Observations of Starclusters in Starburst Galaxies

Team responsible: Lowell Tacconi-Garman (ESO)
Team members: Bastian(?), Lehnert, Mengel, Snijders, Tacconi-Garman, van der Werf

Finding charts: NGC253NGC1808

We aim to demonstrate SINFONI's capabilities while obtaining valuable information on nature of starclusters in two starburst galaxies. The targets chosen include a number of the brighter clusters in NGC1808 and NGC253. Age estimates of these clusters have been made by several authors (Tacconi-Garman, Sternberg, and Eckart 1996, Forbes et al. 2000 and references therein). A SINFONI-based estimate on the ages of these clusters (via Brackett gamma and/or absorption lines), and/or resolving them spatially will help to determine if they are indeed bound as thought from lower resolution work. Thus, both seeing-limited and AO scale observations will be made.
Target list
NameRA(1950)DEC(1950)Plate-Scale(s)Bands(s)Exp.time(on source)

Science Scope:
This is an exercise designed to clearly demonstrate the abilities of SINFONI (combined H+K integral field (3D) spectroscopy at both the seeing-limited and adaptive optics-assisted spatial scales) while at the same time obtaining valuable scientific data. The chosen targets are (super-)star clusters in two nearby starburst galaxies: NGC253 and NGC1808. We have chosen two IR bright knots in NGC253 (one of which was for some time thought to be the nucleus itself), while for NGC1808 we have chosen two clusters which were revealed in the IR through the 0.6"resolution K-Band imaging made on the NTT with MPE's SHARP NIR speckle imager (Tacconi-Garman, Sternberg, and Eckart 1996 [TGSE96]).

For the brightest knot in NGC253 and for the clusters in NGC1808 there are estimates of the ages (Forbes et al. 2000 and references therein, TGSE96) though in order to determine the true nature of these clusters and their boundedness it is highly desirable to have another, independent, measure of their ages and/or physical sizes.

It is therefore the goal of these observations to determine their ages from equivalent widths of either hydrogen recombination lines or stellar absorption features. In order to obtain all of this information in a single shot (another advantage of SINFONI) we will use the H+K grating. This is especially important since, if the clusters are as young as some estimates have them, it is not a priori clear whether we should expect line emission (predominantly K-Band), absorption (H- and K-Band), or both. Additionally, it may be possible to extract physica sizes of these clusters from high resolution imaging (collapsing the 3-dimensional data structure to 2-dimensions). To this end, we propose both seeing-limited and AO scale observations.

Finally, we note that the contrast between these clusters (especially those in NGC1808) and the underlying K-Band emission is strongly accentuated by high resolution observations (cf. Kotilainen et al. 1996). Thus this is also a nice demonstration of what is possible with MACAO/SINFONI.

Observing strategy
FixedSkyOffset with skyoffset of 30-60"