4 K Assembly

4 K stage

Feedhorn

2SB Mixer assembly

Pol 1Pol 0

OMT

4 Low NoiseAmplifiers& isolators

DSB Mixer Unit

Definitive Science with Band 3adapted from the ALMA Design Reference Science Plan

(www.strw.leidenuniv.nl/~joergens/alma/)

EXTRA-GALACTIC:

Unbiased surveys of sub-millimetre galaxies - understanding the process of cosmic star formation

Of order 50% of star formation in the cosmos occurs in galaxies highly obscured by dust, and this fraction may rise with redshift

Dust continuum observations will constrain SED of the galaxy - sensitivity in the µJy range @ 3mm

Molecular line observations will constrain the redshift of the galaxy - predominantly using CO

Molecular line studies of sub-millimetre galaxies - constraining dust obscured galaxy formation

High resolution imaging of CO - ALMA’s 0.2 arcsecond resolution corresponds to approximately 1 kpc

Search for dense gas tracers - for example HCN

Molecular line absorption studies - using background radio galaxies to probe ISM in intervening systems

Full spectral scan through Band 3 range will provide evidence for rare or low-excitation molecules

Sunyaev-Zel’dovich Effect of Proto Clusters -measuring the fine scale structure of high redshift clusters

These observations require two receiver bands (3 and 6) and can be obtained in continuum or lines

Calibration of the CO to molecular hydrogen ratio

Surveying the free-free emission in nearby galaxies

Gas content and dynamics of Elliptical Galaxies

GALACTIC:

Small scale structure in molecular clouds - characterising the threshold for self-similar hierarchy in GMCs

High resolution (0.1 arcseconds) imaging of several nearby molecular clouds using the CO (1-0) line

Searching for the scale on which turbulent or magnetic energy is dissipated

Infall velocity structure of starless cores - understanding the process of collapse

High angular resolution required to map the infall motions across the core using N2H+ or HCO+

Depletion of molecules in low-mass cores - searching for evidence of freeze-out or chemistry

Comparison of tracer molecules and their isotopomers such as CO, HCO+, CS, CCS, N2H+

Unbiased Line surveys of Star-forming regions - searching for new and exotic molecules

Absorption line studies toward background bright point sources - detecting diffuse and translucent clouds

Molecular gas in disks around young stars

The 3 Millimetre (Band 3) Receivers for ALMA

Jim Hesser, Doug Johnstone, Stephane Claude, Keith Yeung, Lewis Knee, and the Band 3 Receiver Team

The Role of Band 3The Atacama Large Millimetre Array (ALMA) will be one of astronomy's most powerful telescopes, providing unprecedented imaging capabilities and sensitivity many orders of magnitude greater than anything of its kind today. The largest Canadian contribution will be the 3-millimetre wavelength band (Band 3) receivers for each of ALMA's antennas. The millimetre instrumentation laboratory of NRC's Herzberg Institute of Astrophysics (HIA) in Victoria, BC, is one of the few facilities in the world with expertise in superconducting detector technology for millimetre waves. Operating at temperatures of -269 °C, these receivers will detect and amplify the incredibly faint whispers of radiation that reach earth from the remotest parts of the cosmos. These receivers are of paramount importance to the project because they will be used not only for many science applications but also for final adjustment of the antenna panels and for regular calibration of the array during operations. The first Band 3 cartridge (cartridge #1) has been assembled at HIA and cartridge #2 will be assembled shortly. This first cartridge has gone through an exhaustive series of acceptance tests at HIA and is scheduled for shipment to the North American Front End Integration Centre at NRAO in Summer 2005.

Receiver Band 3 Main Specifications

•Receiving frequency range is 84-116 GHz (converted down to 6 GHz for processing)

•Receiving signal amplified by 60 dB (that is a gain of 1 million)

•Receiver noise temperature of 37 K (equivalent to the sky noise temperature at the ALMA site)

•Simultaneous reception of two orthogonal polarizations

•Simultaneous reception of both side-bands (2SB mode)

•Total IF output bandwidth of 8 GHz per polarization

•Superconductor-Isolator-Superconductor (SIS) cryogenic detector and low noise amplifier operating at 4K.

92 94 96 98 100 102 104 106 1080

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System Noise Temperature (K)

LO Frequency (GHz)

USB0 LSB0 USB1 LSB1

Broad band 4-8 GHz

4 5 6 7 80

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System Noise Temperature (K)

Intermediate Frequency (GHz)

Cartridge #1 Pol 0 USB LO=92 GHz

100 200 300 400

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Redshift

Z

Observing Frequency GHz

CO Lines in ALMA

ObservingWindows

CO 1-0 2-1

3-2

4-3

5-4

10-9

Day 1

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For Z = 0.5,1,2,3,4 Age of Universe is 55%,35%,19%,12%,9%