Gas Dynamics and Globular Cluster Formation in Interacting Galaxies
Session 68 -- Starbursts and Interacting Galaxies
Oral presentation, Tuesday, 10, 1995, 2:00pm - 3:30pm

## [68.01D] Gas Dynamics and Globular Cluster Formation in Interacting Galaxies

Jayanne English (MSSSO)

Our study tests the idea that globular clusters (GC's) form during the interactions and mergers of disk galaxies that lead to the formation of ellipticals. With $\rm H_{\alpha}$ and 21-cm observations of systems in various stages of merging, we investigate the formation and dynamics of smaller-scale sub-systems like giant HII regions, young populous clusters, and detached HI fragments which are potential GC progenitors. For example, it has been suggested that giant HII regions, with luminosities greater than $\rm 1.5 \times 10^{40} \ erg \ sec^{-1}$, are probably the birthplaces of the young populous clusters (YPC). It has also been proposed that HI fragments with masses greater than $\rm 10^{7 \pm 1} \ \cal M_{\odot}$ could cradle YPC in the spirit of Searle and Zinn's picture for the formation of the galactic metal weak halo. If the idea of globular cluster formation in mergers is correct, then the observed velocities and positions of the GC progenitors during the merger need to be consistent with the ultimate spatial distribution of GC's in the merger remnant, as observed in elliptical galaxies. This consistency will be tested using self-consistent hydrodynamical simulations.

The strategy of the thesis stage of our study has been to acquire $\rm H_{\alpha}$ images and spectra for 17 interacting systems and to study the on-going merger system NGC3256 in detail with optical and HI imaging and spectroscopy. In NGC3256, the giant HII regions have $\rm H_{\alpha}$ luminosities indicating they are potential sites of GC formation. As well, the HI masses of several spatially distinct fragments in this system satisfy the mass criterion. From considerations of merger and HII region timescales, we conclude that several hundred GC progenitor sites are produced in a typical merger of disk galaxies.

An apparently isolated intergalactic cloud with a mass of about $\cal M_{\rm HI} = \rm 3 \times 10^{9} \ h^{-2} \ \cal M_{\odot}$ has serendipitously been discovered in our HI synthesis study of the NGC3256 system.