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ALMA and Cosmology

ALMA and Cosmology. The high-redshift Universe Advantages of mm/submm The need for ALMA ALMA science. Dark ages. Recombination. Today. Reionization. Big Bang. Cosmic Microwave Background. spectrum. fluctuations. (de Bernardis et al 2000). (Netterfield et al 2001). Structure.

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ALMA and Cosmology

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  1. ALMA and Cosmology The high-redshift Universe Advantages of mm/submm The need for ALMA ALMA science

  2. Dark ages Recombination Today Reionization Big Bang

  3. Cosmic Microwave Background spectrum fluctuations (de Bernardis et al 2000) (Netterfield et al 2001)

  4. Structure log J21 time redshift z Ionization (Gnedin, 2000)

  5. Intergalactic Absorption quasar Charlton & Churchill (2000) z = 1.3 Charlton & Churchill (2000) z = 3.6 Becker et al. (2001) z = 6.3

  6. Emerging galaxies (simulations by Theuns, Mo, Schaye, 2001)

  7. Questions about the early Universe The global star formation rate • When did reionization occur? • Was reionization caused by galaxies or quasars? • How did the global star formation rate evolve? • When did elliptical galaxies form? • How did the heavy element content of the Universe evolve? ?

  8. The importance of the mm/submm wavebands for studying the distant Universe • Unobscured by dust absorption • Enhanced by dust emission • Sensitivity to the highest redshifts • Spectral lines for redshift determination • Luminosity at high z dominated by mm/FIR Extragalactic Backgrounds

  9. Dust and molecular emission from optically obscured regions HST optical image HST optical image + CO contours (CO : Wilson et al. 2000) (HST: Whitmore et al. 1999) The “Antennae”

  10. Cluster A1835 z ~ 0.7-2.5 z = 2.55 (Ivison et al., 2000)

  11. Sensitivity to objects at very high redshifts (Negative K-correction) 0 Log F(Jy) -2 -4 0.1 1 10 Redshift

  12. Redshift determination - photometric and spectroscopic Frequency coverage of CO and HCO+ over the 3 mm band (70-116 GHz)

  13. Dust and CO emission at z = 4.69 NTT Deep Field Bertoldi et al. (2000) Omont et al. (1996)

  14. Extragalactic backgrounds CBR ALMA λ range (Franceschini et al. 2001) • Observed mm/FIR background ~ optical/near-IR background • At high redshift, mm/FIR luminosity dominates; ULIRGs produce much of the bolometric output of the Universe at high-z • most of star formation activity obscured observations at mm/submm wavelengths are essential

  15. Recent developments in mm/submm astronomy From z ~ 0 to z ~ 5 in just 5 years CO at z = 2 FIR background SCUBA sources (Eisenhardt et al. 1996) (Guiderdoni et al. 1999) (Hughes et al. 1998)

  16. A next generation mmm/submm telescope is required ALMA will provide: • a mm/submm equivalent of VLT, HST, NGST - with corresponding high sensitivity and angular resolution but unhindered by dust opacity • a capability to see star-forming galaxies out to the highest redshifts

  17. Sensitivity Angular Resolution

  18. High sensitivity ALMA

  19. 158 μm [CII] fine structure line from ULIRGs with ALMA (5σ noise: 2hr integration, resolution 300 km/s, PWV 0.8mm)

  20. High Angular resolution and the identification problem SCUBA resolution ALMA resolution Hughes et al. (1998)

  21. Identification of HDF 850.1 SCUBA beam Downes et al. (1999)

  22. cluster A2125 (1200 mm, MAMBO) Surveys of high redshift populations • Mm/submm searches sensitive to obscured, star-forming galaxies • Present mm/submm surveys SCUBA, MAMBO) can detect only the very strongest sources • over 200 sources now known • consistent number counts at the bright end are obtained • But identifications and accurate redshifts are very difficult to obtain • Sources not associated with cluster galaxies. • Associated with VLA radio sources • Dusty star forming galaxies at z ~ 2.5 (Carilli et al. 2001)

  23. Combined number counts from SCUBA and MAMBO blind surveys • The counts correspond to 850mm (350 GHz). • Contains data from gravitationally lensed sources at low flux densities • Best fit with a Schechter luminosity function with an exponential cut-off at 10 mJy. • (approximately corresponding to LFIR = 1013 Lo) (Carilli et al. 2001)

