6.8 arc min –Redshift range per exposure:  1500 Mpc 3 (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 5<z<15 (dz=10)  1500 Mpc 3 (co-moving) –Sensitivity(5  ); SFR of 1Msol/yr; 70hrs

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~ (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 Galaxies Quasars 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 = 6.000HoOmegaMOmegavacz It is now Gyr since the Big Bang. The age at redshift z was Gyr. The light travel time was Gyr.light travel time The comoving radial distance, which goes into Hubble's law, is Mpc or Gly.comoving radial distance, The comoving volume within redshift z is Gpc3. The angular size distance DA is Mpc or Gly.angular size distance DA This gives a scale of kpc/". The luminosity distance DL is Mpc or Gly.luminosity distance DL

Z=6 Cosmology For Ho = 70, OmegaM = 0.30, Omegavac = 0.70, z = 6.000HoOmegaMOmegavacz It is now Gyr since the Big Bang. The age at redshift z was Gyr. The light travel time was Gyr.light travel time The comoving radial distance, which goes into Hubble's law, is Mpc or Gly.comoving radial distance, The comoving volume within redshift z is Gpc3. The angular size distance DA is Mpc or Gly.angular size distance DA This gives a scale of kpc/". The luminosity distance DL is Mpc or Gly.luminosity distance DL

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 : A Metal-Enriched, Dusty Starburst at z=6.295 astro-ph

Fig. 3.— Spectral energy distribution of the host galaxy of GRB 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 ～ 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 = 6.000HoOmegaMOmegavacz It is now Gyr since the Big Bang. The age at redshift z was Gyr. The light travel time was Gyr.light travel time The comoving radial distance, which goes into Hubble's law, is Mpc or Gly.comoving radial distance, The comoving volume within redshift z is Gpc3. The angular size distance DA is Mpc or Gly.angular size distance DA This gives a scale of kpc/". The luminosity distance DL is Mpc or Gly.luminosity distance DL

GRB redshift records (Kawai et al, Nature,2006) (Anderson et al,2000) (Kulkarni et al, Nature,1998)Kulkarni et al, Nature,1998 z>0 (van Parad, 1997)

The Highest Redshift Object Timeline Galaxies Quasars 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 field Keck HST (fix) Subaru Gemini

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