# Browsing by Author "Brout, Dillon"

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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 It's Dust: Solving the Mysteries of the Intrinsic Scatter and Host-Galaxy Dependence of Standardized Type Ia Supernova BrightnessesBrout, Dillon; Scolnic, DanielThe use of Type Ia Supernovae (SNe Ia) as cosmological tools has motivated significant effort to: understand what drives the intrinsic scatter of SN Ia distance modulus residuals after standardization, characterize the distribution of SN Ia colors, and explain why properties of the host galaxies of the SNe correlate with SN Ia distance modulus residuals. We use a compiled sample of $\sim1450$ spectroscopically confirmed, photometric light-curves of SN Ia and propose a solution to these three problems simultaneously that also explains an empirical 11$\sigma$ detection of the dependence of Hubble residual scatter on SN Ia color. We introduce a physical model of color where intrinsic SN Ia colors with a relatively weak correlation with luminosity are combined with extrinsic dust-like colors ($E(B-V)$) with a wide range of extinction parameter values ($R_V$). This model captures the observed trends of Hubble residual scatter and indicates that the dominant component of SN Ia intrinsic scatter is from variation in $R_V$. We also find that the recovered $E(B-V)$ and $R_V$ distributions differ based on global host-galaxy stellar mass and this explains the observed correlation ($\gamma$) between mass and Hubble residuals seen in past analyses as well as an observed 4.5$\sigma$ dependence of $\gamma$ on SN Ia color. This finding removes any need to prescribe different intrinsic luminosities to different progenitor systems. Finally we measure biases in the equation-of-state of dark energy ($w$) up to $|\Delta w|=0.04$ by replacing previous models of SN color with our dust-based model; this bias is larger than any systematic uncertainty in previous SN Ia cosmological analyses.Item Open Access SOAR/Goodman Spectroscopic Assessment of Candidate Counterparts of the LIGO--Virgo Event GW190814Tucker, Douglas; Wiesner, Matthew; Allam, Sahar; Soares-Santos, Marcelle; Bom, Clecio de; Butner, Melissa; Garcia, Alyssa; Morgan, Robert; Olivares, Felipe; Palmese, Antonella; Santana-Silva, Luidhy; Shrivastava, Anushka; Annis, James; Garcia-Bellido, Juan; Gill, Mandeep; Herner, Kenneth; Kilpatrick, Charles; Makler, Martin; Sherman, Nora; Amara, Adam; Lin, Huan; Smith, Mathew; Swann, Elizabeth; Arcavi, Iair; Bachmann, Tristan; Bechtol, Keith; Berlfein, Federico; Briceno, Cesar; Brout, Dillon; Butler, Bobby; Cartier, Regis; Casares, Jorge; Chen, Hsin-Yu; Conselice, Christopher; Contreras, Carlos; Cook, E; Cooke, Jeff; Dage, Kristen; D'Andrea, Chris; Davis, Tamara; Carvalho, Reinaldo de; Diehl, Tom; Dietrich, Joerg; Doctor, Zoheyr; Drlica-Wagner, Alex; Drout, Maria; Farr, Ben; Finley, David; Fishbach, Maya; Foley, Ryan; Foerster-Buron, Francisco; Fosalba, Pablo; Friedel, Douglas; Frieman, Josh; Frohmaier, Christopher; Gruendl, Robert; Hartley, Will; Hiramatsu, Daichi; Holz, Daniel; Howell, Andy; Kawash, Adam; Kessler, Richard; Kuropatkin, Nikolay; Lahav, Ofer; Lundgren, Andrew; Lundquist, Michael; Malik, Umang; Mann, Andrew; Marriner, John; Marshall, Jennifer; Martinez-Vazquez, Clara; McCully, Curtis; Menanteau, Felipe; Meza, Nico; Narayan, Gautham; Neilsen, Eric; Nicolaou, Constantina; Nichol, Bob; Paz-Chinchon, Francisco; Pereira, Maria; Pineda, Jonathan; Points, Sean; Quirola, Jonathan; Rembold, Sandro; Rest, Armin; Rodriguez, Osmar; Romer, Kathy; Sako, Masao; Salim, Samir; Scolnic, Daniel; Smith, Allyn; Strader, Jay; Sullivan, Mark; Swanson, Molly; Thomas, Daniel; Valenti, Stefano; Varga, Tamas