  24. Surveys with ALMA At 350 GHz: • Over whole sky, ~ 400 million sources to 1 mJy • Over whole sky, ~ 4 billion sources to 100 μJy • 100 sources to 1 mJy can be found in several hours • 100 known sources to 1 mJy can be observed in an hour • 100 sources to 100 μJy can be found in a day (and complete redshift survey finished in a week) • A survey of 100,000 sources to 1 mJy could be done in a year 0 redshift 5

  25. The strongest sources • ALMA provides high angular resolution, rapid acquisition and snapshot observations for the study of the strongest sources • no mm survey of the sky yet, but tens of thousands of sources will come from FIRST, Planck, and the LMT. • ALMA will be able to identify such sources in seconds • A catalogue of all the most luminous mm/submm galaxies and AGN over the southern sky will be produced. High redshift continuum detections High redshift CO emission detections PSS quasars 1.2 mm detections (compiled by T. Wiklind) Omont et al. (2001)

  26. Into the reionization epoch QSOs SFR ? Optical & radio selected • If dust was formed quickly enough in the first luminous objects, they should be significant mm/submm sources • ALMA may detect such objects to redshifts as high as 10-20, if they are there

  27. Molecular absorption lines in AGN spectra HCO+(1-0) absorption towards the nucleus of Centaurus A (Wiklind & Combes 1998)

  28. Cen A PKS 1830-211 z = 0.9 system (Discovered purely by spectral scans in the millimeter wavebands)

  29. The New Quasar Absorption Line Spectroscopy PKS 1830-211 zabs = 0.886 HCO+(2-1) Molecular absorption lines at high redshift (no beam dilution) Detailed chemistry at high redshift Chemical evolution, isotopic ratios as a function of redshift Probes of molecular tori Kinematics at high spectral resolution TCBRvs redshift Fine structure constant at high redshift Thousands of AGN accessible with ALMA Resolution = 0.5 km/s Wiklind & Combes, 1997) CS(3-2), CS(4-3), HCN(2-1), HCN(3-2), HCO+(2-1), HCO+(3-2), HNC(2-1), HNC(3-2), N2H+(2-1), N2H+(3-2), H2CO(211-110), H13CN(2-1), H13CO+(2-1), H13CO+(3-2), H2CO(211-212), HC3N(3-2), HC3N(5-4), C3H2(212-101), H13CN(1-0), H13CN+(1-0), HN13C(1-0), C2H(1-0), HCN(1-0), HCO+(1-0), HNC(1-0)

  30. Gravitational Lensing The fraction of lensed sources may be much greater in the mm/submm than in other wavebands because of the steep source count Strong lensing • high resolution mapping of both continuum and lines • no extinction, facilitating source reconstruction • molecular absorption lines - structure and time delays Cluster arcs • gravitational arcs will be mapped in continuum and molecular lines Weak lensing • large numbers of background sources available

  31. The Cloverleaf (H1413+117) • Gravitationally lensed QSO • Several different molecular transitions detected • Line ratios model dependent (differential magnification?) CO(7-6) line at 0.6” resolution Barvainis et al. 1997 Kneib et al. 1997

  32. Gravitational lensing by a cluster of galaxies submillimeter optical (simulations by A. Blain)

  33. Gamma Ray Bursts Frail et al (2001) • GRB afterglows may be detectable to very high redshifts, probing star formation in the reionization epoch • ALMA can monitor them, possibly detect the host galaxies (especially if star forming galaxies; “dark bursts”) z = 1 cluster Distortions of the CMB • Sunyaev-Zel’dovich effect in clusters: ALMA will provide well resolved images of the SZ effect in clusters Springel et al (2001) ALMA image (J. Carlstrom) • Secondary anisotropies from the reionization epoch: only ALMA will be able to probe the CMB power spectrum at the required scale and sensitivity (Benson et al 2000; Springel et al 2001)

  34. ALMA and Cosmology Summary • Mm/submm is a vital new window on the distant Universe • unobscured view of star-forming galaxies, at wavelengths containing most of the luminosity of the distant Universe • ALMA’s sensitivity and angular resolution are essential to realize this potential • ALMA’s scientific contributions will include studies of the earliest galaxies, an accounting of the bolometric luminosity of the distant Universe, and the evolution of galaxies, quasars and the elements over cosmic time

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