Browsing by Author "Ali, Noor"

Now showing 1 - 2 of 2
  • Thumbnail Image
    ItemOpen Access
    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 $0
  • Thumbnail Image
    ItemOpen Access
    The Pantheon+ Type Ia Supernova Sample: The Full Dataset and Light-Curve Release
    Scolnic, Dan; Brout, Dillon; Carr, Anthony; Riess, Adam G; Davis, Tamara M; Dwomoh, Arianna; Jones, David O; Ali, Noor; Charvu, Pranav; Chen, Rebecca; Peterson, Erik R; Popovic, Brodie; Rose, Benjamin M; Wood, Charlotte; Brown, Peter J; Coulter, David A; Dettman, Kyle G; Dimitriadis, Georgios; Filippenko, Alexei V; Foley, Ryan J; Jha, Saurabh W; Kilpatrick, Charles D; Kirshner, Robert P; Pan, Yen-Chen; Rest, Armin; Rojas-Bravo, Cesar; Siebert, Matthew R; Stahl, Benjamin E; Zheng, WeiKang
    Here we present 1701 light curves of spectroscopically confirmed Type Ia supernovae (SNe Ia) that will be used to infer cosmological parameters as part of the Pantheon+ SN analysis and the SH0ES (Supernovae and H0 for the Equation of State of dark energy) distance-ladder analysis. This effort is one part of a series of works that perform an extensive review of redshifts, peculiar velocities, photometric calibration, and intrinsic-scatter models of SNe Ia. The total number of light curves, which are compiled across 18 different surveys, is a significant increase from the first Pantheon analysis (1048 SNe), particularly at low redshift ($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.