1 / 39

Thomas R. Greve Max-Planck Institute for Astronomy

Galaxy Formation and Evolution from the Epoch of Reionization to z=4. Thomas R. Greve Max-Planck Institute for Astronomy. Purple Mountain Observatory, Nanjing, April 3rd 2009. Outline of this talk. 1) Cosmic history: the Universe beyond z > 4

nibaw
Download Presentation

Thomas R. Greve Max-Planck Institute for Astronomy

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Galaxy Formation and Evolution from the Epoch of Reionization to z=4 Thomas R. Greve Max-Planck Institute for Astronomy Purple Mountain Observatory, Nanjing, April 3rd 2009

  2. Outline of this talk 1) Cosmic history: the Universe beyond z > 4 - Identifying outstanding problems in galaxy formation and evolution and key science drivers for the next decade 2) How do we find galaxies at z > 4? - Dust obscured star formation at z > 4 - All-sky optical/near-IR surveys: hunting for z > 4 QSOs - Pristine galaxies at z > 4: Lyman-α Emitters 3) Understanding the interstellar medium in z > 4 galaxies? - How interstellar medium studies can help solve the key problems in galaxy formation and evolution 4) Summary

  3. Cosmic history: the Universe beyond z > 4 Identifying outstanding problems in galaxy formation and evolution and key science drivers for the next decade

  4. Cosmic History Galaxy (z=6.4) Old Stars Young star/ionized gas Molecular gas Galaxy (z=2.5) z=? The new cosmic frontier Galaxy (z=0) z=4

  5. The new cosmic frontier: the epoch of reionization Key questions to be addressed in the coming decade: -When did the EoR start? -How and when did the first galaxies form? -How and when did the first supermassive black holes form? -What was the inter-relationship between supermassive black hole and host galaxy growth at these early epochs? This requires large, robust samples of z > 4 galaxies! z=? The new cosmic frontier z=4

  6. 2) How do we best observe the first galaxies at z > 4? Dust obscured star formation at z > 4

  7. The dust-obscured Universe HDF-N Hughes et al. (1998) OB stars IR/FIR dust 850μm LIR = 1x1013L (Obscured) star formation rate Far-IR luminosity The submm probes the reionization epoch! UV SCUBA JCMT, Hawaii

  8. Submm/FIR Optical/UV The submm Universe ~1 sq. degree of sky has been surveyed at submm wavelengths to date resulting in the detection of more than ~400 bright SMGs (>3mJy) ~20-30% of the (sub)mm background has been resolved by blank-field surveys. ~80% by galaxy cluster surveys but poor number statistics

  9. Submillimetre/Millimetre Surveys Condon (1992) HDF-N Greve et al. (2008) Borys et al. (2005) Hughes et al. (1998) Submm surveys suffer from poor resolution (FWHM=11-15”) Radio inteferometry, however, offers <1” resolution Optical spectroscopy of 90 radio-ID submm galaxies The radio-FIR correlation ? Radio Chapman et al. (2005)

  10. A significant population of z > 4 SMGs? • ? • Model prediction of the volume density of SCUBA galaxies

  11. A significant population of z > 4 SMGs? Discovery: a z=4.76 submm-selected source not associated with a QSO Extended Chandra Deep Field South 870μm APEX/LABOCA Survey SMMJ033229.5 (z=4.76 from optical spectrum) Weiss et al. (2009) Coppin et al. (2009)

  12. A significant population of z > 4 SMGs? z=4 • Model prediction of the volume density of SCUBA galaxies Student project! A multi-wavelength ‘hunt’ for submm-selected galaxies at z > 4 Quantify their abundance and intrinsic properties

  13. The next submillimetre revolution • SCUBA-2 will deliver thousands of submm-selected sources • SCUBA-2 (first light 2009) • Sub-arcsecond submm/mm interferometry with ALMA: • - immediate identification (no need for radio identification) • A census of the z > 4 submm population • ALMA (first light 2012)

  14. 2) How do we best observe the first galaxies at z > 4? ✔Dust obscured star formation at z > 4 All-sky optical/near-IR surveys: hunting for z > 4 QSOs Pristine galaxies at z > 4: Lyman-α Emitters

