Gemini Spectroscopy of Supernovae from the Supernova Legacy Survey: Improving High-Redshift Supernova Selection and Classification

By D. Howell, Mark Sullivan, K. Perrett, T. Bronder, I. Hook, P. Astier, E. Aubourg, D. Balam, S. Basa, R. Carlberg and 15 more. 2005

184 citations recorded by the source corpus.

We present new techniques for improving the efficiency of supernova (SN) classification at high redshift using 64 candidates observed at Gemini North and South during the first year of the Supernova Legacy Survey (SNLS). The SNLS is an ongoing 5 year project with the goal of measuring the equation of state of dark energy by discovering and following over 700 high-redshift SNe Ia using data from the Canada-France-Hawaii Telescope Legacy Survey. We achieve an improvement in the SN Ia spectroscopic confirmation rate: at Gemini 71% of candidates are now confirmed as SNe Ia, compared to 54% using the methods of previous surveys. This is despite the comparatively high redshift of this sample, in which the median SN Ia redshift is z = 0.81 (0.155 ≤ z ≤ 1.01). These improvements were realized because we use the unprecedented color coverage and light curve sampling of the SNLS to predict whether a candidate is a SN Ia and to estimate its redshift, before obtaining a spectrum, using a new technique called the "SN photo-z." In addition, we have improved techniques for galaxy subtraction and SN template χ2 fitting, allowing us to identify candidates even when they are only 15% as bright as the host galaxy. The largest impediment to SN identification is found to be host galaxy contamination of the spectrum—when the SN was at least as bright as the underlying host galaxy the target was identified more than 90% of the time. However, even SNe in bright host galaxies can be easily identified in good seeing conditions. When the image quality was better than 0.″55, the candidate was identified 88% of the time. Over the 5 year course of the survey, using the selection techniques presented here, we will be able to add ~170 more confirmed SNe Ia than would be possible using previous methods.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/f1b7cdbcf1da50414eeeab41c5859b8739306b8a

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

1. A. Filippenko
2. A. Riess
3. R. Kirshner
4. S. Jha
5. S. Smartt
6. D. Schneider
7. Weidong Li
8. N. Smith

In Nuclear and High Energy Physics

1. R. Kirshner
2. S. Smartt
3. S. Jha
4. A. Filippenko
5. B. Leibundgut
6. A. Riess
7. Weidong Li
8. Daniel J. Eisenstein

