677 research outputs found
Correcting for lensing bias in the Hubble diagram
Gravitational lensing will cause a dispersion in the Hubble diagram for high
redshift sources. This effect will introduce a bias in the cosmological
parameter determination using the distance-redshift relation for Type Ia
supernovae. In this note we show how one can diagnose and correct for this bias
when doing precision cosmology with supernovae.Comment: 5 pages, 5 figures, accepted for publication in A&
Herschel limits on far-infrared emission from circumstellar dust around nearby Type Ia supernovae
We report upper limits on dust emission at far-infrared (IR) wavelengths from
three nearby Type Ia supernovae: SNe 2011by, 2011fe and 2012cg. Observations
were carried out at 70 um and 160 um with the Photodetector Array Camera and
Spectrometer (PACS) on board the Herschel Space Observatory. None of the
supernovae were detected in the far-IR, allowing us to place upper limits on
the amount of pre-existing dust in the circumstellar environment. Due to its
proximity, SN 2011fe provides the tightest constraints, M_dust < 7 * 10^-3
M_sun at a 3 sigma-level for dust temperatures T_dust ~500 K assuming silicate
or graphite dust grains of size a = 0.1 um. For SNe 2011by and 2012cg the
corresponding upper limits are less stringent, with M_dust < 0.1 M_sun for the
same assumptions.Comment: 6 pages, 3 figures, 1 table. Accepted for publication in MNRA
Lensing magnification of supernovae in the GOODS-fields
Gravitational lensing of high-redshift supernovae is potentially an important
source of uncertainty when deriving cosmological parameters from the measured
brightness of Type Ia supernovae, especially in deep surveys with scarce
statistics. Photometric and spectroscopic measurements of foreground galaxies
along the lines-of-sight of 33 supernovae discovered with the Hubble Space
Telescope, both core-collapse and Type Ia, are used to model the magnification
probability distributions of the sources. Modelling galaxy halos with SIS or
NFW-profiles and using M/L scaling laws provided by the Faber-Jackson and
Tully-Fisher relations, we find clear evidence for supernovae with lensing
(de)magnification. However, the magnification distribution of the Type Ia
supernovae used to determine cosmological distances matches very well the
expectations for an unbiased sample, i.e.their mean magnification factor is
consistent with unity. Our results show that the lensing distortions of the
supernova brightness can be well understood for the GOODS sample and that
correcting for this effect has a negligible impact on the derived cosmological
parameters.Comment: 22 pages, 9 figures, accepted for publication by Ap
Near-IR search for lensed supernovae behind galaxy clusters: III. Implications for cluster modeling and cosmology
Massive galaxy clusters at intermediate redshifts act as gravitational lenses
that can magnify supernovae (SNe) occurring in background galaxies. We assess
the possibility to use lensed SNe to put constraints on the mass models of
galaxy clusters and the Hubble parameter at high redshift. Due to the standard
candle nature of Type Ia supernovae (SNe Ia), observational information on the
lensing magnification from an intervening galaxy cluster can be used to
constrain the model for the cluster mass distribution. A statistical analysis
using parametric cluster models was performed to investigate the possible
improvements from lensed SNe Ia for the accurately modeled galaxy cluster A1689
and the less well constrained cluster A2204. Time delay measurements obtained
from SNe lensed by accurately modeled galaxy clusters can be used to measure
the Hubble parameter. For a survey of A1689 we estimate the expected rate of
detectable SNe Ia and of multiply imaged SNe. The velocity dispersion and core
radius of the main cluster potential show strong correlations with the
predicted magnifications and can therefore be constrained by observations of
SNe Ia in background galaxies. This technique proves especially powerful for
galaxy clusters with only few known multiple image systems. The main
uncertainty for measurements of the Hubble parameter from the time delay of
strongly lensed SNe is due to cluster model uncertainties. For the extremely
well modeled cluster A1689, a single time delay measurement could be used to
determine the Hubble parameter with a precision of ~ 10%. We conclude that
observations of SNe Ia behind galaxy clusters can be used to improve the mass
modeling of the large scale component of galaxy clusters and thus the
distribution of dark matter. Time delays from SNe strongly lensed by accurately
modeled galaxy clusters can be used to measure the Hubble constant at high
redshifts.Comment: 10 pages, 8 figures, 3 tables. Accepted for publication in A&
iPTF16abc and the population of Type Ia supernovae: Comparing the photospheric, transitional and nebular phases
Key information about the progenitor system and the explosion mechanism of
Type Ia supernovae (SNe~Ia) can be obtained from early observations, within a
few days from explosion. iPTF16abc was discovered as a young SN~Ia with
excellent early time data. Here, we present photometry and spectroscopy of the
SN in the nebular phase. A comparison of the early time data with a sample of
SNe~Ia shows distinct features, differing from normal SNe~Ia at early phases
but similar to normal SNe~Ia at a few weeks after maximum light (i.e. the
transitional phase) and well into the nebular phase. The transparency
timescales () for this sample of SNe~Ia range between 25 and 41
days indicating a diversity in the ejecta masses. also weakly correlates
with the peak bolometric luminosity, consistent with the interpretation that
SNe with higher ejecta masses would produce more Ni. Comparing the
and the maximum luminosity, L\, distribution of a sample of SNe~Ia to
predictions from a wide range of explosion models we find an indication that
the sub-Chandrasekhar mass models span the range of observed values. However,
the bright end of the distribution can be better explained by Chandrasekhar
mass delayed detonation models, hinting at multiple progenitor channels to
explain the observed bolometric properties of SNe~Ia. iPTF16abc appears to be
consistent with the predictions from the M models.Comment: 13 pages, 8 figures, accepted for publication in MNRA
Massive galaxy clusters as gravitational telescopes for distant supernovae
We investigate the potential of using massive clusters as gravitational
telescopes for searches and studies of supernovae of Type Ia and Type II in
optical and near-infrared bands at central wavelengths in the interval 0.8-1.25
microns. Using high-redshift supernova rates derived from the measured star
formation rate, we find the most interesting effects for the detection of
core-collapse SNe in searches at limiting magnitudes m_lim~25-26.5 mag, where
the total detection rate could be significantly enhanced and the number of
detectable events is considerable even in a small field. For shallower
searches, ~24, a net gain factor of up to 3 in the discovery rate could be
obtained, and yet a much larger factor for very high source redshifts. For
programs such as the GOODS/ACS transient survey, the discovery rate of
supernovae beyond z~2 could be significantly increased if the observations were
done in the direction of massive clusters. For extremely deep observations,
m_lim > 27 mag, or for very bright SNe (e.g. Type Ia) the competing effect of
field reduction by lensing dominates, and fewer supernovae are likely to be
discovered behind foreground clusters.Comment: 9 pages, 17 figures, matches published versio
- âŠ