Journal Article

Warp or lag? The ionized and neutral hydrogen gas in the edge-on dwarf galaxy UGC 1281

P. Kamphuis, R. F. Peletier, P. C. van der Kruit and G. H. Heald

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 414, issue 4, pages 3444-3457
Published in print July 2011 | ISSN: 0035-8711
Published online July 2011 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2011.18641.x
Warp or lag? The ionized and neutral hydrogen gas in the edge-on dwarf galaxy UGC 1281

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The properties of gas in the haloes of galaxies constrain global models of the interstellar medium. Kinematical information is of particular interest since it is a clue to the origin of the gas. Until now mostly massive galaxies have been investigated for their halo properties.

Here we report on deep H i and Hα observations of the edge-on dwarf galaxy UGC 1281 in order to determine the existence of extraplanar gas and the kinematics of this galaxy. This is the first time a dwarf galaxy is investigated for its gaseous halo characteristics. We have obtained Hα integral field spectroscopy using PPAK at Calar Alto and deep H i observations with the Westerbork Synthesis Radio Telescope (WSRT) of this edge-on dwarf galaxy. These observations are compared to 3D models in order to determine the distribution of H i in the galaxy.

We find that UGC 1281 has Hα emission up to 25 arcsec (655 pc) in projection above the plane and in general a low Hα flux. Compared to other dwarf galaxies UGC 1281 is a normal dwarf galaxy with a slowly rising rotation curve that flattens off at 60 km s−1 and a central depression in its H i distribution. Its H i extends 70 arcsec (1.8 kpc) in projection from the plane. This gas can be explained by either a warp partially in the line-of-sight or a purely edge-on warp with rotational velocities that decline with a vertical gradient of 10.6 ± 3.7 km s−1 kpc−1. The line-of-sight warp model is the preferred model as it is conceptually simpler. In either model the warp starts well within the optical radius.

Keywords: galaxies: dwarf; galaxies: haloes; galaxies: ISM; galaxies: kinematics and dynamics; galaxies: spiral; galaxies: structure; UGC 1281

Journal Article.  10602 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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