HI observations of the starburst galaxy NGC 2146^*

¹ Technological Institute of Thessaloniki, Department of Electronics, Al. Papanastasiou 13, Thessaloniki 54639, Greece
² Library Information Services, University of Macedonia, Egnatia 156, Thessaloniki 54006, Greece
³ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
⁴ Kapteyn Astronomical Institute, Postbus 800, 9700 AV Groningen, The Netherlands

A. Taramopoulos

Received: 18 May 2000
Accepted: 16 October 2000

Abstract

NGC 2146 is a peculiar spiral galaxy which is currently undergoing a major burst of star formation and is immersed in a extended H I structure that has morphological and kinematical resemblence to a strong tidal interaction. This paper reports aperture synthesis observations carried out in the 21 cm line with the Very Large Array (VLA) of two fields positioned to optimally cover the H I streams to the north and south of the galaxy, along with a 300 ft total power spectral mapping program to recover the low surface brightness extended emission. The observations reveal elongated streams of neutral hydrogen towards both the north and the south of the optical galaxy extending out up to 6 Holmberg radii. The streams are not in the principle plane of rotation of the galaxy, but instead are suggestive of a tidal interaction between NGC 2146 and a LSB companion that was destroyed by the encounter and remains undetected at optical wavelengths. Part of the southern stream is turning back to fall into the main galaxy, where it will create a long-lived warp in the H I disk of NGC 2146. Analysis of the trajectory of the outlying gas suggests that the closest encounter took place about 0.8 billion years ago and that infall of debris will continue for a similar time span.