Studying the ultraviolet spectrum of the first spectroscopically confirmed supernova at Redshift Two

Smith, M., Sullivan, M., Nichol, R. C., Galbany, L., D'Andrea, C. B., Inserra, Cosimo ORCID: https://orcid.org/0000-0002-3968-4409, Lidman, C., Rest, A., Schirmer, M., Filippenko, A. V., Zheng, W., Cenko, S. Bradley, Angus, C. R., Brown, P. J., Davis, T. M., Finley, D. A., Foley, R. J., González-Gaitán, S., Gutiérrez, C. P., Kessler, R., Kuhlmann, S., Marriner, J., Möller, A., Nugent, P. E., Prajs, S., Thomas, R., Wolf, R., Zenteno, A., Abbott, T. M. C., Abdalla, F. B., Allam, S., Annis, J., Bechtol, K., Benoit-Lévy, A., Bertin, E., Brooks, D., Burke, D. L., Rosell, A. Carnero, Kind, M. Carrasco, Carretero, J., Castander, F. J., Crocce, M., Cunha, C. E., Costa, L. N. da, Davis, C., Desai, S., Diehl, H. T., Doel, P., Eifler, T. F., Flaugher, B., Fosalba, P., Frieman, J., García-Bellido, J., Gaztanaga, E., Gerdes, D. W., Goldstein, D. A., Gruen, D., Gruendl, R. A., Gschwend, J., Gutierrez, G., Honscheid, K., James, D. J., Johnson, M. W. G., Kuehn, K., Kuropatkin, N., Li, T. S., Lima, M., Maia, M. A. G., Marshall, J. L., Martini, P., Menanteau, F., Miller, C. J., Miquel, R., Ogando, R. L. C., Petravick, D., Plazas, A. A., Romer, A. K., Rykoff, E. S., Sako, M., Sanchez, E., Scarpine, V., Schindler, R., Schubnell, M., Sevilla-Noarbe, I., Smith, R. C., Soares-Santos, M., Sobreira, F., Suchyta, E., Swanson, M. E. C., Tarle, G. and Walker, A. R. 2018. Studying the ultraviolet spectrum of the first spectroscopically confirmed supernova at Redshift Two. Astrophysical Journal 854 (1) , 37. 10.3847/1538-4357/aaa126

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Abstract

We present observations of DES16C2nm, the first spectroscopically confirmed hydrogen-free superluminous supernova (SLSN-I) at redshift $z\approx 2$. 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 $U=-22.26\pm 0.06$. 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 (${\lambda }_{\mathrm{rest}}\approx 2500$ 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 ($z\lt 1$) and high redshift ($z\gt 1$), but there is clear evidence of diversity in the spectrum at ${\lambda }_{\mathrm{rest}}\lt 2000\,\mathring{\rm A} $, possibly caused by the variations in temperature between events. No significant correlations are observed between spectral line velocities and photometric luminosity. Using these data, we estimate that SLSNe-I can be discovered to z = 3.8 by DES. While SLSNe-I are typically identified from their blue observed colors at low redshift ($z\lt 1$), we highlight that at $z\gt 2$ 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.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Physics and Astronomy
Publisher:	American Astronomical Society
ISSN:	0004-637X
Date of First Compliant Deposit:	2 January 2019
Date of Acceptance:	2 December 2017
Last Modified:	06 May 2023 09:07
URI:	https://orca.cardiff.ac.uk/id/eprint/118012

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