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Preparing Apertif science: The Bluedisk project

Submitter: Gyula I.G. Jozsa for the Bluedisk team
Description: From 2014 to 2020, the WSRT equipped with the Apertif focal plane array system will offer the opportunity to map the neutral neutral hydrogen content of the local Universe over a quarter of the sky. Meticulous preparation is required for such an ambitious undertaking, and there is no better way to prepare for Apertif than to test and sharpen our tools on real data.

The Bluedisk project, lead by Guinevere Kauffmann (MPA Garching), has recently started with a WSRT neutral-hydrogen survey of 50 galaxies, which are selected based on their optical and ultraviolet properties as observed with the Sloan Digital Sky Survey (SDSS) and GalaxyEvolution Explorer (GALEX) satellite. Based on studies with the Arecibo telescope , we can predict the HI content of these galaxies to better than a factor of two. Half of the sample galaxies with unusually blue outer disks are expected to have an excess neutral hydrogen component. With the Bluedisk project, we will investigate the morphology and kinematics of this excess gas and try to ascertain whether it has been recently accreted from the external environment.

Observations are expected to be completed in May. In February, the Bluedisk team met in Dwingeloo to conduct a first inspection of the observations. It was an inspirational event! The photograph on the left shows some of the team members on a tour of the WSRT. On the right, we show an SDSS colour-composite of the Bluedisk galaxy J110759+352747 overlaid with neutral-hydrogen contours. The galaxy was found to contain 17 billion solar masses of neutral gas and is apparently interacting with several gas-rich companion galaxies.

Are all excess galaxies like this? We will soon see.
Copyright: Image by Bluedisk and ASTRON
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