分类： 天文学 >> 天文学 提交时间： 2023-02-19
Dillon Brout
Dan Scolnic
Brodie Popovic
Adam G. Riess
Joe Zuntz
Rick Kessler
Anthony Carr
Tamara M. Davis
Samuel Hinton
David Jones
W. D'Arcy Kenworthy
Erik R. Peterson
Khaled Said
Georgie Taylor
Noor Ali
Patrick Armstrong
Pranav Charvu
Arianna Dwomoh
Antonella Palmese
Helen Qu
摘要： We present constraints on cosmological parameters from the Pantheon+ analysis of 1701 light curves of 1550 distinct Type Ia supernovae (SNe Ia) ranging in redshift from $z=0.001$ to 2.26. This work features an increased sample size, increased redshift span, and improved treatment of systematic uncertainties in comparison to the original Pantheon analysis and results in a factor of two improvement in cosmological constraining power. For a Flat$\Lambda$CDM model, we find $\Omega_M=0.334\pm0.018$ from SNe Ia alone. For a Flat$w_0$CDM model, we measure $w_0=-0.90\pm0.14$ from SNe Ia alone, H$_0=73.5\pm1.1$ km s$^{-1}$ Mpc$^{-1}$ when including the Cepheid host distances and covariance (SH0ES), and $w_0=-0.978^{+0.024}_{-0.031}$ when combining the SN likelihood with constraints from the cosmic microwave background (CMB) and baryon acoustic oscillations (BAO); both $w_0$ values are consistent with a cosmological constant. We also present the most precise measurements to date on the evolution of dark energy in a Flat$w_0w_a$CDM universe, and measure $w_a=-0.1^{+0.9}_{-2.0}$ from Pantheon+ alone, H$_0=73.3\pm1.1$ km s$^{-1}$ Mpc$^{-1}$ when including SH0ES, and $w_a=-0.65^{+0.28}_{-0.32}$ when combining Pantheon+ with CMB and BAO data. Finally, we find that systematic uncertainties in the use of SNe Ia along the distance ladder comprise less than one third of the total uncertainty in the measurement of H$_0$ and cannot explain the present "Hubble tension" between local measurements and early-Universe predictions from the cosmological model.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Yssavo Camacho-Neves
Saurabh W. Jha
Barnabas Barna
Mi Dai
Alexei V. Filippenko
Ryan J. Foley
Griffin Hosseinzadeh
D. Andrew Howell
Joel Johansson
Patrick Kelly
Wolfgang E. Kerzendorf
Lindsey A. Kwok
Conor Larison
Mark R. Magee
Curtis McCully
John T. O'Brien
Yen-Chen Pan
Viraj Pandya
Jaladh Singhal
Benjamin E. Stahl
摘要： Type Iax supernovae (SN Iax) are the largest known class of peculiar white dwarf supernovae, distinct from normal type Ia supernovae (SN Ia). The unique properties of SN Iax, especially their strong photospheric lines out to extremely late-times, allow us to model their optical spectra and derive physical parameters for the long-lasting photosphere. We present an extensive spectral timeseries, including 21 new spectra, of SN Iax 2014dt from +11 to +562 days after maximum light. We are able to reproduce the entire timeseries with a self-consistent, nearly unaltered deflagration explosion model from Fink et al. (2014) using TARDIS, an open-source radiative transfer code (Kerzendorf & Sim 2014; Kerzendorf et al. 2023). We find that the photospheric velocity of SN 2014dt slows its evolution between +64 and +148 days, which closely overlaps the phase when we see SN 2014dt diverge from the normal spectral evolution of SN Ia (+90 to +150 days). The photospheric velocity at these epochs, ~ 400--1000 km s$^{-1}$, may demarcate a boundary within the ejecta below which the physics of SN Iax and normal SN Ia differ. Our results suggest that SN 2014dt is consistent with a weak deflagration explosion model that leaves behind a bound remnant and drives an optically thick, quasi-steady-state wind creating the photospheric lines at late times. The data also suggest that this wind may weaken at epochs past +450 days, perhaps indicating a depleted radioactive power source.
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