Abstract
We report the discovery of a Type Ia supernova (SNIa) at redshift z=1.55 with the infrared detector of the Wide Field Camera 3 (WFC3-IR) on the Hubble Space Telescope (HST). This object was discovered in CANDELS imaging data of the Hubble Ultra Deep Field, and followed as part of the CANDELS+CLASH Supernova project, comprising the SN search components from those two HST multi-cycle treasury programs. This is the highest redshift SNIa with direct spectroscopic evidence for classification. It is also the first SN Ia at z>1 found and followed in the infrared, providing a full light curve in rest-frame optical bands. The classification and redshift are securely defined from a combination of multi-band and multi-epoch photometry of the SN, ground-based spectroscopy of the host galaxy, and WFC3-IR grism spectroscopy of both the SN and host. This object is the first of a projected sample at z>1.5 that will be discovered by the CANDELS and CLASH programs. The full CANDELS+CLASH SN Ia sample will enable unique tests for evolutionary effects that could arise due to differences in SN Ia progenitor systems as a function of redshift. This high-z sample will also allow measurement of the SN Ia rate out to z~2, providing a complementary constraint on SN Ia progenitor models.
Highlights
In their use as “standardizable” candles, Type Ia supernovae (SNe Ia) have become one of the pillars of modern observational cosmology
The detection and follow-up observations of SN Primo are detailed in §2-6, and in §7 we explore the potential for this survey to extend the SN Ia sample to z ≈ 2
The discovery and confirmation of SN Primo demonstrates the new capability of Hubble Space Telescope (HST) to both detect and follow SNe Ia at redshifts above 1.5 using the WFC3 IR detector
Summary
In their use as “standardizable” candles, Type Ia supernovae (SNe Ia) have become one of the pillars of modern observational cosmology. SNe Ia in the low-redshift regime (0.02 z 0.1) provide the anchor for the SN Ia Hubble diagram (Jha et al 2006; Hicken et al 2009; Contreras et al 2010). These “local” SNe have been used to develop empirical tools for using light curve shapes to classify high-z SNe and measure their luminosities. At intermediate redshifts (0.1 z 1) ground-based surveys such as ESSENCE, SDSS, and SNLS14 have built up samples of hundreds of SNe Ia, testing models that assume a constant dark energy equation-of-state parameter, w0 (WoodVasey et al 2007; Kessler et al 2009a; Sullivan et al 2011). The high-redshift range (0.8 z 1.5) has been populated almost exclusively by the Hubble Space Telescope (HST) with optical surveys using the Advanced Camera for Surveys (ACS)
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