Major construction milestones are now coming thick and fast. On 3 April, SLAC announced the completion of the camera construction project, along with the release of a slick video explaining the science that the camera will enable. As noted in the video, this marks the culmination of two decades of work by a camera team (some shown top right) comprising scientists and engineers from SLAC and other DOE labs, plus international collaborators, notably from IN2P3 in France and Ian Shipsey’s group in Oxford.

Meanwhile, back on the summit, the glass blank for the 8.4-metre primary/tertiary mirror (M1M3) was lifted into its cell. The mirror cell was then moved under the coating chamber to verify the configuration to be used in the coating and, as a final preparation for the coating, the blue protective layer visible in the bottom right photo has been removed.

This month has also seen an operations rehearsal, in which two data streams – one real, from AuxTel, and one simulated, but passed through the ComCam data acquisition system – were transferred from the summit to the US Data Facility in California over the course of three 24-hour cycles. At the USDF, the LSST pipelines were run over the data files, generating the full set of LSST data projects, including alerts from the difference imaging pipeline. These operations were monitored throughout by various Rubin teams, to exercise a number of near-real-time data quality assessment and anomaly detection tools. Further rehearsals are due over the next few months, as the observatory prepares for the first on-sky images.

As noted in the February Newsletter, the Rubin Community Science Team will be running the 2024 Rubin Data Academy on 17, 18, 20 and 21 June. This event is open to all Rubin data rights holders who have registered to be Data Preview 0 (DP0) Delegates (see here for how to do that) and will present an introduction to the DP0.2 and DP0.3 datasets and how to analyse their data products using the Rubin Science Platform (RSP). Sessions will be delivered twice per day to suit attendees in different timezones, with those starting at 16.00 BST likely to be the best for us in the UK. Registration for the Rubin Data Academy remains open, but will close on 16 June.

@Bob Mann

MNRAS has recently published an article by Ilin Lazar and collaborators (including @Sugata Kaviraj and @aaron.watkins) describing the morphological diversity of nearby dwarf galaxies.

The paper, The morphological mix of dwarf galaxies in the nearby Universe, performs a novel, unbiased statistical study of dwarf morphology at z < 0.08. It offers both an unprecedented view of dwarfs using the deep Hyper Suprime-Cam surveys (the precursor to LSST) and a demonstration of the type of science that will be possible in the forthcoming LSST era.

Typical dwarfs are too faint to be visible, outside the local neighbourhood, in past surveys like the SDSS. Unbiased studies of dwarfs requires surveys that are both deep and wide. Lazar et al. use a complete, unbiased sample of 257 dwarf (10⁸ M_⊙ < M_⋆ < 10^9.5 M_⊙) galaxies at z < 0.08 in the COSMOS field, where deep ultraviolet to mid-infrared imaging is available, to study the morphological mix of dwarfs in low-density environments.

The study uses visual inspection of extremely deep optical images from the Hyper Suprime-Cam and their unsharp-masked counterparts to reveal three principal dwarf morphological classes (as shown in the figure). 43 and 45 per cent of dwarfs exhibit the traditional 'early-type' (elliptical/S0) and 'late-type' (spiral) morphologies respectively.

However, 10 per cent populate a 'featureless' class, that lacks both the central light concentration seen in early-types and any spiral structure - this class is missing in the massive-galaxy regime. 14, 27 and 19 per cent of early-type, late-type, and featureless dwarfs respectively show evidence for interactions, which drive around 20 per cent of the overall star formation activity in the dwarf population.

Lazar et al. find that, compared to their massive counterparts, dwarf early-types show a much lower incidence of interactions, are significantly less concentrated and share similar rest-frame colours as dwarf late-types. This suggests that the formation histories of dwarf and massive early-types are different, with dwarf early-types being shaped less by interactions and more by secular processes. The lack of large groups or clusters in COSMOS at z < 0.08, and the fact that the dwarf morphological classes show similar local density, suggests that featureless dwarfs in low-density environments are created via internal baryonic feedback, rather than by environmental processes.

Finally, the study finds that, while interacting dwarfs can be identified using the asymmetry parameter, it is challenging to cleanly separate early and late-type dwarfs using traditional morphological parameters, such as 'CAS', M20, and the Gini coefficient (unlike in the massive-galaxy regime).

Read the open access paper: https://academic.oup.com/mnras/article/529/1/499/7609698

@Sugata Kaviraj

@Mike Watson

@Bob Mann and @Stephen Smartt

The LSST:UK Phase C project includes a Pool Travel Fund to support UK-based astronomers to participate in Rubin-related science meetings and activities, to promote UK science priorities within Rubin and to enable better exploitation of the opportunities presented by Rubin to UK astronomers. This follows on from similar funds in Phase A and Phase B, which you may have been aware of.

