ALMA poll of the month

Talk series: ALMA Recounts of Cosmic Conundrums

The European ARC network is presenting the virtual talk series "ALMA recounts of Cosmic Conundrums". In every talk of this series a major astronomical question is discussed. The invited speaker will describe the context of the question and then focuses on the ALMA contribution to the field, past and future. The aim of the series is to highlight the unparalleled contribution of ALMA to the broader astronomical landscape and to provide an outlook towards the future. 

The sixth talk of this series will take place on 1 June at 14:00 CEST. The talks are broadcast through the Youtube channel of the European ALMA Regional Centre network and will remain available on the same channel afterwards.

Dr. María Díaz Trigo

Maria joined the ESO ARC in 2010. At the ARC she has been involved in several aspects of ALMA user support and operations, such as development of User Policies, Call for Proposals documentation or User Surveys. She has also been Data Reduction Manager and Subsystem Scientist for the Scheduling Subsystem. Maria currently leads an investigation of all aspects of ALMA data optimization to ensure end-to-end consistency. She also co-leads an internal ESO ALMA study to develop new methods for high-fidelity imaging including assessment of sensitivity at all angular scales.

Maria's research interests are accretion and ejection processes in neutron stars and black holes, which she studies with a multi-wavelength approach. She's also contributing to develop the next generation of X-ray observatories including an X-ray interferometry concept for the ESA Voyage 2050 programme and representing the European scientific community at the JAXA/NASA-led mission XRISM.

Dr. Kazi Rygl

Kazi has joined the Italian ARC Node in February 2015. She is involved in a number of activities such as user support, quality assurance and training activities. In the past few years she has concentrated on improving the user experience regarding the exploitation of the ALMA Science Archive. She has given a major contribution to the ALMA document “Using ALMA archival data - A Primer” and is part of the Additional Representative Images for Legacy (ARI-L) development project.

Her scientific focus lies mainly on Galactic star formation and the structure of the Milky Way through VLBI maser parallaxes. She is a member of the Event Horizon Telescope (EHT) Collaboration and is excited about the ALMA phasing developments for doing spectral line VLBI studies.

An icy start for stellar systems

Stellar system like our own are the product of contraction of magnetized cloud cores, called prestellar cores. With a lifetime significantly smaller than 100,000 yr - when the star is formed - these are very rare objects. However, studying the structures of prestellar cores is important as they contain the initial conditions in the process of star and protoplanetary disk formation. Previous observations have shown that molecules such as CO are heavily depleted within pre-stellar cores, due to the efficient molecular freeze-out onto the surface of the cold dust grains. However, nitrogen bearing species (in particular ammonia and its deuterated forms, such as NH₂D) appear to trace very well the central regions, in contrast with CO. This has been a puzzle for many years, as the binding energies of N₂ (precursor of ammonia) is similar to that of CO, while the binding energy of ammonia is significantly larger than that of CO (and close to that measured for water molecules).

Thanks to the high sensitivity of ALMA, Caselli et al. (2022) have unveiled the central 3000 au of the L1544 prestellar core in the Taurus Molecular Cloud, showing a structure which very much resembles that of an inclined elongated envelope (or “pseudo-disk”) predicted by theories of contracting magnetized cloud cores (see Figure above). They also finally clarified what is making the N-bearing molecules such as the observed deuterated ammonia (NH₂D) appear centrally peaked and with strikingly different morphologies compared to CO and its rare isotopologues: this is due to radiative transfer effects caused by the combination of the relatively high critical densities of the observed N-bearing species transitions and the centrally concentrated structure of prestellar cores. In fact, the new ALMA data can be reproduced by chemical models of prestellar cores which predict a catastrophic freeze-out of almost all (99.99%) species heavier than helium within the central 2000 au.

This study has shown that just at the start of stellar system formation, a large reservoir of ice is available in the form of thick (more than 100 monolayers) icy mantles on top of dust grains. This almost complete freeze-out zone is expected to be present in the central regions of all prestellar cores with central volume densities 10⁶ cm^-3 and temperatures below ~20 K.  The icy mantles may promote dust coagulation and allow the preservation of prestellar chemistry for later stages of protostar and protoplanetary disk evolution. This could explain the recent findings of similar molecular composition and isotopic fractionation between star- and planet-forming regions and primitive material in our Solar System.

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

The in-person Symposium 7 at the EAS Meeting 2022 in Valencia (Spain) will take place on 30 June and 1 July. The aim of this meeting is to build bridges between groups studying events of similar nature in the life cycle of dust and gas, but at different astronomical scales and in different environments. More information can be found at https://eas.unige.ch/EAS_meeting/session.jsp?id=S7. 

Registrations to the EAS 2022 are open and abstract submission can be done using this link. The full conference program can be found at this link.

VLA Sky Survey in the Multiwavelength Spotlight

This conference will take place on 7-9 September 2022 and will have a hybrid format, with options for speakers and attendees to choose to attend either in-person in Socorro, NM, or remotely on a virtual platform.

The goal of this conference is to share a diverse range of scientific perspectives, both on the discoveries enabled by the Very Large Array Sky Survey (VLASS, a multi-epoch radio survey of the entire northern sky visible from New Mexico) on its own, and on advances made possible through synergy with other datasets. Opportunities for multiwavelength VLASS synergy include radio/mm observatories and surveys (e.g., ALMA), optical/infrared imaging and spectroscopy, multi-epoch widefield surveys , and the high-energy domain. For more information please visit the conference webpage.