ALMA Programme News

ALMA Band 2 Development

ESO continues to coordinate and support the science case and technical development of a new ALMA receiver covering the original ‘Band 2’ frequency range, 67 to 90 GHz, with the option to extend this out to 116 GHz. Following the ALMA development priorities, the receiver will be the first one to have 16 GHz IF bandwidth per polarization channel.

The work is being done by a consortium of several European institutes, ESO, U Chile, and NAOJ.  Prototype versions of the optical components and layouts, developed by U Chile, INAF, and NAOJ, have been realized and demonstrated in laboratory tests to meet all ALMA requirements for the optics over the 67-116 GHz RF bandwidth, with no compromises in performance over the design optimized for the original Band 2 frequency range of 67-90 GHz. In parallel, test results for the wideband MMIC low noise amplifiers designed by the University of Manchester in collaboration with CRAL and using the NGC 30nm gate length process are extremely promising, with noise temperatures measured to be <28 K over more than 80% of the wide band and little dependence on frequency. There is also a commercial alternative, from the Low Noise Factory, with comparable performance. A full prototype receiver has been designed and was tested in 2017. The design and the achieved performances were presented at the Preliminary Design Review, which took place at ESO on 29-30 November 2017. The feedback from the review panel was very positive with clear recommendations to continue development towards the Critical Design Review, and also to start preparations for the pre-production series of the receivers to be installed and tested in ALMA system.

ALMA Band 5

In the framework of the ALMA Enhancement Program funded by EC FP6 (contract No 515906), the Group for Advanced Receiver Development (GARD) at Chalmers, in collaboration with the Rutherford Appleton Laboratory, UK, developed and built six preproduction ALMA Band 5 cartridges (Billade et al. 2012). After the success of this pathfinder experiment, ESO funded in 2013 an initiative to start the Band 5 production project for the ALMA observatory. Through this, GARD in collaboration with NOVA took the responsibility to produce, verify and deliver the Band 5 cold cartridge assemblies (CCA).  Production of the Band 5 local oscillator (LO) and warm cartridge assembly (WCA) was carried out by NRAO with funding from the National Science Foundation (NSF). ESO also committed to the overall project coordination and providing the Band 5 frontend cryostat windows, IR filters and supplying front-end DC bias modules. Following a project kick-off meeting in February 2013, production started in March 2015 and ended in November 2017.

With the project now complete, 73 Band 5 CCAs – 66 for the Frontends installed in ALMA antennas and 7 spares – have been delivered to the ALMA Observatory. (Belitsky et al, 2018).

The Band 5 interferometric first light with two antennas was achieved in June 2015, the phase closure using 3 antennas in July 2015 and at the end of 2016 the data samples collected in the framework of the science verification have been released to the scientific community (Humphreys et al. 2017, König et al. 2017).

The integration phase of the B5 CCAs started in May 2015, and at the time of writing (March 2018) 57 FEs with Band 5 CCAs are installed in the ALMA antennas – 12 are on the ACA 7 m array, 4 are on the ACA Total Power array, and the remaining 41 are on the 12-meter baseline (BL) array.  Including the FEs in lab at the OSF, 62 out of the 66 ALMA FEs have been already equipped with B5 receiver cartridges, while the remaining 4 should be installed by the end of April 2018.  PI science observations started in December 2017 with the ACA, while observations with the BL array postponed until the minimum complement of 43 CCAs is installed.

Further reading:

• Humphreys, L., Biggs, A., Immer, K., et al. 2017, The Messenger, 167, 7
• Billade, B., Nystrom, O., Meledin, D., et al. 2012, IEEE Transactions on Tera-hertz Science and Technology, 2, 208
• Belitsky, V., et al. 2018, A&A, Accepted
• König, S., et al. 2017, Astronomy & Astrophysics, Volume 602, id.A42, 9 pp.
   

EU ARC QA2 Backlog Reduced to Zero

After a slow start into Cycle 5 where the transition to new administrational tools and a new archive ingestion and delivery system cost a lot of time, the QA2 processing of EU data has now caught up and is faster than ever. The February ALMA shutdown then helped to enable us to process with just a handful of exceptions all remaining observations and deliver them to the PIs.

In the first half of Cycle 5, The European ARC and its nodes again contributed significantly to the data processing, including manual calibration and imaging. The data processed at the EU ARC was to a large extent processed by the ALMA Science Pipeline running on the EU ARC cluster: 85% of the delivered datasets were pipeline-calibrated and 65% were pipeline-imaged. The data processed at JAO on the other hand was 100% pipeline-calibrated and -imaged. I.e., with the help of the pipeline, manual calibration is now only necessary in non-standard cases. Also the need for manual imaging is constantly reduced with every new release of the pipeline. This, however, does not mean that the processing doesn't need human interaction anymore: Experts are still needed to scrutinise the wealth of diagnostic plots in the pipeline logs (so-called weblogs) for every pipeline-processed dataset and, if needed, flag the few occurrences where the pipeline missed a patch of bad data. But also this workload is reduced with every new release of the pipeline.

Similar progress was also made at the other ARCs. With the present system running, we have made a big leap toward our goal of delivering processed data to PIs as soon as possible after observation,  without building up a processing backlog anywhere along the processing chain.

