Estimating Subsurface Anisotropy: Combining Waveform Tomography and Simulated Annealing

Crosshole seismic tomography has been used by Vale to provide geophysical images of mineralized massive sulphides in the Eastern Deeps deposit at Voisey\u27s Bay. High resolution seismic images are presented by applying acoustic waveform tomography to these data. In waveform tomography, an initial model is required which predicts the first arrival traveltimes to within a half-cycle of the lowest frequency in the data. Because seismic velocity anisotropy can be significant, the initial model must quantify the anisotropy, as well as the velocity, in order to meet the half-cycle criterion. In our case study, difficulties were encountered in generating an accurate anisotropy model through traveltime tomography, and the starting model for waveform tomography failed the half-cycle criterion. We formulate a new, semi-global approach for finding the best-fit 1-D elliptical anisotropy model using simulated annealing, and successfully apply this technique to the Vosiey\u27s Bay dataset, as well as synthetically generated datasets

Kinematics and stellar populations of the dwarf elliptical galaxy IC 3653

We present the first 3D observations of a diffuse elliptical galaxy (dE). The good quality data (S/N up to 40) reveal the kinematical signature of an embedded stellar disc, reminiscent of what is commonly observed in elliptical galaxies, though similarity of their origins is questionable. Colour map built from HST ACS images confirms the presence of this disc. Its characteristic scale (about 3 arcsec = 250 pc) is about a half of galaxy's effective radius, and its metallicity is 0.1-0.2 dex larger than the underlying population. Fitting the spectra with synthetic single stellar populations (SSP) we found an SSP-equivalent age of 5 Gyr and nearly solar metallicity [Fe/H]=-0.06 dex. We checked that these determinations are consistent with those based on Lick indices, but have smaller error bars. The kinematical discovery of a stellar disc in dE gives additional support to an evolutionary link from dwarf irregular galaxies due to stripping of the gas against the intra-cluster medium.Comment: 15 pages, 10 figures, accepted to MNRA

Internal kinematics and stellar populations of dE galaxies: Clues to their formation/evolution

What is the origin of the numerous population of diffuse elliptical galaxies (dE) in clusters? These galaxies formed their stars several billion years ago and lost their gas. Though the stellar winds resulting from star formation and the interactions with the environment undoubedtly play a role, their respective role and details of the mechanism of this evolution is still debated. In this presentation we will review the first 3D spectroscopic observations of a handful of dE galaxies. These data reveal complex kinematical structures, with embedded discs and counter rotating cores, and they open extremely promising perspectives for studying the history of the stellar population throughout these various features. The presence of disks, which was already known from detailed image analysis, and of complex kinematics and the new constraints on the stellar population enforce the hypothesis of the evolutionary connection between dEs and disk galaxies.Comment: To be published in the proceedings of IAU Colloquium 198 on a "near-field cosmology with dwarf elliptical galaxies