Norbert; Walker, Alistair; Weller, Jochen; Wood, Mackenna; Yanny, Brian; Zenteno, Alfredo; Aguena, Michel; Andrade-Oliveira, Felipe; Bertin, Emmanuel; Brooks, David; Burke, David; Rosell, Aurelio Carnero; Kind, Matias Carrasco; Carretero, Jorge; Costanzi, Matteo; Costa, Luiz da; Vicente, Juan De; Desai, Shantanu; Everett, Spencer; Ferrero, Ismael; Flaugher, Brenna; Gaztanaga, Enrique; Gerdes, David; Gruen, Daniel; Gschwend, Julia; Gutierrez, Gaston; Hinton, Samuel; Hollowood, Devon L; Honscheid, Klaus; James, David; Kuehn, Kyler; Lima, Marcos; Maia, Marcio; Miquel, Ramon; Ogando, Ricardo; Pieres, Adriano; Malagon, Andres Plazas; Monroy, Martin Rodriguez; Sanchez, Eusebio; Scarpine, Vic; Schubnell, Michael; Serrano, Santiago; Sevilla, Ignacio; Smith, Mathew; Suchyta, Eric; Tarle, Gregory; To, Chun-Hao; Zhang, YuanyuanOn 2019 August 14 at 21:10:39 UTC, the LIGO/Virgo Collaboration (LVC) detected a possible neutron star-black hole merger (NSBH), the first ever identified. An extensive search for an optical counterpart of this event, designated GW190814, was undertaken using DECam on the CTIO Blanco 4-m telescope. Target of opportunity interrupts were issued on 8 separate nights to observe 11 candidates using the SOAR Goodman Spectrograph in order to assess whether any of these transients was likely to be an optical counterpart of the possible NSBH merger. Here, we describe the process of observing with the SOAR Goodman spectrograph, the analysis of our spectra, our spectroscopic typing methodology, and our resultant conclusion that none of the candidates corresponded to the black hole-neutron star merger but were all instead other transient events. Finally, we describe the lessons learned from this effort. Application of these lessons will be critical for a successful community spectroscopic follow-up program for LVC season 4 (O4) and beyond.Item Open Access The Pantheon+ Analysis: Dependence of Cosmological Constraints on Photometric-Zeropoint Uncertainties of Supernova SurveysBrownsberger, Sasha; Brout, Dillon; Scolnic, Daniel; Stubbs, Christopher W; Riess, Adam GType Ia supernovae (SNe Ia) measurements of the Hubble constant, H$_0$, the cosmological mass density, $\Omega_M$, and the dark energy equation-of-state parameter, $w$, rely on numerous SNe surveys using distinct photometric systems across three decades of observation. Here, we determine the sensitivities of the upcoming SH0ES+Pantheon+ constraints on H$_0$, $\Omega_M$, and $w$ to unknown systematics in the relative photometric zeropoint calibration between the 17 surveys that comprise the Pantheon+ supernovae data set. Varying the zeropoints of these surveys simultaneously with the cosmological parameters, we determine that the SH0ES+Pantheon+ measurement of H$_0$ is robust against inter-survey photometric miscalibration, but that the measurements of $\Omega_M$ and $w$ are not. Specifically, we find that miscalibrated inter-survey systematics could represent a source of uncertainty in the measured value of H$_0$ that is no larger than $0.2$ km s$^{-1}$ Mpc$^{-1}$. This modest increase in H$_0$ uncertainty could not account for the $7$ km s$^{-1}$ Mpc$^{-1}$ "Hubble Tension" between the SH0ES measurement of H$_0$ and the Planck $\Lambda$CDM-based inference of H$_0$. However, we find that the SH0ES+Pantheon+ best-fit values of $\Omega_M$ and $w$ respectively slip, to first order, by $0.04$ and $-0.17$ per $25$ mmag of inter-survey calibration uncertainty, underscoring the vital role that cross-calibration plays in accurately measuring these