Introduction to ALMA Al Wootten ALMA Project Scientist/North America

2 The Millimeter Spectrum Millimeter/submillimeter photons are the most abundant photons in the spectrum of the Milky Way and most spiral galaxies, and in the cosmic background. After the 3K cosmic background radiation, millimeter/submillimeter photons carry most of the ‘visible’ energy in the Universe, and 40% of that in for instance the Milky Way Galaxy. ALMA range--wavelengths from 1cm to 0.3 mm. COBE observations

3 Northern Chile Site must be high to make the best use of the atmospheric windows. Site should also be accessible, supported by reasonably close support facilities. Site should be dry for transparency. Chajnantor lies relatively close to the ancient town of San Pedro de Atacama, inhabited for more than two millennia. San Pedro is relatively near the Calama airport, and not far from the ESO site at Paranal. Chajnantor lies astride the paved Pasa de Jama road to Argentina; major gas pipelines from Argentina traverse it.

4 Chajnantor SW from Cerro Chajnantor, 1994 May AUI/NRAO S. Radford Photo: S. Radford

5 Complete Frequency Access N.B. Band GHz not shown Construction Project Bands: 3, 6, 7 & 9. Proposed by Japan: 4, 8 & 10. Post-construction: 1, 2 & 5

6 ALMA Specifications Antennae64  12 m collecting area> 7000 m 2 Configurations150 m – 14 km resolution (300 GHz)1.4 – 0.015" Frequency31 – 950 GHz wavelength10 – 0.3 mm Receiver sensitivityclose to quantum limit Correlator16 GHz / 4096 chan. Siteexcellent Result: A leap of over two orders of magnitude in both spatial resolution and sensitivity

7 ALMA Test Facility Prototyping and testing ALMA Antennas and other equipment at the VLA site in preparation for Chilean Operations.

8 Mercury 3mm 95 GHz VertexRSI Antenna

9 Saturn VertexRSI Antenna 265 GHz

10 ALMA Median Sensitivity (1 minute; AM=1.3; 75%Quartile opacities >1mm, 25% <1mm) ALMA Sensitivity Calculator: Frequency (GHz) Continuum (mJy) Line 1 km s -1 (mJy) Line 25 km s -1 (mJy)

11 ALMA Brightness Temperature Sensitivity (1 minute; AM=1.3; 1” Beam; 75%Quartile opacities >1mm, 25% <1mm) ALMA Sensitivity Calculator: Frequency (GHz) Continuum (K)Line 1 km s -1 (K) Line 25 km s -1 (K)

12 The ALMA Design Reference Science Plan To provide a prototype suite of high-priority ALMA projects that could be carried out in ~3 yr of full ALMA operations => quantitative reference for: Science operations plan Imaging simulations Software design Data rates and dataset sizes Any other application within ALMA project URL: Goal

13 How the DRSP was made Start from ALMA science case –Washington Meeting October 1999 –ESO council proposal 2000 => translate each chapter into one or more observing progams Identify Science IPT members as leaders for various topics; add ASAC, ESAC, ANASAC members where needed Leaders free to involve other experts from the community Spontaneous, unsolicited contributions from community (no open call was made)

14 DRSP status Started planning late April ‘03; outline + teams complete early July; submitted December ‘ submissions received involving ~75 astronomers Review by ASAC members completed; comments included Living document, with periodic updates Current version of DRSP on Website at:

15 Some initial conclusions Overall distribution over receiver bands reasonably consistent with weather statistics Fraction of continuum-only programs varies per receiver band and theme: Band 6 pre-dominantly line; Band 7 and 9 large fraction continuum Fraction of proposals which require total power continuum of order 10% Fraction of proposals which require baselines of at least 1 km % (with peak around ”) Data rate consistent with plans. Image rate to visibility rate ~ 1/30. ~7% of projects result in images of size >100GB.

16 Statistics

17 ALMA Data Product Complexity Primary data product is a calibrated image. Sensitivity – increase of two orders of magnitude over previous millimeter arrays Resolution – increase of up to an order of magnitude Total flux – images include total power data Natural mode mosaicing – large images All data in spectroscopic mode – multiplane images Excellent site – weather downtime minimized 24/7 Operation – instrument productivity maximized High image content suggest that the science content per image is high High data rate suggests high potential science volume –N.B. compare 500 GB/day to ~20 GB/yr typical twenty years ago! –This is ALMA average data rate; peak is 10x higher; potential much higher still. North American ALMA Science Center provides the resources to enable the potentially high volume of science ALMA can produce. Achieving ALMA’s potential requires appropriate resourcing of individual ALMA researchers Questionnaire—have the right resources been identified?

18 Early Science Observing Follows Commissioning and Science Verification Open to community through call for proposals Should demonstrate unique ALMA capabilities to all astronomers Provides feedback to ALMA operations

19 ASAC: Capabilities of Early Science Observing Sensitivity: gain over existing facilities once >6 antennas Long baselines ¬> high angular resolution High frequencies Southern sky Polarization capabilities

20 ALMA Workshop Purpose: Consider DRSP and similar projects to assess community needs for full realization of the potential of ALMA datasets. As ALMA reaches its Early Science milestone, what are the most important ALMA features to incorporate into the Early Science array? What are priorities of the NA community for future ALMA instrumentation initiatives?

