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Stars & Gas in the Galaxy Pair II Zw 70/71

A. L. Cox·L. S. Sparke·A. M. Watson·G. van Moorsel
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Abstract

II Zw 71 (UGC 9562) was classified as a ``probable'' polar-ring galaxy in the Polar-Ring Catalog, based upon its optical appearance. We present 21 cm and optical observations of this galaxy and its companion, the blue star-forming dwarf II Zw 70. Our 21 cm observations show that 5e8 solar masses of HI is present in a polar ring orbiting II Zw 71, and show a spatially and kinematically contiguous streamer with 2.5e8 solar masses of HI gas between the two galaxies. This gaseous bridge, plus our observations of Halpha line emission in the polar ring and in II Zw 70, are strong evidence for an ongoing interaction between the two galaxies. However, the configuration of the streamer suggests that the polar ring itself may well have predated the current interaction, which then stimulated an outburst of star formation in the ring gas.

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A. L. Cox, L. S. Sparke, A. M. Watson, G. van Moorsel. 2000-11-08. Stars & Gas in the Galaxy Pair II Zw 70/71. https://doi.org/10.1086/318750

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