Browsing by Author "Jha, Saurabh W"
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Item Open Access 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 TeamRiess, 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, WeikangWe 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.Item Open Access The Foundation Supernova Survey: Photospheric Velocity Correlations in Type Ia SupernovaeDettman, Kyle G; Jha, Saurabh W; Dai, Mi; Foley, Ryan J; Rest, Armin; Scolnic, Daniel M; Siebert, Matthew R; Chambers, KC; Coulter, DA; Huber, ME; Johnson, E; Jones, DO; Kilpatrick, CD; Kirshner, RP; Pan, Y-C; Riess, AG; Schultz, ASBThe ejecta velocities of type-Ia supernovae (SNe Ia), as measured by the Si II $\lambda 6355$ line, have been shown to correlate with other supernova properties, including color and standardized luminosity. We investigate these results using the Foundation Supernova Survey, with a spectroscopic data release presented here, and photometry analyzed with the SALT2 light-curve fitter. We find that the Foundation data do not show significant evidence for an offset in color between SNe Ia with high and normal photospheric velocities, with $\Delta c = 0.005 \pm 0.014$. Our SALT2 analysis does show evidence for redder high-velocity SN Ia in other samples, including objects from the Carnegie Supernova Project, with a combined sample yielding $\Delta c = 0.017 \pm 0.007$. When split on velocity, the Foundation SN Ia also do not show a significant difference in Hubble diagram residual, $\Delta HR = 0.015 \pm 0.049$ mag. Intriguingly, we find that SN Ia ejecta velocity information may be gleaned from photometry, particularly in redder optical bands. For high-redshift SN Ia, these rest-frame red wavelengths will be observed by the Nancy Grace Roman Space Telescope. Our results also confirm previous work that SN Ia host-galaxy stellar mass is strongly correlated with ejecta velocity: high-velocity SN Ia are found nearly exclusively in high-stellar-mass hosts. However, host-galaxy properties alone do not explain velocity-dependent differences in supernova colors and luminosities across samples. Measuring and understanding the connection between intrinsic explosion properties and supernova environments, across cosmic time, will be important for precision cosmology with SNe Ia.Item Open Access The Impact of Observing Strategy on Cosmological Constraints with LSSTLochner, 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, ChristopherThe 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.Item Open Access The Pantheon+ Type Ia Supernova Sample: The Full Dataset and Light-Curve ReleaseScolnic, 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, WeiKangHere 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.