Current mm interferometers

Sébastien MullerNordic ARCOnsala Space ObservatorySweden

Turku Summer School – June 2009

Current mm interferometers: few facts

- Mm interferometry = Young techniquePdBI: early 90sSMA dedication: 2003

• Design started in 1979

• First antenna completed in 1987

• 3 antennas interferometer observations opened for guest observers 1990

• First fringes at 230 GHz 1995

• 5 antennas configuration 1996

• 6 antennas configuration 2002

• New generation receivers 2007& extension of the tracks

350 GHz receivers 2009…Broad-band correlator

PdBI milestones

1984 The SMA project (6-elements array) was proposed by the SAO.

1996 The ASIAA joined the project, starting SMART (Submillimeter Array of Taiwan) project.

1999 First two SAO antennas were completed at MKand the first fringe was obtained.

2001 First image was obtained with 3 antennas.

2001 First ASIAA antenna was assembled at MK.

2002 2nd ASIAA antenna was assembled at MK.

2003 The SMA (eight elements) was dedicated.

2004 - Regular science operations

SMA milestones

Current mm interferometers: few facts

- Mm interferometry = Young techniquePdBI: early 90sSMA dedication: 2003

- Few mm interferometers, mostly in the Northern hemisphere

Current mm interferometers: few facts

- Mm interferometry = Young techniquePdBI: early 90sSMA dedication: 2003

- Few mm interferometers, mostly in the Northern hemisphere

- Small array Nant < 15limited instantaneous uv-coverage -> super-

synthesis

- Limited total collecting area

- High altitude site for dry and stable atmosphere

Altitude = 2550mN ant = 6D = 15mArea = 1060 m2

Altitude = 2200mN ant = 15D = 6/10mArea = 772 m2

Altitude = 1340mN ant = 6D = 10mArea = 471 m2

Altitude = 4080mN ant = 8D = 6mArea = 226 m2

Altitude = 5060mN ant = 50D = 12mArea = 5652 m2

(Demonstration of the technique)

High spectral resolution

Polarization capability

Bandwidth of up to 4 GHz

Angular resolution up to ~0.3 arcsec

Detection of molecules up to z=6.42

Open the appetite of (radio-mm) astronomers !

-> ALMA

What did the current generationof mm interferometers achieve ?

Let’s take two examples in more details:

Plateau de Bure interferometer&

SubMillimeter Array

SMA

Frequency coverage

PdBI SMA

80 – 116 GHz

129 – 174 GHz

201 – 267 GHz 186 – 242 GHz

277 – 371 GHz 272 – 349 GHz

320 – 420 GHz (7 ant, high Tsys)

635 – 690 GHz

1 band at a time Dual frequency operationspossible (L/H)

+ 22 GHz water vaporradiometer

FWHM primary beam

Freq.(GHz)

SMA PdBI

115 - 42’’

230 52’’ 21’’

345 35’’ 14’’

690 17’’ -

-> Mosaicing for extended sources

Configurations / Angular resolution

PbBI

@100 GHz

D: 5’’ deep integration

CD: 3.5’’ mosaicing

BC: 1.7’’ HRA mapping

B: 1.2’’

AB: 1’’

A: 0.8’’ very compact sources

Bmax = 760 m

SMA

@345 GHz

Subcompact: 5’’ extended sources

Compact: 2.5’’

Compact NS Southern sources

Extended: 0.7’’

(Very extended)

Bmax = 508 m

Sum

mer W

inte

r

Very flexible: multiple lines with different spectral resolution (up to 25 kHz, on a limited bandwidth)

SMA correlator

10 GHz10 GHz

LSBLSB2 GHz2 GHz

USBUSB2 GHz2 GHz

13CO(2-1)C18O(2-1)

12CO(2-1)

LSB

NGC 4945

2 GHzIF x 2

= 10 GHz

Phase

Am

plit

ude

Phase

Am

plit

ude

Simultaneous multiple lines / isotopes observations with the SMA

USB

HOR pola

VER pola

Q1 Q2 Q3 Q4

Dual pola

4 GHz

Simultaneous2 GHz bandwidth

Dual polarization capability 1 GHz bandwidth/unit (2 units possible at the moment)

8 independent spectral units can be allocated:with 20 to 320 MHz bandwidthwith 2.5 MHz to 40 kHz channel spacing

PdBI correlator

A new broadbandcorrelator (WIDEX)

will be installed this year

Example of correlator setup: multi-line survey

Data reduction / Imaging

PdBI

GILDAS: CLIC -> MAPPING

SMA

MIR/IDL -> AIPS, MIRIAD, GILDAS

Tools for proposal preparation

- GILDAS/ASTRO

- IRAM webpageshttp://www.iram.fr

- SMA Observer Centerhttp://

sma1.sma.hawaii.edu

-> Tools

Beam/sensitivity calculatorCalibrator listPassband visualizer

Proposals to PdBI

Increasing pressure on observing time

Courtesy R. Neri

Example values given for PdBICourtesy R. Neri

How to improve the sensitivity ?

Near future

Early Science in 2011More tomorrow

ALMA/ESO

Future of mm interferometry ?

Improve the sensitivity:- Large array- Better receivers- Broad bandwidth (continuum sensitivity, line survey)

Improve the quality:- Real time phase monitoring (~adaptive optic)

Limited fov:- On-the-fly mapping- Multi-beam (pixel) detectors

Longer baselinesMm VLBI … another challenge

Evolution of PdBI -> NOEMA

Northern Extended Millimeter Array

- Double the number of antennas: 6 -> 12

- Broad bandwidth -> 32 GHz

- Extend baselines: 0.8 -> 1.6 km

And possible further evolution(better receivers, multi-beam …)

NOEMA/IRAM

From NOEMA project/IRAM

From NOEMA project/IRAM