Current mm
interferometers
Sébastien Muller
Nordic ARC
Onsala Space Observatory
Sweden
Turku Summer School – June 2009
Current mm interferometers: few facts
- Mm interferometry = Young technique
PdBI: early 90s
SMA dedication: 2003
PdBI milestones
• 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
& extension of the tracks
2007
350 GHz receivers
Broad-band correlator
2009…
SMA 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 MK
and 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
Current mm interferometers: few facts
- Mm interferometry = Young technique
PdBI: early 90s
SMA dedication: 2003
- Few mm interferometers, mostly in the Northern hemisphere
Current mm interferometers: few facts
- Mm interferometry = Young technique
PdBI: early 90s
SMA dedication: 2003
- Few mm interferometers, mostly in the Northern hemisphere
- Small array Nant < 15
limited instantaneous uv-coverage -> super-synthesis
- Limited total collecting area
- High altitude site for dry and stable atmosphere
Altitude = 2200m
N ant = 15
D = 6/10m
Area = 772 m2
Altitude = 4080m
N ant = 8
D = 6m
Area = 226 m2
Altitude = 2550m
N ant = 6
D = 15m
Area = 1060 m2
Altitude = 5060m
N ant = 50
D = 12m
Area = 5652 m2
Altitude = 1340m
N ant = 6
D = 10m
Area = 471 m2
What did the current generation
of mm interferometers achieve ?
(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
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
+ 22 GHz water vapor
radiometer
1 band at a time
320 – 420 GHz
(7 ant, high Tsys)
635 – 690 GHz
Dual frequency operations
possible (L/H)
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
SMA
Summer
Winter
@100 GHz
@345 GHz
D: 5’’ deep integration
Subcompact: 5’’ extended sources
CD: 3.5’’ mosaicing
Compact: 2.5’’
BC: 1.7’’ HRA mapping
Compact NS
B: 1.2’’
Extended: 0.7’’
AB: 1’’
(Very extended)
A: 0.8’’ very compact sources
Bmax = 760 m
Bmax = 508 m
Southern sources
SMA correlator
Very flexible: multiple lines
with different spectral resolution (up to 25 kHz, on a limited bandwidth)
LSB
2 GHz
USB
2 GHz
10 GHz
NGC 4945
12CO(2-1)
Phase
USB
Amplitude
Simultaneous multiple lines / isotopes
observations with the SMA
IF x 2
= 10 GHz
Amplitude
Phase
LSB
2 GHz
C18O(2-1)
13CO(2-1)
PdBI correlator
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 bandwidth
with 2.5 MHz to 40 kHz channel spacing
Q1
Q2
Q3
HOR pola
A new broadband
correlator (WIDEX)
will be installed this
year
Q4
Dual pola
VER pola
4 GHz
Simultaneous
2 GHz
bandwidth
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 webpages
http://www.iram.fr
- SMA Observer Center
-> Tools
http://sma1.sma.hawaii.edu
Beam/sensitivity calculator
Calibrator list
Passband visualizer
Proposals to PdBI
Increasing pressure on observing time
Courtesy R. Neri
How to improve the sensitivity ?
Example values given for PdBI
Courtesy R. Neri
Near future
Early Science in 2011
More 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
Limited fov:
- On-the-fly mapping
- Multi-beam (pixel) detectors
Longer baselines
Mm VLBI … another challenge
(~adaptive optic)
Evolution of PdBI -> NOEMA
Northern Extended Millimeter Array
NOEMA/IRAM
- 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 …)
From NOEMA project/IRAM
From NOEMA project/IRAM