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ALMA Nikolic & Richer

Atacama Large Millimetre Array: Capabilities, Status & Future
B. Nikolic & J. S. Richer
Astrophysics Group, Cavendish Laborator y, University of Cambridge http://www.mrao.cam.ac.uk/~bn204/

Capabilities Current status ALMA Development programme

The future of UK Submillimetre Astronomy Workshop UKATC, Edinburgh December 2011


ALMA
Recent (but already out of date) photo of ALMA with 19 antennas at AOS

ALMA Nikolic & Richer Capabilities Current status ALMA Development programme

Credit: ALMA (ESO/NRAO/NAOJ) / W. Garnier (ALMA)


ALMA ­ aerial view

ALMA Nikolic & Richer Capabilities Current status ALMA Development programme

Credit: ALMA (ESO/NRAO/NAOJ) / ?


Outline

ALMA Nikolic & Richer Capabilities Current status ALMA Development programme

Capabilities

Current status

ALMA Development programme


Summary of key capabilities
1. Very high sensitivity to unresolved sources 2. Resolution as fine as 0.005 arcseconds 3. High image fidelity 4. Good surface brightness sensitivity (compact configuration + ACA + Total Power) 5. Small instantaneous Field-Of-View: 6. 2 в 8 GHz instantaneous bandwidth 7. Full polarisation capability 8. Aiming for ver y high calibration accuracy 9. Very fast mosaicing (OTF interferometry) 10. Aiming for high observing flexibility (very shor t turnaround between projects, multiple arrays, multiple LOs, multiple correlators, target-of-oppor tunity, solar observing, solar system objects)
1 mm

ALMA Nikolic & Richer Capabilities Current status ALMA Development programme

в 17 arcsec


Unresolved source sensitivity
For full ALMA expect total "gain" about 1.7 K/Jy 16 GHz bandwidth for continuum Receiver noise temp spec: 6 - 15 h /k

ALMA Nikolic & Richer Capabilities Current status ALMA Development programme


Unresolved source sensitivity
For full ALMA expect total "gain" about 1.7 K/Jy 16 GHz bandwidth for continuum Receiver noise temp spec: 6 - 15 h /k E.g., spec for Band 7 < 150 K, in practice much better ( 90 K) (+add 40 K for atmosphere) at 850 µm approximately 1 mJy in one second continuum sensitivity will be routine Spectroscopy at 850 µm
100 km/s spectral resolution about 12 mJy / 20 mK sensitivity in one second 1 km/s spectral resolution about 120 mJy / 200 mK sensitivity in one second

ALMA Nikolic & Richer Capabilities Current status ALMA Development programme

http://almascience.eso.org/ call- for- proposals/ sensitivity- calculator


ALMA spectral coverage
1 mm precipitable water vapour
1 0.8 0.6 Tx 0.4 0.2 0 Band 2 100 Band 5 200 (GHz) Band 7 500 1000 Band 3 Band 4 Band 6

ALMA Nikolic & Richer Capabilities Current status ALMA Development programme

Band 8

Band 9 Band 10

Bands 3, 4, 6, 7, 9 in production. Band 10 in development stage. EC FP6 programme building 6 Band 5 car tridges.


ALMA spectral coverage
0.1 mm precipitable water vapour
1 0.8 0.6 Tx 0.4 0.2 0 Band 2 100 Band 5 200 (GHz) Band 7 500 1000 Band 3 Band 4 Band 6

ALMA Nikolic & Richer Capabilities Current status ALMA Development programme

Band 8

Band 9 Band 10

Bands 3, 4, 6, 7, 9 in production. Band 10 in development stage. EC FP6 programme building 6 Band 5 car tridges.


High-z line coverage

ALMA Nikolic & Richer Capabilities Current status ALMA Development programme

[Maiolino(2008)]


Resolution ­ 10+ km baselines
This is what we want to get to [Wolf & A'Angelo, 2005. (50+100pc, 1+5 Mjupiter )]

ALMA Nikolic & Richer Capabilities Current status ALMA Development programme


Image fidelity

ALMA Nikolic & Richer Capabilities Current status ALMA Development programme

One of three ALMA top-level science goals
The ability to provide precise images at an angular resolution of 0.1 arcseconds. Here the term precise image means accurately representing the sky brightness at all points where the brightness is greater than 0.1% of the peak image brightness. This requirement applies to all sources visible to ALMA that transit at an elevation greater than 20 degrees. > 1000 : 1 dynamic range


Image fidelity II

ALMA Nikolic & Richer Capabilities Current status ALMA Development programme

2000 instantaneous baselines 25 configurations ­ non-symmetric, minimally redundant optimised antenna positions with close to Gaussian radial distribution Fast slew (2 s to move 2 degrees and settle) means easy to revisit pointings Accurate primar y beam calibration, other calibrations (Relatively low dynamic range of much of the sky!)


