578 research outputs found
The Velocity Field from Type Ia Supernovae Matches the Gravity Field from Galaxy Surveys
We compare the peculiar velocities of nearby SNe Ia with those predicted by
the gravity fields of full sky galaxy catalogs. The method provides a powerful
test of the gravitational instability paradigm and strong constraints on the
density parameter beta = Omega^0.6/b. For 24 SNe Ia within 10,000 km/s we find
the observed SNe Ia peculiar velocities are well modeled by the predictions
derived from the 1.2 Jy IRAS survey and the Optical Redshift Survey (ORS). Our
best is 0.4 from IRAS, and 0.3 from the ORS, with beta>0.7 and
beta<0.15 ruled out at 95% confidence levels from the IRAS comparison.
Bootstrap resampling tests show these results to be robust in the mean and in
its error. The precision of this technique will improve as additional nearby
SNe Ia are discovered and monitored.Comment: 16 pages (LaTex), 3 postscript figure
The Hubble Diagram of the Calan/Tololo Type Ia Supernovae and the value of Ho
The Calan/Tololo supernova survey has discovered ~30 Type Ia supernovae out
to z~0.1. Using BVI data for these objects and nearby SNe Ia, we have shown
that there exists a significant dispersion in the intrinsic luminosities of
these objects. We have devised a robust chisquare minimization technique
simultaneously fitting the BVI light curves to parametrize the SN event as a
function of (tb,m, m15(B)) where tb is the time of B maximum, m is the peak BVI
magnitude corrected for luminosity variations, and m15(B) is a single parameter
describing the whole light curve morphology. When properly corrected for
m15(B), SNe Ia prove to be high precision distance indicators,yielding relative
distances with errors 7-10%. The corrected peak magnitudes are used to
construct BVI Hubble diagrams (HD), and with Cepheid distances recently
measured with the HST to four nearby SNe Ia (37C, 72E, 81B, 90N) we derive a
value of the Hubble constant of 63.1+/-3.4 (internal) km/s/Mpc. This value is
~10-15% larger than the value obtained by assuming that SNe Ia are perfect
standard candles. As we have shown in Paper V, there is now strong evidence
that galaxies with younger stellar population appear to host the
slowest-declining, and therefore most luminous SNe Ia. Hence, the use of Pop I
objects such as Cepheids to calibrate the zero point of the SNe Ia HD can
easily bias the results toward luminous SNe Ia, unless the absolute
magnitude-decline relation is taken into account.Comment: 32 pages, figures attached, all tables available, to appear in the
Astronomical Journa
The Absolute Luminosities of the Calan/Tololo Type Ia Supernovae
We examine the absolute luminosities of 29 SNe Ia in the Calan/Tololo survey.
We confirm a relation between the peak luminosity of the SNe and the decline
rate as measured by the light curve, as suggested by Phillips (1993). We derive
linear slopes to this magnitude-decline rate relation in BV(I)kc colors, using
a sample with Bmax-Vmax < 0.2 mag. The scatter around this linear relation (and
thus the ability to measure SNe Ia distances) ranges from 0.13 mag (in the I
band) to 0.17 mag (in the B band). We also find evidence for significant
correlations between the absolute magnitudes or the decline rate of the light
curve, and the morphological type of the host galaxy.Comment: 21 pages, 4 figures, to appear in the Astronomical Journa
Photometry of SN 2002ic and Implications for the Progenitor Mass-Loss History
We present new pre-maximum and late-time optical photometry of the Type
Ia/IIn supernova 2002ic. These observations are combined with the published
V-band magnitudes of Hamuy et al. (2003) and the VLT spectrophotometry of Wang
et al. (2004) to construct the most extensive light curve to date of this
unusual supernova. The observed flux at late time is significantly higher
relative to the flux at maximum than that of any other observed Type Ia
supernova and continues to fade very slowly a year after explosion. Our
analysis of the light curve suggests that a non-Type Ia supernova component
becomes prominent days after explosion. Modeling of the non-Type Ia
supernova component as heating from the shock interaction of the supernova
ejecta with pre-existing circumstellar material suggests the presence of a
cm gap or trough between the progenitor system and the
surrounding circumstellar material. This gap could be due to significantly
lower mass-loss years prior to explosion or
evacuation of the circumstellar material by a low-density fast wind. The latter
is consistent with observed properties of proto-planetary nebulae and with
models of white-dwarf + asymptotic giant branch star progenitor systems with
the asymptotic giant branch star in the proto-planetary nebula phase.Comment: accepted for publication in Ap
The Local Environments of Core-Collapse SNe within Host Galaxies
We present constraints on core-collapse supernova progenitors through
observations of their environments within host galaxies. This is achieved
through 2 routes. Firstly, we investigate the spatial correlation of supernovae
with host galaxy star formation using pixel statistics. We find that the main
supernova types form a sequence of increasing association to star formation.
The most logical interpretation is that this implies an increasing progenitor
mass sequence going from the supernova type Ia arising from the lowest mass,
through the type II, type Ib, and the supernova type Ic arising from the
highest mass progenitors. We find the surprising result that the supernova type
IIn show a lower association to star formation than type IIPs, implying lower
mass progenitors. Secondly, we use host HII region spectroscopy to investigate
differences in environment metallicity between different core-collapse types.
