Very Large Array The VLA of the National Radio Astronomy Observatory is operated by Associated Universities , Inc. under cooperative agreement with the National Science Foundation . ( VLA ) neutral hydrogen observations of the shell elliptical NGCÂ 3656 reveal an edge-on , warped minor axis gaseous disk ( M _ { HI } \sim 2 \times 10 ^ { 9 } M _ { \odot } ) 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 .
These complexes link with the outer edges of the inner disk , and appear displaced with respect to the two optical tails in the galaxy .
The disk kinematics is strongly lopsided , suggesting recent or ongoing accretion .

Integral-field optical fiber spectroscopy at the region of the bright southern shell of NGCÂ 3656 has provided a determination of the stellar velocities of the shell .
The shell , at 9 kpc from the center , 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 probed a region of 40 ’ \times 40 ’ ( 480 kpc \times 480 kpc ) \times 1160 km/s down to an HI mass sensitivity ( 6 \sigma ) of 3 \times 10 ^ { 7 } M _ { \odot } and detect five dwarf galaxies with HI masses ranging from 2 \times 10 ^ { 8 } M _ { \odot } to 2 \times 10 ^ { 9 } M _ { \odot } all within 180 kpc from NGC 3656 and all within the velocity range ( 450 km s ^ { -1 } ) of the HI of NGC 3656 .
The dwarfs were previously catalogued but none had a known redshift .
For the NGC 3656 group to be bound requires a total mass of 3 - 7.4 \times 10 ^ { 12 } M _ { \odot } , yielding a mass to light ratio from 125 to 300 .

The overall HI picture presented by NGCÂ 3656 supports the hypothesis of a disk-disk merger origin , or possibly an ongoing process of multiple merger with nearby dwarfs .