Amplitude and phase calibration errors

Self-calibration and improving image fidelity for ALMA and other interferometers

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The high quality of ALMA calibrated data sets allows researchers to tune the imaging parameters to their preferences, and to produce images ready for publication in few steps.
Sometimes the exploratory analysis of calibrated datasets can also show the need for post-calibration processing. Identifying and/or diagnosing imaging problems from structured artifacts, or to identify errors induced from the observations and/or prior calibration, could save valuable time when researchers deal with challenging datasets.

Although there is extensive documentation out there for experts, a document accessible for researchers less experienced with radio interferometry was still missing. Recently, Anita Richards et al. published an internal ALMA memo (620), also available in the ArXiv, with the title “Self-calibration and improving image fidelity for ALMA and other interferometers”.

This document is an up-to-date manual with practical explanations of the errors normally found in interferometric data, and corrections that can be applied.
The main topic is self-calibration, in particular with ALMA data. However, the concepts explained are also relevant for other long-baseline interferometers.
The document includes examples and a quick-start guide for continuum self-calibration, as well as special cases.

Complementary to the ALMA Memo is the I-Train tutorial on self-calibration. In this tutorial, Anita Richards, Emily Moravec, Carmen Toribio, and Andrés Pérez explain and show examples of self-calibration.

Images from Bouwens et al. and Brunken et al.

ALMA probes atoms and molecules, near and far

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ALMA’s supreme capabilities to detect spectral lines across the Universe are beautifully illustrated in two recently published papers by astronomers in the Netherlands. Bouwens et al. (2022, ApJ 931, 160) give an overview of the design and results of the ALMA Large Program REBELS. Using an efficient selection scheme, REBELS detects no less than 18 star-forming galaxies with bright [CII] 158 µm ISM cooling lines, out of a sample of 40 z>6.5 systems. This makes ALMA [CII] searches as efficient as Lyα to find high-redshift star-forming galaxies. Brunken et al. (2022, A&A 659, A29) stay closer to home and detect Complex Organic Molecules (COMs) in the highly asymmetric planet-forming disk around the young star IRS48. The disk around this star has a very pronounced ‘dust and ice trap’ where material accumulates, and future planet(esimals) may form. Brunken et al. report the first detection of dimethyl ether (CH3OCH3) vapor in a planet-forming disk, and a tentative detection of methyl formate (CH3OCHO) vapor. The presence of these molecules shows that a wide variety of oxygen-carrying COMs are present in the birth environment of planets. As these two papers show, wherever ALMA turns its ‘eye’, atoms and molecules leap out at us.

ALMA Proposal Preparation Day 2022

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The Allegro ARC Node would like to invite you to attend a proposal preparation workshop on March 28, 2022. The aim of this workshop is to assist you in making the most out of ALMA’s new capabilities, getting an overview of the new modes offered, and proposal preparation through the ALMA Observing Tool (OT). We will also offer guidance with writing double-anonymous proposals and in the new stages of proposal writing and reviewing (the “distributed proposal review process”) that has been in use from Cycle 8 2021. An overview of important dates and what’s offered in Cycle 9 will be released with the Call for Proposals on March 24, 2022.

The workshop will consist of:

  1. an in-person event with the Allegro team on March 28th with a few presentations and an extensive Q&A session. The workshop will take place at Leiden Observatory, but we will organise streaming for those unable to travel.
  2. individual 1-1 support that can be booked at any time (e-mail us)

You can register to attend the workshop using this registration form. Deadline for registration: March 20, 2022

