Astronomical instrumentation

Abstract:

I present recent spectroscopic observations of nearby AGN obtained at 8-13 mu m with TReCS on Gemini-S. The observations reveal variations in absorption depth on subarcsecond scales in Circinus and NGC 5506 and delineate the regions of ionized gas and PAH emission region in Circinus. Several nearby active galaxies show evidence of resolved circumnuclear dusty structures with sizes of 10s of parsecs. The silicate absorption profile towards the most heavily obscured nuclei are narrower than those in the galaxies with tau((9.7 mu m)) < 3, possibly reflecting larger average grain sizes in the latter resulting from destruction of the smallest grains by the AGN.

Abstract:

We discuss the implementation of the complex wavefront modulation model in practical optical alignment procedures and present its interim results. This modulation model describes the relation between the alignment state and the wavefront of a system, both are expressed in mathematical complex quantities. It addresses the importance of the coupled inter-element alignment effect to the resultant system wavefront. We utilise this effect in order to extract the alignment state of a system from measured optical wavefronts. We demonstrate the method's practical applicability to the real optical alignment procedure by showing alignment simulations of a centered three-mirror system.

Abstract:

We present results from our ongoing effort to understand the nature and evolution of nearby galaxies using the SAURON integral-field spectrograph. In this proceeding we focus on the study of the particular case formed by the interacting galaxies NGC 5953 and NGC 5954. We present stellar and gas kinematics of the central regions of NGC5953. We use a simple procedure to determine the age of the stellar populations in the central regions and argue that we may be witnessing the formation of a kinematically decoupled component (hereafter KDC) from cold gas being acquired during the ongoing interaction with NGC 5954.

Abstract:

We present selected results from integral-field spectroscopy of 48 early-type galaxies observed as part of the SAURON survey. Maps of the H beta, Fe5015, Mgb and Fe5270 indices in the Lick/IDS system were derived for each of the survey galaxies. The metal line strength maps show generally negative gradients with increasing radius roughly consistent, with the morphology of the light profiles. Remarkable deviations from this general trend exist, particularly the Mg b isoindex contours appear to be flatter than the isophotes of the surface brightness for about 40% of our galaxies without significant dust features. Generally these galaxies exhibit significant rotation. We infer from this that the fast-rotating component features a higher metallicity and/or an increased Mg/Fe ratio, as compared to the galaxy as a whole.We also use the line strength maps to compute average values integrated over circular apertures of one effective radius, and derive luminosity weighted ages and metallicities. The lenticular galaxies show a, wide range in age and metallicity estimates, while elliptical galaxies tend to occupy regions of older stellar populations.