This Month at the NAASC April, 2011
"Open for Business!" - DRAFT
On March 30th, the Joint ALMA Observatory (JAO) and the ALMA Regional Centers (ARCs) issued the first Call for Proposals with ALMA. Following months of intense preparation, the North American ALMA Science Center (NAASC) is very pleased to announce that we are Open for Business. Find us through the ALMA Science Portal at https://almascience.nrao.edu/
The following articles describe a few of the many ways in which the NAASC
and NRAO are prepared to provide support to our colleagues in the scientific community as ALMA opportunities unfold over the coming months and years.
ALMA in the Coming Decade: A Development Workshop
ALMA will transform astronomy beginning with Early Science results later this year. ALMA will reach full operation shortly; by then it will extend current millimeter or submillimeter imaging capabilities in sensitivity and resolution by nearly two orders of magnitude. ALMA will operate from 3mm to 0.3mm across a decade of nearly complete frequency access as enabled by its broad bandwidth receivers, powerful correlators and spectacular site. Having invested so much to realize this biggest historical advance in ground-based astronomy, it is vital to maintain and expand ALMA’s capabilities. Toward this end, the ALMA Operations Plan envisages an ongoing program of development and upgrades that may include hardware, software or data analysis tools. With a planned modest investment of less than 1% of capital cost per year divided among the three funding regions (North America, Europe, East Asia), ALMA will continue to lead astronomical research through the 2011-2020 decade and beyond.
In recent years, several programs that could comprise a development plan have been identified by the scientific community. For example, ALMA's wavelength coverage could be extended to cover from 1 cm to 350 microns with the only gaps those imposed by the atmosphere and thereby encompass additional unique spectral features and important scientific topics. To further explore such ideas, the ALMA partners have begun to explore in detail the programs which could become elements of an ALMA Development Plan. Studies are under way in Europe on several such programs. The North American ALMA Science Center (NAASC
) will soon invite Proposals from North American entities for studies relevant to the crafting of an ALMA Development Plan.
A Development Workshop was held in Charlottesville on 21-22 March to discuss the astronomical motivation for a spectrum of key science goals inspiring possible development projects. The Workshop was attended by about seventy people in the NRAO auditorium. Others participated via video or audio links or listened via webcast. Among the topics discussed were the development activities of the other partners, presented by Leonardo Testi (ESO) and Masao Saito (NAOJ), in addition to discussions of the science enabled by specific projects. Johnstone (HIA) led a discussion of the science opportunities at the lowest frequency band, including a repositioning of the nominal 31-45 GHz range to extend nearer the 53 GHz limit imposed by atmospheric oxygen. Frayer and Friesen (NRAO) identified opportunities in the 67-93 GHz band, for which a receiver is under construction for the Green Bank Telescope. Samoska (JPL) and Church (Stanford) discussed detector work in the 2mm window undertaken at JPL and Stanford. Hunter (NRAO) discussed opportunities at the other extreme of ALMA’s capabilities, even exploring the possibilities for receivers at higher frequencies than currently planned. Kern (NRAO) and Russell (HIA) discussed opportunities for software upgrades. Other talks covered topics as diverse as VLBI with ALMA, improved photonic LO and alternative energy sources for ALMA. In addition to these specific upgrade opportunities, an important aspect of the workshop was to use community feedback to inform the Call for studies of upgrades to ALMA, to be issued soon.
Figure 1 About 70 astronomers and engineers attended the workshop in the NRAO auditorium; additional folks attended via video, audio or web links.
ALMA Training Workshops Continue
The North American ALMA Science Center (NAASC) and the NA ARC continue to provide training on using ALMA through its ALMA Comm
unity Events. On March 7th, NAASC
and UPenn brought together both new and experienced researchers to learn about and discuss the capabilities of ALMA. Kim Scott, a UPenn organizer, noted that the event "provided a great forum to get our group talking about Early Science projects, and the step-by-step software tutorials lead by the NRAO staff were extremely helpful for learning how to prepare proposals for this new facility."
