ALMA NRAO News January 2007
ALMA News from the January 2007 Issue of the NRAO Newsletter
ATACAMA LARGE MILLIMETER/SUBMILLIMETER ARRAY
Second NAASC ALMA Science Workshop:
Transformational Science with ALMA: Through Disks to Stars and Planets
On June 22-24, 2007, the North American ALMA Science Center at NRAO and the University of Virginia will sponsor a workshop in Charlottesville, Virginia on protostellar disks. The focus of the meeting will be to discuss how ALMA will impact our understanding in several key areas of disk formation and evolution including: The members of the Scientific Organizing Committee are John Bally (University of Colorado), Crystal Brogan (Chair, NRAO), Masa Hayashi (NAOJ), Michiel Hogerheijde (Leiden University), Doug Johnstone (HIA), Zhi-Yun Li (University of Virginia), Lee Mundy (University of Maryland), Jonathan Williams (University of Hawaii), and Al Wootten (NRAO). The first announcement and other information are available at http://www.cv.nrao.edu/naasc/disk07.html. It is our hope that the meeting will generate extensive discussion and new ideas regarding how ALMA may be used to transform the subjects of protostellar and protoplanetary disks through presentations on the current state of our understanding, predictive theories, as well as simulations. In order to solicit talks on the most cutting-edge research, we will be requesting proposals for specific presentation topics in the near future. Students and post-docs are especially encouraged to attend. Please bookmark our meeting page, and visit often for updates. Pre-registration is now available and we will be open for abstract submission soon!
The North American ALMA Science Center (NAASC)
The proposal for funding North American ALMA operations and the North American ALMA Science Center was submitted to the NSF on October 31, 2006. Prior to submission, intensive reviews were held, including an internal review by key NRAO operations staff and Canadian representatives, and an external review by the ALMA North American Science Advisory Committee. The global ALMA operations plan was also submitted on November 3 to the ALMA Board for review. A summary of the plan was presented to the Board in Madrid in November. The next quarter will see extensive external reviews of the operations plan and the NSF proposal.
The NAASC staff are participating in extensive software testing in Socorro and Charlottesville, including tests of the ALMA pipeline and the CASA-PY reduction software. The NAASC was well represented at the Madrid ALMA science meeting, Science with ALMA: A New Era for Astrophysics, with a number of talks and posters being presented on recent scientific research by the staff. The second NAASC science workshop entitled Transformational Science with ALMA: Through Disks to Stars and Planets, to be held in June, 2007 in Charlottesville, is accepting pre-registrants (see associated Newsletter article). Lastly, a concerted effort has been made to establish a spectral line working group whose primary purpose is to provide ALMA a complete database of molecular and recombination lines.
This database can be used by all astronomers interested in spectral line astrophysics and, in particular, astrochemistry. This effort is being led by Anthony Remijan (see associated Newsletter article) and includes members from all the interested international institutions, including JPL, Herschel, Illinois, NIST, Manchester, Koln, and others.
ALMA commissioning is imminent, and early science soon after. The NAASC staff are available for presentations on ALMA capabilities, status, and science at North American institutions. Please contact the undersigned if you are interested in a visit by a NAASC staff member.
ALMA's Lab Testing Moves to the Field
As the physical plant in Chile grows in preparation for the arrival of the first antennas in 2007, the electronics has moved from laboratory testing to field testing. The components of ALMA have been extensively tested in the laboratory, first in Tucson and more recently at the Array Operations Center (AOC) in Socorro. The controlled conditions of the lab provided engineers and scientists with an opportunity to test the timing, phase and amplitude stability, robustness, and other qualities of the backend electronics. With the lab goals achieved, the elements of the backend are in the process of being moved to the two remaining prototype antennas at the Antenna Test Facility (ATF) near the VLA. There they will be integrated with remaining components of the prototype ALMA system to provide preliminary astronomical data on its performance.
Holography using the system that will be used during Q2 2007 in Chile at the Operations Support Facility (OSF) is in its final stages at the ATF. This system has been installed on the Vertex antenna. The holography system tests a complete system as it will be installed in Chile, including data collection in an ALMA format, storage in an ALMA archive, and retrieval from the archive for analysis. Holography images of the antenna surface will be compared with photogrammetric measurements for verification.
Meanwhile, at the NRAO Technology Center (NTC) in Charlottesville, cartridges for ALMA Bands 3 (3 mm), 6 (1.3 mm) and 7 (.85 mm) have been installed in the dewar with all their associated electronics. The Band 9 cartridge will be installed shortly to comprise the first ALMA Front End incorporating all receiver elements. After a period of testing at the North American Front End Integration Center at the NTC, this first Front End will be integrated into the prototype system at the ATF in New Mexico. After testing there it will be shipped to the OSF in Chile for integration into the first production antenna for testing on the sky. Also at the NTC, work continues on the second quadrant of the ALMA correlator, which will be populated with tunable filter bank (TFB) cards produced in France to increase the flexibility of the correlator. The first quadrant, running at the NTC for many months, will be retrofitted with TFBs. During early 2007 work will begin on moving the correlator to the Technical Building at the Array Operations Site, its permanent home.