Program March 28, 2022
before 11:00 Arrival to Allegro offices (HL 1122)
11:00-11:30 Welcome coffee/tea & cookies (HL 11th floor)
11:30-12:00 ALMA science overview Katharina Immer & Aida Ahmadi
12:00-12:20 ALMA Call for proposals & capabilities in Cycle 9 Violette Impellizzeri
12:20-13:15 Lunch
13:15-13:35 Distributed peer review Katharina Immer
13:35-13:50 Dual anonymous proposal review Andrés Pérez-Sánchez
13:50-14:15 How to write an ALMA proposal Violette Impellizzeri
14:15-14:35 Break
14:35-15:10 The ALMA Observing Tool Ashley Bemis
15:10-15:30 Simulating ALMA observations Alex Hygate
15:30-15:50 Mining the ALMA archive Aida Ahmadi
15:50-16:10 Break
16:10-16:30 Open Q&A session
 
Registered participants

Michiel Hogerheijde Leiden Observatory
Violette Impellizzeri Leiden Observatory
Alex Hygate Leiden Observatory
Andrés Pérez-Sánchez Leiden Observatory
Ashley Bemis Leiden Observatory
Aida Ahmadi Leiden Observatory
Katharina Immer Leiden Observatory
Marco Grossi Observatório do Valongo, UFRJ
Sander Schouws Leiden Observatory
Maren Hempel Universidad Andres Bello , Chile
Veronica Allen University of Groningen
Wuji Wang Center for Astronomy of Heidelberg University
Pooneh Nazari Leiden Observatory
Simin Tong Leiden Observatory
Thomas Steinmetz Nicolaus Copernicus Center for Astronomy (Torun)
Di Wen Kapteyn Astronomical Institute
Agnieszka Kobak Nicolaus Copernicus Center for Astronomy (Torun)
Alice Booth Leiden Observatory
Lucas Stapper Leiden Observatory
Margot Leemker Leiden Observatory
Bayron Portilla Revelo Kapteyn Astronomical Institute
Marta Frias Castillo Leiden Observatory
Fernanda Roman de Oliveira University of Groningen
Ko-Yun (Monica) Huang Leiden Observatory

 
Directions to Leiden Observatory

The address of Leiden Observatory is Niels Bohrweg 2, 2333 CA Leiden. Note that this is not the old observatory in the center of Leiden. Instructions on how to get to Leiden Observatory, including transportation from Schiphol Airport or the central trains station, can be found here. Leiden Observatory is located on the 4-5th floors of the Oort building (seen on the right in the photo below), and the Huygens building (the taller building seen on the left in the photo below). Allegro offices are located on the 11th floor of the Huygens building.

Upon arrival and before the start of the event, join us on the 11th floor of the Huygens building for tea, coffee, and cookies. The workshop will take place in room HL 106-109 on the 1st floor of the Huygens building. We will have signs and there is also a reception at the entrance of the building where they can provide you with directions.

For those joining us online, connection details will be sent to you by email before the start of the event.

lorentzcenter

 

Useful resources:

I-TRAIN logo

I-TRAIN: Writing & Reviewing ALMA proposals

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The European ARC Network invites users to an online training on good practices for writing and reviewing ALMA proposals on March 18th, 11:00 CET.

This training is organised in view of the upcoming ALMA proposal deadline in April, and will serve as a guideline for writing ALMA proposals and in particular anonymous proposals. The training will also offer guidelines on reviewing proposals, how to best give feedback and the ALMA Reviewer Tool. It will include some tips and tricks and plenty of time for discussion and questions at the end. No preparation will be needed for this session, but we encourage everyone to bring plenty of questions for the Q&A.

The duration of this training session will be about one hour. If you have any doubts or questions, do not hesitate to contact the Allegro node at alma@strw.leidenuniv.nl.

Hands up for a community assembly!

Fifth European ALMA Regional Centre community assembly

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The Fifth European ALMA Regional Centre community assembly meeting will take place virtually on the 24th of March at 11:00 AM CET and can be accessed via this Microsoft Teams link. During the meeting, staff from the European ALMA Regional Centre will present updates on the current and future ALMA cycle, including the imminent ALMA cycle 9, which is scheduled to be announced the day before the meeting. In addition, you will hear about the support for using ALMA that the European ARC network offers the community. There will also be a dedicated question and answer session where staff from the European ALMA Regional Centre will be on hand to answer your questions.

