Type Ia Supernova Cosmology

Leibundgut, B.; Sullivan, M.

doi:10.1007/s11214-018-0491-8

Cited by 11 publications

(5 citation statements)

References 98 publications

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“…Type Ia supernovae (SNe Ia) are believed to be 'standardisable candles' whose magnitudes can be accurately inferred from the observed light-curve by exploiting empirical correlations between the peak magnitude and the light-curve width, and are thus among the best distance indicators known (Leibundgut 2000;Leibundgut & Sullivan 2018). When their redshifts have also been measured, the luminosity distance can then be used to distinguish between cosmological models.…”

Section: Introductionmentioning

confidence: 99%

The impact of peculiar velocities on supernova cosmology

Mohayaee,

Rameez,

Sarkar

2020

Preprint

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We study correlated fluctuations of Type Ia supernova observables due to peculiar velocities of both the observer and the supernova host galaxies, and their impact on cosmological parameter estimation. We demonstrate using the CosmicFlows-3 dataset that at low redshifts the corrections for peculiar velocities in the JLA catalogue have been systematically underestimated. By querying a horizon-size N-body simulation we find that compared to a randomly placed Copernican observer, an observer in an environment like our local universe will see 2-5 times stronger correlations between supernovae in the JLA catalogue. Hence the covariances usually employed which assume a Copernican observer underestimate the effects of coherent motion of the supernova host galaxies. Although previous studies have suggested that this should have < 2% effect on cosmological parameter estimation, we find that when peculiar velocities are treated consistently the JLA data favours significantly smaller values of matter and dark energy density than in the standard ΛCDM model. A joint fit to simultaneously determine the cosmological parameters and the bulk flow finds a bulk flow faster than 200 km s −1 continuing beyond 200 Mpc. This demonstrates that the local bulk flow is an essential nuisance parameter which must be included in cosmological model fitting when analysing supernova data.

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Section: Introductionmentioning

confidence: 99%

The impact of peculiar velocities on supernova cosmology

Mohayaee,

Rameez,

Sarkar

2020

Preprint

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“…Following calibration procedures, for example the one by Phillips (1993), that correlate the width of the light curve with the peak brightness, SNe Ia exhibit a very small dispersion in their absolute magnitudes. As such, their use in cosmology is extensive and understanding them is of general interest (Leibundgut & Sullivan 2018). Colgate & McKee (1969) proposed powering of the optical and infrared (IR) displays of SNe to originate in energy deposition from the decay of radioactive 56 Ni to 56 Co and subsequently to 56 Fe.…”

Section: Introductionmentioning

confidence: 99%

Limits on stable iron in Type Ia supernovae from near-infrared spectroscopy

Flörs

Spyromilio

Maguire

et al. 2018

A&A

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We obtained optical and near-infrared spectra of Type Ia supernovae (SNe Ia) at epochs ranging from 224 to 496 days after the explosion. The spectra show emission lines from forbidden transitions of singly ionised iron and cobalt atoms. We used non-local thermodynamic equilibrium (NLTE) modelling of the first and second ionisation stages of iron, nickel, and cobalt to fit the spectra using a sampling algorithm allowing us to probe a broad parameter space. We derive velocity shifts, line widths, and abundance ratios for iron and cobalt. The measured line widths and velocity shifts of the singly ionised ions suggest a shared emitting region. Our data are fully compatible with radioactive 56 Ni decay as the origin for cobalt and iron. We compare the measured abundance ratios of iron and cobalt to theoretical predictions of various SN Ia explosion models. These models include, in addition to 56 Ni, different amounts of 57 Ni and stable 54,56 Fe. We can exclude models that produced only 54,56 Fe or only 57 Ni in addition to 56 Ni. If we consider a model that has 56 Ni, 57 Ni, and 54,56 Fe then our data imply that these ratios are 54,56 Fe / 56 Ni = 0.272 ± 0.086 and 57 Ni / 56 Ni = 0.032 ± 0.011.

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“…Type Ia supernovae (SNe Ia), owing to their standardisable luminosity, are excellent cosmological probes in the late-time Universe (see Leibundgut & Sullivan 2018, for a review of SN Ia cosmology). The SN Ia magnitude-redshift relation -or Hubble diagram 1 -is an independent probe of isotropy in the late Universe.…”

Section: Introductionmentioning

confidence: 99%

The quadrupole in the local Hubble parameter: first constraints using Type Ia supernova data and forecasts for future surveys

Dhawan¹,

Borderies²,

MacPherson³

et al. 2022

Preprint

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The cosmological principle asserts that the Universe looks spatially homogeneous and isotropic on sufficiently large scales. Given the fundamental implications of the cosmological principle, it is important to empirically test its validity on various scales. In this paper, we use the Type Ia supernova (SN Ia) magnitude-redshift relation, from both the Pantheon and JLA compilations, to constrain theoretically motivated anisotropies in the Hubble flow. In particular, we constrain the quadrupole moment in the effective Hubble parameter and the dipole moment in the effective deceleration parameter. We find no significant quadrupole term regardless of the redshift frame we use. Our results are consistent with the theoretical expectation of a quadrupole moment of a few percent at scales of ∼ 100 ℎ −1 Mpc. We place an upper limit of a ∼ 10% quadrupole amplitude relative to the monopole, 𝐻 0 , at these scales. We find that we can detect a ∼ 7% quadrupole moment at the 5𝜎 level, for a forecast low-𝑧 sample of 1055 SNe Ia. We find an exponentially decaying dipole moment of the deceleration parameter varies in significance depending on the redshift frame we use. In the heliocentric frame, as expected, it is detected at ∼ 3𝜎 significance. In the rest-frame of the cosmic microwave background (CMB), we find a marginal ∼ 2𝜎 dipole, however, after applying peculiar velocity corrections, the dipole is insignificant. Finally, we find the best-fit frame of rest relative to the supernovae to differ from that of the CMB.

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Type Ia Supernova Cosmology

Cited by 11 publications

References 98 publications

The impact of peculiar velocities on supernova cosmology

The impact of peculiar velocities on supernova cosmology

Limits on stable iron in Type Ia supernovae from near-infrared spectroscopy

The quadrupole in the local Hubble parameter: first constraints using Type Ia supernova data and forecasts for future surveys

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