by Ann » Wed Sep 09, 2015 5:53 am
APOD robot wrote:
Their investigation indicates that NGC 1316 is an enormous elliptical galaxy that started, about 100 million years ago, to devour a smaller spiral galaxy neighbor, NGC 1317, just above it.
That's interesting. NGC 1317 looks rather undisturbed. I would have thought that the distorted outer layers of NGC 1316, as well as the strange and misshapen dust lanes in its inner bulge, indicated a previous merger that NGC 1316 had undergone with another small and probably spiral galaxy. That other small galaxy would now have been completely devoured, leaving only the chaotic tidal streamers and strange inner dust lanes of NGC 1316 as testimony to what had happened.
As I noted during a discussion of an APOD featuring the Andromeda galaxy, NGC 1316 is very slightly bluer than Andromeda overall. To me this suggests a recent, but not too recent, merger involving NGC 1316.
One thing that remains unexplained is the unusually small globular star clusters, seen as faint dots on the image. Most elliptical galaxies have more and brighter globular clusters than NGC 1316. Yet the observed globulars are too old to have been created by the recent spiral collision. One hypothesis is that these globulars survive from an even earlier galaxy that was subsumed into NGC 1316.
Indeed. That, too, suggests that NGC 1316 has undergone a merger some time ago, perhaps two billion years ago or so. It also suggests that the history of NGC 1316 previous to the merger that left the small globulars, the chaotic tidal streamers and the shredded inner dust lanes behind, was a peaceful one. The elliptical galaxies that are chock full of bright globulars have likely had a violent history with lots of giant mergers.
Ann
[quote]APOD robot wrote:
Their investigation indicates that NGC 1316 is an enormous elliptical galaxy that started, about 100 million years ago, to devour a smaller spiral galaxy neighbor, NGC 1317, just above it. [/quote]
That's interesting. NGC 1317 looks rather undisturbed. I would have thought that the distorted outer layers of NGC 1316, as well as the strange and misshapen dust lanes in its inner bulge, indicated a previous merger that NGC 1316 had undergone with another small and probably spiral galaxy. That other small galaxy would now have been completely devoured, leaving only the chaotic tidal streamers and strange inner dust lanes of NGC 1316 as testimony to what had happened.
As I noted during a discussion of an APOD featuring the Andromeda galaxy, NGC 1316 is very slightly bluer than Andromeda overall. To me this suggests a recent, but not too recent, merger involving NGC 1316.
[quote]One thing that remains unexplained is the unusually small globular star clusters, seen as faint dots on the image. Most elliptical galaxies have more and brighter globular clusters than NGC 1316. Yet the observed globulars are too old to have been created by the recent spiral collision. One hypothesis is that these globulars survive from an even earlier galaxy that was subsumed into NGC 1316.[/quote]
Indeed. That, too, suggests that NGC 1316 has undergone a merger some time ago, perhaps two billion years ago or so. It also suggests that the history of NGC 1316 previous to the merger that left the small globulars, the chaotic tidal streamers and the shredded inner dust lanes behind, was a peaceful one. The elliptical galaxies that are chock full of bright globulars have likely had a violent history with lots of giant mergers.
Ann