We find that supernovae of types Ibc arise in slightly higher metallicity
environments than type II events. However, this difference is not significant,
implying that progenitor metallicity does not play a dominant role in deciding
supernova type.Comment: to appear in Proceedings of IAU 279 "Death of Massive Stars:
Supernovae and Gamma-ray Bursts
Evidence for short-lived SN Ia progenitors
We use the VESPA algorithm and spectra from the Sloan Digital Sky Survey to
investigate the star formation history of the host galaxies of 257 Type Ia
supernovae. We find 5 evidence for a short-lived population of
progenitors with lifetimes of less than 180 Myr, indicating a Type Ia supernova
channel arising from stars in the mass range 3.5-8 . As
standardizeable candles, Type Ia supernovae play an important role in
determining the expansion history of the Universe, but to be useful for future
cosmological surveys, the peak luminosity needs to be free of uncorrected
systematic effects at the level of 1-2%. If the different progenitor routes
lead to supernovae with even moderately small differences in properties, then
these need to be corrected for separately, or they could lead to a systematic
bias in future supernovae surveys, as the prompt route is likely to increase in
importance at high redshift. VESPA analysis of hosts could be a valuable tool
in this, by identifying which progenitor route is most likely.Comment: Accepted version by the journal, no changes in the result
The absolute infrared magnitudes of type Ia supernovae
The absolute luminosities and homogeneity of early-time infrared (IR) light
curves of type Ia supernovae are examined. Eight supernovae are considered.
These are selected to have accurately known epochs of maximum blue light as
well as having reliable distance estimates and/or good light curve coverage.
Two approaches to extinction correction are considered. Owing to the low
extinction in the IR, the differences in the corrections via the two methods
are small. Absolute magnitude light curves in the J, H and K-bands are derived.
Six of the events, including five established ``Branch-normal'' supernovae show
similar coeval magnitudes. Two of these, SNe 1989B and 1998bu, were observed
near maximum infrared light. This occurs about 5 days {\it before} maximum blue
light. Absolute peak magnitudes of about -19.0, -18.7 and -18.8 in J, H & K
respectively were obtained. The two spectroscopically peculiar supernovae in
the sample, SNe 1986G and 1991T, also show atypical IR behaviour. The light
curves of the six similar supernovae can be represented fairly consistently
with a single light curve in each of the three bands. In all three IR bands the
dispersion in absolute magnitude is about 0.15 mag, and this can be accounted
for within the uncertainties of the individual light curves. No significant
variation of absolute IR magnitude with B-band light curve decline rate, Delta
m_{15}(B), is seen over the range 0.87<Delta m_{15}(B)<1.31. However, the data
are insufficient to allow us to decide whether or not the decline rate relation
is weaker in the IR than in the optical region. IR light curves of type Ia
supernovae should eventually provide cosmological distance estimates which are
of equal or even superior quality to those obtained in optical studies.Comment: 19 pages, 9 figures, MNRAS in press (includes Referee's changes
The Distance to the Coma Cluster from Surface Brightness Fluctuations
We report on the first determination of the distance to the Coma Cluster
based on surface brightness fluctuation (SBF) measurements obtained from Hubble
Space Telescope WFPC2 observations of the bright E0 galaxy NGC 4881 in the Coma
Cluster and ground-based observations of the standard E1 galaxy NGC 3379 in the
Leo-I group. Relative distances based on the I-band fluctuation magnitude,
I(SBF), are strongly dependent on metallicity and age of the stellar
population. However, the radial changes in the stellar populations of the two
giant ellipticals, NGC 3379 and NGC 4881, are well described by published Mg_2
gradients, and the ground-based measurements of I(SBF) at several radial points
in NGC 3379 are used to calibrate I(SBF) in terms of the Mg_2 index. The
distance to NGC 3379, assumed to be identical to the average SBF distance of
the Leo-I group, is combined with the new SBF measurements of NGC 4881 to
obtain a Coma Cluster distance of 102+-14 Mpc. Combining this distance with the
cosmic recession velocity of Coma (7186+-428 km/s), we find the Hubble constant
to be H_0 = 71+-11 km/s/Mpc.Comment: 12 pages, LaTex, includes aaspp4.sty and 3 eps figures. To appear in
ApJ Letter
Observations and analysis of two type IIP supernovae: the intrinsically faint object SN 2005cs and the ambiguous object SN 2005ay
Aims: To derive observational properties and physical parameters of the
progenitor stars of type IIP supernovae SN 2005ay and SN 2005cs from their
U,B,V,R,I CCD photometry, and to define their velocity behaviour. Methods:
Light curves are analysed, and the velocities and spectral characteristics of
SN 2005cs are obtained using synthetic spectra modeling. Results: Both
supernovae are found to be fainter than the average
SN IIP, with SN 2005cs being more subluminous and showing slight brightening
in the second half of plateau stage in the
V,R,I bands and a low expansion velocity.
The effects of two different plausible distance moduli on the derived
physical parameters of SN 2005ay are considered.
Two approaches are used to recover the amounts of the ejected 56Ni,
indicating masses of the order of
0.02 Msun, although late luminosities might indicate a higher amount for SN
2005ay, especially for the large distance case.
Constraints on the progenitor properties are also presented, based on
empirical analytical models. Two approaches are used to estimate the expansion
velocities at the middle of the plateau phase. SN 2005cs represents an example
of where all 3 physical parameters, velocity, energy and 56Ni mass are lower
than average, a correlation not always observed in SNe IIP. SN 2005ay may
belong to the same class if the shorter distance possibility is adopted.
Furthermore, the estimated mass range for SN 2005cs is in agreement with limits
established by using pre-supernova imaging.Comment: 8 pages, 6 figures, to be published in A&A vol.460, issue 3, December
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