parameters. Because the Pantheon+ compendium contains many surveys that share low-$z$ Hubble Flow and Cepheid-paired SNe, the SH0ES+Pantheon+ joint constraint of H$_0$ is robust against inter-survey photometric calibration errors, and such errors do not represent an impediment to jointly using SH0ES+Pantheon+ to measure H$_0$ to 1% accuracy.Item Open Access The Pantheon+ Analysis: Evaluating Peculiar Velocity Corrections in Cosmological Analyses with Nearby Type Ia SupernovaePeterson, Erik R; Kenworthy, W D'Arcy; Scolnic, Daniel; Riess, Adam G; Brout, Dillon; Carr, Anthony; Courtois, Helene; Davis, Tamara; Dwomoh, Arianna; Jones, David O; Popovic, Brodie; Rose, Benjamin M; Said, KhaledSeparating the components of redshift due to expansion and motion in the nearby universe ($z<0.1$) is critical for using Type Ia Supernovae (SNe Ia) to measure the Hubble constant ($H_0$) and the equation-of-state parameter of dark energy ($w$). Here, we study the two dominant 'motions' contributing to nearby peculiar redshifts: large-scale, coherent-flow (CF) motions and small-scale motions due to gravitationally-associated galaxies deemed to be in a galaxy group. We use a set of 585 low-$z$ SNe from the Pantheon+ sample, and evaluate the efficacy of corrections to these motions by measuring the improvement of SN distance residuals. We study multiple methods for modeling the large and small-scale motions and show that while group assignments and CF corrections individually contribute to small improvements in Hubble residual scatter, the greatest improvement comes from the combination of the two (relative standard deviation of the Hubble residuals RSD improves from 0.167 mag to 0.157 mag). We find the optimal flow corrections derived from various local density maps significantly reduce Hubble residuals while raising $H_0$ by $\sim0.4$ km s$^{-1}$ Mpc$^{-1}$ as compared to using CMB redshifts, disfavoring the hypothesis that unrecognized local structure could resolve the Hubble tension. We estimate that the systematic uncertainties in cosmological parameters after optimally correcting redshifts are 0.08-0.17 km s$^{-1}$ Mpc$^{-1}$ in $H_0$ and 0.02-0.03 in $w$ which are smaller than the statistical uncertainties for these measurements: 1.5 km s$^{-1}$ Mpc$^{-1}$ for $H_0$ and 0.04 for $w$.Item Open Access The Pantheon+ Analysis: Forward-Modeling the Dust and Intrinsic Colour Distributions of Type Ia Supernovae, and Quantifying their Impact on Cosmological InferencesPopovic, Brodie; Brout, Dillon; Kessler, Richard; Scolnic, DanielRecent studies have shown that the observed colour distributions of Type Ia SNe (SNIa) are well-described by a combination of distributions from dust and intrinsic colour. Here we present a new forward-modeling fitting method (Dust2Dust) to measure the parent dust and colour distributions, including their dependence on host-galaxy mass. At each fit step, the SNIa selection efficiency is determined from a large simulated sample that is re-weighted to reflect the proposed distributions. We use five separate metrics to constrain the Dust2Dust parameters: distribution of fitted light-curve colour $c$, cosmological residual trends with $c$, cosmological residual scatter with $c$, fitted colour-luminosity relationship $\beta_{\rm SALT2}$, and intrinsic scatter $\sigma_{\rm int}$. Using the Pantheon+ data sample, we present results for a Dust2Dust fit that includes 4 parameters describing intrinsic colour variations and 8 parameters describing dust. Furthermore, we propagate the Dust2Dust parameter uncertainties and covariance to the dark energy equation-of-state $w$ and Hubble constant