Using Line Profiles to Test the Fraternity of Type Ia Supernovae at High and Low Redshifts**Based in part on observations obtained at the Cerro Tololo Inter-American Observatory, which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under cooperative agreement with the National Science Foundation (NSF); the European Southern Observatory, Chile (ESO program 170.A-0519); the Gemini Observatory, which is operated by AURA under a cooperative agreement with the NSF on behalf of the Gemini partnership (the NSF [United States], the Particle Physics and Astronomy Research Council [United Kingdom], the National Research Council [Canada], CONICYT [Chile], the Australian Research Council [Australia], CNPq [Brazil], and CONICET [Argentina]) (programs GN-2002B-Q-14, GN-2003B-Q-11, and GS-2003B-Q-11); the Magellan Telescopes at Las Campanas Observatory; the MMT Observatory, a joint facility of the Smithsonian Institution and the University of Arizona; and the F
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Using archival data of low-redshift (z < 0.01; Center for Astrophysics and SUSPECT databases) Type Ia supernovae (SNe Ia) and recent observations of high-redshift (0.16 < z < 0.64) SNe Ia, we study the "uniformity" of the spectroscopic properties of nearby and distant SNe Ia. We find no difference in the measurements we describe here. In this paper we base our analysis solely on line-profile morphology, focusing on measurements of the velocity location of maximum absorption (v abs) and peak emission (v peak). Our measurement technique makes it easier to compare low and high signal-to-noise ratio observations. We also quantify the associated sources of error, assessing the effect of line blending with assistance from the parameterized code SYNOW. We find that the evolution of v abs and v peak for our sample lines (Ca II 3945, Si II 6355, and S II 5454, 5640) is similar for both the low- and high-redshift samples. We find that v abs for the weak S II 5454, 5640 lines and v peak for S II 5454 can be used to identify fast-declining [m 15(B) > 1.7] SNe Ia, which are also subluminous. In addition, we give the first direct evidence in two high-z SN Ia spectra of a double-absorption feature in Ca II 3945, an event also observed, although infrequently, in low-redshift SN Ia spectra (6 out of 22 SNe Ia in our local sample). Moreover, echoing the recent studies of Dessart & Hillier in the context of Type II supernovae (SNe II), we see similar P Cygni line profiles in our large sample of SN Ia spectra. First, the magnitude of the velocity location at maximum profile absorption may underestimate that at the continuum photosphere, as observed, for example, in the optically thinner line S II 5640. Second, we report for the first time the unambiguous and systematic intrinsic blueshift of peak emission of optical P Cygni line profiles in SN Ia spectra, by as much as 8000 km s -1. All the high-z SNe Ia analyzed in this paper were discovered and followed up by the ESSENCE collaboration and are now publicly available. 2006. The American Astronomical Society. All rights reserved.
Blondin, S., Dessart, L., Leibundgut, B., Branch, D., Hflich, P., Tonry, J. L., ... Suntzeff, N. B.
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Blondin, Stéphane||Dessart, Luc||Leibundgut, Bruno||Branch, David||Höflich, Peter||Tonry, John L||Matheson, Thomas||Foley, Ryan J||Chornock, Ryan||Filippenko, Alexei V||Sollerman, Jesper||Spyromilio, Jason||Kirshner, Robert P||Wood-Vasey, W Michael||Clocchiatti, Alejandro||Aguilera, Claudio||Barris, Brian||Becker, Andrew C||Challis, Peter||Covarrubias, Ricardo||Davis, Tamara M||Garnavich, Peter||Hicken, Malcolm||Jha, Saurabh||Krisciunas, Kevin||Li, Weidong||Miceli, Anthony||Miknaitis, Gajus||Pignata, Giuliano||Prieto, Jose Luis||Rest, Armin||Riess, Adam G||Salvo, Maria Elena||Schmidt, Brian P||Smith, R Chris||Stubbs, Christopher W||Suntzeff, Nicholas B
