Adaptive Spatial Binning of 2D Spectra and Images Using Voronoi Tessellations

We present new techniques to perform adaptive spatial binning of two-dimensional (2D) data to reach a chosen constant signal-to-noise ratio per bin. These methods are required particularly for the proper analysis of Integral Field Spectrograph (IFS) observations, but can also be used for standard photometric imagery. Various schemes are tested and compared using data obtained with the panoramic IFS SAURON.Comment: 8 pages, 6 figures. To appear in ASP Conf. Ser., Galaxies: The Third Dimension, ed. M. Rosado, L. Binette, and L. Aria

Kinemetry: a generalisation of photometry to the higher moments of the line-of-sight velocity distribution

We present a generalisation of surface photometry to the higher-order moments of the line-of-sight velocity distribution of galaxies observed with integral-field spectrographs. The generalisation follows the approach of surface photometry by determining the best fitting ellipses along which the profiles of the moments can be extracted and analysed by means of harmonic expansion. The assumption for the odd moments (e.g. mean velocity) is that the profile along an ellipse satisfies a simple cosine law. The assumption for the even moments (e.g velocity dispersion) is that the profile is constant, as it is used in surface photometry. We find that velocity profiles extracted along ellipses of early-type galaxies are well represented by the simple cosine law (with 2% accuracy), while possible deviations are carried in the fifth harmonic term which is sensitive to the existence of multiple kinematic components, and has some analogy to the shape parameter of photometry. We compare the properties of the kinematic and photometric ellipses and find that they are often very similar. Finally, we offer a characterisation of the main velocity structures based only on the kinemetric parameters which can be used to quantify the features in velocity maps (abridged).Comment: 17 pages, 11 figures. MNRAS in press. High resolution version of the paper is available at http://www.strw.leidenuniv.nl/sauron/papers/krajnovic2005_kinemetry.pdf and software implementation of the method is freely available at http://www-astro.physics.ox.ac.uk/~dxk/idl

Reconsidering photometric estimation of local star formation environment and its correlation with Type Ia Supernova luminosity

Recent studies on the environmental dependence of Type Ia supernova (SN Ia) luminosity focus on the local environment where the SN exploded, considering that this is more directly linked to the SN progenitors. However, there is a debate about the local environmental, specifically local star formation rate (SFR), dependence of the SN Ia luminosity. A recent study claims that the dependence is insignificant ($0.051 \pm 0.020$ mag; $2.6\sigma$), based on the local SFR measurement by fitting local $ugrizy$ photometry data. However, we find that this photometric local SFR measurement is inaccurate. We argue this based on the theoretical background of SFR measurement and the methodology used to make that claim with their local $ugrizy$ photometry data, especially due to a limited range of extinction parameters used when fitting the data. Therefore, we re-analyse the same host galaxies with the same fitting code, but with more physically motivated extinction treatments and global $ugriz$ photometry of host galaxies. We estimate global stellar mass and SFR. Then, local star formation environments are inferred by using the method which showed that SNe Ia in globally passive galaxies have locally passive environments, while those in globally star-forming low-mass galaxies have locally star-forming environments. We find that there is significant local environmental dependence of SN Ia luminosities: SNe Ia in locally star-forming environments are $0.072\pm0.021$ mag ($3.4\sigma$) fainter than those in locally passive environments, even though SN Ia luminosities have been further corrected by the BBC method that reduces the size of the dependence.Comment: 10 pages, 7 figures, 3 tables and 1 appendix table containing data we used; accepted for publication in MNRA

Probing the stellar populations of early-type galaxies: the SAURON survey

The SAURON project will deliver two-dimensional spectroscopic data of a sample of nearby early-type galaxies with unprecedented quality. In this paper, we focus on the mapping of their stellar populations using the SAURON data, and present some preliminary results on a few prototypical cases.Comment: 12 pages, 6 figures. ASP Conference, Galaxies: the Third Dimension, Cozumel. Version with higher resolution figures available at http://www-obs.univ-lyon1.fr/eric.emsellem/papers/cozumel_emsellem.ps.g

Feasibility of luminescent multilayer sol-gel thermal barrier coating manufacturing for future applications in through-thickness temperature gradient sensing

This paper investigates the feasibility of manufacturing sol-gel multilayer thermal barrier coatings (TBC) functionalized with different lanthanide ions Ln3 + having distinct photo-luminescence emission wavelengths (Ln = Sm, Eu, Dy, Er, Tm) for future applications in temperature gradient sensing. Ln3 + doped 9.75 mol% yttria stabilized zirconia (YSZ) powders were produced to study the effect of activator concentration on luminescence intensity and host matrix crystal structure. Self-quenching was found to limit the maximum signal-to-noise ratio achievable with Sm3 +, Dy3 +, Er3 + and Tm3 + activators, which was not the case for Eu3 + in the 1–10 mol% range. The increase in activator was found to affect the crystal structure of YSZ. A solution was proposed that suppressed this effect while significantly increasing the luminescence intensity of all activators. Finally a TBC sensor prototype integrating Eu3 +, Er3 + and Dy3 + doped layers distributed throughout the thickness was successfully deposited by a dip-coating sol-gel process and showed promising through-thickness luminescence sensing capabilities

