Exoplanets and Stellar Physics

Abstract:

We present K, L and M diffraction-limited images of NGC 1068 obtained with NAOS+CONICA at VLT/YEPUN over a 3.5" field around the central engine. Hot dust (Tcol = 550-650 K) is found in three different regions : (a) in the true nucleus, seen as a slightly NS elongated, core of extremely hot dust, "resolved" in K and L with respective diameters of ~5 pc and 8.5 pc ; (b) along the NS direction, as a "spiral arm" and a southern tongue ; (c) as a set of parallel elongated nodules ("wave-like") bracketting the jet. Several structures observed on radio maps, mid-IR or HST UV-visible maps are seen, so that a precise registration can be done from UV to 6 cm. These results do support the current interpretion that source (a) corresponds to emission from dust near sublimation temperature delimiting the walls of the cavity in the central obscuring torus. Structure (b) is thought to be a mixture of hot dust and active star forming regions along a micro spiral structure that could trace the tidal mechanism bringing matter to the central engine. Structure c)which was not known, exhibits too high a temperature for "classical'' grains ; it is most probably the signature of transiently heated very small dust grains (VSG) : "nano-diamonds", which are resistant and can form in strong UV field or in shocks, are very attractive candidates. The "waves'' can be condensations triggered by jet induced shocks, as predicted by recent models. First estimates, based on a simple VSG model and on a detailed radiative transfer model, do agree with those interpretations, both qualitatively and quantitatively.

Abstract:

We are using adaptive optics on Keck and the VLT to probe the dynamics and star formation in Seyfert and QSO nuclei, obtaining spatial resolutions better than 0.1" in the H- and K-bands. The dynamics are traced via the 2.12um H_2 1-0S(1) line, while the stellar cluster is traced through the CO 2-0 and 6-3 absorption bandheads at 2.29um and 1.62um respectively. Matching disk models to the H_2 rotation curves allows us to study nuclear rings, bars, and warps; and to constrain the mass of the central black hole. The spatial extent and equivalent width of the stellar absorption permits us to estimate the mass of stars in the nucleus and their contribution to the emission. Here we report on new data for I Zwicky 1, Markarian 231, and NGC 7469.

Abstract:

Simulations of frigid Neoproterozoic climates have not considered the tendency of thick layers of floating marine ice to deform and spread laterally. We have constructed a simple model of the production and flow of marine ice on a planetary scale, and determined ice thickness and flow in two situations: when the ocean is globally ice‐covered (“hard snowball”) and when the tropical waters remain open (“soft snowball”). In both cases, ice flow strongly affects the distribution of marine ice. Flowing ice probably carries enough latent heat and freshwater to significantly affect the transition into a Snowball Earth climate. We speculate that flowing marine ice, rather than continental ice sheets, may be the erosive agent that created some Neoproterozoic glacial deposits.