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M. I. Jones,
Mario Hamuy,
P. Lira,
J. Maza,
A. Clocchiatti, M. Phillips,
N. Morrell,
M. Roth,
N. B. Suntzeff,
T. Matheson,
A. V. Filippenko,
R. J. Foley,
and D. C. Leonard
[show abstract]
[hide abstract]
ABSTRACT: We use early-time photometry and spectroscopy of 12 Type II plateau supernovae (SNe IIP) to derive their distances using the expanding photosphere method (EPM). We perform this study using two sets of Type II supernova (SN II) atmosphere models, three filter subsets ({BV}, {BVI}, and {VI}), and two methods for the host-galaxy extinction, which leads to 12 Hubble diagrams. We find that systematic differences in the atmosphere models lead to ~50% differences in the EPM distances and to a value of H 0 between 52 and 101 km s-1Mpc–1. Using the {VI} filter subset we obtain the lowest dispersion in the Hubble diagram, σμ = 0.32 mag. We also apply the EPM analysis to the well observed SN IIP 1999em. With the {VI} filter subset we derive a distance ranging from 9.3 ± 0.5 Mpc to 13.9 ± 1.4 Mpc depending on the atmosphere model employed.
The Astrophysical Journal 04/2009; 696(2):1176. · 6.02 Impact Factor
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D. A. Howell,
A. Conley,
M. Della Valle,
P. E. Nugent,
S. Perlmutter,
G. H. Marion,
K. Krisciunas,
C. Badenes,
P. Mazzali,
G. Aldering, [......],
R. Quimby,
A. Rest,
A. Riess,
M. Sako,
A. M. Soderberg,
L. Strolger,
R Thomas,
M. Turatto,
S. Van Dyk,
W. M. Wood-Vasey
[show abstract]
[hide abstract]
ABSTRACT: In the next decade Type Ia supernovae (SNe Ia) will be used to test theories predicting changes in the Dark Energy equation of state with time. Ultimately this requires a dedicated space mission like JDEM. SNe Ia are mature cosmological probes --- their limitations are well characterized, and a path to improvement is clear. Dominant systematic errors include photometric calibration, selection effects, reddening, and population-dependent differences. Building on past lessons, well-controlled new surveys are poised to make strides in these areas: the Palomar Transient Factory, Skymapper, La Silla QUEST, Pan-STARRS, the Dark Energy Survey, LSST, and JDEM. They will obviate historical calibrations and selection biases, and allow comparisons via large subsamples. Some systematics follow from our ignorance of SN Ia progenitors, which there is hope of determining with SN Ia rate studies from 0<z<4. Aside from cosmology, SNe Ia regulate galactic and cluster chemical evolution, inform stellar evolution, and are laboratories for extreme physics. Essential probes of SNe Ia in these contexts include spectroscopy from the UV to the IR, X-ray cluster and SN remnant observations, spectropolarimetry, and advanced theoretical studies. While there are an abundance of discovery facilities planned, there is a deficit of follow-up resources. Living in the systematics era demands deep understanding rather than larger statistics. NOAO ReSTAR initiative to build 2-4m telescopes would provide necessary follow-up capability. Finally, to fully exploit LSST, well-matched wide-field spectroscopic capabilities are desirable.
04/2009;
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B. Leibundgut,
R. Schommer, M. Phillips,
A. Riess,
B. Schmidt,
J. Spyromilio,
J. Walsh,
N. Suntzeff,
M. Hamuy,
J. Maza,
P. Kirshner,
P. Challis,
P. Garnavich,
C. Smith,
A. Dressler,
and R. Ciardullo
[show abstract]
[hide abstract]
ABSTRACT: The light curve of a distant Type Ia supernova acts like a clock that can be used to test the expansion of the universe. SN 1995K, at a spectroscopic redshift of z = 0.479, provides one of the first meaningful data sets for this test. We find that all aspects of SN 1995K resemble local Type Ia supernova events when the light curve is dilated by (1 + z), as prescribed by cosmological expansion. In a static, nonexpanding universe, SN 1995K would represent a unique object with a spectrum identifying it as a regular Type Ia supernova but with a light-curve shape and luminosity that do not follow the well-established relations for local events. We conclude that SN 1995K provides strong evidence for an interpretation of cosmological redshifts as being due to universal expansion. Theories in which photons dissipate their energy during travel are excluded as are age-redshift dependencies.
