Galaxy Clustering Science Working Group meeting

Euclid Consortium Galaxy Clustering Science Working Group meeting, Milan, February 2023

Authors: L. Guzzo, W. Percival & Y. Wang (GC-SWG leads)

Introduction & motivation

During the week of February 20-24, a meeting dedicated to the Galaxy Clustering (GC) measurements to be made by Euclid was held at the “Universitá Statale”, in Milan. This was the first in-person meeting focussed on galaxy clustering after 3 years of the pandemic break, and gathered together all units constituting the spectroscopic pipeline of Euclid, from the raw data to the cosmological parameter measurements. Participation was strong, with 90 people attending in person and an average of 20 connected remotely. Having an in-person joint meeting bringing together all steps along the data analysis chain, was a natural extension of the series of online meetings, which are now held every 2 weeks, bringing together managers and key personnel for the GC pipeline. There was much to review and to plan for, following a busy 2022, which included the Mission Key Point (MKP) review, and a focussed meeting on Observational Systematics organised at IFPU in Trieste.

Universita Statale, Milano
Universita Statale, Milano

The meeting

The broad nature of the meeting gave everyone involved a chance to take a holistic view of the GC pipeline, improving the interfaces between the existing units. The group of managers attending the biweekly GC pipeline meetings became the nucleus of the SOC (with some key additions). Speakers were proactively invited to the meeting, from all groups that were deemed critical to the GC science success (e.g., OU-MER, SIM, SIR, SPE, LE3, IST:NL, IST:Like). Although initially a number of parallel splinter sessions were conceived, we eventually included only two afternoon sessions of this kind, each with only 2 splinters in parallel. The desire to share as much as possible with all participants emerged as the most important goal for this meeting, which is why these sessions were limited.

Overview talks of all involved units were presented, coupled to keynote “hands-on” presentations from specifically suggested speakers. All speakers were requested to openly share the current critical issues, stimulating cross-fertilisation. The meeting included a “Rapid Fire Talks” session, in which 25 early-career scientists presented themselves and their work, enhancing their visibility within Euclid and letting everyone know about the work being done. As well as hearing about the official methods we also heard about existing “alternative approaches”, geared towards the validation of the official pipeline, and were able to work towards a better connection and integration with the standard developments.

Conclusions from the meeting

The imminence of launch means that we now need to focus on what is achievable and what is required, rather than what is desirable. It is clear that the data pipeline will develop and improve as the mission progresses. Early data will need to be rapidly reduced and made accessible in order to be validated to respond to ESA reviews. A validation group will be needed, pulling together experts from all along the GC-pipeline to do this. The sequential nature of the data processing pipeline means that getting timely results will be challenging. Access to early data, and regular updates needs to be considered by the relevant groups with Euclid. The joint nature of the meeting and having organised it mostly as a plenary meeting where all units participated in all discussions, was key to its success. In fact, the main positive comment made by several participants was that we should keep this format from now on. A tentative date in fall 2023 has already been set for the next meeting, which will be organised with a very similar format.

As organisers, our main positive feeling was that of having contributed to breaking important barriers, fostering a unitary spirit for this group of people to perceive themselves as a single entity with a specific common goal, i.e. getting the best possible science out of the Euclid galaxy clustering probe.

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