Atomic Hydrogen and Star Formation in the Bridge/Ring Interacting Galaxy Pair NGC 7714/7715 (Arp 284)
Abstract
We present high spatial resolution 21 cm H I maps of the interacting galaxy pair NGC 7714/7715. We detect a massive (2 × 109 M⊙) H I bridge connecting the galaxies that is parallel to but offset from the stellar bridge. A chain of H II regions traces the gaseous bridge, with Hα peaks near but not on the H I maxima. An H I tidal tail is also detected to the east of the smaller galaxy NGC 7715, similarly offset from a stellar tail. The strong partial stellar ring on the east side of NGC 7714 has no H I counterpart, but on the opposite side of NGC 7714 there is a 109 M⊙ H I loop ~11 kpc in radius. Within the NGC 7714 disk, clumpy H I gas is observed associated with star formation regions. Redshifted H I absorption is detected toward the strong starburst nucleus. We compare the observed morphology and gas kinematics with gas dynamical models in which a low-mass companion has an off-center prograde collision with the outer disk of a larger galaxy. These simulations suggest that the bridge in NGC 7714/7715 is a hybrid between the tidal bridges seen in systems like M51 and the purely gaseous ``splash'' bridges found in ring galaxies like the Cartwheel. The offset between the stars and gas in the bridge may be due to dissipative cloud-cloud collisions occurring during the impact of the two gaseous disks.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 1997
- DOI:
- 10.1086/304286
- arXiv:
- arXiv:astro-ph/9702089
- Bibcode:
- 1997ApJ...483..754S
- Keywords:
-
- Galaxies: Individual: NGC Number: NGC 7714/7715;
- Galaxies: Interactions;
- Galaxies: Kinematics and Dynamics;
- Astrophysics
- E-Print:
- 31 pages, Latex, 11 figures, to be published in the July 10, 1997 issue of the Astrophysical Journal