Browsing by Author "Scolnic, Dan"

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    A Comprehensive Measurement of the Local Value of the Hubble Constant with 1 km/s/Mpc Uncertainty from the Hubble Space Telescope and the SH0ES Team
    Riess, Adam G; Yuan, Wenlong; Macri, Lucas M; Scolnic, Dan; Brout, Dillon; Casertano, Stefano; Jones, David O; Murakami, Yukei; Breuval, Louise; Brink, Thomas G; Filippenko, Alexei V; Hoffmann, Samantha; Jha, Saurabh W; Kenworthy, W D'arcy; Mackenty, John; Stahl, Benjamin E; Zheng, Weikang
    We report observations from HST of Cepheids in the hosts of 42 SNe Ia used to calibrate the Hubble constant (H0). These include all suitable SNe Ia in the last 40 years at z<0.01, measured with >1000 orbits, more than doubling the sample whose size limits the precision of H0. The Cepheids are calibrated geometrically from Gaia EDR3 parallaxes, masers in N4258 (here tripling that Cepheid sample), and DEBs in the LMC. The Cepheids were measured with the same WFC3 instrument and filters (F555W, F814W, F160W) to negate zeropoint errors. We present multiple verifications of Cepheid photometry and tests of background determinations that show measurements are accurate in the presence of crowding. The SNe calibrate the mag-z relation from the new Pantheon+ compilation, accounting here for covariance between all SN data, with host properties and SN surveys matched to negate differences. We decrease the uncertainty in H0 to 1 km/s/Mpc with systematics. We present a comprehensive set of ~70 analysis variants to explore the sensitivity of H0 to selections of anchors, SN surveys, z range, variations in the analysis of dust, metallicity, form of the P-L relation, SN color, flows, sample bifurcations, and simultaneous measurement of H(z). Our baseline result from the Cepheid-SN sample is H0=73.04+-1.04 km/s/Mpc, which includes systematics and lies near the median of all analysis variants. We demonstrate consistency with measures from HST of the TRGB between SN hosts and NGC 4258 with Cepheids and together these yield 72.53+-0.99. Including high-z SN Ia we find H0=73.30+-1.04 with q0=-0.51+-0.024. We find a 5-sigma difference with H0 predicted by Planck+LCDM, with no indication this arises from measurement errors or analysis variations considered to date. The source of this now long-standing discrepancy between direct and cosmological routes to determining the Hubble constant remains unknown.
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    Cosmology with the Wide-Field Infrared Survey Telescope -- Multi-Probe Strategies
    Eifler, Tim; Miyatake, Hironao; Krause, Elisabeth; Heinrich, Chen; Miranda, Vivian; Hirata, Christopher; Xu, Jiachuan; Hemmati, Shoubaneh; Simet, Melanie; Capak, Peter; Choi, Ami; Doré, Olivier; Doux, Cyrille; Fang, Xiao; Hounsell, Rebekah; Huff, Eric; Huang, Hung-Jin; Jarvis, Mike; Kruk, Jeffrey; Masters, Dan; Rozo, Eduardo; Scolnic, Dan; Spergel, David N; Troxel, Michael; von der Linden, Anja; Wang, Yun; Weinberg, David H; Wenzl, Lukas; Wu, Hao-Yi
    We simulate the scientific performance of the Wide-Field Infrared Survey Telescope (WFIRST) High Latitude Survey (HLS) on dark energy and modified gravity. The 1.6 year HLS Reference survey is currently envisioned to image 2000 deg$^2$ in multiple bands to a depth of $\sim$26.5 in Y, J, H and to cover the same area with slit-less spectroscopy beyond z=3. The combination of deep, multi-band photometry and deep spectroscopy will allow scientists to measure the growth and geometry of the Universe through a variety of cosmological probes (e.g., weak lensing, galaxy clusters, galaxy clustering, BAO, Type Ia supernova) and, equally, it will allow an exquisite control of observational and astrophysical systematic effects. In this paper we explore multi-probe strategies that can be implemented given WFIRST's instrument capabilities. We model cosmological probes individually and jointly and account for correlated systematics and statistical uncertainties due to the higher order moments of the density field. We explore different levels of observational systematics for the WFIRST survey (photo-z and shear calibration) and ultimately run a joint likelihood analysis in N-dim parameter space. We find that the WFIRST reference survey alone (no external data sets) can achieve a standard dark energy FoM of >300 when including all probes. This assumes no information from external data sets and realistic assumptions for systematics. Our study of the HLS reference survey should be seen as part of a future community driven effort to simulate and optimize the science return of WFIRST.
