792 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
Do the photometric colors of Type II-P Supernovae allow accurate determination of host galaxy extinction?
We present infrared photometry of SN 1999em, plus optical photometry,
infrared photometry, and optical spectroscopy of SN 2003hn. Both objects were
Type II-P supernovae. The V-[RIJHK] color curves of these supernovae evolved in
a very similar fashion until the end of plateau phase. This allows us to
determine how much more extinction the light of SN 2003hn suffered compared to
SN 1999em. Since we have an estimate of the total extinction suffered by SN
1999em from model fits of ground-based and space-based spectra as well as
photometry of SN 1999em, we can estimate the total extinction and absolute
magnitudes of SN 2003hn with reasonable accuracy. Since the host galaxy of SN
2003hn also produced the Type Ia SN 2001el, we can directly compare the
absolute magnitudes of these two SNe of different types.Comment: 24 pages, 6 figure
Unresolved versus resolved: testing the validity of young simple stellar population models with VLT/MUSE observations of NGC 3603
CONTEXT. Stellar populations are the building blocks of galaxies including
the Milky Way. The majority, if not all extragalactic studies are entangled
with the use of stellar population models given the unresolved nature of their
observation. Extragalactic systems contain multiple stellar populations with
complex star formation histories. However, their study is mainly based upon the
principles of simple stellar populations (SSP). Hence, it is critical to
examine the validity of SSP models. AIMS. This work aims to empirically test
the validity of SSP models. This is done by comparing SSP models against
observations of spatially resolved young stellar population in the
determination of its physical properties, i.e. age and metallicity. METHODS.
Integral field spectroscopy of a young stellar cluster in the Milky Way, NGC
3603, is used to study the properties of the cluster both as a resolved and
unresolved stellar population. The unresolved stellar population is analysed
using the H equivalent width as an age indicator, and the ratio of
strong emission lines to infer metallicity. In addition, spectral energy
distribution (SED) fitting using STARLIGHT, is used to infer these properties
from the integrated spectrum. Independently, the resolved stellar population is
analysed using the color-magnitude diagram (CMD) for age and metallicity
determination. As the SSP model represents the unresolved stellar population,
the derived age and metallicity are put to test whether they agree with those
derived from resolved stars. RESULTS. The age and metallicity estimate of NGC
3603 derived from integrated spectroscopy are confirmed to be within the range
of those derived from the CMD of the resolved stellar population, including
other estimates found in the literature. The result from this pilot study
supports the reliability of SSP models for studying unresolved young stellar
populations.Comment: 9 pages, 5 figures, accepted to A&
Determination of cosmological parameters: an introduction for non-specialists
I start by defining the cosmological parameters and
. Then I show how the age of the universe depends on them,
followed by the evolution of the scale parameter of the universe for various
values of the density parameters. Then I define strategies for measuring them,
and show the results for the recent determination of these parameters from
measurements on supernovas of type 1a. Implications for particle physics is
briefly discussed at the end.Comment: 12 pages, Latex with epsf.sty. Invited talk at the ``Discussion
meeting on Recent Developments in Neutrino Physics'', held at the Physical
Research Laboratory, Ahmedabad, February 2--4, 199
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 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
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
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