Figure 1. Artist's concept of the ALMA Array as it might appear near the end of construction. Illustrated is the VertexRSI antenna (left foreground, the ALMA antenna trannsporter (center mid-distance), the AEM antenna (right foreground), and the Melco ACA antenna (right back-
A Workshop on Water Vapor Radiometry (WVR) was held in October at Wettzell, Germany to exchange and compare information among the astronomical, meteorological and geodetic communities. R. Hills presented interim results from the prototype ALMA WVRs, deployed at the Smithsonian Millimeter Array on Mauna Kea. The correction is meeting the ALMA specifications under good conditions. However the comparison between observed interferometer phase and that inferred from the WVRs was limited in good conditions by a mismatch between the radiometer designed for the ALMA system and the SMA system which is was deployed. A better match has been achieved and measurements continue on Mauna Kea.
Preparations proceed for the arrival of the elements of ALMA in Chile, and for their Assembly, Integration, Verification (AIV), Commissioning, and Operation. Many of the AIV staff have been hired and have commenced training at various ALMA sites around the world. As ALMA's focus shifts to Chilean operations over the next years, the staff will outgrow the current offices in Santiago. A Call for Tender for a more permanent Santiago home for ALMA, to be located adjacent to ESO, is being prepared. Several key Operations posts are being filled: the Head of Administration and Head of Science Operations are already working on planning a smooth transition from construction to operations over the next few years. The training of the next generation of scientists and engineers also continues; about 138 attended a school on interferometry in December held at the Universidad Católica in Santiago. As the current round of schools featuring use of ALMA closes with the winter school in Tokyo in January, nearly 600 young astronomers will have been introduced to the ALMA system and its promise of transformational science.
Much of the ALMA equipment arrives at the OSF where it receives its first level of testing and integration. The heart of this activity is in the OSF Technical Building (OSF TB), well under construction now on the site and the focus of a fixed webcam, linked to www.alma.info. The antennas first arrive at the individual contractor's Site Erection Facilities (SEF). Construction of the first of these, for the Vertex antenna, is well under way-27 containers of construction materials arrived in December from Texas and are being installed.
Figure 2. Work on the building for the VertexRSI Site Erection Facility has begun in prepration for receiving the first production antenna in early 2007. The ALMA camp is in the right background, in front of Licancabur.
While the OSF TB proceeds toward first quarter 2008 completion, AIV activities will be conducted from a temporary building at the OSF, which was completed in November. One of the first activities testing the production antennas will be holography; the tower for the holography transmitter is also nearing completion. The very active construction on the site now involves over 300 people. This number will grow as ALMA grows, so expansion of the already full camps currently on the site is being pursued.
Final outfitting of the 16,570 foot elevation Array Operations Site Technical Building (AOS TB) is well under way, with the installation of the HVAC (heating, ventilating and air conditioning) systems just completed. By the time this article appears, the building will be completely enclosed, powered by a temporary generator, and connected to the OSF via an interim link. Nearby, the design of the road and fiber network at the AOS is nearing final stages, including the design of the outermost antenna station network. Just north of the AOS, preparations are being finalized for installation of the stations for the central stations of the array, its most compact configuration.
At its November meeting, the ALMA Board welcomed several new members to the ALMA Science Advisory Committee (ASAC), while thanking several members for their service during the past three years. Jean Turner (UCLA) and Christine Wilson (McMaster University) have provided the ALMA Board advice for many years; both have chaired the Committee. Joining the ASAC will be Jacqueline van Gorkom (Columbia) and Douglas Johnstone (HIA).
Todd Hunter arrived in Charlottesville from the Smithsonian Submillimeter Array at the Center for Astrophysics. At NRAO he will work on both the Green Bank Telescope and ALMA. Robert Reid arrived as an ALMA postdoc in Charlottesville from the Dominion Radio Astrophysical Observatory (DRAO) in Penticton. Antonio Hales joined the Charlottesville ALMA group from University College London, where he recently completed his dissertation on the circumstellar environments of stars with infrared excesses.
ALMA is operated by the Executives through the Joint ALMA Observatory in Santiago. Key staff positions recently filled include the Head of Administration, Mr. Russell Smeback, who will join the Santiago staff in December, and the Head of Science Operations. At ESO, Thomas Wilson has left the position of European Project Scientist to join the Office of the Director General; Robert Laing is filling the post of European Project Scientist during the interim.
