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Astron. Astrophys. 354, L21-L24 (2000)

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6. Conclusions

In this letter we have demonstrated a morphological method of deciphering the triggering mechanisms of starbursts galaxies through the use of a color-asymmetry diagram. Based on a sample of nearby starbursts, we have demonstrated that those starbursts generally regarded as triggered by interactions or mergers are located in a special region of CAD characterized by large optical asymmetry at a given color. In contrast, the two starbursts in our sample (NGC 3310 and NGC 7678) that are probably not triggered from a major interaction/merger fall nearly on the fiducial color-asymmetry sequence of normal galaxies.

While our sample is small, we suggest that the color-asymmetry diagram can be used to separate starbursts triggered by mergers/interactions from those triggered from other causes. We confirm this interpretation by comparing the degree of deviation from the fiducial color-asymmetry sequence to HI line-width ratios, which serves as a dynamical indicator of strong gravitational interactions. This physical-morphological method is quantitative and appears to be superior to analyses of outliers in, e.g., two-color plots such as [FORMULA] and [FORMULA]. This physical-morphological method is also well-suited for studying the nature and evolution of distant galaxies where it is difficult to gather information beyond images, magnitudes, and redshifts.

This work was funded by NASA contract WAS7-1260 to JPL; AR7539, AR7518 and GO7875, and GO7339 from STScI which is operated by AURA, Inc. under NASA contract NAS5-26555; NASA LTSA contract NAG5-6032; and NSF contract AST-9970780. JSG and CJC thank the WFPC-2 team.

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© European Southern Observatory (ESO) 2000

Online publication: January 31, 2000