A Counterrotating Bulge in the S(b) Galaxy NGC 7331

Astronomy and Astrophysics – Astronomy

Scientific paper

Rate now

  [ 0.00 ] – not rated yet Voters 0   Comments 0

Details

55

Galaxies: Individual Ngc Number: Ngc 7331, Galaxies: Kinematics And Dynamics, Galaxies: Spiral, Galaxies: Structure, Galaxies: Formation

Scientific paper

We have found that the bulge of the large, nearby Sb galaxy NGC 7331 rotates retrograde to its disk. Analysis of spectra in the region of the near-IR Ca II triplet along the major axis shows that, in the radial range between 5" and ~20", the line-of-sight velocity distribution of the absorption lines has two distinct peaks and can be decomposed into a fast-rotating component with {v} / sigma > 3, and a slower rotating, retrograde component with {v} / sigma ~ 1--1.5. The radial surface brightness profile of the counterrotating component follows that of the bulge, obtained from a two-dimensional bulge-disk decomposition of a near-infrared K-band image, while the fast-rotating component follows the disk. At the radius at which the disk starts to dominate, the isophotes change from being considerably boxy to being very disky. Although a number of spiral galaxies have been found that contain cold, counterrotating disks, this is the first galaxy known to have a boxy, probably triaxial, fairly warm, counterrotating component, which is dominating in the central regions. If it is a bar seen end-on, this bar has to be thicker than the disk. We find that NGC 7331, even though it is a fairly early-type spiral, does not have a conventional, corotating bulge. The fact that the inner component is retrograde makes us believe that it was formed from infalling material in either stellar or gaseous form (see, e.g. Balcells & Quinn). Another possibility, however, is that the structure has been there since the formation of the galaxy. In this case, it will be a challenge to explain the large change in orientation of the angular momentum when going outward radially.

No associations

LandOfFree

Say what you really think

Search LandOfFree.com for scientists and scientific papers. Rate them and share your experience with other people.

Rating

A Counterrotating Bulge in the S(b) Galaxy NGC 7331 does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with A Counterrotating Bulge in the S(b) Galaxy NGC 7331, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and A Counterrotating Bulge in the S(b) Galaxy NGC 7331 will most certainly appreciate the feedback.

Rate now

     

Profile ID: LFWR-SCP-O-1357021

  Search
All data on this website is collected from public sources. Our data reflects the most accurate information available at the time of publication.