Optimizing the LSST Observing Strategy for Dark Energy Science : DESC Recommendations for the Wide-Fast-Deep Survey

Author(s): Lochner, Michelle; Scolnic, Daniel M; Awan, Humna; Regnault, Nicolas; Gris, Philippe; Mandelbaum, Rachel; Gawiser, Eric; Almoubayyed, Husni; Setzer, Christian N; Huber, Simon; Graham, Melissa L; Hložek, Renee; Biswas, Rahul; Eifler, Tim; Rothchild, Daniel; Jr, Tarek Allam; Blazek, Jonathan; Chang, Chihway; Collett, Thomas; Goobar, Ariel; Hook, Isobel M; Jarvis, Mike; Jha, Saurabh W; Kim, Alex G; Marshall, Phil; McEwen, Jason D; Moniez, Marc; Newman, Jeffrey A; Peiris, Hiranya V; Petrushevska, Tanja; Rhodes, Jason; Sevilla-Noarbe, Ignacio; Slosar, Anže; Suyu, Sherry H; Tyson, J Anthony; Yoachim, Peter | Abstract: Cosmology is one of the four science pillars of LSST, which promises to be transformative for our understanding of dark energy and dark matter. The LSST Dark Energy Science Collaboration (DESC) has been tasked with deriving constraints on cosmological parameters from LSST data. Each of the cosmological probes for LSST is heavily impacted by the choice of observing strategy. This white paper is written by the LSST DESC Observing Strategy Task Force (OSTF), which represents the entire collaboration, and aims to make recommendations on observing strategy that will benefit all cosmological analyses with LSST. It is accompanied by the DESC DDF (Deep Drilling Fields) white paper (Scolnic et al.). We use a variety of metrics to understand the effects of the observing strategy on measurements of weak lensing, large-scale structure, clusters, photometric redshifts, supernovae, strong lensing and kilonovae. In order to reduce systematic uncertainties, we conclude that the current baseline observing strategy needs to be significantly modified to result in the best possible cosmological constraints. We provide some key recommendations: moving the WFD (Wide-Fast-Deep) footprint to avoid regions of high extinction, taking visit pairs in different filters, changing the 2x15s snaps to a single exposure to improve efficiency, focusing on strategies that reduce long gaps (g15 days) between observations, and prioritizing spatial uniformity at several intervals during the 10-year survey.

[1]  Yen-Ting Lin,et al.  Second data release of the Hyper Suprime-Cam Subaru Strategic Program , 2019, Publications of the Astronomical Society of Japan.

[2]  Robert J. Vanderbei,et al.  A Framework for Telescope Schedulers: With Applications to the Large Synoptic Survey Telescope , 2018, The Astronomical Journal.

[3]  David Alonso,et al.  The LSST Dark Energy Science Collaboration (DESC) Science Requirements Document , 2018, 1809.01669.

[4]  Yukiko Kamata,et al.  First data release of the Hyper Suprime-Cam Subaru Strategic Program , 2017, 1702.08449.

[5]  D. Gerdes,et al.  How Many Kilonovae Can Be Found in Past, Present, and Future Survey Data Sets? , 2017, 1710.05845.

[6]  Andrew J. Connolly,et al.  Photometric Redshifts with the LSST: Evaluating Survey Observing Strategies , 2017, 1706.09507.

[7]  Hu Zhan,et al.  TESTING LSST DITHER STRATEGIES FOR SURVEY UNIFORMITY AND LARGE-SCALE STRUCTURE SYSTEMATICS , 2016, 1605.00555.

[8]  W. M. Wood-Vasey,et al.  Spectroscopic Needs for Imaging Dark Energy Experiments , 2013, 1309.5384.

[9]  Rahul Biswas,et al.  Improving the LSST dithering pattern and cadence for dark energy studies , 2014, Astronomical Telescopes and Instrumentation.

[10]  Andrew J. Connolly,et al.  The LSST metrics analysis framework (MAF) , 2014, Astronomical Telescopes and Instrumentation.

[11]  Chris Bebek,et al.  The Dark Energy Spectroscopic Instrument (DESI) , 2019, 1907.10688.

[12]  Abhijit Saha,et al.  The LSST operations simulator , 2005, Astronomical Telescopes and Instrumentation.

[13]  Bernard Muschielok,et al.  4MOST: 4-metre multi-object spectroscopic telescope , 2012, Other Conferences.

[14]  Jan Swevers,et al.  Ground-based and airborne instrumentation for astronomy , 2010 .

[15]  Donald W. Sweeney,et al.  LSST Science Book, Version 2.0 , 2009, 0912.0201.

[16]  M. Sullivan,et al.  SALT2: using distant supernovae to improve the use of type Ia supernovae as distance indicators , 2007, astro-ph/0701828.

[17]  Wendy L. Freedman,et al.  Report of the Dark Energy Task Force , 2006, astro-ph/0609591.

[18]  D. Schlegel,et al.  Maps of Dust Infrared Emission for Use in Estimation of Reddening and Cosmic Microwave Background Radiation Foregrounds , 1998 .

[19]  D. Schlegel,et al.  Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds , 1997, astro-ph/9710327.