On March 11th, in conjunction with the Building on New Worlds, New Horizons science conference in Santa Fe, New Mexico, staff from the NAASC
presented a one-day tutorial describing the process for applying for Early Science time with the ALMA. Participants were provided the latest information on ALMA Early Science observing modes and capabilities, shown how to create and submit an observing proposal using the ALMA Observing Tool and Simulator, and given an introduction to the Common Astronomy Software Application (CASA) package that will be used to reduce ALMA data.
Rounding out the March workshops, NAASC staff presented a Community Day at the California Institute of Technology (Caltech), March 15-16. The first day of the event, which was focused primarily on ALMA science talks by the local community, drew 60-80 researchers from Caltech, UCLA and the Carnegie Observatories. On day two, hands-on tutorials of the proposal submission tool and the ALMA data simulated were supervised by NRAO staff.
Information about upcoming ALMA Community Training events can be found on the ALMA Community Day Events registration
Figure Caption: Participants in the CalTech Community Day Event.
by Adam Leroy
Why do stars form where they do? What sets the rate at which interstellar gas and dust transform into the stars that make up the galaxies around us? My collaborators and I try to answer these questions by studying star formation on the scale of galaxies. We use observations at wavelengths from the radio to the ultraviolet to assemble a broad picture of star formation in galaxies. From these data we infer where stars formed in the past, where they form now, and the distributions of the gas and dust that fuel star formation. We also look at key conditions that may influence the ability of gas to form stars, for example the motions of the gas, the pull of gravity, the abundance of dust, and the radiation field. Combining this information, we try to identify what physical processes set the rate of star formation in galaxies. Carrying out these studies in tiny dwarf galaxies, big spiral galaxies like the Milky Way, and blazing starbursts we aim to help understand why galaxies look the way they do and what underlying physics governs these diverse systems.
This work is possible because our knowledge of nearby galaxies has taken a massive leap forward over the last decade. Legacy surveys with space-based telescopes like Spitzer, Herschel, and GALEX have given us a new view of dust and young stars in galaxies. My collaborators and I work to ensure that data tracing the interstellar medium keeps up with these amazing advances. NRAO’s VLA Large Program THINGS took a big step in this direction, producing uniform, high-resolution maps of atomic gas for a broad sample of nearby galaxies. We continue to use the VLA in this capacity, building new HI maps to match observations from Spitzer and Herschel.
A large part of my work involves mapping the molecular gas in galaxies. Clouds of cold, dense, molecular material play a central role in star formation. Unfortunately the main constituent of these clouds, H2, can be directly observed only with great difficulty. This forces us to study molecular gas via tracers, visible species that do not make up most of the mass. The most common tracer of H2 is the CO molecule, and my colleagues and I have surveyed CO emission from several large samples of galaxies using IRAM’s 30-m telescope (the HERACLES survey) and the CARMA interferometer (the CARMA STING). In a few nearby galaxies like M51 (the PAWS survey) and M31, we are even able to use interferometers like CARMA and IRAM’s PdBI
to pick out individual star-forming clouds.
While useful, CO does not always trace H2 perfectly. My colleagues and I have used infrared emission from dust as an independent way to trace H2 and to explore the shortcomings of CO. At the same time we are following up our CO mapping with observations of other lines and molecules to try to understand how the physical state of molecular gas varies across galaxies.
ALMA and the EVLA promise huge leaps forward in this field. The new sensitivity and frequency coverage of the EVLA make it a powerful tool to trace recent star formation in an unbiased way (a very tricky problem). In collaboration with colleagues at NRAO and around the world, I am now applying this capability to study the most luminous starbursts in the nearby universe. ALMA will allow several transformational advances. We will be able to regularly work with resolution matched to individual star-forming clouds, to study how density, temperature, and chemistry vary within and among galaxies, and we will be able to expand these studies to a wider range of systems.