H$_0$: we find $\sigma_w = 0.005$ and $\sigma_{\textrm{H}_0} = 0.145~$km/s/Mpc. The Dust2Dust code is publically available.Item Open Access The Pantheon+ Analysis: Improving the Redshifts and Peculiar Velocities of Type Ia Supernovae Used in Cosmological AnalysesCarr, Anthony; Davis, Tamara M; Scolnic, Daniel; Said, Khaled; Brout, Dillon; Peterson, Erik R; Kessler, RichardWe examine the redshifts of a comprehensive set of published Type Ia supernovae, and provide a combined, improved catalog with updated redshifts. We improve on the original catalogs by using the most up-to-date heliocentric redshift data available; ensuring all redshifts have uncertainty estimates; using the exact formulae to convert heliocentric redshifts into the Cosmic Microwave Background (CMB) frame; and utilizing an improved peculiar velocity model that calculates local motions in redshift-space and more realistically accounts for the external bulk flow at high-redshifts. In total we reviewed 2821 supernova redshifts; 534 are comprised of repeat-observations of the same supernovae and 1764 pass the cosmology sample quality cuts. We found 5 cases of missing or incorrect heliocentric corrections, 44 incorrect or missing supernova coordinates, 230 missing heliocentric or CMB frame redshifts, and 1200 missing redshift uncertainties. Of the 2287 unique Type Ia supernovae in our sample (1594 of which satisfy cosmology-sample cuts) we updated 990 heliocentric redshifts. The absolute corrections range between $10^{-8} \leq \Delta z \leq 0.038$, and RMS$(\Delta z) \sim 3\times 10^{-3}$. The sign of the correction was essentially random, so the mean and median corrections are small: $4\times 10^{-4}$ and $4\times 10^{-6}$ respectively. We examine the impact of these improvements for $H_0$ and the dark energy equation of state $w$ and find that the cosmological results change by $\Delta H_0 = -0.11$ km s$^{-1}$ Mpc$^{-1}$ and $\Delta w = -0.001$, both significantly smaller than previously reported uncertainties for $H_0$ of 1.4 km s$^{-1}$ Mpc$^{-1}$ and $w$ of 0.04 respectively.Item Open Access The Pantheon+ Analysis: SuperCal-Fragilistic Cross Calibration, Retrained SALT2 Light Curve Model, and Calibration Systematic UncertaintyBrout, 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, ChristopherWe 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 $0Item Open Access The Pantheon+ Type Ia Supernova Sample: The Full Dataset and Light-Curve ReleaseScolnic, Dan; Brout, Dillon; Carr, Anthony; Riess, Adam G; Davis, Tamara M; Dwomoh, Arianna; Jones, David O; Ali, Noor; Charvu, Pranav; Chen, Rebecca; Peterson, Erik R; Popovic, Brodie; Rose, Benjamin M; Wood, Charlotte; Brown, Peter J; Coulter, David A; Dettman, Kyle G; Dimitriadis, Georgios; Filippenko, Alexei V; Foley, Ryan J; Jha, Saurabh W; Kilpatrick, Charles D; Kirshner, Robert P; Pan, Yen-Chen; Rest, Armin; Rojas-Bravo, Cesar; Siebert, Matthew R; Stahl, Benjamin E; Zheng, WeiKangHere we present 1701 light curves of spectroscopically confirmed Type Ia supernovae (SNe Ia) that will be used to infer cosmological parameters as part of the Pantheon+ SN analysis and the SH0ES (Supernovae and H0 for the Equation of State of dark energy) distance-ladder analysis. This effort is one part of a series of works that perform an extensive review of redshifts, peculiar velocities, photometric calibration, and intrinsic-scatter models of SNe Ia. The total number of light curves, which are compiled across 18 different surveys, is a significant increase from the first Pantheon analysis (1048 SNe), particularly at low redshift ($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.