By Chris Wilson, Canadian ALMA Project Scientist
with material from the NRAO newsletters and the ALMA web site
ALMA Current Status
ALMA construction continues to wind down. In late June, 2014, the final ALMA antenna was taken up to the high-level site 5000 meters above sea level. Its arrival completes the complement of 66 ALMA antennas on the Chajnantor Plateau in the Atacama Desert of northern Chile. Images and video of the antenna move can be found at http://www.almaobservatory.org/
The ALMA Phasing Project team, with support from the Extension and Optimization of Capabilities (EOC) Team, the ALMA Department of Engineering, and the ALMA Department of Computing, integrated the new hydrogen maser into the ALMA system. This is an important milestone toward incorporating ALMA as a Very Long Baseline Interferometry array element. Tests have shown the maser performance is excellent, and it has replaced the rubidium clock as the ALMA time standard.
The August weather at Chajnantor was very good, as is usual for the austral winter, and the high frequency campaign made good use of the resulting excellent high frequency transparency. Multiple objectives were met, including the imaging of Uranus with 29 array elements at ALMA Band 10 (350 microns, 810 GHz) by the EOC team. The EOC team also demonstrated the transfer of phase information from lower frequencies, where calibrators are brighter and more densely distributed, to higher frequencies. Simultaneous sub-arraying within the main 12 m array was demonstrated for the first time, a key goal for achieving simultaneous EOC and Early Science operations.
On September 1, 2014, the EOC Team started the Long Baseline Campaign and will continue commissioning-type observations through the end of November. This critical campaign is essential for Cycle 3 proposed capabilities and will test the calibration and imaging characteristics of ALMA out to baselines of at least 10 km. All ALMA Early Science Observations (both Cycle 2 and carryover Cycle 1 programs) have been halted until the end of the campaign. This break in Early Science observing is needed because of the time required to move antennas out to the largest configurations and the fact that once the antennas are spread out to 5-10 km, the antennas remaining nearer the center of the array are not sufficient to populate any of the Cycle 2 configurations.
ALMA Cycle 2 progress
Results of the Cycle 2 proposal review process were sent to the PI on April 9, 2014 and the full list was released May 2, 2014. A full listing of the 353 highest priority proposals is available here. More recently, a detailed report on the outcome of the ALMA Early Science Cycle 2 Proposal Review Process has become available. The report describes the proposal review process, proposal statistics and regional distributions as well as the proposal distribution across science categories and receiver bands. The report can be downloaded as a pdf document here.
Cycle 2 observing began in a higher resolution configuration, with a longest baseline of 650 m, and is planned to cycle into larger configurations as the austral winter progresses. As noted above, all ALMA Early Science Observations have been halted until the end of the long baseline campaign. Early Science observations are scheduled to resume in December 2014 in array configuration C34-3. Observations in array configuration C34-1 are expected to begin in January 2015.
PIs and Co-Investigators can consult the Project Tracker for information on the execution of an accepted project. PIs can also modify their user profile at the Science Portal to receive e-mail notifications whenever a component of a project is first observed, fully observed, or successfully processed.
Archival and Science Verification Data
All the data from Cycle 0 Early Science projects have been delivered. The data are made publicly available via the ALMA archive as the one-year proprietary period expires. A total of 109 of the 116 Cycle 0 projects are available in the ALMA Science Archive; only a few projects are still within their proprietary period. Twenty-five of the 69 North American high priority Cycle 1 projects have been fully delivered and two-thirds of the highest-ranked NA Cycle 1 projects have seen deliveries of some data.
Data for two new ALMA Science Verification targets were released on September 7, 2014. The targets are (1) the evolved star VY Cma observed in water maser lines in Bands 7 (~850 microns) and 9 (~450 microns) and demonstrating ALMA capabilities on 1-3 km baselines and (2) Comet Lemmon observed in the HCN line in Band 6 (~1.1 mm) and demonstrating Doppler tracking of ephemeris targets. All Science Verification targets are listed on the Science Verification web page and the data sets are available through the ALMA Science Portal.
ALMA software news
CASA release 4.2.2 is now available from the CASA homepage: http://casa.nrao.edu/. This is a patch release of CASA 4.2.0/4.2.1 to introduce SIGMA and WEIGHT columns defined according to channel width and integration time. The patch also adds the plotms capability to export iterated plots in multiple files. A detailed description of the CASA visibility weighting scheme can be found at http://casa.nrao.edu/Memos/CASA-data-weights.pdf. CASA, the Common Astronomy Software Applications (CASA) package, is being developed by NRAO, ESO, and NAOJ and is used for the offline reduction and analysis of both ALMA and VLA data. CASA is fully scriptable. Full support is provided for ALMA and VLA but almost any data that can be written in uvfits format can be imported and reduced in CASA (for example, CARMA, SMA, ATCA).
ALMA has begun routine data reduction using the automated pipeline. The pipeline is now the principle means of data calibration and flagging for PI projects at ALMA. Previously, all ALMA data were reduced manually by ALMA’s team of scientists around the globe. For example, for North American projects the data have been reduced by staff scientists at the North American ALMA Science Center (NAASC) at NRAO Headquarters in Charlottesville and in Victoria, Canada, and at the Joint ALMA Observatory in Santiago, Chile. This transition to pipeline processing comes at a critical time when the ALMA data rate is high and continuing to grow. The pipeline is essential to allowing the ALMA observatory to cope with the current and anticipated future data rates. The pipeline has been developed by a dedicated team of engineers and scientists (including, from 2002-2010, C. Wilson as the sub-system scientist) with the aim of being able to handle the majority of ALMA observing projects. Some non-standard modes will continue to need manual reduction. The pipeline currently handles flagging and calibration while the imaging step continues to be done manually. The imaging portion of the pipeline is still under development and testing.
There are two workshops and one major ALMA meeting planned in the next year:
“Revolution in Astronomy with ALMA: The Third Year” will be held from December 8-11, 2014, in Tokyo, Japan. Registration is still open and the deadline for abstracts for posters and registration is October 15, 2014. The web site is http://www.almasc2014.jp/.
A NAASC workshop on “The Filamentary Structure in Molecular Clouds” is being held 10-11 October 2014 in Charlottesville Virginia. Registration is now closed but there is a waiting list. The conference web site is https://science.nrao.edu/science/meetings/2014/filamentary-structure/.
“Dissecting Galaxies Near and Far” is the subject of a workshop to be held March 23-27, 2015 in Santiago, Chile. Preliminary information is available on the conference web site, http://www.eso.org/sci/meetings/2015/Galaxies2015.html.
A good source for monthly updates on the ALMA project is the electronic NRAO newsletter http://science.nrao.edu/enews/. And don’t forget the ALMA observatory web site http://www.almaobservatory.org/ which contains wide range of information about the observatory, including details about science and technology, infrastructure, and geographical location.
An email list has been created for Canadian astronomers interested in ALMA. This moderated list will periodically send out updates on ALMA’s status, news of software releases, notices of upcoming ALMA science meetings and workshops, etc., which would be of interest to Canadian astronomers. Those who wish to be subscribe to the alma-users list are encouraged to visit the web page http://lists.astrosci.ca/mailman/listinfo/alma-users/ or send an email to Gerald.Schieven(at)nrc-cnrc.gc.ca.