They may slow down in the chill, but they won't stop growing entirely.
If it really gets too cold you can get plant heat mats that will help. These are usually used for seed starting purposes, but no reason they won't work with your herbs.
Alternatively, get a foam cooler and rig a socket so you can keep a lightbulb (regular incandescent) of a bout 15-20 watts burning. Rest a tray over the top of it and put your herb containers on it. That'll provide all the warmth they need.
Scallions can be grown like any other indoor plant, except the container needs to be deeper. You want at least four inches under the bulb (six would be better), and it should be buried to the point where the tip barely breaks the ground.
For growing things like scallions, radishes, greens, etc. indoors I use an oversized window box as the container, and put it in my grow stand under a bank of flourescents.