The science that can be pursued in those areas depends critically on the quality of the photometry, and on the effectiveness of the methodology with which data are analyzed.

The TVS/SMWLV crowded fields task force proposed a dedicated session to this topic, open to all interested in this important problem, and bringing together project and community personnel. Issues would include:

1. Census of the critically crowded areas;
2. The impact of PSF photometry;
3. The effectiveness of DIA analysis for detection of variable objects in these environments;
4. Caveats on the homogeneity of photometric calibration, and the impact of reddening;
5. Observing strategy and yield from crowded regions;
6. Indications from commissioning - plans and needs;
7. Impact of in-kind contributions on this topic

… which stem from the over-arching question: what is needed between now and main-survey start to enable the best crowded-field science with LSST?

Session Plan

Talk time slots are 10 minutes (7+3) to allow plenty of time for discussion. Talks submitted as google slides appear as links in this list.

Will Clarkson - Welcome, session aims

Natasha Abrams - Microlensing Discovery and Characterization Efficiency in the Vera C. Rubin Legacy Survey of Space and Time

Abi Saha - DECam Bulge photometry and calibration as a pathway to Rubin-LSST

Ian Sullivan - Processing Crowded Field Images with the LSST Science Pipelines

Fred Moolekamp - Crowded-field challenges for data release processing (DRP)

Keith Bechtol - Commissioning and crowded fields

All - discussion (prompts provided if needed)

Contributed abstracts

Microlensing Discovery and Characterization Efficiency in the Vera C. Rubin Legacy Survey of Space and Time (Natasha Abrams)
The Vera C. Rubin Legacy Survey of Space and Time will find thousands of microlensing events across the sky. It will go to deeper limiting magnitudes over a wider footprint than any previous survey. This will allow us to probe microlensing events across the Galaxy. We evaluate Rubin Operation Simulations (OpSims) to assess the discovery and characterization efficiencies of microlensing events. We have implemented three metrics: a discovery metric and two characterization metrics, where one estimates how well the lightcurve is covered and the other quantifies how precisely event parameters can be determined. We find, given Rubin's baseline cadence, the discovery efficiency will be higher for longer duration events. The more that Rubin observes the Galactic Plane, particularly the Galactic Bulge due to the higher stellar density, the discovery rate will increase. However, if the observations are stretched over too wide an area, event characterization suffers. Even without full characterization of events, Rubin observations will be invaluable as discovery alerts for other telescopes.