I spent the morning in the science session devoted to galaxy morphologies – shapes- and environments and the lunch break with my press hat on listening to the latest results from Hubble (the telescope, not the astronomer; even a repair mission won’t help him now). There was lots of good stuff at both, but three items in particular grabbed my attention.
The first was the talk by Preethi Nair from the University of Toronto who has classified 15,000 of the brightest Sloan galaxies by eye. Her classification is much more detailed than ours, and includes many of the things we’ll try to do with Zoo 2 when it launches (hopefully in a month or so). The important thing from our point of view is that she agrees that visual classification makes a huge difference to the results; she found 20% difference between her ellipticals and those classified by looking at the concentrations of the galaxies. (Ellipticals – on average – are more concentrated – there’s more stuff in the middle – than spirals).
The second came in the press conference talk by Duilia de Mello. Her group have been studying a ‘blue blob’ near the classic spiral galaxy M81, which turned out to be a group of stars forming outside the main disks, probably as a result of interaction between M81 and its neighbours, the most prominent of which is M82. Indeed, Hubble images show some older stars which date to the time of the last major interaction between the systems.
The story of the blue blob should be ringing bells for all of you who read the Galaxy Zoo forum. We’ve been puzzling about a blue blob known as Hanny’s Voorwerp for a while, and on face value it does look like the blue blobs discussed by de Mello’s team. We’re working on getting a quick spectrum of the Voorwerp; the other possibility is that it’s a distant galaxy from which we’re only seeing one spectral line. Either way, it’d be great to find out which.
Finally, a cautionary tale from Gene Byrd. He was talking about NGC4622, a seemingly ordinary spiral galaxy. The only problem is that its two outer arms are rotating in the opposite direction to the two inner arms Byrd’s team managed to identify via some very clever image processing. Some of our GZ results assume that our results assume that the direction the spiral arms are pointing tells us about the direction of rotation of a galaxy. Most (more than 90% of galaxies do), but this sort of thing is a reminder that we don’t really understand spiral arms at all.
Update : You really should keep an eye on the hard work being done over at the Astronomy Cast conference page. With multiple people covering (almost) all the things going on at the meeting, this is the future of reporting from big conferences like this. And I’m not just saying that because they’re hosting drinks later this evening.