Emmanuel Pecontal

Overview of the Nearby Supernova Factory

The Nearby Supernova Factory (Snfactory) is an international experiment designed to lay the foundation for the next generation of cosmology experiments (such as CFHTLS, wP, SNAP and LSST) which will measure the expansion history of the Universe using Type Ia supernovae. The Snfactory will discover and obtain frequent lightcurve spectrophotometry covering 3200-10000Å for roughly 300 Type Ia supernovae at the low-redshift end of the smooth Hubble flow. The quantity, quality, breadth of galactic environments, and homogeneous nature of the Snfactory dataset will make it the premier source of calibration for the Type Ia supernova width-brightness relation and the intrinsic supernova colors used for K-correction and correction for extinction by host-galaxy dust. This dataset will also allow an extensive investigation of additional parameters which possibly influence the quality of Type Ia supernovae as cosmological probes. The Snfactory search capabilities and follow-up instrumentation include wide-field CCD imagers on two 1.2-m telescopes (via collaboration with the Near Earth Asteroid Tracking team at JPL and the QUEST team at Yale), and a two-channel integral-field-unit optical spectrograph/imager being fabricated for the University of Hawaii 2.2-m telescope. In addition to ground-based follow-up, UV spectra for a subsample of these supernovae will be obtained with HST. The pipeline to obtain, transfer via wireless and standard internet, and automatically process the search images is in operation. Software and hardware development is now underway to enable the execution of follow-up spectroscopy of supernova candidates at the Hawaii 2.2-m telescope via automated remote control of the telescope and the IFU spectrograph/imager.

SNIFS: a wideband integral field spectrograph with microlens arrays

SNIFS is an integral field spectrograph devoted to the observation of supernovae. This instrument is today in the manufacturing phase and should be able to observe supernovae at the end of this year (2003) on the 2.2m telescope of University Hawaii. The concept of SNIFS is to split the 6” x 6” field of view into 225 samples of 0.4” x 0.4” through a microlens array. Then the spectral decomposition of each sample is imaged on a 2k x 4k CCD. In order to cover all the large spectral range with a high resolution, the spectrograph is composed of two modules, one for the blue wavelengths (320 nm to 560nm)with a resolution around 1000 at 430 nm and one for the red wavelengths (520 nm to 1 µm) with a resolution around 1300 at 760 nm. First we will present the optical design and detail the function of each optical component. Then the mechanical design will be shown with some maps of the structure. Finally the first pictures taken during the alignments will be displayed.

Type Ia supernova bolometric light curves and ejected mass estimates from the Nearby Supernova Factory

We present a sample of normal type Ia supernovae from the Nearby Supernova Factory dataset with spectrophotometry at sufficiently late phases to estim ate the ejected mass using the bolometric light curve. We measure 56 Ni masses from the peak bolometric luminosity, then compare the luminosity in the 56 Co-decay tail to the expected rate of radioactive energy release from ejecta of a given mass. We infer the ejected mass in a Bayesian context using a semi-analytic model of the ejecta, incorporating constra ints from contemporary numerical models as priors on the density structure and distribution o f 56 Ni throughout the ejecta. We find a strong correlation between ejected mass and light curv e decline rate, and consequently 56 Ni mass, with ejected masses in our data ranging from 0.9‐1.4 M⊙. Most fast-declining (SALT2x1 < 1) normal SNe Ia have significantly sub-Chandrasekhar ejecte d masses in our fiducial analysis.

Visible and Near-Infrared Spectrophotometry of the Deep Impact Ejecta of Comet 9P/Tempel 1

Abstract We have obtained optical spectrophotometry of the evolution of Comet 9P/Tempel 1 after the impact of the Deep Impact probe, using the Supernova Integral Field Spectrograph (SNIFS) at the UH 2.2-m telescope, as well as simultaneous optical and infrared spectra using the Lick Visible-to-Near-Infrared Imaging Spectrograph (VNIRIS). The spatial distribution and temporal evolution of the “violet band” CN (0–0) emission and of the 630 nm [OI] emission was studied. We found that CN emission centered on the nucleus increased in the 2 h after impact, but that this CN emission was delayed compared to the light curve of dust-scattered sunlight. The CN emission also expanded faster than the cloud of scattering dust. The emission of [OI] at 630 nm rose similarly to the scattered light, but then remained nearly constant for several hours after impact. On the day following the impact, both CN and [OI] emission concentrated on the comet nucleus had returned nearly to pre-impact levels. We have also searched for differences in the scattering properties of the dust ejected by the impact compared to the dust released under normal conditions. Compared to the pre-impact state of the comet, we find evidence that the color of the comet was slightly bluer during the post-impact rise in brightness. Long after the impact, in the following nights, the comet colors returned to their pre-impact values. This can be explained by postulating a change to a smaller particle size distribution in the ejecta cloud, in agreement with the findings from mid-infrared observations, or by postulating a large fraction of clean ice particles, or by a combination of these two.

A Mega Integral Field Spectrograph for the VLT

We describe MIFS, a second generation integral-field spectrograph for the VLT, operating in the visible wavelength range. It combines a 1′×1′ field of view with the improved spatial resolution provided by multi-conjugate adaptive optics and covers a large simultaneous spectral range (0.6–1.0 μm). A separate mode exploits the highest spatial resolution provided by adaptive optics. With this unique combination of capabilities, MIFS has a wide domain of application and a large discovery potential.

Subarcsecond Observations of Galactic Nuclei

Subarcsecond two-dimensional imagery and spectrometry of the stellar component of galactic nuclei show complex systems, with multiple components and the possible presence of supermassive black-holes. Strategies for observation with the VLT, both with and without adaptive optics, are discussed, in terms of presently planned or future instrumentation.