  15. All-sky optical/near-IR surveys: hunting for z>4 QSOs All-sky surveys such as the SLOAN have found numerous, extremely luminous z > 4 QSOs by means of drop-out techniques in the optical They represent massive, extremely rare, overdensities in the primordial density distribution. z=4 • Gunn-Peterson trough • Becker et al. (2006)

  16. All-sky optical/near-IR surveys: hunting for z>4 QSOs The extreme luminosities of z > 4 QSOs make them ideal laboratories to study galaxy formation and black hole growth at the high-mass-end Submm/mm photometry: 1/3 of optically selected QSOs are IR hyper-luminous (LIR ≥ 1013L) 5 arcsec The most distant QSO known Walter et al. (2003) SDSSJ1148+5152 (z=6.42) Bertoldi et al. (2003) mm-emission/near-IR CO (3-2) 1 arcmin Wang et al. (2007)

  17. All-sky optical/near-IR surveys: hunting for z>4 QSOs The extreme luminosities of z > 4 QSOs make them ideal laboratories to study galaxy formation and black hole growth at the high-mass-end Submm/mm photometry: 1/3 of optically selected QSOs are IR hyper-luminous (LIR ≥ 1013L) The most distant QSO known SDSSJ1148+5152 (z=6.42) Bertoldi et al. (2003) mm-emission/near-IR Extreme galaxy in place <1Gyr after the Big Bang! 1 arcmin Wang et al. (2007) LFIR ≈ 1013L Mgas ≈ 7 x 1010M Mdust ≈ 109M

  18. Future large samples of distant QSOs Full UKIDSS Large Area Survey (4000 deg2, Y<19): # 8.0 > z > 5.8 QSOs: 17 Full Pan-STARRS Survey (10,000 deg2, Y<20.5): # 8.0 > z > 5.8 QSOs: 73 These samples of QSOs will be prime targets for multi-line molecular/atomic follow-up observations!

  19. 1) How do we best observe the first galaxies at z > 4? ✔Dust obscured star formation at z > 4 ✔All-sky optical/near-IR surveys: hunting for z > 4 QSOs Pristine galaxies at z > 4: Lyman-α Emitters

  20. Pristine galaxies at z > 4: Lyman-α Emitters i’ i’ z’ z’ In the absence of dust and strong optical continuum, the easiest way to find the first galaxies is via the Lyα recombination line: the strongest emission line produced by the hydrogen atom (Partridge & Peebles 1967) NB z=4 z=6.541 NB z=6.578 Kodaira et al. (2003)

  21. Pristine galaxies at z > 4: Lyman-α Emitters Lyman-α Emitters (LAEs) are likely to be pure starbursts – and representing the first building-blocks of galaxies The large number of z > 6 LAEs (30 per 0.25 sq. deg) implies that they could play a dominant role in reionizing the Universe Low stellar masses (<109M) and star formation rates (<30M/yr). No dust (very metal-poor) Small linear scales (<1kpc) • Gawiser et al. (2007)

  22. Future samples of distant Lyman-α emitters • Extremely Large Telescope • 30m optical/near-IR ground-based telescope • James Webb space telescope • 6.5m optical/near-IR/mid-IR telescope in space There are currently several hundreds known LAEs at z > 4 JWST+ELT will be able to detect the smallest and most distant galaxies (z > 7), increasing the number of LAEs by order of magnitude

  23. 1) How do we best observe the first galaxies at z > 4? ✔Dust obscured star formation at z > 4 ✔All-sky optical/near-IR surveys: hunting for z > 4 QSOs ✔Pristine galaxies at z > 4: Lyman-α Emitters What is the most effective way of studying these first galaxies in order to maximize constraints on formation and evolution models?

