1. Radio Interferometry and ALMA T. L. Wilson ESO

2. A few basics: Wavelength and frequency  -1 temperature max (mm) ~ 3/T(K) (for blackbody) Hot gas radiates in X rays or optical, cooler gas in FIR. mm Angles: resolution of ALMA=0.2 (mm)/baseline(km) (at =1 mm, ALMA better than HST) Flux Density and Temperature in the Rayleigh-Jeans limit: S(mJy)=73.6 T(K)    (’’)/  (mm) Minimum theoretical receiver noise: T rx =h /k=5.5( /115 GHz) Sensitivity calculator: ESO home page under ALMA

3. Opacity of the Atmosphere

4. Prime focus Secondary focus A parabolic radio telescope

5. Cover up parts of the dish. Then sample only certain structural components of the source

6. The regions where power is received are wider apart, so one is sensitive to smaller structures

7. Sketch of 2 element interferometer

8. Equations to describe 2 element interferometer

9. Dirty Beams, Improving Images

10. A single source, not centered by the interferometer

11. A double source with equal intensity

12. (u,v) plane and image plane These are related by Fourier transforms The previous relationships are valid, but are cast in a different form On the next overhead, we show some plots of the amplitude and phase of u for one dimensional distributions

13. 1-Dimensional distributions in the u and image planes u plane distribution in amplitude and phase Image plane distributions for simple sources

14. Earth Rotation Aperture Synthesis Above: the 2 antennas on the earth’s surface have a different orientation as a function of time. Below: the ordering of correlated data in (u,v) plane.

15. Gridding and sampling in (u,v) plane

16. VLA picture Inner part of the compact configuration of the Very Large Array

17. VLA uv plane response

18. Data as taken Data with MEM Data with MEM and Self- Calibration The radio galaxy Cygnus A as measured with all configurations of the VLA

19. A Next Generation Millimeter Telescope A major step in astronomy  a mm/submm equivalent of VLT, HST, NGST, EVLA Capable of seeing star-forming galaxies across the Universe Capable of seeing star-forming regions across the Galaxy These Objectives Require: An angular resolution of 0.1” at 3 mm A collecting area of >7,000 sq m An array of antennas A site which is high, dry, large, flat - a high Andean plateau is ideal

20. A mm/submm equivalent of VLT, NGST 64 x 12-meter antennas, surface < 25 µm rms Zoom array: 150m  16 kilometers Receivers covering wavelengths 0.3 - 10 mm Located at Chajnantor (Chile), altitude 5000 m Europe and North America sharing the construction (US$552 million) cost and operations costs Hopefully Japan will soon join! http://www.eso.org/projects/alma/ ALMA: The Atacama Large Millimeter Array

21. 10 km The ALMA site: Chajnantor, Chile Altitude 5000m ALMA Site

22. ALMA Compact Configuration

23. ALMA Intermediate Configuration

24. ALMA extended configuration

25. Simulations: L. Mundy

26. The Atacama Large Millimeter Array ALMA