Prof. Niranjan Thatte

Abstract:

We report new results on the stellar kinematics and the mass distribution of the galaxy NGC 3115 based on NIR integral field spectroscopic data. Investigations using long slit spectroscopic data have yielded strong evidence for the presence of a massive dark object of ca. 10(9) solar masses. NGC 3115 therefore appears to be a prominent candidate for hosting a black hole in its center. We demonstrate that with integral field spectroscopy the rotation and velocity dispersion can be much better constrained by sampling in both spatial dimensions. This yields revised and more secure results.

Abstract:

Knowledge of the pattern speed in a barred galaxy is an important prerequisite for determining the radii of its dynamical resonances. Once identified, these can in turn be used to constrain models for nuclear fueling and secular evolution. Here, we present measurements of the pattern speeds in two barred galaxies-one direct (in NGC 1068, using the Tremaine-Weinberg method in the near infrared) and one indirect (in NGC 7479, using a fit to three-dimensional molecular emission-line data). We find good evidence that a configuration of dynamically decoupled "bars within bars" is present in each system.

Abstract:

We present results from integral field spectroscopy of the narrow line region of NGC 1068, carried out with the MPE 3D near infrared imaging spectrometer. A map and velocity field of the [Fe II] fine structure line at 1.64mum is presented. The kinematics of the [Fe II] emission, which arises in partially ionized zones, shows red shifted emission in the north eastern cone of the NLR, and blue shifted emission in the south west, reversed relative to high ionization species such as [Si VI] or [0 111]. We propose a model geometry of the narrow line region which is consistent with existing data and explains the observed [Fe II] kinematics.

Abstract:

The SINFONI integral field spectrometer for the VLT will provide near-infrared spatially resolved spectra at spatial resolutions close to the diffraction limit of the telescope (0." 05 at 2 pm). 1024 spectra can be simultaneously obtained, covering a 32x32 pixel field of view with similar to 100% filling factor. The spectral resolution is R similar to 4500, corresponding to a kinematic resolution of 67 km s(-1). SINFONI is ideally suited to study stellar kinematics in the nuclear regions of normal spiral galaxies, using the near-infrared H and K band CO stellar absorption features. Integral field data from SINFONI will provide high-resolution two-dimensional maps of nuclear velocity dispersion and rotation, which in turn will constrain the anisotropy parameter and yield robust estimates of the central dark mass.

Abstract:

The large populations of young star clusters observed in interacting galaxies like NGC4038 4039 ("The Antennae") are widely believed to be the progenitors of part of the globular cluster systems seen in local elliptical galaxies. For a comprehensive study of the young clusters in the Antennae we have obtained near infrared broad and narrow band images (SOFI on the NTT). integral field spectroscopy (MPE-3D at the AAT) and medium and high resolution spectroscopy (ISAAC VLT-UT1 and UVES VLT-UT2). We find that all of the bright star clusters are young (< 20 Myr), with the interaction region hosting the youngest clusters (similar to 5 Myr). The nuclear starbursts are older (similar to 65 Myr), but also show snore recent star formation activity. Age variations on small spatial scales are seen throughout the merger. Cluster masses range from 10(5) to a few x 10(6) M-circle dot. A comparison between dynamically determined masses and those estimated from photometry in combination with starburst models suggests variations in the IMF from cluster to cluster.