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Measuring Outer Disk Warps with Optical Spectroscopy

Published online by Cambridge University Press:  01 June 2008

Daniel Christlein  and
Joss Bland-Hawthorn
Daniel Christlein
Affiliation:
Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, 85748 Garching, Germany email: dchristl@mpa-garching.mpg.de
Joss Bland-Hawthorn
Affiliation:
Institute of Astronomy, School of Physics, University of Sydney, NSW 2006, Australia email: jbh@physics.usyd.edu.au
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Abstract

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Warps in the outer gaseous disks of galaxies are a ubiquitous phenomenon, but it is still unclear what generates them. One theory is that warps are generated internally through spontaneous bending instabilities. Other theories suggest that they result from the interaction of the outer disk with accreting extragalactic material. In this case, we expect to find cases where the circular velocity of the warp gas is poorly correlated with the rotational velocity of the galaxy disk at the same radius. Optical spectroscopy presents itself as an interesting alternative to 21-cm observations for testing this prediction, because (i) separating the kinematics of the warp from those of the disk requires a spatial resolution that is higher than what is achieved at 21 cm at low HI column density; (ii) optical spectroscopy also provides important information on star formation rates, gas excitation, and chemical abundances, which provide clues to the origin of the gas in warps. We present here preliminary results of a study of the kinematics of gas in the outer-disk warps of seven edge-on galaxies, using multi-hour VLT/FORS2 spectroscopy.

Keywords

galaxies: evolutiongalaxies: formationgalaxies: kinematics and dynamicsgalaxies: structure
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 4 , Issue S254: The Galaxy Disk in Cosmological Context , June 2008 , pp. 283 - 288
Copyright
Copyright © International Astronomical Union 2009

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