Browsing by Author "Riess, AG"

Now showing 1 - 5 of 5

Open Access
A Reference Survey for Supernova Cosmology with the Nancy Grace Roman Space Telescope
Rose, BM; Baltay, C; Hounsell, R; Macias, P; Rubin, D; Scolnic, D; Aldering, G; Bohlin, R; Dai, M; Deustua, SE; Foley, RJ; Fruchter, A; Galbany, L; Jha, SW; Jones, DO; Joshi, BA; Kelly, PL; Kessler, R; Kirshner, RP; Mandel, KS; Perlmutter, S; Pierel, J; Qu, H; Rabinowitz, D; Rest, A; Riess, AG; Rodney, S; Sako, M; Siebert, MR; Strolger, L; Suzuki, N; Thorp, S; Dyk, SD Van; Wang, K; Ward, SM; Wood-Vasey, WM
This note presents an initial survey design for the Nancy Grace Roman High-latitude Time Domain Survey. This is not meant to be a final or exhaustive list of all the survey strategy choices, but instead presents a viable path towards achieving the desired precision and accuracy of dark energy measurements using Type Ia supernovae (SNe Ia). We describe a survey strategy that use six filters (RZYJH and F) and the prism on the Roman Wide Field Instrument. This survey has two tiers, one "wide" which targets SNe Ia at redshifts up to 1 and one "deep" targeting redshifts up to 1.7; for each, four filters are used (with Y and J used in both tiers). We propose one field each in the north and south continuous viewing zones, and expect to obtain high-quality distances of $\sim$12,000 SNe Ia with $\sim$5,000 at z > 1. We propose a wide-tier area of $\sim$19 deg$^2$ and a deep tier of $\sim$5 deg$^2$. Exposure times range from 100 s to 900 s for imaging and 900 s to 3600 s for the prism. These exposure times would reach $\sim$25.5 mag and $\sim$26.5 mag for the wide and deep tiers respectively, with deep co-add stacks reaching $\sim$28 mag and $\sim$29 mag. The total survey spans two years, with a total allocation time of six months, and a cadence of $\sim$5 days.
Open Access
Cosmic Distances Calibrated to 1% Precision with Gaia EDR3 Parallaxes and Hubble Space Telescope Photometry of 75 Milky Way Cepheids Confirm Tension with LambdaCDM
Riess, AG; Casertano, S; Yuan, W; Bradley Bowers, J; Macri, L; Zinn, JC; Scolnic, D
We present an expanded sample of 75 Milky Way Cepheids with Hubble Space Telescope (HST) photometry and Gaia EDR3 parallaxes which we use to recalibrate the extragalactic distance ladder and refine the determination of the Hubble constant. All HST observations were obtained with the same instrument (WFC3) and filters (F555W, F814W, F160W) used for imaging of extragalactic Cepheids in Type Ia supernova (SN Ia) hosts. The HST observations used the WFC3 spatial scanning mode to mitigate saturation and reduce pixel-to-pixel calibration errors, reaching a mean photometric error of 5 millimags per observation. We use new Gaia EDR3 parallaxes, vastly improved since DR2, and the Period-Luminosity (PL) relation of these Cepheids to simultaneously calibrate the extragalactic distance ladder and to refine the determination of the Gaia EDR3 parallax offset. The resulting geometric calibration of Cepheid luminosities has 1.0% precision, better than any alternative geometric anchor. Applied to the calibration of SNe~Ia, it results in a measurement of the Hubble constant of 73.0 +/- 1.4 km/sec/Mpc, in good agreement with conclusions based on earlier Gaia data releases. We also find the slope of the Cepheid PL relation in the Milky Way, and the metallicity dependence of its zeropoint, to be in good agreement with the mean values derived from other galaxies. In combination with the best complementary sources of Cepheid calibration, we reach 1.8% precision and find H_0=73.2 +/- 1.3 km/sec/Mpc, a 4.2 sigma difference with the prediction from Planck CMB observations under LambdaCDM. We expect to reach ~1.3% precision in the near term from an expanded sample of ~40 SNe Ia in Cepheid hosts.
Open Access
Cosmological model insensitivity of local $H_0$ from the Cepheid distance ladder
Dhawan, S; Brout, D; Scolnic, D; Goobar, A; Riess, AG; Miranda, V
The observed tension ($\sim 9\%$ difference) between the local distance ladder measurement of the Hubble constant, $H_0$, and its value inferred from the cosmic microwave background (CMB) could hint at new, exotic, cosmological physics. We test the impact of the assumption about the expansion history of the universe ($0.01
Open Access
No Evidence for Type Ia Supernova Luminosity Evolution: Evidence for Dark Energy is Robust
Rose, BM; Rubin, D; Cikota, A; Deustua, SE; Dixon, S; Fruchter, A; Jones, DO; Riess, AG; Scolnic, DM
Type Ia Supernovae (SNe Ia) are powerful standardized candles for constraining the cosmological model and provided the first evidence of accelerated expansion. Their precision derives from empirical correlations now measured from $>1000$ SNe Ia between their luminosities, light curve shapes, colors and most recently a modest relationship with the mass of their host galaxy. As mass correlates with other host properties, these have been investigated to improve SN Ia standardization though none have been shown to significantly alter the determination of cosmological parameters. We re-examine a recent claim, based on 34 SN Ia in nearby passive host galaxies, of a 0.05 mag/Gyr dependence of standardized SN Ia luminosity on host age which if extrapolate to higher redshifts, might accrue to 0.25 mag challenging the inference of dark energy. We reanalyze this sample of hosts using both the original method and a Bayesian Hierarchical Model and find after a fuller accounting of the errors the significance for a dependence on age to be $\leq2\sigma$ and $\sim1\sigma$ after removal of a single poorly-measured SN. To test the claim that a trend seen in old stellar populations can be applied to younger ages, we extend our analysis to a larger sample which includes young hosts. We find the residual dependence of host age (after all standardization typically employed for cosmological measurements) to be $0.0011\pm0.0018$ mag/Gyr ($0.6\sigma$) for 254 SNe Ia from the Pantheon sample, consistent with no trend and strongly ruling out the large but low significance trend claimed from the passive hosts.
Open Access
The Foundation Supernova Survey: Photospheric Velocity Correlations in Type Ia Supernovae
Dettman, 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, ASB
The 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.