I have not worked with thermopiles before.
Essentially, for the best performance with Arduino (and Galileo), you would like to get a voltage between 0-5V or 0-3.3V. I don't think the thermopile outputs those voltages. However, it does output some voltage. That voltage can be amplified by an OpAmp, so that it is in a nice measureable range for the analog inputs of the Galileo.
Here is someone who wrote an instructable with a different thermopile, but the circuit should be similar (if not the exact same) Thermopile Sensor.