Report on the AtLAST Workshop

The Atacama Large Millimeter/Submillimeter Array (ALMA) is currently the most sensitive millimeter/submillimeter-wave observatory spanning 84–950 GHz, and will soon be extended to down to 35 GHz through the Band 1 and, hopefully, the Band 2 projects.  Yet the small field of view of ALMA limits its mapping speed, and the size of the array elements restricts its ability to recover extended scales (the “zero-spacing problem”).  

In January 2018, a broad international community came together to discuss a possible large, 40-meter-class single dish called the Atacama Large Aperture Submm/mm Telescope (atlast-telescope.org) that would address these issues.  Single dish facilities, such as the AtLAST project, are generally more flexible to upgrade than an interferometer, and are capable of surveying wide areas of the sky when coupled to wide field instrumentation.  This comes at the expense of reduced spatial resolution compared to an interferometer, and thus the two are highly complementary.   AtLAST would feature a large focal plane capable of hosting multi-element, multi-chroic, wide bandwidth instrumentation, ultimately upgradeable to megapixel cameras, wideband spectrometers coupled to large focal plane arrays, and large mm/submm integral field units capable of tomography of the universe out to the redshift of formation for dusty galaxies.   Notably, there are currently no mm/submm telescopes in the southern hemisphere larger than 12 meters in diameter.

The AtLAST workshop (https://www.eso.org/sci/meetings/2018/AtLAST2018.html) considered sites in the Atacama, one of the world’s best locations for millimeter and submillimeter science, as well as telescope designs, instrumentation, and some of the science cases.  The presentations are available online: https://www.eso.org/sci/meetings/2018/AtLAST2018/program.html.   A new workshop to address specifically the many AtLAST science cases will be held at the University of Edinburgh in late September or early October this year (2018), and white papers covering the science, site selection, telescope design, and instrumentation will follow by the beginning of 2019.  To get involved in this community effort, please contact atlast@eso.org.

This event has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 730562 [RadioNet].  This project is a community effort, and is not officially endorsed by ESO or ALMA — in order to succeed, we must come together as a community and strongly support this effort.

Missing the Short Spacings?

A two-day workshop was organized at ESO on Submillimetre Single-dish Data Reduction and Array Combination Techniques. The workshop was held at ESO on 15 and 16 March 2018.

One of the pleasant side-effects of a single-dish observation that it can supply interferometric data with all the important short spacings information, in order to recover larger scale emission that was filtered out by the interferometer. It is not uncommon to miss half of the flux in a more extended component when considering only the interferometer data. The majority of the second day in the workshop was spent on a number of techniques that have been developed and fine-tuned over the past 30-40 years, including a tutorial following the standard M100 example using CASA, supplemented with two new techniques. The default method in CASA is called "feather", but two new techniques, "ssc" and "tp2vis" were also highlighted. In particular, the "tp2vis" replaces the single dish map with "pseudo-visibilities", which then can be used in a standard joint deconvolution method to create images.

Talk slides, example scripts and links to the example data are available on the ESO workshop page as well as via a github repository, by which the participants were updated during the workshop. Through Zenodo the github repository also has a DOI.

This event has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 730562

Upcoming ALMA or ALMA-related Meetings

• ALMA Community Events 2018
  5 April 2018, Argelander-Institut für Astronomie, Bonn, Germany
  To prepare the local astronomical community for the Cycle 6 proposal deadline, the German ARC node offers a number of ALMA Community Events, including remote proposal preparation support and outreach sessions as well as the traditional German ALMA Community Day. The Community Day will take place on 5 April. The remote training sessions are scheduled between 15 March and 10 April.

• Allegro Proposal Preparation Day
  9 April 2018, Allegro, Leiden, The Netherlands
  Prior to the deadline for the ALMA Cycle 6 proposal submission (April 19th), Allegro will host a Proposal Preparation Day. Bring in your proposals and we will assist you with the technical aspects and help you exploring their feasibility, while you work on it during that day. Allegro staff will be there to provide tips & tricks and answer all your questions.

• Radio Interferometry: Methods and Science
  Starting April 2018, Bonn, Germany
  The course will be organized by the German ARC node and offers a hands-on overview of major aspects of radio/mm/submm interferometry for master students, PhD students and senior astronomers. The course is planned to start in April 2018.

• Tracing the Flow: Galactic Environments and the Formation of Massive Stars
  2 – 6 July 2018, Lake Windermere, UK
  With the massive increase in spatial dynamic range and the volume of data now becoming available this meeting will provide the opportunity to assess the current state of our knowledge of massive star formation. In addition, it will help identify the key issues for future work and look forward to the expanding opportunities ALMA will continue to offer in the fields of galactic and extragalactic massive star formation as well as those provided by JWST, ELTs, SKA, ngVLA and other facilities in the future.

• Announcement for the 10th IRAM Millimeter Interferometry School
  1 – 5 October 2018, IRAM, Grenoble, France
  The 10th IRAM millimeter interferometry school will be held October  1st - 05th 2018 at the IRAM headquarters (Grenoble, France). It is  intended for students, post-docs and scientists who want to acquire a  good knowledge of interferometry and data reduction techniques at  millimeter wavelengths, with a special emphasis on the NOEMA  interferometer and its new capabilities.