1. Basic Concepts An interferometer measures coherence in the electric field between pairs of points (baselines). Direction to source Because of the geometric path difference c , the incoming wavefront arrives at each antenna at a different phase. wavefront Correlator B  Bsin  cc T1 T2 For good image quality: many baselines n antennas: n(n-1)/2 spacings (ALMA 50 antennas: 1225 baselines)

2. Aperture Synthesis As the source moves across the sky (due to Earth’s rotation), the baseline vector traces part of an ellipse in the (u,v) plane. B sin  = (u 2 + v 2 ) 1/2 v (k ) u (k ) T1 T2  Actually we obtain data at both (u,v) and (-u,-v) simultaneously, since the two antennas are interchangeable. Ellipse completed in 12h, not 24! B  Bsin  T1 T2

3. Synthesis observing Correlate signals between telescopes: visibilities Assign the visibilities to correct position on the u-v disc Fourier Transform the u-v plane : image

4. Deconvolution There are gaps in u-v plane. Need algorithms such as CLEAN and Maximum Entropy to guess the missing information This process is called deconvolution

5.  clean image dirty image visibilities

6. Calibration Amplitude and flux Phase –Fast switching –Water vapour radiometry Bandpass Polarization Pointing Antenna locations …

7. Data flow “Every astronomer, including novices to aperture synthesis techniques, should be able to use ALMA” Data flow: 1.Data taking 2.Quality Assurance (QA) programme 3.Data reduction pipeline 4.Archive 5.User

8. ALMA data reduction After every observation: Data reduction pipeline starts –Flagging (data not fulfilling given conditions) –Calibration (antenna, baseline, atmosphere, …) bandpass, phase and amplitude, flux –Fourier transform (u-v to map) –Deconvolution –(Mosaicking, combination, ACA and main array,…) Output: fully calibrated u-v data sets and images or cubes (x,y,freq)  Archive Pipeline part of CASA (f.k.a. aips++)

10. Dirty Mosaic Clean Mosaic ALMA Imaging Simulations

11. A simple interferometer For good image quality: Need many baselines n antennas: n(n-1)/2 spacings For 50 ALMA antennas: 1225 baselines

12. Using earth’s rotation: “filling the aperture” top view Source baseline telescopes v u T1 T2  The u-v plane (one baseline, full synthesis)

13. Dusty Disks in our Galaxy: Physics of Planet Formation Vega debris disk simulation: PdBI & ALMA Simulated ALMA image Simulated PdBI image

14. ALMA Resolution Simulation Contains: * 140 AU disk * inner hole (3 AU) * gap 6-8 AU * forming giant planets at: 9, 22, 46 AU with local 9, 22, 46 AU with local over-densities over-densities * ALMA with 2x over-density * ALMA with 20% under-density under-density * Each letter 4 AU wide, 35 AU high 35 AU high Observed with 10 km array At 140 pc, 1.3 mm Observed Model Observed Model L. G. Mundy

15. ALMA 950 GHz simulations of dust emission from a face-on disk with a planet Simulation of 1 Jupiter Mass planet around a 0.5 Solar mass star (orbital radius 5 AU) The disk mass was set to that of the Butterfly star in Taurus Integration time 8 hours; 10 km baselines; 30 degrees phase noise (Wolf & D’Angelo 2005)

16. Protoplanetary disk at 140pc, with Jupiter mass planet at 5AU ALMA simulation –428GHz, bandwidth 8GHz –total integration time: 4h –max. baseline: 10km Contrast reduced at higher frequency as optical depth increases Will push ALMA to its limits Wolf, Gueth, Henning, & Kley 2002, ApJ 566, L97 Imaging Protoplanetary Disks

17. SMA 850  m of Massive Star Formation in Cepheus A-East Brogan et al., in prep. 2 GHz Massive stars forming regions are at large distances  need high resolution Clusters of forming protostars and copious hot core line emission Chemical differentiation gives insight to physical processes SMA 850  m dust continuum VLA 3.6 cm free-free 1” = 725 AU ALMA will routinely achieve resolutions of better than 0.1”

18. Orion at 650 GHz (band 9) : A Spectral Line Forest Schilke et al. (2000) LSBUSB

19. ALMA: A Unique probe of Distant Galaxies Galaxies z < 1.5 Galaxies z > 1.5

20. submillimeter optical Gravitational lensing by a cluster of galaxies (simulations by A. Blain)

21. ALMA into the Epoch of Reionization Spectral simulation of J1148+5251 at z=6.4  Detect dust emission in 1sec (5  ) at 250 GHz  Detect multiple lines, molecules per band => detailed astrochemistry  Image dust and gas at sub-kpc resolution – gas dynamics! CO map at 0”.15 resolution in 1.5 hours HCN HCO+ CO CCH Atomic line diagnostics [C II] emission in 60sec (10σ) at 256 GHz [O I] 63 µm at 641 GHz [O I] 145 µm at 277 GHz [O III] 88 µm at 457 GHz [N II] 122 µm at 332 GHz [N II] 205 µm at 197 GHz HD 112 µm at 361 GHz Band 3 at z=6.4 4 GHz BW 93.296.1

22. Why do we need all those telescopes?  Mosaicing and Precision Imaging 3.0’ 1.5’ SMA ~1.3 mm observations Primary beam ~1’ Resolution ~3” Petitpas et al. 2006, in prep. CFHT ALMA 1.3mm PB ALMA 0.85mm PB

23. ALMA Mosaicing Simulation Spitzer GLIMPSE 5.8  m image Aips++/CASA simulation of ALMA with 50 antennas in the compact configuration (< 100 m) 100 GHz 7 x 7 pointing mosaic +/- 2hrs

24. 50 antenna + Single Dish ALMA Clean results Clean Mosaic Model + 12m SD + 24m SD Similar effect to adding both total power from 12m and ACA  need to fill in 15m gap in ALMA compact config.