Sebastien Blais-Ouellette

Accurate Determination of the Mass Distribution in Spiral Galaxies. II. Testing the Shape of Dark Halos

New high-resolution Fabry-Perot data at the Canada-France-Hawaii Telescope combined with published VLA 21 cm observations are used to determine the mass distribution of NGC 3109 and IC 2574. The multiwavelength rotation curves allow us to test with confidence different dark halo functional forms from the pseudoisothermal sphere to some popular halo distributions motivated by cold dark matter N-body simulations. It appears that the density distributions with high central concentration, predicted by these simulations, are very hard to reconcile with rotation curves of late-type spiral galaxies. Modified Newtonian dynamics (MOND) is also considered a potential solution to missing mass and is tested the same way. Using the higher resolution Hα data and new H I data for NGC 3109, one can see that MOND can reproduce in detail the rotation curves of IC 2574 and NGC 3109. However, the value for the MOND universal constant is ~2 times larger than the value found for more massive spiral galaxies.

Visible Imaging Fourier Transform Spectrometer: Design and Calibration

We present details of the design, operation and calibration of an astronomical visible-band imaging Fourier transform spectrometer (IFTS). This type of instrument produces a spectrum for every pixel in the field of view where the spectral resolution is flexible. The instrument is a dual-input/dual-output Michelson interferometer coupled to the 3.5 meter telescope at the Apache Point Observatory. Imaging performance, and interferograms and spectra from calibration sources and standard stars are discussed.

Gallery of Datacubes Obtained with the Livermore Imaging Fourier Transform Spectrometer

We have acquired spatial-spectral datacubes of astronomical objects using the Livermore visible-band imaging Fourier transform spectrometer at Apache Point Observatory. Each raw datacube contains hundreds of thousands of spectral interferograms. We present in-progress demonstrations of these observations.

Imaging Fourier Transform Spectrometer for Visible Band Astronomy

The Livermore Visible Imaging Spectrometer is an astronomical dual-input, dual-output Michelson interferometer. The instrument has been used at the Palomar Observatory and data have been collected at both low and moderate spectral resolution.