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Abstract: We present new dynamical models of the merger remnant NGC 7252 which includestar formation simulated according to various phenomenological rules. By usinginteractive software to match our model with the observed morphology and gasvelocity field, we obtain a consistent dynamical model for NGC 7252. In ourmodels, this proto-elliptical galaxy formed by the merger of two similargas-rich disk galaxies which fell together with an initial pericentricseparation of ~2 disk scale lengths approximately 620 Myr ago. Results from twodifferent star formation rules- density-dependent and shock-induced- showsignificant differences in star formation during and after the first passage.Shock-induced star formation yields a prompt and wide-spread starburst at thetime of first passage, while density-dependent star formation predicts a moreslowly rising and centrally concentrated starburst. A comparison of thedistributions and ages of observed clusters with results of our simulationsfavors shock-induced mechanism of star formation in NGC 7252. We also presentsimulated color images of our model of NGC 7252, constructed by incorporatingpopulation synthesis with radiative transfer and dust attenuation. Overall thepredicted magnitudes and colors of the models are consistent with observations,although the simulated tails are fainter and redder than observed. We suggestthat a lack of star formation in the tails, reflected by the redder colors, isdue to an incomplete description of star formation in our models rather thaninsufficient gas in the tails.

Author: Li-Hsin Chien, Joshua Edward Barnes

Source: https://arxiv.org/

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