Today (and really over the last few days as well) I had a long discussion with Ana Bonaca (Harvard) about the results of our spectroscopy in the GD-1 stellar-stream fields. As my loyal reader knows, Bonaca, Price-Whelan, and I have a prediction for what the radial velocities should look like in the stream, if it is a cold stream that has been hit by a massive perturber. Our new velocity measurements (with the Hectochelle instrument) are not the biggest and best possible confirmation of that prediction!
However, our velocities are not inconsistent with our predictions either. The question is: What to say in our paper about them? We listed the top conclusions of the spectroscopy, and also discussed the set of figures that would bolster and explain those conclusions. Now to plotting and writing.
Along the way to understanding these conclusions, I think Bonaca has found a systematic issue (at extremely fine radial-velocity precision) in the way that the Hectochelle instrument measures radial velocities. I hope we are right, because if we are, the GD-1 stream might become very cold, and our velocity constraints on any perturbation will become very strong. But we will follow up with the Hectochelle team next week. It's pretty subtle.
No comments:
Post a Comment