The Astrophysical Journal 01/2009; 466(1):L21. · 6.02 Impact Factor
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A. Clocchiatti,
B Schmidt,
A. Filippenko,
P. Challis,
A. Coil,
R. Covarrubias,
A. Diercks,
P. Garnavich,
L. Germany,
R. Gilliland, [......],
A. Riess,
R. Schommer,
R Smith,
A. Soderberg,
J. Spyromilio,
C. Stubbs,
N. Suntzeff,
J. Tonry,
P. Woudt,
for the High Z SN Search Collaboration
[show abstract]
[hide abstract]
ABSTRACT: We present observations of the Type Ia supernovae (SNe) 1999M, 1999N, 1999Q, 1999S, and 1999U, at redshift z~0.5. They were discovered in early 1999 with the 4.0~m Blanco telescope at Cerro Tololo Inter-American Observatory by the High-z Supernova Search Team (HZT) and subsequently followed with many ground-based telescopes. SNe 1999Q and 1999U were also observed with the Hubble Space Telescope. We computed luminosity distances to the new SNe using two methods, and added them to the high-z Hubble diagram that the HZT has been constructing since 1995. The new distance moduli confirm the results of previous work. At z~0.5, luminosity distances are larger than those expected for an empty universe, implying that a ``Cosmological Constant,'' or another form of ``dark energy,'' has been increasing the expansion rate of the Universe during the last few billion years.
11/2005;
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J. Millard,
D. Branch,
E. Baron,
K. Hatano,
A. Fisher,
A. Filippenko,
R. Kirshner,
P. Challis,
C. Fransson,
N. Panagia, M. Phillips,
G. Sonneborn,
N. Suntzeff,
R. Wagoner,
J. Wheeler
[show abstract]
[hide abstract]
ABSTRACT: Synthetic spectra generated with the parameterized supernova synthetic-spectrum code SYNOW are compared to observed photospheric-phase spectra of the Type Ic supernova 1994I. The observed optical spectra can be well matched by synthetic spectra that are based on the assumption of spherical symmetry. We consider the identification of the infrared absorption feature observed near 10,250 \AA, which previously has been attributed to He I $\lambda10830$ and regarded as strong evidence that SN 1994I ejected some helium. We have difficulty accounting for the infrared absorption with He I alone. It could be a blend of He I and C I lines. Alternatively, we find that it can be fit by Si I lines without compromising the fit in the optical region. In synthetic spectra that match the observed spectra, from 4 days before to 26 days after the time of maximum brightness, the adopted velocity at the photosphere decreases from 17,500 to 7000 \kms. Simple estimates of the kinetic energy carried by the ejected mass give values that are near the canonical supernova energy of $10^{51}$ ergs. The velocities and kinetic energies that we find for SN 1994I in this way are much lower than those that we find elsewhere for the peculiar Type Ic SNe 1997ef and 1998bw, which therefore appear to have been hyper-energetic. Comment: 18 pages, 12 figures, ApJ, in press
06/1999;
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B. P. Schmidt,
N. B. Suntzeff, M. Phillips,
R. Schommer,
A. Clocchiatti,
R. P. Kirshner,
P. Garnavich,
P. Challis,
B. Leibundgut,
J. Spyromilio,
C. Hogan,
C. Stubbs,
D. Reiss,
A. Diercks,
A. Filippenko,
A. Reiss,
C. Smith,
M. Hamuy,
R. Gilliland,
J. Tonry
[show abstract]
[hide abstract]
ABSTRACT: The High-Z SN Search is an international collaboration to discover and
follow SNe Ia at z > 0.2 with the aim of tracing out cosmic
deceleration and global curvature. This project has discovered 37
supernovae (0.09 <z< 0.84) using the Blanco 4-meter telescope at
CTIO over the past two years. We have obtained spectra and two color
photometry for most of these supernovae and find that 25 of the objects
are SNe Ia useful for measuring distances. Using the extensive nearby
set of supernovae gathered by members of our group, we demonstrate that
it is possible to overcome problems associated with K-corrections,
Malmquist Bias, extinction, and evolution which could affect the
distances derived from SNe Ia. In addition to the SNe Ia, the search has
uncovered several normal Type II supernovae on which the Expanding
Photosphere can be applied, several Kuiper Belt asteroids, and a few
short duration events of unknown origin.
11/1996; 28:1420.
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[show abstract]
[hide abstract]
ABSTRACT: Supernovae are unpredictable events. For this reason, despite the fact
that their interest spreads over numerous different fields, from
stellar evolution to the interstellar medium and to cosmology, they
have been observed, generally, with medium/small telescopes, whose
schedules are flexible enough to ensure prompt observation of new
objects. Therefore, the observations have been limited to the first
months after outburst, and even in this period hardly on a regular
basis.
The Messenger. 05/1990; 60:15-16.