Calibration capability

ALMA Nikolic & Richer Capabilities Current status

Amplitude calibration consistency over time/different directions in sky:
Better than 1% at < 370 GHz (Bands 1-7) Better than 3% at > 370 GHz (Bands 8-10)

ALMA Development programme

Accuracy of overall flux density scale 5% Primary beam pattern: better than 1% at < 400 GHz / 2% otherwise Polarisation accuracy: 0.1% flux error and 6 degree position angle
c Phase fluctuations 10 µm(1 + 1 mm ) 20 µm in median conditions, even on 10 km baselines!


Mosaicing

ALMA Nikolic & Richer Capabilities Current status ALMA Development programme

Should perform close to radiometer equation Move between pointing centres < 2 seconds On-the-fly interferometry: antennas continuously scanning (Commissioning of both hardware and software already star ted) 1000-pointing mosaics should be easy!


Outline

ALMA Nikolic & Richer Capabilities Current status ALMA Development programme

Capabilities

Current status

ALMA Development programme


SV: Antennae Galaxies

ALMA Nikolic & Richer Capabilities Current status ALMA Development programme


SV: NGC 3625 I

ALMA Nikolic & Richer Capabilities Current status ALMA Development programme


SV: NGC 3625 II

ALMA Nikolic & Richer Capabilities Current status ALMA Development programme


TW Hydra
CO J=3 2:

ALMA Nikolic & Richer Capabilities Current status ALMA Development programme

HCN J=4 3:


SV: [C I I] from a z4.4 QSO

ALMA Nikolic & Richer Capabilities Current status ALMA Development programme


ALMA Current Status

ALMA Nikolic & Richer Capabilities Current status

Currently 26 antennas up at the AOS (22в12 m-diameter and 4в7 m-diameter) Bands 3, 4, 6, 7 and 9 are in use (4 not offered for Cycle 0) Baseline + ACA correlator. Both antenna transpor ters. Full set of WVRs. Sufficient number of FEs for available antennas. ACDs. Commissioning and Science Verification observations ongoing Shor t baselines only (< 250 m). Currently being commissioned: polarisation, solar observing, complex correlator modes, new releases of the software.

ALMA Development programme


ALMA Early Science Cycle 0
Over 900 proposals ( observed) 16+ antennas Obser ving in 5 в 12 hour blocks Data calibrated and reduced by JAO & ARC staff with deliver y as science-grade data cubes First Cycle 0 data delivered to PIs last week top 10% are likely to be

ALMA Nikolic & Richer Capabilities Current status ALMA Development programme

Obser ving begun 30th September, right on schedule!

Note about availability
300 days of 24 hour/day observing would approximately allow every Cycle 0 proposal to be done! That level is not quite feasible, but ALMA will do a lot of science


Cycle 1
Draft proposal (taken from Al Wooten's presentation, 30 Nov)

ALMA Nikolic & Richer Capabilities Current status ALMA Development programme

Minimum 32в12 m-diameter antennas + ACA (5в 7 m-diameter + 1в 12 m-diameter), maximum 1 km baselines Bands 3, 6, 7, 9 (same as Cycle 0) More flexibility in the correlator No large proposals Polarisation unlikely to be offered More programmatic flexibility (ToO/DDT)


Outline

ALMA Nikolic & Richer Capabilities Current status ALMA Development programme

Capabilities

Current status

ALMA Development programme


Overview of the development programme

ALMA Nikolic & Richer Capabilities Current status

Aim to enhance ALMA beyond capabilities envisaged by the baseline project Not pre-committed to any par ticular area, science driven Ramp up between now and end of construction 5 M USD /par tner/year budget (10% of operations) Coordinated by the JAO and the ALMA Board implemented by the executives (ESO/NRAO/NAOJ) Already star ted in Europe, about to commence in Nor th America/East Asia

ALMA Development programme


Development ­ Possibilities for Hardware
Ongoing already: Building 6 Band 5 receivers (EC FP6 funding) VLBI capability (NSF funding) Some possibilities: Filling in bands in the system design: Bands 1, 2 & 5 New bands: Band 11, combine Bands 2/3? Increase IF bandwidth? (currently 4 GHz / sideband with best performance for 2SB receivers) Faster correlator? Focal plane array receivers? Stopping down the aper ture?? More antennas??

ALMA Nikolic & Richer Capabilities Current status ALMA Development programme


Development ­ Possibilities for Software

ALMA Nikolic & Richer Capabilities Current status ALMA Development programme

Some possibilities: Visualisation/analysis of spectral cubes Radiative transfer modelling? Better calibration software? Advanced model fitting


Development ­ Possibilities for scientific and operational efficiency

ALMA Nikolic & Richer Capabilities Current status ALMA Development programme

Some possibilities: Better scheduling? Continuous parallel observing in Band 3? (Needs also hardware + software) Archive tools? Spectral line databases?


References

ALMA Nikolic & Richer Capabilities Current status ALMA Development programme

Maiolino R., 2008, New Astronomy Review, 52, 339. arXiv:0806.0695