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Session 82 - Spirals & Irregulars.
Display session, Friday, January 09
NGC 4485 and NGC 4490 are closely interacting spiral galaxies in the NGC 4631 group, separated by a projected distance of 7.7 kpc. Images in B and I bands were obtained with the Burrell-Schmidt telescope at Kitt Peak National Observatory in order to study star-forming regions in their tidal features, including a previously undetected faint tail in NGC 4490. A comparison of the tidal morphology with published simulations suggests that this is a prograde encounter with perigalacticon about 4 x 10^8 yr ago. This time is also the age of the star-forming regions in the tail, based on a comparison of observed (B-I) colors with evolutionary models. Calculations of the Q instability parameter using on a rotation curve derived from published H I observations support the conclusion that star formation was enhanced in the tail at perigalacticon.
Program listing for Friday