In Phase C, we have £130k funding, for the four years of the award (April 2023 to March 2027), which is administered by the University of Edinburgh. Anyone based at an LSST:UK Consortium institution (https://www.lsst.ac.uk/governance#partners ) is eligible to apply for support for Rubin-related activities, following the procedure described on the LSST:UK wiki ( ). Applications can be made at any time and we aim to review and respond to all applications within one month.

We also maintain a page with upcoming meetings that we think will be interesting to the UK Community. This is always accessible on Confluence ( ) and topical meetings are summarised in each edition of this newsletter.

For meetings that are likely to be particularly popular, we may choose to issue a specific call for applications to help ensure we can review and prioritise the range of cases fairly. Typically this is done for larger events such as the Rubin Community Workshop or the LSST@Europe meetings. Any such calls are publicised via the LUSC-ANNOUNCE mailing list ( ) and posted on the Relevant Meetings page.

Funding is awarded at 80% FEC as is the norm for UKRI grants: the remaining 20% of the cost would usually be contributed by the applicant's institution. If in doubt, we recommend you speak to your local finance team to confirm this.

New in Phase C is the opportunity to request funding for hosting meetings. Up to 25% of the Pool Travel Fund has been earmarked by the LSST:UK to support Rubin-focused meetings held in the UK. As for travel applications, more details are available on the wiki page noted above (that is, ). 

If you have any questions about the Pool Travel Fund, please contact the project management team (mailto:lusc-pm@jiscmail.ac.uk).

@George Beckett

The latest science release from Rubin explains how the observatory’s camera will use six different colour filters to detect stellar streams that are around five times more distant than is currently possible.

The article explains how these glittering streams of stars often show telltale signs of disturbance which scientists suspect may be caused by dark matter. The Rubin’s camera will allow these slender trails to be studied in more detail than ever before to uncover their back story. Observing stellar streams allows scientists to probe a different aspect of dark matter because they bear the impact of dark matter’s gravitational effects at small scales.

The artist’s impression, right, shows a myriad of stellar streams in and around the Milky Way. These stretched-out remnants of dwarf galaxies and star clusters showcase gravitational interactions between stars, clumps of dark matter, and the entire galaxy.

@Eleanor O'Kane

The observing strategy implemented by the Vera C. Rubin Observatory's (Rubin's) Legacy Survey of Space and Time (LSST) will be the outcome of a significant multi-year community consultation exercise. UK astronomers continue to play key roles in this process through participation in the Survey Cadence Optimization Committee (SCOC), prominent roles in Rubin/LSST Science Collaborations, and representation on the Scientific Advisory Committee (SAC). With first light approaching, and the cadence of routine LSST survey observations now largely settled, attention recently returned to the 3% of observing time that the SCOC have recommended to Rubin leadership to spend on target of opportunity (ToO) observations. 

From 18-20 March 2024, over 100 colleagues from around the world joined a workshop hosted at the University of California Berkeley to build the community consensus on the content of the Rubin/LSST ToO program at Rubin ToO 2024: Envisioning the Vera C. Rubin Observatory LSST Target of Opportunity program.

The team worked round the clock for three days, benefitting from asynchronous working across multiple time-zones in this hybrid meeting. Collaborating in thematically organised groups, workshop participants developed a consensus position on the design of ToO observations for follow-up of gravitational wave sources including candidate gravitationally lensed gravitational waves, high energy neutrino sources, Galactic supernovae, and potentially hazardous asteroids. 

The community consensus was documented in a 60-page report that has been submitted to the SCOC, and will be made publicly available. Further community-wide discussion of the ToO program will take place at the Rubin Community Workshop 2024 (July 22-26; SLAC), and feedback from the SCOC is anticipated late-summer this year. In the meantime, further information is available from within the respective Rubin/LSST Science Collaborations, and from @Graham Smith (Member, Rubin ToO 2024 Scientific Organising Committee). 

@Graham Smith

A new paper by @Roy Williamsand collaborators published on arXiv sheds light on Lasair, the UK community broker for transient alerts from LSST.

Enabling Science from the Rubin Alert Stream with Lasair explains the system's capabilities, how users can achieve their scientific goals, and how Lasair is implemented. As a mature system, Lasair has been processing and serving data from the similarly formatted stream of the Zwicky Transient Facility (ZTF) alerts.

Pronounced L-AH-s-uh-r, Lasair means flame or flash in Scots and Irish Gaelic.

Read the open access paper: Enabling Science from the Rubin Alert Stream with Lasair

@Roy Williams