The Properties of NGC 2777: Are Companion Galaxies Young?
Abstract
Observations of NGC 2777 show it to be a disturbed, high surface brightness galaxy with a very early type stellar spectrum. It has a "hot" 60/100 micron infrared flux ratio, and there is evidence for galaxy-wide expansion of gas as a result of strong current star formation. NGC 2777 contains a large amount of hydrogen including an H I tail extending toward the larger nearby Sa galaxy, NGC 2775. Evidence for an extension of non-thermal continuum radiation from NGC 2775 toward the companion NGC 2777 is discussed. NGC 2777 is shown to be typical of a class of galaxies that are composed predominantly of recently formed stars and that are companions to larger galaxies. It is argued, however, that star formation activity is not stimulated by gravitational or collisional encounter with the main galaxy. Evidence is discussed which suggests that these kinds of companions are formed in ejection events from older galaxies and that they are more recently created galaxies. Star formation in jets is proposed as the explanation for the strong, general correlation between nonthermal and infrared emission in galaxies.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 1991
- DOI:
- 10.1086/170218
- Bibcode:
- 1991ApJ...375..569A
- Keywords:
-
- Companion Stars;
- Galactic Evolution;
- Interacting Galaxies;
- Star Formation;
- Brightness Distribution;
- H I Regions;
- Infrared Astronomy;
- Interstellar Matter;
- Astrophysics;
- GALAXIES: EVOLUTION;
- GALAXIES: INDIVIDUAL NGC NUMBER: NGC 2775;
- GALAXIES: INDIVIDUAL NGC NUMBER: NGC 2777;
- GALAXIES: INTERACTIONS;
- GALAXIES: INTERSTELLAR MATTER;
- STARS: FORMATION