The La Silla Schmidt Southern Survey

Miller, Adam A. and Abrams, Natasha S. and Aldering, Greg and Anand, Shreya and Angus, Charlotte R. and Arcavi, Iair and Baltay, Charles and Bauer, Franz E. and Brethauer, Daniel and Bloom, Joshua S. and Bommireddy, Hemanth and Catelan, Márcio and Chornock, Ryan and Clark, Peter and Collett, Thomas E. and Dimitriadis, Georgios and Faris, Sara and Förster, Francisco and Franckowiak, Anna and Frohmaier, Christopher and Galbany, Lluís and Galleguillos, Renato B. and Goobar, Ariel and Graur, Or and Gutiérrez, Claudia P. and Hall, Saarah and Hammerstein, Erica and Herner, Kenneth R. and Hook, Isobel M. and Huston, Macy J. and Johansson, Joel and Kilpatrick, Charles D. and Kim, Alex G. and Knop, Robert A. and Kowalski, Marek P. and Kwok, Lindsey A. and LeBaron, Natalie and Lin, Kenneth W. and Liu, Chang and Lu, Jessica R. and Lu, Wenbin and Lunnan, Ragnhild and Maguire, Kate and Makrygianni, Lydia and Margutti, Raffaella and Maoz, Dan and Veres, Patrik Milán and Moore, Thomas and Nayana, A. J. and Nicholl, Matt and Nordin, Jakob and Oates, S. R. and Pignata, Giuliano and Polin, Abigail and Poznanski, Dovi and Prieto, Jose L. and Rabinowitz, David L. and Rehemtulla, Nabeel and Rigault, Mickael and Ryczanowski, Dan and Sarin, Nikhil and Schulze, Steve and Shah, Ved G. and Sheng, Xinyue and Shilling, Samuel P. R. and Simmons, Brooke D. and Singh, Avinash and Smith, Graham P. and Smith, Mathew and Sollerman, Jesper and Soumagnac, Maayane T. and Stubbs, Christopher W. and Sullivan, Mark and Suresh, Aswin and Trakhtenbrot, Benny and Ward, Charlotte and Wiston, Eli and Xiong, Helen and Yao, Yuhan and Nugent, Peter E. (2025) The La Silla Schmidt Southern Survey. Publications of the Astronomical Society of the Pacific, 137 (9): 094204. ISSN 0004-6280

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Abstract

We present the La Silla Schmidt Southern Survey (LS4), a new wide-field, time-domain survey to be conducted with the 1 m ESO Schmidt telescope. The 268 megapixel LS4 camera mosaics 32 2k × 4k fully depleted CCDs, providing a ∼20 deg2 field of view with 1″ pixel−1 resolution. The LS4 camera will have excellent performance at longer wavelengths: in a standard 45 s exposure the expected 5σ limiting magnitudes in g, i, z are ∼21.5, ∼20.9, and ∼20.3 mag (AB), respectively. The telescope design requires a novel filter holder that fixes different bandpasses over each quadrant of the detector. Two quadrants will have i band, while the other two will be g and z band with color information obtained by dithering targets across the different quadrants. The majority (90%) of the observing time will be used to conduct a public survey that monitors the extragalactic sky at both moderate (3 days) and high (1 day) cadence, as well as focused observations within the Galactic plane and bulge. Alerts from the public survey will be broadcast to the community via established alert brokers. LS4 will run concurrently with the Vera C. Rubin Observatory’s Legacy Survey of Space and Time (LSST). The combination of LS4+LSST will enable detailed holistic monitoring of many nearby transients: high-cadence LS4 observations will resolve the initial rise and peak of the light curve while less-frequent but deeper observations by LSST will characterize the years before and after explosion. Here, we summarize the primary science objectives of LS4 including microlensing events in the Galaxy, extragalactic transients powered by massive black holes or stellar explosions, the search for electromagnetic counterparts to multi-messenger events, and supernova cosmology.