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    Optimization of the Observing Cadence for the Rubin Observatory Legacy Survey of Space and Time: a pioneering process of community-focused experimental design
    Bianco, Federica B; Ivezić, Željko; Jones, R Lynne; Graham, Melissa L; Marshall, Phil; Saha, Abhijit; Strauss, Michael A; Yoachim, Peter; Ribeiro, Tiago; Anguita, Timo; Bauer, Franz E; Bellm, Eric C; Blum, Robert D; Brandt, William N; Brough, Sarah; Catelan, Màrcio; Clarkson, William I; Connolly, Andrew J; Gawiser, Eric; Gizis, John; Hlozek, Renee; Kaviraj, Sugata; Liu, Charles T; Lochner, Michelle; Mahabal, Ashish A; Mandelbaum, Rachel; McGehee, Peregrine; Jr, Eric H Neilsen; Olsen, Knut AG; Peiris, Hiranya; Rhodes, Jason; Richards, Gordon T; Ridgway, Stephen; Schwamb, Megan E; Scolnic, Dan; Shemmer, Ohad; Slater, Colin T; Slosar, Anže; Smartt, Stephen J; Strader, Jay; Street, Rachel; Trilling, David E; Verma, Aprajita; Vivas, AK; Wechsler, Risa H; Willman, Beth
    Vera C. Rubin Observatory is a ground-based astronomical facility under construction, a joint project of the National Science Foundation and the U.S. Department of Energy, designed to conduct a multi-purpose 10-year optical survey of the southern hemisphere sky: the Legacy Survey of Space and Time. Significant flexibility in survey strategy remains within the constraints imposed by the core science goals of probing dark energy and dark matter, cataloging the Solar System, exploring the transient optical sky, and mapping the Milky Way. The survey's massive data throughput will be transformational for many other astrophysics domains and Rubin's data access policy sets the stage for a huge potential users' community. To ensure that the survey science potential is maximized while serving as broad a community as possible, Rubin Observatory has involved the scientific community at large in the process of setting and refining the details of the observing strategy. The motivation, history, and decision-making process of this strategy optimization are detailed in this paper, giving context to the science-driven proposals and recommendations for the survey strategy included in this Focus Issue.
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    The Impact of Observing Strategy on Cosmological Constraints with LSST
    Lochner, Michelle; Scolnic, Dan; Almoubayyed, Husni; Anguita, Timo; Awan, Humna; Gawiser, Eric; Gontcho, Satya Gontcho A; Gris, Philippe; Huber, Simon; Jha, Saurabh W; Jones, R Lynne; Kim, Alex G; Mandelbaum, Rachel; Marshall, Phil; Petrushevska, Tanja; Regnault, Nicolas; Setzer, Christian N; Suyu, Sherry H; Yoachim, Peter; Biswas, Rahul; Blaineau, Tristan; Hook, Isobel; Moniez, Marc; Neilsen, Eric; Peiris, Hiranya; Rothchild, Daniel; Stubbs, Christopher
    The generation-defining Vera C. Rubin Observatory will make state-of-the-art measurements of both the static and transient universe through its Legacy Survey for Space and Time (LSST). With such capabilities, it is immensely challenging to optimize the LSST observing strategy across the survey's wide range of science drivers. Many aspects of the LSST observing strategy relevant to the LSST Dark Energy Science Collaboration, such as survey footprint definition, single visit exposure time and the cadence of repeat visits in different filters, are yet to be finalized. Here, we present metrics used to assess the impact of observing strategy on the cosmological probes considered most sensitive to survey design; these are large-scale structure, weak lensing, type Ia supernovae, kilonovae and strong lens systems (as well as photometric redshifts, which enable many of these probes). We evaluate these metrics for over 100 different simulated potential survey designs. Our results show that multiple observing strategy decisions can profoundly impact cosmological constraints with LSST; these include adjusting the survey footprint, ensuring repeat nightly visits are taken in different filters and enforcing regular cadence. We provide public code for our metrics, which makes them readily available for evaluating further modifications to the survey design. We conclude with a set of recommendations and highlight observing strategy factors that require further research.