Citations in the corpus

• A CONTINUUM OF H- TO He-RICH TIDAL DISRUPTION CANDIDATES WITH A PREFERENCE FOR E+A GALAXIES (2014, methodology): “These events were typed using both visual and automatic classifications carried out with the SN spectral fitting codes Superfit (Howell et al. 2005) and SNID (Blondin & Tonry 2007).”
• Rates and Properties of Type Ia Supernovae as a Function of Mass and Star Formation in Their Host Galaxies (2006, background): “SN candidates are observed spectroscopically at the ESO-VLT, Gemini or W. M. Keck telescopes to confirm their nature and to measure a spectroscopic redshift either from host galaxy features or from the SN itself (see Howell et al. 2005, for an overview of the spectroscopic typing).”
• SPECTRA AND HUBBLE SPACE TELESCOPE LIGHT CURVES OF SIX TYPE Ia SUPERNOVAE AT 0.511 < z < 1.12 AND THE UNION2 COMPILATION (2010, methodology): “To classify the SNe, we used the classification scheme described in Lidman et al. (2005) and added to it the confidence index (CI) described in Howell et al. (2005).”
• IMPROVED DARK ENERGY CONSTRAINTS FROM ∼100 NEW CfA SUPERNOVA TYPE Ia LIGHT CURVES (2009, background): “Comparisons of high and low redshift spectra reveal good agreement (e.g., Matheson et al. 2005; Hook et al. 2005; Howell et al. 2005; Foley et al. 2005; Blondin et al. 2006; Foley et al. 2008).”
• OPTICAL SPECTRA OF 73 STRIPPED-ENVELOPE CORE-COLLAPSE SUPERNOVAE (2014, background): “…2010; Dessart et al. 2011; Hachinger et al. 2012; Dessart et al. 2012) and for inclusions in SN identification schemes, both spectroscopic (e.g., Howell et al. 2005; Blondin & Tonry 2007; Harutyunyan et al. 2008) and photometric ones that need to include the spectrally derived k-corrections…”
• CORE-COLLAPSE SUPERNOVAE FROM THE PALOMAR TRANSIENT FACTORY: INDICATIONS FOR A DIFFERENT POPULATION IN DWARF GALAXIES (2010, methodology): “Both visual and automatic classification, using Superfit (Howell et al. 2005) and SNID (Blondin et al. 2007), were carried out.”
• PESSTO: survey description and products from the first data release by the Public ESO Spectroscopic Survey of Transient Objects (2014, methodology): “Classifications are then made using one (or a combination) of the SN classification tools SNID (Blondin & Tonry 2007), GELATO (Harutyunyan et al. 2008), or SuperFIT (Howell et al. 2005).”
• Determining the Type, Redshift, and Age of a Supernova Spectrum (2006, methodology): “75%; Howell et al. 2005).”
• The Supernova Legacy Survey 3-year sample: Type Ia supernovae photometric distances and cosmological constraints , (2010, methodology): “…the spectroscopic identfication: certain SN Ia are denoted “SN Ia” (corresponding to the confidence indices CI 5 and 4 in the classification scheme of Howell et al. 2005), and probable SN Ia (CI 3) are labeled 1 SupplementaryuM-band data was also acquired as part of CFHTLS; these data were not…”
• Observational Constraints on the Nature of Dark Energy: First Cosmological Results from the ESSENCE Supernova Survey (2007, methodology): “The question of whether distant supernovae have spectra that are the same as nearby supernovae has been investigated by Coil et al. (2000), Lidman et al. (2005), Matheson et al. (2005), Hook et al. (2005), Howell et al. (2005), and Blondin et al. (2006).”
• SNLS3: CONSTRAINTS ON DARK ENERGY COMBINING THE SUPERNOVA LEGACY SURVEY THREE-YEAR DATA WITH OTHER PROBES (2011, methodology): “Nearly all our SN spectra are published1 (Howell et al. 2005; Bronder et al. 2008; Ellis et al. 2008; Balland et al. 2009; Walker et al. 2011).”
• New Hubble Space Telescope Discoveries of Type Ia Supernovae at z ≥ 1: Narrowing Constraints on the Early Behavior of Dark Energy (2006, methodology): “…properties of SNe Ia (including the far-UV flux, e.g., as presented in the last section) provide strong evidence for uniformity across redshift and no indication (thus far) of redshiftdependent differences (e.g., M. Sullivan, 2005, private communication; Howell et al. 2005; Blondin et al. 2006).”
• VARIABLE SODIUM ABSORPTION IN A LOW-EXTINCTION TYPE Ia SUPERNOVA, (2009, methodology): “Analysis with the Superfit spectral fitting code of Howell et al. (2005) indicates that SN 2007le is most similar to spectra of the highly reddened type Ia SN 2002bo at 11 days before maximum from Benetti et al. (2004), while the SNID package (Blondin & Tonry 2007) finds a best fit to early spectra…”
• The dependence of Type Ia Supernovae luminosities on their host galaxies (2010, background): “The light curves and other details for these SNe can be found in Guy et al. (2010), and spectroscopic information is taken from Howell et al. (2005), Bronder et al. (2008), Ellis et al. (2008), Balland et al. (2009), and Walker et al. (2010).”
• K-Corrections and Spectral Templates of Type Ia Supernovae (2007, background): “For this we use three actual SNLS SNe Ia, 03D4dy (z ¼ 0:604), 04D1si (z ¼ 0:701), and 04D1ks (z ¼ 0:798).”
• SUPERNOVA CONSTRAINTS AND SYSTEMATIC UNCERTAINTIES FROM THE FIRST THREE YEARS OF THE SUPERNOVA LEGACY SURVEY (2011, methodology): “=3 in the scheme of Howell et al. (2005)) lies somewhere between the “gold” and “silver” classification scheme of Riess et al. (2007) for spectroscopically typed SN.”
• Improved cosmological constraints from a joint analysis of the SDSS-II and SNLS supernova samples (2014, background): “About 1000 supernovae were discovered in the redshift range 0.2 < z < 1, and 420 of them have been confirmed as a type Ia by massive spectroscopic follow-up programs (Howell et al. 2005; Bronder et al. 2008; Ellis et al. 2008; Balland et al. 2009; Walker et al. 2011).”