Two-dimensional kinematics and stellar populations of early-type galaxies: First results from the SAURON survey

We present the SAURON project, which is aimed at studying the morphology, two-dimensional kinematics and stellar populations of a representative sample of elliptical galaxies and spiral bulges. SAURON, a dedicated integral-field spectrograph that is optimized for wide-field observations and has high throughput, was built in Lyon and is now operated at the WHT 4.2m telescope. At present, we have observed approximately two thirds of the seventy-two sample galaxies with SAURON. A comparison with published long-slit measurements demonstrates that the SAURON-data is of equal or better quality, and provides full two-dimensional coverage. The velocity and velocity dispersion fields exhibit a large variety of morphologies: from simple rotating systems to cylindrical, disky and triaxial velocity fields, bars and decoupled cores. Most of these kinematical signatures do not have counterparts in the light distribution. While some galaxies are consistent with axisymmetry, most are more complex systems than assumed previously. This suggests that the kinematical properties of nearby E/S0 galaxies do not agree with the often assumed simplistic two-family model, in which the giant non-rotating triaxial ellipticals are opposed to the fast-rotating axisymmetric faint ellipticals and S0s.Comment: 10 pages, 6 figures, conference "galaxies: the third dimension", cozumel, mexico, 3-7 december 200

Slitless spectrophotometry with forward modelling: principles and application to atmospheric transmission measurement

In the next decade, many optical surveys will aim to tackle the question of dark energy nature, measuring its equation of state parameter at the permil level. This requires trusting the photometric calibration of the survey with a precision never reached so far, controlling many sources of systematic uncertainties. The measurement of the on-site atmospheric transmission for each exposure, or on average for each season or for the full survey, can help reach the permil precision for magnitudes. This work aims at proving the ability to use slitless spectroscopy for standard star spectrophotometry and its use to monitor on-site atmospheric transmission as needed, for example, by the Vera C. Rubin Observatory Legacy Survey of Space and Time supernova cosmology program. We fully deal with the case of a disperser in the filter wheel, which is the configuration chosen in the Rubin Auxiliary Telescope. The theoretical basis of slitless spectrophotometry is at the heart of our forward model approach to extract spectroscopic information from slitless data. We developed a publicly available software called Spectractor (https://github.com/LSSTDESC/Spectractor) that implements each ingredient of the model and finally performs a fit of a spectrogram model directly on image data to get the spectrum. We show on simulations that our model allows us to understand the structure of spectrophotometric exposures. We also demonstrate its use on real data, solving specific issues and illustrating how our procedure allows the improvement of the model describing the data. Finally, we discuss how this approach can be used to directly extract atmospheric transmission parameters from data and thus provide the base for on-site atmosphere monitoring. We show the efficiency of the procedure on simulations and test it on the limited data set available.Comment: 30 pages, 36 figures, submitted to Astronomy and Astrophysic

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

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 2.2m telescope, as well as simultaneous optical and infrared spectra using the Lick Visible-to-Near-Infrared Imaging Spectrograph (VNIRIS) spectrograph. 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 two hours 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 observatons, or by postulating a large fraction of clean ice particles, or by a combination of these two.Comment: 28 pages of text and 8 figures. Paper is accepted for publication in Icaru

Formation and evolution of S0 galaxies: a SAURON case study of NGC7332

We present SAURON integral-field observations of the S0 galaxy NGC7332. Existing broad-band ground-based and HST photometry reveals a double disk structure and a boxy bulge interpreted as a bar viewed close to edge-on. The SAURON two-dimensional stellar kinematic maps confirm the existence of the bar and inner disk but also uncover the presence of a cold counter-rotating stellar component within the central 250 pc. The Hbeta and [OIII] emission line maps show that the ionised gas has a complex morphology and kinematics, including both a component counter-rotating with respect to the stars and a fainter co-rotating one. Analysis of the absorption line-strength maps show that NGC7332 is young everywhere. The presence of a large-scale bar can explain most of those properties, but the fact that we see a significant amount of unsettled gas, together with a few peculiar features in the maps, suggest that NGC7332 is still evolving. Interactions as well as bar-driven processes must thus have played an important role in the formation and evolution of NGC7332, and presumably of S0 galaxies in general.Comment: 12 pages, 12 figures, accepted for publication in MNRA