Atacama Large Millimeter Array

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The high-z Universe with ALMA Carlos De Breuck (ESO)

The ALMA project: 

The ALMA project ALMA is a collaboration between Europe (ESO + Spain), North America (US + Canada), and Japan. It is the merger of individual projects to build a large (sub)millimeter interferometer. Located on a 5000m high plateau in Northern Chile to take advantage of the excellent sky transparency. ALMA will be Easy to use for non-experts.

The Location: Chajnantor plateau: 

The Location: Chajnantor plateau


Configurations ALMA will consist of 50 operational antennas. Antennas can be moved to ~185 different pads. Maximum baselines from 150m to 18km → resolutions from 1' to andlt;0.01' at 850 µm.

Japanese contribution: Atacama Compact Array: 

Japanese contribution: Atacama Compact Array Japan will provide an array of 12 smaller (7m) antennas in a very compact configuration Also 4 single-dish 12m antennas to provide total power. First total power antennas arrive in Chile in September 2007. Even at the shortest baselines (15m), ALMA will not be sensitive to large-scale structure.

Observing in different frequency bands: 

Observing in different frequency bands 10 Frequency bands coincident with atmospheric windows have been defined. Bands 3, 6, 7 and 9 will be available from the start. Bands 4, 8 and 10 will be built by Japan. Some band 5 receivers built with EU funding.

Powerful receivers: 

Powerful receivers Receivers will have an 8 GHz instantaneous bandwidth. System temperatures (~ sensitivity) close to quantum noise limit. Spectral resolution 31.5 kHz (0.01 km/s) at 100 GHz. Will observe in dual polarization mode.

Timeline (1): 

Timeline (1) Operation Support Facilty @2800m: construction in progress. Array Operations Site @5000m: construction starts on 1 Sept 2005. 12m wide road connecting both sites: almost ready.

Timeline (2): 

Timeline (2) First antenna delivered on site in September 2007. Further antennas coming from July 2008 with new antenna every 2 months. First science: end of 2008. Full completion: 2012.

ULIRG SED: dust and molecular lines: 

ULIRG SED: dust and molecular lines

Dust continuum: negative k-corrections: 

Dust continuum: negative k-corrections At zandgt;1, the peak of thermal dust emission shifts to submm wavelengths. For a given luminosity, the observed flux density remains the same, or increases slightly for zandgt;1.

CO rotational transitions (‘ladders’): 

CO rotational transitions (‘ladders’) Line ratios of CO rotational transitions depend on density and temperature. In Milky Way type galaxies: low-order transitions are brighter → low densities. In dense cores of starburst galaxies, higher-order transitions are brighter. Radio observations with eVLA, ATCA andamp; SKA will be needed (see Ron Ekers’ talk). Weiss et al. astro-ph/0508037

Detecting normal galaxies at z=3: 

Detecting normal galaxies at z=3 CO emission now detected in 25 zandgt;2 objects. To date only in AGN, starbursts and gravitationally lensed objects. Normal galaxies are 20 to 30 times fainter. Detecting CO or C+ in Milky Way type galaxies out to z=3 in andlt;24h is one of the 3 primary science requirements of ALMA. Assuming L’CO(3-2)=5x108 K km/s pc2 (COBE results, Bennett et al 1994), MW galaxy at z=3 has ~0.037 mJy km/s → requires 24 hr with full array to get 3σ detection

The [CII] 158µm line: 

[CII] 158µm is the main coolant in the Milky Way. However, it is much fainter in ULIRGs. First detection in z=6.4 QSO. With high-frequency ALMA bands → observe [CII] 158µm at 1andlt;zandlt;8. The [CII] 158µm line Maiolino et al. astro-ph/0508064

Example: ALMA deep field at 300 GHz: 

Example: ALMA deep field at 300 GHz 4’ x 4’ Field (3000² pixels). Sensitivity: 0.1 mJy (5σ). 30 minutes per field, 140 pointings → total of 3 days. 100-300 sources. Alternative: deep bolometer surveys (wider fields, but lower sensitivity andamp; resolution).

HDF: rich in nearby galaxies, poor in distant galaxies.: 

HDF: rich in nearby galaxies, poor in distant galaxies. Nearby galaxies in HDF Distant galaxies in HDF Source: K. Lanzetta, SUNY-SB

ALMA deep field: poor in nearby galaxies, rich in distant galaxies.: 

ALMA deep field: poor in nearby galaxies, rich in distant galaxies. Nearby galaxies in ALMA deep field Distant galaxies in ALMA deep field Source: Wootten and Gallimore, NRAO

ALMA as a redshift machine: 

ALMA as a redshift machine ALMA will provide 0.1' images of submm sources. 3 frequency settings will cover the entire 84-116 GHz band → at least one CO line. (1h per source) At zandgt;3, at least 2 CO lines in a single band. Confirm with observation of high/lower order CO line. (1h per source)

Follow-up studies with ALMA: 

Follow-up studies with ALMA High resolution andamp; high fidelity (comparable to HST) dust andamp; CO imaging to determine morphology (mergers?), derive rotation curves → Mdyn, density, temperature, ... Observe sources in HCN to trace dense regions of star-formation. Expected results of an ALMA deep survey: Fully resolve the cosmic IR background into individual sources and determine FIR properties of LBGs and EROs as well as SMGs Map the cosmic evolution of dusty galaxies and their contribution to the cosmic star formation history.

Dark matter and intervening absorbers: 

Dark matter and intervening absorbers Detailed kinematical studies of galaxies: CO will provide reliable kinematics of galaxies (better than optical and HI 21cm) → dark matter distribution. CO Tully-Fisher relation is more accurate because CO is less broadened by galaxy interactions than HI. Intervening absorbers: With ALMA’s sensitivity, the number of background continuum sources will increase by 2 orders of magnitude → studies of intervening absorbers becomes possible. Explore chemistry, CMB temperature, variations of the fine structure constant, … as a function of redshift.

Sunyaev-Zell’dovich effect: 

Sunyaev-Zell’dovich effect ALMA will observe at frequencies where the SZE is the strongest. Increase in sensitivity combined with improved resolution will allow to map the SZE in less massive clusters out to higher z. ALMA will have the sensitivity to detect not only the thermal, but also the kinetic SZE.→ trace possible cluster rotation.

Sunyaev-Zel’dovich effect: 

Sunyaev-Zel’dovich effect Most clusters will be detected in other experiments such as Planck, AMIBA, SZA, APEX. ALMA will provide (sub)arcsec resolution imaging of these clusters. SZE scientific goals include: Constrain cosmological parameters w, Ωm, σ8 through cluster counts; variation of TCMB as function of z. Study physics of clusters, by mapping their hot gas and radial velocity (kSZ), obtaining baryon fraction, …

Ostriker-Vishniac effect: 

Ostriker-Vishniac effect Dark matter halos with M~109Mʘ have formed by z~30; those with M~1011Mʘ by z~9. Between initial re-ionization and complete baryonic condensation, most baryons in these halos are ionized gas. Typical diameters are D=2.5 to 30 kpc, corresponding to 1' to 6' at z=9-30 (Peebles andamp; Juszkiewicz 1998). Thomson scattering of the CMB by these structures will dominate its anisotropy at arcsec scale: the OV-effect. For peculiar velocities ~200 km/s, 6' beam (z~9), ΔT(rms)/T~2x10-5, corresponding to ~150μJy at 100GHz. Easily detectable with ALMA in a few hours.

For more information on the ALMA construction, see the ALMA newsletter: 

For more information on the ALMA construction, see the ALMA newsletter

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