The Data Release of the Sloan Digital Sky Survey-II Supernova Survey (1401.3317v1)

Abstract: This paper describes the data release of the Sloan Digital Sky Survey-II (SDSS-II) Supernova Survey conducted between 2005 and 2007. Light curves, spectra, classifications, and ancillary data are presented for 10,258 variable and transient sources discovered through repeat ugriz imaging of SDSS Stripe 82, a 300 deg2 area along the celestial equator. This data release is comprised of all transient sources brighter than r~22.5 mag with no history of variability prior to 2004. Dedicated spectroscopic observations were performed on a subset of 889 transients, as well as spectra for thousands of transient host galaxies using the SDSS-III BOSS spectrographs. Photometric classifications are provided for the candidates with good multi-color light curves that were not observed spectroscopically. From these observations, 4607 transients are either spectroscopically confirmed, or likely to be, supernovae, making this the largest sample of supernova candidates ever compiled. We present a new method for SN host-galaxy identification and derive host-galaxy properties including stellar masses, star-formation rates, and the average stellar population ages from our SDSS multi-band photometry. We derive SALT2 distance moduli for a total of 1443 SN Ia with spectroscopic redshifts as well as photometric redshifts for a further 677 purely-photometric SN Ia candidates. Using the spectroscopically confirmed subset of the three-year SDSS-II SN Ia sample and assuming a flat Lambda-CDM cosmology, we determine Omega_M = 0.315 +/- 0.093 (statistical error only) and detect a non-zero cosmological constant at 5.7 sigmas.

Overview of the Sloan Digital Sky Survey-II Supernova Survey Data Release

The publication titled "The Data Release of the Sloan Digital Sky Survey-II Supernova Survey" presents a comprehensive release of data collected from the SDSS-II Supernova Survey, conducted over three years from 2005 to 2007. The survey primarily focused on identifying and documenting transient astronomical phenomena, including a significant number of supernovae (SNe), within a dedicated 300 square degree area known as Stripe 82 along the celestial equator. This release includes data on 10,258 variable and transient sources, emphasizing the catalog's depth and the significance of the dataset in ongoing and future cosmological research.

Key Components of the Data Release

1. Extensive Dataset: The dataset encompasses light curves, spectra, and classifications for the transient sources brighter than an apparent magnitude of 22.5 in the r-band. Out of the transients identified, 4607 are confirmed or likely supernovae, making it the largest compilation of SN candidates.
2. Methodologies for Classification and Analysis: The team employed both spectroscopic and photometric approaches for SN classification. A notable contribution is the introduction of a new method for host galaxy identification, crucial for deriving galaxy properties such as stellar masses and star-formation rates.
3. Cosmological Implications: Using spectroscopically confirmed supernovae and assuming a flat ΛCDM cosmology, the researchers derived parameters such as the matter density parameter Ω_M = 0.315±0.093. The survey provides evidence for a non-zero cosmological constant at high significance, reinforcing the model of dark energy-driven acceleration in the universe's expansion.
4. Astronomical Infrastructure: The survey utilized data from a multitude of telescopes and instruments for spectroscopic confirmation, involving collaborations across various astronomical institutions.
5. Analysis and Calibration Methods: The survey used robust methods for photometric calibration and error estimation, accounting for systematic uncertainties and instrumental variations. The results from light curve models such as SALT2 and MLCS2k2 are included to facilitate comparative studies.

Implications for Future Research

The meticulous organization of the SDSS-II Supernova Survey data provides a versatile foundation for both observational and theoretical advancements in supernova cosmology. The extensive data release allows for recalibration against future datasets, offers insights into the host galaxy environments of supernovae, and supports the development of classification algorithms that can be applied to current and upcoming surveys like DES and LSST. Moreover, the constraints on cosmological parameters contribute to the growing body of evidence necessary for understanding dark energy, thus guiding theoretical approaches in cosmology.

Prospects for the Community

The availability of such a detailed dataset has multifaceted implications:

• Cosmology: Researchers can refine cosmological models by integrating these parameters with higher redshift data from other surveys.
• SN Physics: The properties derived from host galaxies also provide a probe into the progenitor systems of Type Ia supernovae, which is crucial for fine-tuning standard candle assumptions.
• Machine Learning Applications: Future machine learning algorithms can leverage this dataset for improved automated SN classification, considering the comprehensive ground-truth classifications provided.

In conclusion, the SDSS-II Supernova Survey data release not only serves as a milestone in astronomical data collection and analysis but also as a stepping stone for future explorations in the field of transient phenomena and cosmology. The rigorous approach to data classification and error management enhances the reliability of findings derived from this substantial dataset.