AAS 195th Meeting, January 2000
Session 104. Dust and Star Formation in Galaxies
Display, Saturday, January 15, 2000, 9:20am-4:00pm, Grand Hall

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[104.06] An ISO View of Secular Evolution in Galaxy Pairs?

D.L. Domingue, J.W. Sulentic (U. Alabama), C. Xu, J.M. Mazzarella (IPAC/Caltech)

Isolated galaxy pairs with mixed morphology (E/S0 + S/I) provide a unique opportunity to study the gravitational effects of a massive perturber on the gas and dust content of a spiral disk. This is the only kind of binary galaxy where one can unambiguously search for evidence of cross-fueling between the components. We address these issues with H\alpha and ISOCAM imaging of four interacting galaxy pairs taken from a larger study that is currently underway. The pairs (NGC 7752/3, CPG542, CPG552, and CPG468) were observed with the broad-band ISOCAM LW3(12--18 \mum) and narrow-band LW8(11.3 \mum) filters. LW3 samples the continuum emission from very warm dust while LW8 maps the spatial distribution of the 11.3 \mum PAH emission. We also obtained ISOPHOT P32 data at 60 and 100 \mum for these pairs.

The H/alpha emission morphologies of the sample can be classified as: 1) nuclear concentrated emission, 2) disk-wide emission, 3) tidal-arm emission and 4) compact emission displaced from the nucleus. All of the pairs show self-consistent structure in the LW3 and LW8 bands as well as a high spatial correllation with H\alpha images convolved to the same resolution. This is a general confirmation that warm dust is heated most in sites of star formation. There is no evidence for a decrease in the 11.3/15 \mum ratio with equivalent width excess, as is seen for extreme starburst knots in the Antennae. The NGC 7752/3 system is of particular interest because the companion shows an unusually high gas mass and dynamical models point to evidence for a continuous fueling of the companion from the spiral disk of the more massive component. A comparitive morphology of H\alpha and ISOCAM images indicates that the two strongest mid-IR `hotspots' are giant HII regions at the edge of spiral arms involved in disk-wide star formation. The companion with the largest H\alpha equivalent width in our sample shows a warmer 60/100 H\alpha emission color than NGC 7753 the dominant spiral. This is indicated by both our ISOPHOT maps and HIRES IRAS data. This work has been partially supported by a University of Alabama Research Fellowship.

The author(s) of this abstract have provided an email address for comments about the abstract: domingue@hera.astr.ua.edu

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