TY - JOUR
T1 - Hubble Space Telescope studies of nearby Type Ia supernovae
T2 - The mean maximum light ultraviolet spectrum and its dispersion
AU - Cooke, Jeff
AU - Ellis, Richard S.
AU - Sullivan, Mark
AU - Nugent, Peter
AU - Howell, D. Andrew
AU - Gal-Yam, Avishay
AU - Lidman, Chris
AU - Bloom, Joshua S.
AU - Cenko, S. Bradley
AU - Kasliwal, Mansi M.
AU - Kulkarni, Shrinivas R.
AU - Law, Nicholas M.
AU - Ofek, Eran O.
AU - Quimby, Robert M.
PY - 2011/2/1
Y1 - 2011/2/1
N2 - 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 intermediateredshifts, z̄ ≃ 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.
AB - 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 intermediateredshifts, z̄ ≃ 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.
KW - Cosmological parameters
KW - Supernovae: general
KW - Ultraviolet: general
UR - http://www.scopus.com/inward/record.url?scp=79960232632&partnerID=8YFLogxK
U2 - 10.1088/2041-8205/727/2/L35
DO - 10.1088/2041-8205/727/2/L35
M3 - Article
AN - SCOPUS:79960232632
SN - 2041-8205
VL - 727
JO - Astrophysical Journal Letters
JF - Astrophysical Journal Letters
IS - 2 PART II
ER -