This contribution was written by Martha Haynes during the 5th annual Undergraduate ALFALFA team workshop at Arecibo Jan 16-19 2012 when we conducted a first set of observations designed to explore the most interesting candidate signals without optical counterparts.

Despite what people might think, our annual trips to Arecibo in January are not spent lying on the beach under a palm tree. We work hard… and sleep little! In addition to full days devoted to lectures and activities centered on radio astronomy and ALFALFA science plus interesting topics presented by Patrick Taylor (“Planetary Radar Astronomy”), Ellen Howell (“The Geology of Puerto Rico”) and Julia Deneva (“Pulsars”) of the Arecibo staff, plus the great tours of the platform (thanks to Dana again!) and the dish itself, we also have conducted 3 nights of observing. Everyone on the UAT has had a chance to participate in the observations for an hour or so on two different nights, so all of us now are a bit sleep deprived.

Cornell ALFALFA grad students Greg and Betsey led the observing runs from midnight until 7am. Unfortunately, there was a power failure before the end of the run on the 3rd morning, so we lost a little time. But, observing on these three nights has given us the change to test and finalize our observing strategy so that we could write up our documentation and develop some routines to schedule, log and undertake quick checks of data quality. And, furthermore, we also have confirmed the reality of some of the “dark galaxy” HI signals, candidate detections found in the main ALFALFA dataset but without any evidence of a stellar counterpart.

These 3 nights are just the first part of a more extensive program we hope to conduct later this spring, and over the next few years. But even with this short run, we have taken a first significant step forward. By making these “follow-up” observations, we have eliminated any possibility of man-made radio interference as the source of the apparent HI signal. Next we will have to go use other telescopes to look harder at the positions where we detect the HI signal for associated starlight, but now we know where to look: the hunt for “dark galaxies” is ready to continue!!!