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How large do HI disks grow?

Submitter: Gyula I. G. Józsa on behalf of the Bluedisk team
Description: One important aspect of the Bluedisk" multi-wavelength survey of ~50 Milky Way-sized galaxies are the neutral hydrogen observations conducted with the WSRT until June last year. The main goal of the survey, lead from MPA Garching (Guinevere Kauffmann & Jing Wang) and ASTRON (Gyula Józsa, Paolo Serra), is to study how galaxies accrete material from their ambient intergalactic medium, but it also serves as an appetizer for the future large-area blind surveys that will be done with Apertif.

Using findings from the GASS survey we predicted that half of our galaxies, those forming stars in their outskirts, would contain significantly more neutral gas than the other half. Surprisingly, our images show that in neutral-gas , the "blue-rimmed" galaxies seem to be pretty undisturbed systems, except that they are much larger than the "normal" galaxies. If anything, they are even more symmetric, despite some small clumps in their projected disks (which might be gaseous counterparts of small satellites). This speaks against a scenario where systems similar to ours acquire their gas in big, violent mergers of large systems.

The image shows a comparison of four systems of our sample, the neutral gas shown in contours, overlaid on an optical SDSS image. All panels have a size of 140 kpc (450.000 light years). Guess which ones are from which half.

Read on about our first findings here: arXiv: 1303.3538.
Copyright: Image by Jing Wang and MPA
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