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    The Pantheon+ Analysis: SuperCal-Fragilistic Cross Calibration, Retrained SALT2 Light Curve Model, and Calibration Systematic Uncertainty
    Brout, Dillon; Taylor, Georgie; Scolnic, Dan; Wood, Charlotte M; Rose, Benjamin M; Vincenzi, Maria; Dwomoh, Arianna; Lidman, Christopher; Riess, Adam; Ali, Noor; Qu, Helen; Dai, Mi; Stubbs, Christopher
    We present here a re-calibration of the photometric systems used in the Pantheon+ sample of Type Ia supernovae (SNe Ia) including those used for the SH0ES distance-ladder measurement of H$_0$. We utilize the large and uniform sky coverage of the public Pan-STARRS stellar photometry catalog to cross-calibrate against tertiary standards released by individual SN Ia surveys. The most significant updates over the `SuperCal' cross-calibration used for the previous Pantheon and SH0ES analyses are: 1) expansion of the number of photometric systems (now 25) and filters (now 105), 2) solving for all filter offsets in all systems simultaneously in order to produce a calibration uncertainty covariance matrix that can be used in cosmological-model constraints, and 3) accounting for the change in the fundamental flux calibration of the HST CALSPEC standards from previous versions on the order of $1.5\%$ over a $\Delta \lambda$ of 4000~\AA. The re-calibration of samples used for light-curve fitting has historically been decoupled from the retraining of the light-curve model. Here, we are able to retrain the SALT2 model using this new calibration and find the change in the model coupled with the change to the calibration of the light-curves themselves causes a net distance modulus change ($d\mu/dz$) of 0.04 mag over the redshift range $0
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    The Pantheon+ Type Ia Supernova Sample: The Full Dataset and Light-Curve Release
    Scolnic, Dan; Brout, Dillon; Carr, Anthony; Riess, Adam G; Davis, Tamara M; Dwomoh, Arianna; Jones, David O; Ali, Noor; Charvu, Pranav; Chen, Rebecca; Peterson, Erik R; Popovic, Brodie; Rose, Benjamin M; Wood, Charlotte; Brown, Peter J; Coulter, David A; Dettman, Kyle G; Dimitriadis, Georgios; Filippenko, Alexei V; Foley, Ryan J; Jha, Saurabh W; Kilpatrick, Charles D; Kirshner, Robert P; Pan, Yen-Chen; Rest, Armin; Rojas-Bravo, Cesar; Siebert, Matthew R; Stahl, Benjamin E; Zheng, WeiKang
    Here we present 1701 light curves of spectroscopically confirmed Type Ia supernovae (SNe Ia) that will be used to infer cosmological parameters as part of the Pantheon+ SN analysis and the SH0ES (Supernovae and H0 for the Equation of State of dark energy) distance-ladder analysis. This effort is one part of a series of works that perform an extensive review of redshifts, peculiar velocities, photometric calibration, and intrinsic-scatter models of SNe Ia. The total number of light curves, which are compiled across 18 different surveys, is a significant increase from the first Pantheon analysis (1048 SNe), particularly at low redshift ($z$). Furthermore, unlike in the Pantheon analysis, we include light curves for SNe with $z<0.01$ such that SN systematic covariance can be included in a joint measurement of the Hubble constant (H$_0$) and the dark energy equation-of-state parameter ($w$). We use the large sample to compare properties of 170 SNe Ia observed by multiple surveys and 12 pairs/triplets of "SN siblings" - SNe found in the same host galaxy. Distance measurements, application of bias corrections, and inference of cosmological parameters are discussed in the companion paper by Brout et al. (2022b), and the determination of H$_0$ is discussed by Riess et al. (2022). These analyses will measure w with $\sim3\%$ precision and H$_0$ with 1 km/s/Mpc precision.