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)

8. ? Questions about the early Universe When did reionization occur?
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? ?

9. 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

10. 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”

11. Cluster A1835
z ~
z = 2.55
(Ivison et al., 2000)

12. Sensitivity to objects at very high redshifts (Negative K-correction)
Log F(Jy) -2 -4
Redshift

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

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

15. 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

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

17. 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

18. Sensitivity Angular Resolution

19. High sensitivity
ALMA

20. 158 μm [CII] fine structure line from ULIRGs with ALMA (5σ noise: 2hr integration, resolution 300 km/s, PWV 0.8mm)

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

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

23. Surveys of high redshift populations
cluster A2125
(1200 mm, MAMBO)
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)

24. 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)

25. 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
redshift

26. 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)

27. ? 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

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

29. Cen A
PKS
z = 0.9 system
(Discovered purely by spectral scans in the millimeter wavebands)

30. Quasar Absorption Line Spectroscopy
The New
Quasar Absorption Line
Spectroscopy
PKS 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
TCBR vs 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( ), H13CN(2-1), H13CO+(2-1), H13CO+(3-2), H2CO( ), HC3N(3-2), HC3N(5-4), C3H2( ), H13CN(1-0), H13CN+(1-0), HN13C(1-0), C2H(1-0), HCN(1-0), HCO+(1-0), HNC(1-0)

31. 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

32. The Cloverleaf (H )
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

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

34. Gamma Ray Bursts Distortions of the CMB
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)

35. 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