21 Operations Stages Early Pre-Operations –Prior to 3-antenna interferometer Late Pre-Operations –Prior to 6-antenna interferometer Early Operations: 2007 Q3 –6-antenna interferometer, Band 3 + one other –Baselines up to one (1) km –Basic user tools commissioned –Etc, etc, etc Full Operations: 2011 Q4

22 Early Science Operations: Concepts Staff hired into/trained by Integration and Commissioning teams Not 24/7 science operations Limited array configurations No breakpoints, limited eavesdropping Limited pipeline Central archive at OSF Only two (2) proposal calls in first 24 months Other issues, see Operations Plan In 2007:

23 Early Science Operations: Time-Line Relative time-line analysis on-going Note the compressed timeframe, which calls for a simple set of modes for Early Science

24 Simplicity With fringes expected around Jan 2005, ATF Interferometer offers more time for debugging modes BUT Some ATF equipment will not be production ALMA equipment (including the antennas!) Hence, an appealing philosophy is to offer only those modes which can be demonstrated at the ATF, augmented by a very few additional modes. We explore modes possible under this philosophy

25 What is a mode? What is a mode anyway? –A mode is an element of an observational setup, including Configurations Receivers Correlator setups Calibration strategy Reduction strategy –A description of all modes, or combinations of them, would be difficult

26 Configurations First Science Array Configurations –Defined in ALMA A-SPE (John Conway) –Encompass the spacings available from 172 inner pads –Assumes 6 antennas available –Resolution steps of about a factor of 3 3 moves at a time – 15 baselines of which 3 are sequentially shared Provide a range of spatial frequencies –Six configurations C1: Closest spacing, high brightness sensitivity but poor sidelobes C2: Slightly larger, still a 15m baseline, better sidelobes. GHz C3-6: Resolution increases to GHz Recommend: Begin with C2

27 Proposed Early Science Configurations

28 Early Science Configuration Properties

29 Receivers Current schedule forsees B3, B6, B7 and B9 available Only B3 and B6 reasonably usable at ATF; B7 marginal –Target having these available for Early Science –Augment as commissioning and science verification allows WVRs available

30 Correlator ATF prototype one baseline correlator modes. Four basebands available in correlator; unclear if hardware support will exists ALMA correlator could support additional modes— e.g. four bits? Bandwidth Single Polzn Dual Polzn Full Polzn 2GHz MHz MHz

31 Calibration Strategy Phase correction –Fast switching useful for larger baselines. –WVR usage after some testing of prototype devices at ATF. Amplitude calibration – As with final array Total Power –Single ACA 12m antenna, continuum and spectral line –All antennas, spectral line

32 Imaging Strategy Pipeline rudimentary or unavailable Mosaics supported Combination of total power plus interferometric data Data rate limited, brought on line to scale with number of available baselines Implications for ARC support appreciated

33 ALMA Early Science Median Sensitivity (6 antennas; 1 minute; AM=1.3; 75%Quartile opacities >1mm, 25% <1mm) Frequency (GHz) Continuum (mJy) Line 1 km s -1 (mJy) Line 25 km s -1 (mJy)

34 Comparison

35 Animation

36 Example: Dataset final ALMA As galaxies get redshifted into the ALMA bands, dimming due to distance is offset by the brighter part of the spectrum being redshifted in. Hence, galaxies remain at relatively similar brightness out to high distances. M82 from ISO, Beelen and Cox, in preparation

37 ALMA Deep Field Poor in Nearby Galaxies, Rich in Distant Galaxies Nearby galaxies in ALMA Deep Field Source: Wootten and Gallimore, NRAO Distant galaxies in ALMA Deep Field

38 Hubble Deep Field Rich in Nearby Galaxies, Poor in Distant Galaxies Nearby galaxies in HDF Source: K. Lanzetta, SUNY-SB Distant galaxies in HDF

39 An ALMA Redshift Survey in a 4’×4’ Field Step 1 A continuum survey at 300 GHz, down to 0.1 mJy (5σ). This requires 140 pointings, each with 30 minutes of observation, for a total of 3 days. Such a survey should find about sources, of which sources will be brighter than 0.4 mJy. This field is twice the size of the HDF. Image 3000x3000 pixels x 1024 frequencies. Step 2 A continuum and line survey in the 3 mm band down to a sensitivity of 7.5 mJy (at 5σ). This requires 16 pointings, each with 12 hours of observation, so a total of 8 days. The survey is done with 4 tunings covering the GHz frequency range. Image 1000 x 1000 pixels x 4096 frequencies. The 300 to 100 GHz flux density ratio gives the photometric redshift distribution for redshifts z > 3-4. For expected line widths of 300 km/s, the line sensitivity of this survey is 0.02 Jy.km/s at 5σ. Using the typical SED presented earlier this should detect CO lines in all sources detected in Step 1. At least one CO line would be detected for all sources above z = 2, and two for all sources above z = 6. The only ``blind'' redshift regions are and Step 3 A continuum and line survey in the GHz band down to a sensitivity of 50 mJy (at 5σ). 8 adjacent frequency tunings would be required. On average, 90 pointings would be required, each with 1.5 hours, giving a total of 6 days. Together with Step 2, this would allow detection of at least one CO line for all redshifts, and two lines for redshifts greater than x2000 pixels by 8192 frequencies. N.B. Three ‘data products’ of substantial complexity to assimilate.

40 Example: Early Science Unbiased line surveys of high mass star forming regions (Design Reference Science Plan project 2.3.4) 64X64 pixels x 100,000 channels in four bands Spectral confusion limited, hence does not need full ALMA sensitivity (100 baselines sufficient) Example of complex data product from Early Science