NGC 6438: A Triple System?
Abstract
We provide photographic and photoelectric information as well as CCD imaging and medium resolution spectroscopy on this system located at a distance of ~32 Mpc. The S0 galaxy has twisted isophotes which also show changes in the ellipticity. Profiles toward the north of this galaxy are 0.1 and 0.2 mag brighter in the B and V bands, respectively, than in any other direction, probably due to the presence of dust in the Irregular system. Several blue regions (B-V = 0.26-0.40) are found in the Irregular object indicating ongoing star formation. One of these regions is located in an extreme of the northern arm, its luminosity being similar to that of the nucleus which is very close to it. Analysis of the spectra shows typical absorption lines and a weak [N II] emission in the S0 galaxy, whereas Hα, [N II], and [S II] emission lines are observed both in the nucleus and in the blue region mentioned above. We determine a high reddening E(B - V) = 1.4 in the nuclear region of this system. Rotation curves show a different behavior for the nucleus and the blue region, which have V_max_ >= 180 km/s and V_max_ = 80 km/s, respectively. All this evidence could support the idea that NGC 6438 is an interacting triplet, one S0 galaxy and two disk galaxies undergoing a merger.
- Publication:
-
The Astronomical Journal
- Pub Date:
- March 1996
- DOI:
- 10.1086/117851
- Bibcode:
- 1996AJ....111.1057D
- Keywords:
-
- GALAXIES: INDIVIDUAL: NGC 6438;
- GALAXIES: INTERACTIONS;
- GALAXIES: IRREGULAR