67 research outputs found
[Sabbatical Report]
I spent my AY2014 sabbatical year at the Space Telescope Science Institute (STScI), with plans of completing the analyses of supernova rates for both thermonuclear and corecolliape events in high redshift galaxies from the Multi-cycle Treasury Projects with the Hubble Space Telescope
The Deepest Supernova Search is Realized in the Hubble Ultra Deep Field Survey
The Hubble Ultra Deep Field Survey has not only provided the deepest optical
and near infrared views of universe, but has enabled a search for the most
distant supernovae to z~2.2. We have found four supernovae by searching spans
of integrations of the Ultra Deep Field and the Ultra Deep Field Parallels
taken with the Hubble Space Telescope paired with the Advanced Camera for
Surveys and the Near Infrared Multi Object Spectrometer. Interestingly, none of
these supernovae were at z>1.4, despite the substantially increased sensitivity
per unit area to such objects over the Great Observatories Origins Deep Survey.
We present the optical photometric data for the four supernovae. We also show
that the low frequency of Type Ia supernovae observed at z>1.4 is statistically
consistent with current estimates of the global star formation history combined
with the non-trivial assembly time of SN Ia progenitors.Comment: 24 pages (6 figures), submitted to the Astronomical Journa
Kindling the First Stars II: Dependence of the Predicted PISN Rate on the Pop III Initial Mass Function
Population III (Pop III) stars formed out of metal free gas in minihalos at
. While their ignition ended the Dark Ages and begin enrichment of the
IGM, their mass distribution remains unconstrained. To date, no confirmed Pop
III star has been observed and their direct detection is beyond the reach of
the James Webb Space Telescope (JWST) without gravitational lensing. However, a
subset of massive Pop III stars end their lives in pair instability supernova
(PISN). With typical energies of ~erg, PISN light curve peaks are
bright enough to be detectable by JWST and the Roman Space Telescope. The
fundamental question of this work is whether or not observed PISN can be used
as a diagnostic of the Pop III IMF. In this work, we use a model of the
formation of the first stars to determine the dependence of PISN rates at
for a range of Pop III power law IMFs () and,
critically, the method by which the IMF is populated. At , we predict
typical rates of per deg per year which will produce
/year in a single NIRCam pointing and /year in a
single Roman pointing with per year detected in the HLTDS. Our
work highlights that theoretical modeling of PISN rates is required if upcoming
PISN studies with JWST and Roman are going to constrain the Pop III IMF.Comment: 8 pages, 5 figures, submitted to the Open Journal of Astrophysic
Empirical Delay Time Distributions of Type Ia Supernovae From The Extended GOODS/HST Supernova Survey
Using the Hubble Space Telescope ACS imaging of the GOODS North and South
fields during Cycles 11, 12, and 13, we derive empirical constraints on the
delay-time distribution function for type Ia supernovae. We extend our previous
analysis to the three-year sample of 56 SNe Ia over the range 0.2<z<1.8, using
a Markov chain Monte Carlo to determine the best-fit unimodal delay-time
distribution function. The test, which ultimately compares the star formation
rate density history to the unbinned volumetric SN Ia rate history from the
GOODS/HST-SN survey, reveals a SN Ia delay-time distribution that is tightly
confined to 3-4 Gyrs (to >95% confidence). This result is difficult to resolve
with any intrinsic delay-time distribution function (bimodal or otherwise), in
which a substantial fraction (e.g., >10%) of events are ``prompt'', requiring
less than approximately 1 Gyr to develop from formation to explosion. The
result is, however, strongly motivated by the decline in the number of SNe Ia
at z>1.2. Sub-samples of the HST-SN data confined to lower redshifts (z<1) show
plausible delay-time distributions that are dominated by prompt events, which
is more consistent with results from low-redshift supernova samples and
supernova host galaxy properties. Scenarios in which a substantial fraction of
z>1.2 supernovae are extraordinarily obscured by dust may partly explain the
differences in low-z and high-z results. Other possible resolutions may include
environmental dependencies (such as gas-phase metallicity) that affect the
progenitor mechanism efficiency, especially in the early universe.Comment: 12 pages, 9 figures, accepted to the Astrophysical Journa
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