  24. The role of gas in galaxy formation and evolution • The gravitational hierarchical build-up of dark matter structures provides the framework for galaxy formation and evolution • The interstellar medium (gas and dust) is a key ingredient in galaxy formation and evolution as it provides the ‘fuel’ for star formation and supermassive black hole accretion • …so understanding the physical properties of the interstellar medium (ISM) in distant galaxies is fundamental to our picture of galaxy formation and evolution Galaxy Galaxy Galaxy Dark matter Dark matter Dark matter z = 0 (t = 13.6 Gyr) z = 2.5 (t = 4.0 Gyr) z = 6.4 (t = 0.9 Gyr) Springel et al. (2006), Nature

  25. Observing the interstellar medium Molecular hydrogen (H2) is by far the main component of the ISM – but its lack of a permanent dipole moment makes it virtually impossible to observe directly Instead the rotational lines of CO are mainly used to study the ISM J=1-0 (ν = 115GHz) J=2-1 (ν = 230GHz) . . . Density Temperature C O Other important molecular gas tracers: HCN and HCO+ Atomic fine-structure lines: [CI] and [CII] (ν = 490-1900GHz) CO 1-0 2-1 3-2 … 5-4 Atmospheric transmission vs. frequency The CO J=1-0 line from a local galaxy falls within the 3mm atmospheric window, …as does the (redshifted) CO J=5-4 line from a galaxy at z=4 (νobs = 575GHz/(1+z) = 115GHz)

  26. Observational status • This excitation-bias prevents a meaningful comparison between the molecular gas properties of local and high-z galaxies High-J CO lines Dense, warm gas CO 3-2 in SDSSJ1148+5152 (z=6.42) Walter et al. (2003) Low-J CO lines Diffuse gas z > 4 The highest CO detection to date Universe was 1/16 of its current age Greve (2009)

  27. A new golden era in ISM astronomy • The next five years will see a quantum leap in our ability to study the ISM in galaxies across the Cosmos - one that will take us from an epoch of merely detecting molecular lines at high-z to multi-line surveys capable of fully characterizing the ISM • Herschel, launch 2009 • ALMA, first light 2012 • EVLA, first light 2012 • z = 0

  28. A new golden era in ISM astronomy A full understanding of galaxy formation and evolution at z > 4… • Requires: • An exhaustive inventory of the microscopic properties (e.g. chemistry, density, thermal balance) of the ISM in z > 4 galaxies, and their effect on macroscopic properties (e.g. star formation, luminosity, morphology) Key Questions: -When did the EoR start? -How and when did the first galaxies form? -How and when did the first supermassive black holes form? -What was the inter-relationship between supermassive black hole and host galaxy growth at these early epochs? • Method: • - Sampling of the spectral line distributions of CO, HCN and HCO+, [CII] 158μm and [CI] 369μm • - Spatially and kinematically resolved dust and molecular line observations • - For large samples of z > 4 objects (QSOs, SMGs, and LAEs)

  29. High-z ISM studies at sub-kpc scales High-resolution observations of the dust and molecular gas provide a direct image of the formation morphology, and can distinguish between several scenarios A major merger between two gas-rich components (‘wet’ merger) Many minor bursts distributed within an extended potential and interspersed with periods of no star formation A single monolithic collapse In addition, one obtains accurate dynamical masses, merger fractions etc. • Submm galaxy at (z=2.49) SDSSJ1148+5152 (z=6.42) Walter et al. (2003) Imaging galaxy formation • Tacconi et al. (2008) CO(3-2)

  30. High-z ISM studies at sub-kpc scales An unusually tight relation between the mass of the supermassive black hole and that of its host spheriod has been established in the local Universe. This relation connects a phenomenon ocuring on spatial scales of ≈10-5pc (black hole accretion) to the spheriod which is 8 orders of magnitude larger (≈103pc ) This suggest a deep, co-evolutionary link between the supermassive black hole and the galaxy spheriod. What is the underlying physics? How does the relation evolve with redshift? The local MBH-Mbulge relation (Magorrian et al. 1997) Black hole and galaxy host growth at z > 4 Mbulge=0.002MBH scatter < 0.30dex Häring & Rix (2004)

  31. High-z ISM studies at sub-kpc scales Black hole and galaxy host growth at z > 4 High-resolution CO studies can uniquely probe the MBH-Mbulge relation at high-z Did the black holes start to grow first? QSOs SDSSJ1148+5152 (z=6.42) Local relation Walter et al. (2003) Local relation CO(3-2)

