Science IPT A. Wootten Lead NRAO is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.

ALMA Project AMAC March 2003 Science IPT Science IPT Organization Chart Smallest IPT; ~5 members

ALMA Project AMAC March 2003 Science IPT Science IPT Milestones

ALMA Project AMAC March 2003 Science IPT Milestones Configuration: Level 2: Oct. 2002: J. Conway –Plan for compact and intermediate configurations staked at Chajnantor –Document approved; construction planning under way. Level 2: June 2003: M. Holdaway – Plan for Y+ configuration finalized, iteration with site engineers testing subsoil quality under way; alternative locations proposed for possible problem sites. Level 2: June 2004: J. Conway – Plan for Early Science configurations complete Configuration and Calibration formed focus for

ALMA Project AMAC March 2003 Science IPT Compact Array – Highest Brightness Sensitivity All 64 antennas cluster within circle of r~150m Filling factor of about 50% NS extension for high zenith angle objects. All antennas accessible

ALMA Project AMAC March 2003 Science IPT Compact Array Beam

ALMA Project AMAC March 2003 Science IPT Holdaway Y+ Configuration (Early Version)  Nearin sidelobe response optimized (~6-7% goal)  Uses older, less accurate but large coverage digital elevation maps, so ~100m errors  Positions staked out April 2003; plan submitted June New Y+ configuration achieves better point source discrimination performance than previous or than ring designs.

ALMA Project AMAC March 2003 Science IPT Milestones: Calibration Level 2: February 2003 S. Guilloteau, Butler –Review of calibration requirements with science examples complete.Includes: - Phase - Amplitude - Bandpass - Baselines - Polarization - Illumination Offset – Opacity - Decorrelation Correction- Pointing and Focus Level 2: April 2003 Hills, Richer – Review of technical specifications for calibration items complete: WVR, FTS, weather station Level 2: Q B. Butler – Calibration strategy finalized Level 2: September 2004 –Selection of WVR strategy Level 2: December 2004 Butler – Review of tests of calibration strategies on prototype interferometer complete with evaluation receivers.

ALMA Project AMAC March 2003 Science IPT Status of Calibration Draft plan available, discussed in Cal Group telecon Submitted to Project Q Some questions remain about amplitude calibration –Semi-transparent vane tests suspended by FE Group at 30m –No device appears capable of producing 1% goal errors –Propose a specification of ~3% accuracy < 300 GHz, ~5% above –Tests to begin at Berkeley of absolute calibration scheme as proposed by Welch, Guilloteau and Gibson. Implementation at ATF with evaluation front ends 2004 Status of WVR tests remains undecided.

ALMA Project AMAC March 2003 Science IPT Semi -Transparent Vane Device Purpose: provide accurate calibration, particularly for nearly saturated detectors. Design: Rotary actuator (switch time 1 s) 90 and 230 GHz observations Standard calibration system Position 1 * 1.5 m from the receiver * Orthogonal linear polarizations Position 2 * cm from the receiver * No polarization Goal: Decision on whether to pursue this method following tests on IRAM 30m Semi-Transparent Vane Device: 30m 1 2

ALMA Project AMAC March 2003 Science IPT Design Reference Science Plan Under construction, early compilation under way. Provides a quantitative reference for –developing the science operations plan, –for performing imaging simulations, –for software design, and –for other applications within the ALMA project. Specifically, it can be used to: allow cross-checking of the ALMA specifications against "real" experiments allow a first look at the time distribution for – configurations – frequencies – experimental difficulty (fraction of projects pushing ALMA specs) start developing observing strategies derive "use-cases" for the Computing IPT be ready in case some ALMA rescoping is required, or in case some ALMA specifications cannot be met.

