Laurie Rousseau-Nepton

New scientific results with SpIOMM: a testbed for CFHT's imagingFourier transform spectrometer SITELLE

We present new data obtained with SpIOMM, the imaging Fourier transform spectrometer attached to the 1.6-m telescope of the Observatoire du Mont-Megantic in Québec. Recent technical and data reduction improvements have significantly increased SpIOMMs capabilities to observe fainter objects or weaker nebular lines, as well as continuum sources and absorption lines, and to increase its modulation efficiency in the near ultraviolet. To illustrate these improvements, we present data on the supernova remnant Cas A, planetary nebulae M27 and M97, the Wolf-Rayet ring nebula M1-67, spiral galaxies M63 and NGC 3344, as well as the interacting pair of galaxies Arp 84.

Hydrogen volume densities in nearby galaxies – I. An automated approach

Using a simple model of photodissociated atomic hydrogen on a galactic scale, it is possible to derive total hydrogen volume densities. These densities, obtained through a combination of atomic hydrogen, far-ultraviolet and metallicity data, provide an independent probe of the combined atomic and molecular hydrogen gas in galactic disks. We present a new, flexible and fully automated procedure using this simple model. This automated method will allow us to take full advantage of a host of available data on galaxies in order to calculate total hydrogen volume densities of giant molecular clouds surrounding sites of recent star formation. So far this was only possible on a galaxy-by-galaxy basis using by-eye analysis of candidate photodissociation regions. We test the automated method by adopting different models for the dust-to-gas ratio and comparing the resulting densities for M74, including a new metallicity map of M74 produced by integral field spectroscopy. We test the procedure against previously published M83 volume densities based on the same method and find no significant differences. The range of total hydrogen volume densities obtained for M74 is approximately 5-700 cm-3 . Different dust-to-gas ratio models do not result in measurably different densities. The cloud densities presented here add M74 to the list of galaxies analyzed using the assumption of photodissociated atomic hydrogen occurring near sites of recent star formation and further solidify the method. For the first time, full metallicity maps were included in the analysis as opposed to metallicity gradients. The results will need to be compared to other tracers of the interstellar medium and photodissociation regions, such as CO and CII, in order to test our basic assumptions, specifically, our assumption that the HI we detect originates in photodissociation regions.

Imaging FTS: A Different Approach to Integral Field Spectroscopy

Imaging Fourier transform spectroscopy (iFTS) is a promising, although technically very challenging, option for wide-field hyperspectral imagery. We present in this paper an introduction to the iFTS concept and its advantages and drawbacks, as well as examples of data obtained with a prototype iFTS, SpIOMM, attached to the 1.6 m telescope of the Observatoire du Mont-Megantic: emission line ratios in the spiral galaxy NGC 628 and absorption line indices in the giant elliptical M87. We conclude by introducing SpIOMMs successor, SITELLE, which will be installed at the Canada-France-Hawaii Telescope in 2014.

HII Regions of NGC 628 and M101 as seen with SpIOMM

With SpIOMM, we obtained numerous spectra in the visible range covering simul- taneously several emission lines of bright Hii regions in the spiral galaxies NGC628 and M101. We measured the size and luminosity of the Hii regions as well as the gas metallicity, tempera- ture, and density. We estimated the age and star forming rate of the young stellar populations associated with the Hii regions. We looked for gradients along the galaxy radius and search for relations with the galactic arm positions. This is a first step in a project, based on a de- tailed study of stellar populations, to rebuild the history of spiral galaxies and to identify the mechanisms responsible for their evolution.

Commissioning SITELLE: an imaging Fourier transform spectrometer for the Canada France Hawaii Telescope

The SITELLE Imaging Fourier Transform Spectrometer was successfully commissioned at the Canada France Hawaii Telescope starting in July 2015. Here we discuss the commissioning process, the outcome of the early tests on-sky as well as the ensuing work to optimize the modulation efficiency at large optical path difference and the image quality of the instrument.

The Study of Barred Spiral Galaxies with Integral-Field Units

Integral-Field Units have been used to describe the morphology in numerous continuum and line wavebands of a sample of barred spirals galaxies (some of which known as starbursts and LINERs) and to characterize their gas and stellar populations. The central region of eight galaxies was studied with OASIS and an iterative technique developed to separate superposed stellar populations. Young populations, responsible for nebular emission lines, are found in nuclear structures. Older stellar components are mostly uniformly distributed. The mass distribution of the different populations indicates a long sequence of burst events over the whole galaxy history. An activity of the type composite/transition region is often seen over the whole central region. SpIOMM was also used to map the emission lines over the entire disk of one of these galaxies. Among other results, it confirms the peculiar line ratio.