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HI in the shell elliptical NGC 3656

M. Balcells·J. H. van Gorkom·R. Sancisi·C. del Burgo
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Abstract

VLA neutral hydrogen observations of the shell elliptical NGC 3656 reveal an edge-on, warped minor axis gaseous disk (M_HI ~ 2.10^9 Msun) extending 7 kpc. HI is also found outside the optical image, on two complexes to the North-East and North-West that seem to trace an outer broken HI disk or ring, or possibly one or two tidal tails. Integral-field optical fiber spectroscopy at the region of the bright southern shell of NGC 3656 has provided a determination of the stellar velocities of the shell. The shell has traces of HI with velocities bracketing the stellar velocities, providing evidence for a dynamical association of HI and stars at the shell. Within the errors the stars have systemic velocity, suggesting a possible phase wrapping origin for the shell. We detect five dwarf galaxies with HI masses ranging from 2.10^8 Msun to 2.10^9 Msun all within 180 kpc from NGC 3656 and all within the velocity range (450 \kms) of the HI of NGC 3656. For the NGC 3656 group to be bound requires a total mass of 3-7.4x10^{12} Msun, yielding a mass to light ratio from 125 to 300. The overall HI picture presented by NGC 3656 supports the hypothesis of a disk-disk merger origin, or possibly an ongoing process of multiple merger with nearby dwarfs.

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M. Balcells, J. H. van Gorkom, R. Sancisi, C. del Burgo. 2001-07-09. HI in the shell elliptical NGC 3656. https://doi.org/10.1086/323310

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