e-Article
Studying the Ultraviolet Spectrum of the First Spectroscopically Confirmed Supernova at Redshift Two
Document Type
article
Author
Smith, M; Sullivan, M; Nichol, RC; Galbany, L; D’Andrea, CB; Inserra, C; Lidman, C; Rest, A; Schirmer, M; Filippenko, AV; Zheng, W; Cenko, S Bradley; Angus, CR; Brown, PJ; Davis, TM; Finley, DA; Foley, RJ; González-Gaitán, S; Gutiérrez, CP; Kessler, R; Kuhlmann, S; Marriner, J; Möller, A; Nugent, PE; Prajs, S; Thomas, R; Wolf, R; Zenteno, A; Abbott, TMC; Abdalla, FB; Allam, S; Annis, J; Bechtol, K; Benoit-Lévy, A; Bertin, E; Brooks, D; Burke, DL; Rosell, A Carnero; Kind, M Carrasco; Carretero, J; Castander, FJ; Crocce, M; Cunha, CE; da Costa, LN; Davis, C; Desai, S; Diehl, HT; Doel, P; Eifler, TF; Flaugher, B; Fosalba, P; Frieman, J; García-Bellido, J; Gaztanaga, E; Gerdes, DW; Goldstein, DA; Gruen, D; Gruendl, RA; Gschwend, J; Gutierrez, G; Honscheid, K; James, DJ; Johnson, MWG; Kuehn, K; Kuropatkin, N; Li, TS; Lima, M; Maia, MAG; Marshall, JL; Martini, P; Menanteau, F; Miller, CJ; Miquel, R; Ogando, RLC; Petravick, D; Plazas, AA; Romer, AK; Rykoff, ES; Sako, M; Sanchez, E; Scarpine, V; Schindler, R; Schubnell, M; Sevilla-Noarbe, I; Smith, RC; Soares-Santos, M; Sobreira, F; Suchyta, E; Swanson, MEC; Tarle, G; Walker, AR
Source
The Astrophysical Journal. 854(1)
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Language
Abstract
We present observations of DES16C2nm, the first spectroscopically confirmed hydrogen-free superluminous supernova (SLSN-I) at redshift z ≊ 2. DES16C2nm was discovered by the Dark Energy Survey (DES) Supernova Program, with follow-up photometric data from the Hubble Space Telescope, Gemini, and the European Southern Observatory Very Large Telescope supplementing the DES data. Spectroscopic observations confirm DES16C2nm to be at z = 1.998, and spectroscopically similar to Gaia16apd (a SLSN-I at z = 0.102), with a peak absolute magnitude of U = -22.26 ± 0.06. The high redshift of DES16C2nm provides a unique opportunity to study the ultraviolet (UV) properties of SLSNe-I. Combining DES16C2nm with 10 similar events from the literature, we show that there exists a homogeneous class of SLSNe-I in the UV (λrest ≊ 2500 Å), with peak luminosities in the (rest-frame) U band, and increasing absorption to shorter wavelengths. There is no evidence that the mean photometric and spectroscopic properties of SLSNe-I differ between low (z < 1) and high redshift (z > 1), but there is clear evidence of diversity in the spectrum at λrest < 2000 Å, possibly caused by the variations in temperature between events. No significant correlations are observed between spectral line velocities and photometric luminosity. Using these data, we estimate that SLSNe-I can be discovered to z = 3.8 by DES. While SLSNe-I are typically identified from their blue observed colors at low redshift (z < 1), we highlight that at z > 2 these events appear optically red, peaking in the observer-frame z-band. Such characteristics are critical to identify these objects with future facilities such as the Large Synoptic Survey Telescope, Euclid, and the Wide-field Infrared Survey Telescope, which should detect such SLSNe-I to z = 3.5, 3.7, and 6.6, respectively.