ALMA Working Group on Spectral Line Frequencies and The Molecular Spectroscopy Database (Splatalogue)
The next generation of powerful radio and millimeter/submillimeter observatories (e.g. EVLA, ALMA, and Herschel) will require extensive resources to help identify the thousands of spectral line transitions that will undoubtedly be present toward numerous astronomical objects including high and low mass star forming regions, protoplanetary nebulae and comets. The abundance of spectral line features at millimeter/submil-limeter wavelengths present toward high mass star forming regions is already apparent with recent work done with the CSO and APEX toward Orion. Thus, in order to provide the astronomical community with the tools needed to conduct research in spectral line astrophysics, the ALMA Working Group on Spectral Line Frequencies (AWGSLF) was convened on Thursday, July 27, 2006. The AWGSLF mission statement is:
"The ALMA Working Group on Spectral Line Frequencies is dedicated to generating a collated and rationalized database of spectral line frequencies, transitions, and line strengths from radio to infrared wavelengths that can be freely accessed and used by the entire astronomical community interested in spectral line astrophysics."
To that end, the charter members and present chairs of the AWGSLF, Anthony J. Remijan of NRAO, Charlottesville and Andrew J. Markwick-Kemper of the University of Manchester have developed the Molecular Spectroscopy Database (Splatalogue). Splatalogue is an attempt to collate, rationalize, and extend existing spectroscopic resources for use by the astronomical community. The Jet Propulsion Laboratory (JPL) database, the Cologne Database of Molecular Spectroscopy (CDMS) and the Lovas/National Institute of Standards and Technology (NIST) database provide an enormous amount of data - collecting the data in all three online databases together generates over 3.5 million transition data entries across almost 700 molecular species. As part of the ALMA and EVLA scientific plans, one of the main goals of telescope operations is that each new instrument be easy to use by a "novice" observer. Thus, a molecular spectroscopy database needs to be available that is as descriptive as possible in the way it represents molecular, atomic, and recombination line transitions.
Currently, the databases that are used for this search, the JPL and CDMS databases, do not describe transitions in the most user-friendly way, and where the catalogs overlap, these descriptions are not in general consistent and have to be compared and resolved to be made so. Furthermore, the Lovas/NIST database tabulates only observed interstellar transitions, but it does provide the user with a much better representation of molecular transitions by using a full description.
One of the main goals of the Splatalogue is to update the procedure by which a user searches for spectral lines-the Splatalogue will contain at least one example of every detected line. The linelists on which the Splatalogue builds are primarily ordered by species, then by frequency. The Splatalogue is different-it is ordered by species, then by transition, which is more sensible. In this way, every observation, calculation or measurement of a transition can be easily cross-referenced against that table. So you can ask for e.g. CH3CN 4(3)-3(3) and see all the entries for that species/transition, be they observation, measurement, or calculation. Furthermore, it is the goal of the members of the AWGSLF to provide the astronomical community a prioritized list of frequencies for the most common molecules and their transitions based on what the AWGSLF believes to the most accurate measurement of that transition as well as to assist the observer in deciding which molecular species and transitions are astronomically relevant.
From a querying point-of-view, the Splatalogue has two major modes of operation-one user-friendly, the other application-friendly. The former is a PHP based web interface, an example of which is shown in Table 1. The latter returns results of IVOA-compliant queries in VO-table XML. Clearly there is scope for other data formats as well.
Table 1. Here we query the splatalogue to show the lines of SiO v=0 which lie in the ALMA receiver bands.
Service is also designed to be fully extensible. The interface between the Splatalogue and the ALMA Archive is key, but extension from within the astronomical spectroscopy community itself will also be possible and encouraged. We are collaborating with the ALMA Archive group to ensure that the Splatalogue and the Archive can communicate and share spectral line data with as much flexibility as possible. We envision updating the Archive with new spectral line data by using the timestamp field of Splatalogue (which shows when a given entry was created) in conjunction with the time of the last update the Archive received.
Currently, meetings are taking place between the members of the AWGSLF. The minutes of each meeting and the current progress taking place in the AWGSLF and with Splatalogue can be found at:
Finally, the initial public release of Splatalogue is planned for December 31, 2006 and it will exist at http://www.splatalogue.net. Furthermore, it is the intention of the members of the AWGSLF, NRAO, and ALMA to continue work on updating and maintaining the Splatalogue as new astronomical and laboratory data become available. In general, a new species or a re-measured species will be added no later than one week upon receipt of the new data from the laboratory community and after the public release. Overall the agreement by almost all the laboratory spectroscopists contacted in North America to work on updating the Splatalogue is very encouraging and we anticipate worldwide cooperation for this effort.
For further information about Splatalogue or the AWGSLF, please contact Anthony Remijan: firstname.lastname@example.org or Andrew Markwick-Kemper: email@example.com.