MAYA2022 Group Photo

MAYA – Meeting of ALMA Young Astronomers – First Edition

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From March 2 to 4, 2022, the first Meeting of ALMA Young Astronomers (MAYA) took place fully online. The conference was dedicated to undergraduate and PhD students as well as postdocs. The goal of the meeting was to allow participants to share their ALMA projects in an open and friendly atmosphere, interact with other participants and staff from the ARC nodes, and potentially trigger new collaborations and projects.

The organising committee received more than 150 registrations and more than 90 submitted abstracts for the program. In the end, the program covered all types of astronomical subjects from solar observations to distant galaxies as well as two invited talks about the history of ALMA and the European ARC network. The presentations were recorded and are available in the MAYA playlist on the European ALMA Regional Centre Network YouTube channel. Participants who were not awarded presentation time during the conference were given the opportunity to pre-record their talks and upload them to the same playlist.

The high quality of the presentations and the friendly interaction in the Q&A time after each talk as well as on Slack was impressive. Besides the presentations, the meeting offered ample time for the participants to get to know each other in Zoom breakout rooms and during the social evenings. A quiz with ALMA trivia questions added a playful tone to some of the breaks.

An overwhelming 93% of participants who filled the feedback survey were overall satisfied with the meeting, making this first MAYA conference a great success! The survey participants stated that they most enjoyed the variety of the program and the early career attendees. More than 90% of the survey participants are interested in participating in the next MAYA event in 2023!

ALminer: ALMA archive mining and visualization toolkit

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Allegro has developed a tool to ease the scientific exploration of the rich ALMA Science Archive (ASA). ALminer is a novel Python-based code that enables users to efficiently query, analyse, and visualise the contents of the ASA. Users can programmatically query the archive for positions, target names, or any other keywords in the archive metadata (e.g. proposal title, abstract, scientific category) in a simple way. ALminer’s plotting routines allow the query results to be visualised, and its analysis functions allow users to filter the results and check whether certain frequencies of interest are covered in the queried observations. The code also allows users to directly download ALMA data products in FITS format and/or the raw data that can be used for manual image processing. ALminer has been designed to make mining the ALMA archive as simple as possible, while being flexible to be customised according to the user’s scientific interests. The code is released with a detailed tutorial Jupyter notebook, introducing ALminer’s common functions as well as some of its more advanced options.

Users are strongly encouraged to use ALminer in the lead-up to the ALMA Cycle 9 Call for Proposals to design their projects. ALminer can also aid users in ensuring their proposed observations do not duplicate observations of the same location on the sky with similar observing parameters (frequency, angular resolution, coverage, and sensitivity). Feel free to contact us if you need support in using ALminer.

ALMAxLeiden - Lettering

ALMAxLeiden – Astronomy-inspired, self-guided city walking tours through Leiden

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As part of the European City of Science Leiden 2022 project, Allegro is developing the ALMAxLeiden project: a series of self-guided walking tours in Leiden. The aim of ALMAxLeiden is to introduce the public to the concept of interferometry and specifically to ALMA in a fun and creative way. The ALMA observatory spans roughly the same size as the city of Leiden. By virtually stationing each of the 66 ALMA antennas at public locations in Leiden, we have turned Leiden into an ALMA observatory. Through self-guided walking tours, participants embark on journeys to ‘observe’ an astronomical object by visiting a subset of these virtual antennas. At each location a new part of the story gets revealed, and participants get to answer trivia questions about ALMA or solve astronomy puzzles. Visiting each location means observations from that antenna have been obtained, hence the astronomical object being ‘observed’ becomes clearer. By the end of the walking tour, the participants will have learned about ALMA and gained a better understanding of radio astronomy and the interferometric technique. The first ALMAxLeiden walking tour is ready to be launched on March 30th, and we are currently in the process of developing a walking tour intended for young kids. Stay tuned for more information!

