Gas-Rich Companions of Isolated Galaxies

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Abstract
We have used the VLA to search for gaseous remnants of the galaxy formation process around six extremely isolated galaxies. We found two distinct H I clouds around each of two galaxies in our sample (UGC 9762 and UGC 11124). These clouds are rotating and appear to have optical counterparts, strongly implying that they are typical dwarf galaxies. The companions are currently weakly interacting with the primary galaxy but look to be in stable orbits as they have dynamical friction timescales of 5–100 Gyr. In one case, (UGC 11124N), we see ongoing accretion of the companion onto the primary galaxy. The small mass ratio involved in this interaction means that the resulting merger will be a minor one. The companion does, however, contain enough gas that the merger will represent a significant infusion of fuel to drive future star formation in UGC 11124 while building up the mass of the disk.