Volume 529, May 2011
|Number of page(s)||10|
|Published online||31 March 2011|
The apparent “reversed” motion of gas and stars in M 82
Institut de Radio Astronomie Millimétrique, Domaine
38406 St. Martin d’Hères,
Received: 4 October 2010
Accepted: 27 January 2011
We summarize earlier and unpublished long-slit spectroscopic measurements of radial velocities of ionized gas and stars along and parallel to M 82’s major axis to a radial distance of ~±2.5 kpc (~±140′′) from the center. In the position-velocity diagram, these measurements indicate a velocity reversal of ~100 km s-1 of gas and/or stars at ~±1.0 kpc (~±50−70′′) on either side of the center, outside the bar. Although seen in earlier observations, and perhaps neglected because they were assumed to be only an effect of heavy local extinction, the positional symmetry of the velocity reversal with respect to the center of M 82, as well as the absence of the reversal in the motion of stars seen in the near-IR Ca ii absorption lines, points to another origin. M 82’s two-armed spiral, as outlined by Mayya et al. (2005, ApJ, 628, L33), may explain a part of the velocity reversal, although this interpretation leaves inconsistencies so that other explanations must also be investigated. A simple, conclusive explanation of the velocity reversal has not yet been found.
While restricted observationally in radial distance to ~120′′ (2 kpc), the near-IR stellar Ca ii absorption lines, which do not show the velocity reversal, indicate a flat radial velocity curve of the stellar disk that remained after the encounter with M 81.
Key words: galaxies: individual: M 82 / galaxies: kinematics and dynamics
© ESO, 2011
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.