Cooke, Jeff and Ellis, Richard S. and Sullivan, Mark and Nugent, Peter and Howell, D. Andrew and Gal-Yam, Avishay and Lidman, Chris and Bloom, Joshua S. and Cenko, S. Bradley and Kasliwal, Mansi M. and Kulkarni, Shrinivas R. and Law, Nicholas M. and Ofek, Eran O. and Quimby, Robert M. (2011) Hubble Space Telescope Studies of Nearby Type Ia Supernovae: The Mean Maximum Light Ultraviolet Spectrum and its Dispersion. Astrophysical Journal Letters, 727 (2). Art. No. L35. ISSN 0004-637X http://resolver.caltech.edu/CaltechAUTHORS:20110315-085705825
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We present the first results of an ongoing campaign using the STIS spectrograph on board the Hubble Space Telescope (HST), whose primary goal is the study of near-ultraviolet (UV) spectra of local Type Ia supernovae (SNe Ia). Using events identified by the Palomar Transient Factory and subsequently verified by ground-based spectroscopy, we demonstrate the ability to locate and classify SNe Ia as early as 16 days prior to maximum light. This enables us to trigger HST in a non-disruptive mode to obtain near UV spectra within a few days of maximum light for comparison with earlier equivalent ground-based spectroscopic campaigns conducted at intermediate-redshifts, ^-_z ≃ 0.5. We analyze the spectra of 12 SNe Ia located in the Hubble flow with 0.01 < z < 0.08. Although a fraction of our eventual sample, these data, together with archival data, already provide a substantial advance over that previously available. Restricting samples to those of similar phase and stretch, the mean UV spectrum agrees reasonably closely with that at intermediate redshift, although some differences are found in the metallic absorption features. A larger sample will determine whether these differences reflect possible biases or are a genuine evolutionary effect. Significantly, the wavelength-dependent dispersion, which is larger in the UV, follows similar trends to those observed at intermediate redshift and is driven, in part, by differences in the various metallic features. While the origin of the UV dispersion remains uncertain, our comparison suggests that it may reflect compositional variations among our sample rather than being predominantly an evolutionary effect.
|Additional Information:||© 2011 American Astronomical Society. Received 2010 October 11; accepted 2010 December 6; published 2011 January 10. R.S.E. acknowledges support from DOE grant DESC0001101, M.S. from the Royal Society, A.G. from the Israeli Science Foundation and a European Union Marie Curie fellowship. Support for program GO 11721 was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA Contract NAS5-26555. The National Energy Research Scientific Computing Center, which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02- 05CH11231, provided staff, computational resources, and data storage for this project. P.E.N. acknowledges support from the US Department of Energy Scientific Discovery through Advanced Computing program under contract DE-FG02-06ER06- 04. S.B.C. acknowledges generous support from Gary and Cynthia Bengier and the Richard and Rhoda Goldman Foundation.|
|Subject Keywords:||cosmological parameters – supernovae: general – ultraviolet: general|
|Classification Code:||PACS: 97.60.Bw, 97.10.Ri, 95.30.Ky|
|Official Citation:||Jeff Cooke et al. 2011 ApJ 727 L35 doi: 10.1088/2041-8205/727/2/L35|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Benjamin Perez|
|Deposited On:||15 Mar 2011 16:29|
|Last Modified:||26 Dec 2012 13:02|
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