Tracking merger-driven evolution of galactic nuclei

Are we seeing evolution of nuclei, or just "variance"? Can we actually track the evolution of nuclei as a function of dynamical phase in mergers?

The Toomre Sequence of Merging Galaxies:

range of dynamical ages
morphologically selected -- biased towards major mergers of disk galaxies
well studied at many wavelengths
however, still a pretty heterogenous sample!

(partial) montage from Arp Atlas
courtesy John Hibbard

HST study of the nuclei of the Toomre sequence

Goals:

Can we detect coherent patterns of inflow, starbursts, and superwinds?
Can we connect nuclear morphology with star formation (bars, rings, etc)?
Can we identify low level AGN activity, or presence of a black hole?
Can we characterize the stellar populations in the nuclei of merging galaxies?

Dataset:

optical (V,I) imaging (in hand)
Halpha narrowband (in hand)
medium resolution (2.2A) STIS spectra (obtaining)
low resolution (11A) STIS spectra (obtaining)
NICMOS imaging (obtaining)

Optical Imaging:
(Laine etal 2003)

So, do we see evolution?

Centrally concentrated star formation?

Increasing central density?

Evolution?

no clear trends morphologically or quantitatively
perhaps a hint of rising central density at late times
could be evolution, could be dust, could be variance...