ALMA Project AMAC March 2003 Science IPT DRSP Themes Theme 1: Galaxies and Cosmology [Leader: Guilloteau] –1.1 The high-redshift universe –1.2 Gravitational lenses –1.3 Quasar absorption lines –1.4 SZ with ALMA –1.5 Gas in galactic nuclei –1.6 The AGN engine –1.7 Galaxies in the local universe –1.8 ALMA and the Magellanic Clouds Theme 2: Star and planet formation [Leader: Wootten] –2.1 Initial conditions of star formation –2.2 Young stellar objects –2.3 Chemistry of star-forming regions –2.4 Protoplanetary disks Theme 3: Stars and their evolution [Leader: Cox] –3.1 The Sun –3.2 Mm continuum from stars –3.3 Circumstellar envelopes –3.4 Post-AGB sources –3.5 Supernovae –3.6 Gamma ray bursts Theme 4: Solar system [Leader: Butler] –4.1 Planetary atmospheres –4.2 Asteroids and comets –4.3 Extrasolar planets

ALMA Project AMAC March 2003 Science IPT Three Year Duration Theme 1: Galaxies and Cosmology: 40% = 14.4 months = hr Theme 2: Star and Planet Formation: 30% = 10.8 months = 7880 hr Theme 3: Stars and their evolution: 20% = 7.2 months = 5250 hr Theme 4: Solar system: 10% = 3.6 months = 2620 hr Employ sensitivities on the ESO ALMA Web at: – –Based on ALMA memo 393. Ninety ‘Proposals’ as of 2003-August-22

ALMA Project AMAC March 2003 Science IPT Schedule Sep 1: First analysis by Project Scientists complete Sep 5-6: Presentation to ASAC Sep 22: Semi-final document sent to all contributors for review Oct. 1: Comments due Oct 15: Delivery of document to project

ALMA Project AMAC March 2003 Science IPT Imaging: Total Power Simulations A science requirement is to `provide precise images at an angular resolution of 0”.1. Here the term precise image means representing within the noise level the sky brightness of all points where the brightness is greater than 0.1% of the peak image brightness. This requirement applies to all sources visible to ALMA that transit at an elevation greater than 20 degrees.’ --Project Plan Chapter 2. Estimates suggest that the sky will permit this at Chajnantor, and the receiver complement will if the gain stability is ΔG/G ~ in 1 sec (Wright Memo; Welch Memo). This is a canonical value for cm receivers and has been obtained with mm receivers. However, the revolutionary ALMA receivers may not come within an order of magnitude of this stability. Preliminary Band 6 tests suggest ΔG/G ~ in 1 sec—can ALMA meet the imaging goal above? Simulations of on the fly imaging under way show that the sky is not a limiting factor; techniques of OTF may improve on this.

ALMA Project AMAC March 2003 Science IPT Holdaway’s Simulation Suite AIPS++ implementation includes –Latest atmospheric models (Pardo 2003) –Site testing database (data from site) –ALMA array sensitivity from Draft Front End Specifications –Antenna motion profiles from VERTEX documents; 1 msec grid –Receiver gain stability –Beam switching (nutator) –Routine to produce statistics of site database Results include; –Optimal slew velocity, given particular weather conditions –Very large parameter space, but one can select OTF parameters such that thermal noise rather than atmosperhic fluctuations dominate in all studied cases. –Original surmise, that nutators are superfluous, is supported. –Receiver stability is now the focus of the investigation.

ALMA Project AMAC March 2003 Science IPT Dual Load Calibration System: BIMA Purpose: provide accurate calibration, particularly for nearly saturated detectors. Tests completed at BIMA writeup in progress. Tests concentrate on accurate and reproducible measurements of the coupling coefficient, on elimination of standing waves Standing waves Standing wave seen: due to some mismatch in the coupling to the loads? Solution awaits measurement of the broadband coupling coefficient. Standing wave problem unsolved; not understood. Test the scheme in interferometric mode, calibrate actual observations Replicate the system on a second antenna Outlook: Probably not employed on ALMA but research continues through tests of alternative system during May for June decision. June 2003: Decision not to pursue this design.

ALMA Project AMAC March 2003 Science IPT Compact Array – Highest Brightness Sensitivity