galaxy mergers, day 2

Another great day at the meeting on galaxy–galaxy mergers at STScI. Among the many contributions was a nice discussion of the role of dissipation in shaping merger remnants by Rothberg (STScI), who cited some nice old papers by Carlberg, Gunn, and Kormendy that I have not previously seen; they discuss the issue I go on about: you can't make (high density) ellipticals from the mergers of (low density) spirals. Along the same lines, Novak (UCSC) showed that realistic simulations of disk–disk mergers tend to produce oblate galaxies in prolate halos, with a perpendicular alignment of the symmetry axes. This is testable right now by weak lensing.

McIntosh (Amherst) can show that the merger probability is relatively insensitive to environment (where environment means here the mass of the hosting dark-matter halo). This relates strongly to results in preparation here at NYU by Blanton and Ignarra. He also quipped that we have A growing but dead red sequence and a star-forming but static blue sequence. But we all knew that McIntosh is a poet.

van Dokkum (Yale) showed his evidence for dry merging from very low surface-brightness tidal features in red galaxies. He gave a wonderful presentation of the material, and drew out the tension with Masjedi's work, and Brown's (NOAO). He nicely set up Masjedi for his talk tomorrow! There is a lot to do with the inter-comparison of Bell, Brown, van Dokkum, and Masjedi, because they all have slightly different things to say about the merger rate.

Just like yesterday, there were good talks too numerous for me to mention, but one highlight was Puech's (Paris) result on the near-infrared Tully–Fisher relation at redshift 0.7: When he trims his sample to galaxies with very clean two-dimensional velocity maps, he gets exactly the local relation. So it isn't just the luminosity function of blue galaxies that is static!