658 research outputs found
Fixing the U-band photometry of Type Ia supernovae
We present previously unpublished photometry of supernovae 2003gs and 2003hv.
Using spectroscopically-derived corrections to the U-band photometry, we
reconcile U-band light curves made from imagery with the Cerro Tololo 0.9-m,
1.3-m and Las Campanas 1-m telescopes. Previously, such light curves showed a
0.4 mag spread at one month after maximum light. This gives us hope that a set
of corrected ultraviolet light curves of nearby objects can contribute to the
full utilization of rest frame U-band data of supernovae at redshift ~0.3 to
0.8. As pointed out recently by Kessler et al. in the context of the Sloan
Digital Sky Survey supernova search, if we take the published U-band photometry
of nearby Type Ia supernovae at face value, there is a 0.12 mag U-band anomaly
in the distance moduli of higher redshift objects. This anomaly led the Sloan
survey to eliminate from their analyses all photometry obtained in the rest
frame U-band. The Supernova Legacy Survey eliminated observer frame U-band
photometry, which is to say nearby objects observed in the U-band, but they
used photometry of high redshift objects no matter in which band the photons
were emitted.Comment: 25 pages, 9 figures, accepted for publication in the Astronomical
Journa
Clustering of Very Red Galaxies in the Las Campanas IR Survey
We report results from the first 1000 square arc-minutes of the Las Campanas
IR survey. We have imaged 1 square degree of high latitude sky in six distinct
fields to a 5-sigma H-band depth of 20.5 (Vega). Optical imaging in the
V,R,I,and z' bands allow us to select color subsets and
photometric-redshift-defined shells. We show that the angular clustering of
faint red galaxies (18 3) is an order of magnitude stronger
than that of the complete H-selected field sample. We employ three approaches
to estimate in order to invert w(theta) to derive r_0. We find that our
n(z) is well described by a Gaussian with = 1.2, sigma(z) = 0.15. From this
we derive a value for r_0 of 7 (+2,-1) co-moving H^{-1} Mpc at = 1.2. This
is a factor of ~ 2 larger than the clustering length for Lyman break galaxies
and is similar to the expectation for early type galaxies at this epoch.Comment: 5 pages, 2 figures, 1 table. To appear in proceedings of the
ESO/ECF/STScI workshop "Deep Fields" held in Garching, Germany, 9-12 October
200
Searching for light echoes due to circumstellar matter in SNe Ia spectra
We present an analytical model for light echoes (LEs) coming from circumstellar material (CSM) around Type Ia Supernovae (SNe Ia). Using this model we find two spectral signatures at 4100 Å and 6200 Å that are useful to identify LEs during the Lira law phase (between 35 and 80 days after maximum light) coming from nearby CSM at distances of 0.010.25 pc. We analyze a sample of 89 SNe Ia divided into two groups according to their B V decline rate during the Lira law phase, and search for LEs from CSM interaction in the group of SNe with steeper slopes by comparing their spectra with our LE model. We find that a model with LEs + pure extinction from interstellar material (ISM) fits the observed spectra better than a pure ISM extinction model that is constant in time, but we find that a decreasing extinction alone explains the observations better without the need of LEs, possibly implying dust sublimation due to the radiation from the SN.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat
Polarimetry of the superluminous supernova LSQ14mo: no evidence for significant deviations from spherical symmetry
We present the first polarimetric observations of a Type I superluminous
supernova (SLSN). LSQ14mo was observed with VLT/FORS2 at five different epochs
in the V band, with the observations starting before maximum light and spanning
26 days in the rest frame (z=0.256). During this period, we do not detect any
statistically significant evolution (< 2) in the Stokes parameters. The
average values we obtain, corrected for interstellar polarisation in the
Galaxy, are Q = -0.01% ( 0.15%) and U = - 0.50% ( 0.14%). This low
polarisation can be entirely due to interstellar polarisation in the SN host
galaxy. We conclude that, at least during the period of observations and at the
optical depths probed, the photosphere of LSQ14mo does not present significant
asymmetries, unlike most lower-luminosity hydrogen-poor SNe Ib/c.
Alternatively, it is possible that we may have observed LSQ14mo from a special
viewing angle. Supporting spectroscopy and photometry confirm that LSQ14mo is a
typical SLSN I. Further studies of the polarisation of Type I SLSNe are
required to determine whether the low levels of polarisation are a
characteristic of the entire class and to also study the implications for the
proposed explosion models.Comment: ApJ Letters, 4 Figures, 3 Tables. The previous version was accepted.
This version contains minor modifications to match proofs (as much as
possible
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