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07-01-2009
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NGC 1167: Interacting with its neighbour?

Submitter: Christian Struve
Description: Recently I (under supervision of Raffaella Morganti and Tom Oosterloo) have finished very deep neutral hydrogen (HI) observations with the Westerbork Synthesis Radio Telescope of the early-type galaxy NGC 1167. The image above shows an overlay of HI contours on an optical image (taken from the Digital Sky Survey). Most of the HI of NGC 1167 (top left galaxy) is in ordered rotation, i.e. it rotates around the nucleus in circular orbits. However, part of the gas on the right side of the galaxy does not follow this rotation, indicating some accretion or interaction event in the past.

To the right of NGC 1167 another galaxy (named UGC 2465) with HI is located that also shows a perturbed HI kinematics. The figure to the right shows a position-velocity diagram along the major axis of UGC 2465 (solid line). The velocity of the HI increases as expected for a disk galaxy seen "edge-on", but on the right side the velocities drop again by about 100 km/s.

Did NGC 1167 interact with UGC 2465 in the past? The question of an interaction between the two galaxies is important because such an interaction could provide unsettled gas to the nuclear regions of NGC 1167 where an active, super massive black hole is currently accreting gas. Alternatively, the accretion of small gas clouds from intergalactic space could also provide a mechanism to feed the black hole. We will study these, and other, questions in detail in the coming months.
Copyright: Astron
 
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