ALMA at the European Astronomical Society meeting

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The next meeting of the European Astronomical Society will take place in Valencia (Spain) from 27 June to 1 July 2022. This conference will be in-person. The abstract submission deadline has already passed but registration is open until the start of the conference.

Building bridges: The lifecycle of dust and gas in the Milky Way with ALMA and SKA – EAS S7 symposium

Our Galaxy and its immediate neighbourhood are the only regions where we can undertake detailed studies of the physics driving the formation and evolution of astrophysical objects throughout the entire life cycle of the interstellar medium. ALMA is playing a groundbreaking and fundamental role in the study of a broad range of environments and phenomena due to its unprecedented spatial resolution and sensitivity. At the same time, the Square Kilometre Array (SKA) is now under construction, and it will provide a unique perspective on our Galaxy, complementary to that of ALMA.

Within the life cycle of dust and gas, accretion, fragmentation, feedback, astrochemistry, and temporal changes are common to many astrophysical objects. The respective communities investigating these objects often do not interact – even though they are using many of the same techniques. Symposium 7 is dedicated to building bridges between communities studying events of similar nature in the life cycle of gas and dust but at different astronomical scales and in different environments. The program of the symposium contains five invited talks focusing on accretion and fragmentation on large and small spatial scales, feedback in star-forming regions and evolved stars as well as synergies between ALMA/SKA and other observing facilities.

This style of event- instead of object-focused symposium will hopefully attract many contributors from different fields and communities, lead to interesting discussions and foster new collaborations.

More information about the topics and programme of the symposium can be found here:

ALMA in Europe: support by the European ALMA Regional Centre Network and new ways of interacting with data through the ALMA Science Archive

In this lunch session we aim to present to the European astronomical community how ALMA user support in Europe has evolved over the last years, the various types of support it offers, and the ways the European astronomical community can make use of this support. We will provide an update on the ALMA Science Archive and the tools that were developed to maximise its science output. We will furthermore discuss the outcomes of the ALMA Redesign the User eXperience (RedUX) project and show some of the actions that have been taken regarding user support and archive development. We will finish by taking time to discuss recent relevant changes within ALMA that are of direct interest to the astronomical community, including for example the distributed peer review system of proposals and how the connection between the astronomical community and the European ARC network can be further improved. More information can be found here.

During the conference, ALMA will have a booth in the exhibition space where interested conference participants can visit to ask questions about ALMA and the ARC network and take home merchandise.

ALMA antennas

ALMA Cycle 9 Proposal Preparation Workshop

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The Allegro team will host the ALMA Cycle 9 Proposal Preparation Workshop on March 28th, 2022. You should not miss this workshop if you are planning to write an observing proposal for the coming cycles of the ALMA telescope! The registration deadline is Monday, March 21st 2022.

We plan to have presentations/talks to explain the brand new capabilities offered for the new ALMA cycle, the Observing Tool, and how to make simulation of ALMA observations which could make your science case stronger. For newcomers, we will also have a presentation about ALMA use cases to inspire proposal ideas. In addition, we will present overviews about the Dual Anonymous procedure and the Distributed Peer Review process.

In fact, all proposals will be reviewed using the dual anonymous procedure, and for this new call, proposals requesting less than 50 hours on the 12-m Array, and less than 150 hours with the 7-m antennas, will be reviewed through the distributed peer review system.

The long baselines configurations are back in the list of array configurations for Cycle 9. With that, minimum and maximum baselines offered are 0.16 and 16.2 km, respectively. In addition, high frequency observations with long baselines can now be requested.

Moreover, new for this new cycle is the possibility to request VLBI observations of Continuum in Band 7, and VLBI Spectral Line observations in Band 3, as well as localised Solar mapping scans in bands 3, 5, 6 and 7 with Total Power antennas.
For more details, check the Cycle 9 pre-announcement!