Carnegie Supernova Project: Classification of Type Ia Supernovae

Abstract

We use the spectroscopy and homogeneous photometry of 97 Type Ia supernovae obtained by the \emph{Carnegie Supernova Project} as well as a subset of 36 Type Ia supernovae presented by Zheng et al. (2018) to examine maximum-light correlations in a four-dimensional (4-D) parameter space: $B$-band absolute magnitude, $M_B$, \ion{Si}{2}~$\lambda 6355$ velocity, \vsi, and \ion{Si}{2} pseudo-equivalent widths pEW(\ion{Si}{2}~$\lambda 6355$) and pEW(\ion{Si}{2}~$\lambda 5972$). It is shown using Gaussian mixture models (GMMs) that the original four groups in the Branch diagram are well-defined and robust in this parameterization. We find three continuous groups that describe the behavior of our sample in [$M_B$, \vsi] space. Extending the GMM into the full 4-D space yields a grouping system that only slightly alters group definitions in the [$M_B$, \vsi] projection, showing that most of the clustering information in [$M_B$, \vsi] is already contained in the 2-D GMM groupings. However, the full 4-D space does divide group membership for faster objects between core-normal and broad-line objects in the Branch diagram. A significant correlation between $M_B$ and pEW(\ion{Si}{2}~$\lambda 5972$) is found, which implies that Branch group membership can be well-constrained by spectroscopic quantities alone. In general, we find that higher-dimensional GMMs reduce the uncertainty of group membership for objects between the originally defined Branch groups. We also find that the broad-line Branch group becomes nearly distinct with the inclusion of \vsi, indicating that this subclass of SNe Ia may be somehow different from the other groups.

arXiv comment26 pages, 19 figures, ApJ, in press

References in corpus (30)

• The NumPy array: a structure for efficient numerical computation
• Improved Distances to Type Ia Supernovae with Multicolor Light Curve Shapes: MLCS2k2
• The Reddening-Free Decline Rate Versus Luminosity Relationship for Type Ia Supernovae
• A Precise Distance Indicator: Type Ia Supernova Multicolor Light Curve Shapes
• An Open Catalog for Supernova Data
• The diversity of Type Ia Supernovae: evidence for systematics?
• Evidence for a Spectroscopic Sequence Among SNe Ia
• Timescale Stretch Parameterization of Type Ia Supernova B-band Light Curves
• The Carnegie Supernova Project: Light Curve Fitting with SNooPy
• Comparative Direct Analysis of Type Ia Supernova Spectra. II. Maximum Light
• Improved Distances to Type Ia Supernovae with Two Spectroscopic Subclasses
• The Hubble Diagram of the Calan/Tololo Type Ia Supernovae and the value of Ho
• The Carnegie Supernova Project: Intrinsic Colors of Type Ia Supernovae
• The Carnegie Supernova Project I: Third Photometry Data Release of Low-Redshift Type Ia Supernovae and Other White Dwarf Explosions
• The Carnegie Supernova Project: Absolute Calibration and the Hubble Constant
• Maximum Brightness and Post-Maximum Decline of Light Curves of SN~Ia: A Comparison of Theory and Observations
• Observational Predictions for Sub-Chandrasekhar Mass Explosions: Further Evidence for Multiple Progenitor Systems for Type Ia Supernovae
• Evidence for Two Distinct Populations of Type Ia Supernovae
• Measuring Ejecta Velocity Improves Type Ia Supernova Distances
• Spectroscopy of Type Ia Supernovae by the Carnegie Supernova Project
• Constraints on the explosion mechanism and progenitors of type Ia supernovae
• Carnegie Supernova Project-II: Extending the Near-Infrared Hubble Diagram for Type Ia Supernovae to $z\sim 0.1$
• Using Spectral Flux Ratios to Standardize SN Ia Luminosities
• Carnegie Supernova Project-II: The Near-infrared Spectroscopy Program
• Type Ia Supernova Spectral Line Ratios as Luminosity Indicators
• A probabilistic approach to emission-line galaxy classification
• Carnegie Supernova Project-II: A new method to photometrically identify sub-types of extreme Type Ia Supernovae
• High-Velocity Type Ia Supernova Has a Unique Host Environment
• An Empirical Fitting Method to Type Ia Supernova Light Curves. III. A Three-Parameter Relationship: Peak Magnitude, Rise Time, and Photospheric Velocity
• A Possible Distance Bias for Type Ia Supernovae with Different Ejecta Velocities

Cited by in corpus (16)

• Multi-Dimensional Radiative Transfer Calculations of Double Detonations of Sub-Chandrasekhar-Mass White Dwarfs
• Carnegie Supernova Project: The First Homogeneous Sample of "Super-Chandrasekhar Mass"/2003fg-like Type Ia Supernova
• The Absolute Magnitudes of 1991T-like Supernovae
• The Foundation Supernova Survey: Photospheric Velocity Correlations in Type Ia Supernovae
• Using 1991T/1999aa-like Type Ia Supernovae as Standardizable Candles
• SN 2012ij: A low-luminosity type Ia supernova and evidence for continuous distribution from 91bg-like explosion to normal ones
• Strong Near-Infrared Carbon Absorption in the Transitional Type Ia SN 2015bp
• ZTF SN Ia DR2: The spectral diversity of Type Ia supernovae in a volume-limited sample
• SN 2021fxy: Mid-Ultraviolet Flux Suppression is a Common Feature of Type Ia Supernovae
• SN 2022joj: A Peculiar Type Ia Supernova Possibly Driven by an Asymmetric Helium-shell Double Detonation
• Direct Analysis of the Broad-Line SN 2019ein: Connection with the Core-Normal SN 2011fe
• ZTF SN Ia DR2: Improved SN Ia colors through expanded dimensionality with SALT3+
• The Type Ia Supernova 2021hem: A 2003fg-like Event in an Apparently Hostless Environment
• SN 2025ogs: A Spectroscopically-Normal Type Ia Supernova at z = 2 as a Benchmark for Redshift Evolution
• Normal or transitional? The evolution and properties of two type Ia supernovae in the Virgo cluster
• SN 2021pfs: A Type Ia Supernova Likely Affected by Progenitor Metallicity, as Revealed by Comparison with Its Twin Counterpart