Spotlight on NAASC Services
Contribution to Data Services: The NAASC Data Services Group
The data challenge posed by ALMA is one of the most severe in current astronomy. The size of the raw data is predicted to grow by ~200 terabytes per year. Unlike most astronomy facilities with this order of data volume, which tend to take uniform survey datasets, ALMA data is taken in a traditional, proposal driven manner, in a wide variety of user-specified modes. Only the EVLA archive will rival it in both size and complexity for the forseeable future. In addition, ALMA will be the first and only interferometric telescope with a pipeline capable of dealing with a wide range of observational setups. Although the main ALMA pipeline will be run in Santiago, the nature of interferometric data, and the many modes in which ALMA can operate means that multiple reprocessings of these data are to be expected. For North American users, these reprocessings will use the pipeline installation at the NAASC
The Data Services Group (DSG)
coordinates the processing, archiving and distribution of ALMA data at the NAASC
, and is also responsible for the development and maintenance of tools for proposal preparation, data processing and data analysis that are produced in North America, but are not part of the main ALMA project. These tools supplement the ALMA project software development effort, and currently consist of Splatalogue and the Simdata task (within CASA). Eventually, the DSG will also direct the effort within North America to produce tools to analyze the large datacubes ALMA will produce. The DSG also coordinates the deployment of the NAASC
instance of the ALMA User Portal, and the provision of the ALMA helpdesk to the ALMA project. The DSG coordinates with the NRAO Computing and Information Services (CIS) division to ensure the provision of the hardware necessary to undertake the data transfer, processing and storage tasks, and to ensure that software environments are set up correctly to allow the pipeline and associated software to function efficiently.
will host a full copy of the ALMA archive, both to provide convenient local access to ALMA data, and to provide a backup copy to the main archive in Santiago (along with copies at the ALMA regional centers in Europe and Japan). Data storage will be through the Next Generation Archive System (NGAS), developed by the European Southern Observatory as part of their contribution to the ALMA project. The NGAS nodes will be linked to a fast Lustre file system that will act as a staging area for the data processing cluster. The exact details of the processing cluster are yet to be defined, but it is expected to be a near-clone of the main pipeline processing cluster in Santiago, with up to 64 processing nodes.
There is a large overlap with the archiving, data processing and software interests within NRAO Observatory Science Operations. The NAASC
DSG will be working with colleagues at the other NRAO sites to identify areas of common interest, and will also work closely with the Virtual Observatory (VO), its US incarnation, the Virtual Astronomical Observatory, and the ALMA archive development group to ensure the transparent integration of ALMA data into the VO. NAASC
data services is currently a small group, consisting of 1.5 staff (Mark Lacy and Remy Indebetouw) and two postdocs (Robin Pulliam and Amy Kimball) with Mike Hatz and Dan Klopp matrixed in from CIS, but is expected to grow as the emphasis of the NAASC
shifts from face-to-face user support during ALMA Early Science to supporting users remotely after the pipeline is fully operational.
Figure 1. The Data Services racks at the NAASC. The left-hand rack houses the pair of high-availability servers for the helpdesk and user portal at the NAASC. The upper four boxes in the right-hand rack are the first installment of the NGAS storage nodes that will eventually house the ALMA archive. These machines will be joined within the next few months by the first of the pipeline processing cluster nodes and the high speed filestore for data processing.
Meet the NAASC
The ALMA data services described in the previous article are provided by the NAASC computing and data management team, pictured below in front of NRAO headquarters in Charlottesville, Virginia.
CAPTION: The NAASC
Computing and Data Processing Team (left to right): Anthony Remijan, Adam Leroy, Amy Kimball, Robin Pulliam, Dave Mehringer, Remy Indebetouw, Mark Lacy, Kelly Sharp, Brian Kent, Dong-chan Kim, Mike Hatz (not pictured, Dan Klopp and David Halstead)