Carnegie Supernova Project-II: The Near-infrared Spectroscopy Program

Abstract

Corresponding author: E. Y. Hsiao ehsiao@fsu.edu * This paper includes data gathered with the 6.5-m Magellan telescopes at Las Campanas Observatory, Chile. Hsiao et al.Shifting the focus of Type Ia supernova (SN Ia) cosmology to the near-infrared (NIR) is a promising way to significantly reduce the systematic errors, as the strategy minimizes our reliance on the empirical width-luminosity relation and uncertain dust laws. Observations in the NIR are also crucial for our understanding of the origins and evolution of these events, further improving their cosmological utility. Any future experiments in the rest-frame NIR will require knowledge of the SN Ia NIR spectroscopic diversity, which is currently based on a small sample of observed spectra. Along with the accompanying paper, Phillips et al. (2018), we introduce the Carnegie Supernova Project-II (CSP-II), to follow up nearby SNe Ia in both the optical and the NIR. In particular, this paper focuses on the CSP-II NIR spectroscopy program, describing the survey strategy, instrumental setups, data reduction, sample characteristics, and future analyses on the data set. In collaboration with the Harvard-Smithsonian Center for Astrophysics (CfA) Supernova Group, we obtained 661 NIR spectra of 157 SNe Ia. Within this sample, 451 NIR spectra of 90 SNe Ia have corresponding CSP-II follow-up light curves. Such a sample will allow detailed studies of the NIR spectroscopic properties of SNe Ia, providing a different perspective on the properties of the unburned material, radioactive and stable nickel produced, progenitor magnetic fields, and searches for possible signatures of companion stars.

LSQ13ddu: a rapidly evolving stripped-envelope supernova with early circumstellar interaction signatures

“…A telluric correction was applied to the IMACS and FLOYDS spectra following the method used for the EFOSC2 spectra. Two NIR spectra were obtained with Magellan+FIRE (Simcoe et al 2013) and were reduced following the method described in Hsiao et al (2019) using the tailored pipeline firehose (Simcoe et al 2013). An absolute flux calibration was applied using coeval photometric data.…”

Type Ia Supernovae Are Excellent Standard Candles in the Near-infrared

“…This was followed by a second SweetSpot data release, which included a total of 33 SN Ia with 168 JHK s observations in the redshift range 0.02 < z < 0.09, well into the smooth Hubble flow, but which did not yet include NIR Hubble diagrams (Weyant et al 2018 Krisciunas et al 2017), was recently analyzed in Burns et al (2018), which found peculiar velocity corrected Hubble diagram dispersions of ∼ 0.08 − 0.15 mag, depending on the subset of the 120 SN Ia they considered. Additional CSP-II photometric data, to be published in 2019, was recently described in Phillips et al 2019. Hsiao et al (2019 present an overview of the NIR SN Ia spectroscopy obtained by the CSP and the Center for Astrophysics (CfA) Supernova Group.…”

SN 2017gmr: An Energetic Type II-P Supernova with Asymmetries

“…Gemini/GNIRS data were taken in cross-dispersed mode with the 0 675 slit, yielding continuous wavelength coverage from 0.8 to 2.5 μm and an R∼1000. These data were reduced with the XDGNIRS pipeline provided by Gemini Observatory, as described in Sand et al (2016) and Hsiao et al (2019).…”

“…IRTF spectra were taken in SXD mode and the 0 5 slit, yielding wavelength coverage from ∼0.8 to 2.4 μm and R∼1200. These data were reduced using the publicly available Spextool software package (Cushing et al 2004), as described in Hsiao et al (2019).…”