First Cosmology Results using Type Ia Supernovae from the Dark Energy Survey: Constraints on Cosmological Parameters (1811.02374v4)

Abstract: We present the first cosmological parameter constraints using measurements of type Ia supernovae (SNe Ia) from the Dark Energy Survey Supernova Program (DES-SN). The analysis uses a subsample of 207 spectroscopically confirmed SNe Ia from the first three years of DES-SN, combined with a low-redshift sample of 122 SNe from the literature. Our "DES-SN3YR" result from these 329 SNe Ia is based on a series of companion analyses and improvements covering SN Ia discovery, spectroscopic selection, photometry, calibration, distance bias corrections, and evaluation of systematic uncertainties. For a flat LCDM model we find a matter density Omega_m = 0.331 +_ 0.038. For a flat wCDM model, and combining our SN Ia constraints with those from the cosmic microwave background (CMB), we find a dark energy equation of state w = -0.978 +_ 0.059, and Omega_m = 0.321 +_ 0.018. For a flat w0waCDM model, and combining probes from SN Ia, CMB and baryon acoustic oscillations, we find w0 = -0.885 +_ 0.114 and wa = -0.387 +_ 0.430. These results are in agreement with a cosmological constant and with previous constraints using SNe Ia (Pantheon, JLA).

Summary of "First Cosmology Results using Type Ia Supernovae from the Dark Energy Survey: Constraints on Cosmological Parameters"

The paper in discussion presents the first constraints on cosmological parameters using type Ia supernovae (SNe Ia) data from the Dark Energy Survey Supernova Program (DES-SN). The paper utilizes a robust subsample of 207 spectroscopically confirmed SNe Ia from the initial three years of DES-SN observations, augmented by a complementary low-redshift sample of 122 SNe from previous literature.

Overview of Methodology

The analysis focuses on refining key techniques across several domains of observational cosmology. Notable advances include enhanced spectroscopic selection methodologies, improved photometric calibration, and more precise distance bias correction models. The researchers implemented improvements in instrumentation, notably utilizing detectors with elevated $z$-band sensitivity and expansive photometric calibration, allowing for increased precision in high-redshift supernovae observations.

Two cosmological models were primarily assessed: the flat ΛCDM model and the flat $w_0w_a$CDM model. The analysis concerning the flat ΛCDM model offers insights into matter density ($\Omega_m$) and the equation of state parameter $w$. A combination of SN Ia data with cosmic microwave background (CMB) observations yielded a dark energy equation of state of $w = -0.978$ and a matter density of $\Omega_m = 0.321$, indicating consistency with previous studies such as Pantheon and JLA.

Key Numerical Findings

For the flat ΛCDM model, the analysis revealed:

• A matter density ($\Omega_m$) value of $0.331$ derived from combining DES-SN data.
• With the addition of CMB constraints, $\Omega_m$ was refined to $0.321$. This added dataset led to the dark energy equation of state parameter $w = -0.978$, maintaining compatibility with the cosmological constant hypothesis.

In addressing the flat $w_0w_a$CDM model, incorporating both SNe Ia, CMB, and baryon acoustic oscillations (BAO) gave evidence of:

• A dynamic dark energy equation-of-state parameterization, with $w_0 = -0.885$ and $w_a = -0.387$. The research underscores that these findings align with a cosmological constant framework, affirming the results that are considered within the observational and theoretical precision of current cosmic measurements.

Implications and Future Directions

This research contributes significantly to the understanding of cosmological parameters, offering refined constraints that substantiate a cosmological constant as a viable explanation for dark energy.

The continuing work within DES will aim to mitigate systematic uncertainties and enhance calibration processes in anticipation of the more extensive five-year data release. Planned revisions in instrumentation and analysis techniques are expected to further diminish systematic errors. As the DES expands its observational dataset, future analyses will provide more granular insights into the fundamental questions of dark energy and cosmic acceleration.

The group emphasizes the importance of these findings as a precursor to forthcoming Stage-IV dark energy experiments such as LSST and WFIRST, which are predicted to harness significantly larger datasets and implement even more advanced calibrations and methodological refinements for astronomically driven inquiries into the universe's expansion.