  32. High-z ISM studies at sub-kpc scales Black hole and galaxy host growth at z > 4 High-resolution CO studies can uniquely probe the MBH-Mbulge relation at high-z • High-resolution CO studies of submm galaxies Or did the bulges grow first? QSOs Local relation SMGs • Tacconi et al. (2008) Student project: Spatially resolve (<1” FWHM) the gas-kinematics in a large sample of z>4 QSOs and SMGs in order to study the MBH-Mbulge relation in the early Universe CO-detected SMGs (Alexander et al. 2007)

  33. A new golden era in ISM astronomy A full understanding of galaxy formation and evolution at z > 4… • Requires: • An exhaustive inventory of the microscopic properties (e.g. chemistry, density, thermal balance) of the ISM in z > 4 galaxies, and their effect on macroscopic properties (e.g. star formation, luminosity, morphology) Key Questions: -When did the EoR start? -How and when did the first galaxies form? -How and when did the first supermassive black holes form? -What was the inter-relationship between supermassive black hole and host galaxy growth at these early epochs? • Method: • - Sampling of the spectral line distributions of CO, HCN and HCO+, [CII] 158μm and [CI] 369μm • - Spatially and kinematically resolved dust and molecular line observations • - For large samples of z > 4 objects (QSOs, SMGs, and LAEs)

  34. The dense gas fraction of the ISM in a galaxy may govern its star formation efficiency and hence its evolutionary path. Determining the density structure of the ISM requires a very complete sampling of the CO rotational ladder APM0827 (z=3.9) Weiss et al. (2006) CO(4-3) CO(6-5) CO(9-8) Is the ISM in QSOs more excited than in submm-selected galaxies? Weiss et al. (2006) CO(10-9) CO(11-10) The ISM conditions at z > 4: the density structure of the gas

  35. Determining the density structure of the ISM requires a very complete sampling of the CO rotational ladder. As well as of dense gas tracers such as HCN and HCO+ APM0827 (z=3.9) Weiss et al. (2006) CO(4-3) CO(6-5) CO(9-8) Weiss et al. (2006) HCO+(1-0) in the Cloverleaf (z=2.6) CO(10-9) CO(11-10) HCN(5-4) The ISM conditions at z > 4: the density structure of the gas Riechers et al. (2006)

  36. The [CII] 158μm line is the main cooling line in our Galaxy and in typical local starburst (L[CII]/LIR ≈ 5x10-3) However, [CII] cools 10x less efficiently in the most IR-luminous galaxies (at low- and high-z) The first fully sampled CO spectrum (up to J=6-5) of a local IR-luminous galaxy (Papadopoulos et al. 2007) Normal local galaxies Local ultra IR-luminous galaxies The ISM conditions at z > 4: gas cooling [CII] SDSSJ1148+5152 (z=6.42) High-z CO(6-5) Walter et al. (2009) Hailey-Dunsheath (2008)

  37. The [CII] 158μm line is the main cooling line in our Galaxy and in typical local starburst (L[CII]/LIR ≈ 5x10-3) However, [CII] cools 10x less efficiently in the most IR-luminous galaxies (at low- and high-z) In metal-poor systems, however, we can have L[CII]/LIR ≈ 0.5-1x10-2 An z=7 LAE with LIR ≈ 2x1011L(SFR=30M/yr) will be detectable with ALMA! Normal local galaxies Local ultra IR-luminous galaxies The ISM conditions at z > 4: gas cooling SDSSJ1148+5152 (z=6.42) [CII] High-z Student project CO(6-5) Hailey-Dunsheath (2008) Maiolino et al. (2005)

  38. [CII] CO(8-7) The [CII] 158μm line may be the line of choice for z > 7 objects with ALMA Weiss et al. (2006) Detecting the first objects at z > 7 with ALMA [CII] CO J > 8 no highly excited [CII] is 5x brighter than CO(6-5) CO(6-5) Maiolino et al. (2005)

  39. Summary Future surveys with PanSTARRS/UKIDSS, SCUBA-2, and JWST/ELT will drastically increase sample sizes of z > 4 galaxies The next 5-10 years will see the advent of a number of new, ground-breaking cm/submm/far-IR facilities (e.g. ALMA, EVLA) allowing us to study such samples effectively For the first time it will be possible to do a detailed characterization of the ISM in primeval galaxies during the epoch of reionization This will revolutionize our understanding of galaxy formation and evolution at all cosmic epochs

More Related