by Ann » Mon Apr 04, 2011 3:53 pm
Hi, Rich! glad you appreciated my comments!
Let me speculate a bit about NGC 5101 and 5078.
You said about NGC 5101:
is it a dead galaxy?? Or is its devoid state the result of a super massive black hole at its core that has stripped it of all stars and left over debris ??.. What are your thoughts....??
Yes, if you ask me, I'd say that this is a good example of a galaxy that is "red and dead". You can tell that it is by looking at it. Its shape is extremely symmetrical, with no sign of any upheaval anywhere. At least not in the central region, the bar or inner ring, or in the part of the galaxy that is inside the inner ring. This part of the galaxy looks perfectly smooth and "settled", the way you'd expect it to look if nothing has happened there for a long time. And that "nothing" includes star formation!
There is probably a tiny, tiny amount of star formation in the outer ring. Outer rings like this one are typically relatively good at star formation. Well, this ring isn't doing a very good job of it, seriously, but it may have churned out a Regulus - a B7V star - or two. Here is a GALEX image of 5101. GALEX is particularly good at detecting the ultraviolet light from newly formed, hot stars:
The galaxy is so faint in the ultraviolet that you can barely see it in this image. Still, the blue parts of it contain a tiny, tiny amount of star formation.
Does NGC 5101 have a big black hole which has quenched star formation in this galaxy? Yes, I think that is quite possible. There appears to be quite a strong link between the mass of the black hole at the center of a galaxy and the galaxy's rate of star formation: the bigger and more massive the hole, the fewer new stars will be born. The reason for this appears to be that massive black holes are often associated with jets that blow a lot of the star forming gas and dust clear out of a galaxy, and when the gas that falls back onto the galaxy it is either swallowed by the black hole, or else it is kept turbulent, so that it becomes useless for star formation.
My software classifies NGC 5101 as SB0-a. That means that it is midway between a barred lenticular galaxy with no gas, dust or star formation and an Sa-type spiral. Sa spirals have large yellow centers and arms with some, but not a lot of, star formation.
My software classifies NGC 5078, on the other hand, as an Sa spiral. So my software thinks that NGC 5078 has more dust and gas than NGC 5101 and probably also more star formation. I think that may well be true. In most cases, a thick dust lane like the one we see in NGC 5078 will be associated with
some star formation. Interestingly, my software tells me that NGC 5078 is more ultraviolet than NGC 5101, which fits in with the idea that NGC 5079 has more star formation than NGC 5101. Admittedly, when I checked out images of NGC 5078 on the net, I couldn't find a single image that showed any obvious sign of star formation anywhere in this galaxy. Actually I think your image is doing the best job of it, because there are brightenings in the dust lane in your image which might be evidence of some star formation.
You also said:
While edge on Ngc5078 exhibits a huge amount of dust, gas and galactic building matter, (said to be from the remnants of a spirals interaction with it billions ?? of years prior), but now, tidal forces that the 'S' shaped companion IC879 are exerting on it, pulling the perhaps, already settled core (after the collision) of Ngc5078 apart. And at the same time, IC879 is in a death struggle that you would think it surely can't win!
You are right that IC879 is doomed!
You are also right that IC879 is creating tidal forces that are pulling at NGC 5078. You are also right, I'm sure, that NGC 5078 has undergone mergers during its many billion year old lifetime. These mergers have undoubtedly made NGC 5078 grow, and they have influenced its spiral shape. I don't think, however, that there is any chance or risk that the nucleus of NGC 5078 will be torn apart, certainly not by a small galaxy like IC 879. In a galaxy as large as NGC 5078, with as little star formation as this one has, chances are that the nucleus of this galaxy contains a really big black hole. You don't tear such objects apart.
You are right that these two galaxies are a fascinating old couple! Imagine, they may have been "married" for a really long time!
Ann
Hi, Rich! glad you appreciated my comments!
Let me speculate a bit about NGC 5101 and 5078.
You said about NGC 5101:
[quote]is it a dead galaxy?? Or is its devoid state the result of a super massive black hole at its core that has stripped it of all stars and left over debris ??.. What are your thoughts....??[/quote]
Yes, if you ask me, I'd say that this is a good example of a galaxy that is "red and dead". You can tell that it is by looking at it. Its shape is extremely symmetrical, with no sign of any upheaval anywhere. At least not in the central region, the bar or inner ring, or in the part of the galaxy that is inside the inner ring. This part of the galaxy looks perfectly smooth and "settled", the way you'd expect it to look if nothing has happened there for a long time. And that "nothing" includes star formation!
There is probably a tiny, tiny amount of star formation in the outer ring. Outer rings like this one are typically relatively good at star formation. Well, this ring isn't doing a very good job of it, seriously, but it may have churned out a Regulus - a B7V star - or two. Here is a GALEX image of 5101. GALEX is particularly good at detecting the ultraviolet light from newly formed, hot stars:
[img]http://upload.wikimedia.org/wikipedia/commons/thumb/2/2d/NGC_5101_GALEX.jpg/220px-NGC_5101_GALEX.jpg[/img]
The galaxy is so faint in the ultraviolet that you can barely see it in this image. Still, the blue parts of it contain a tiny, tiny amount of star formation.
Does NGC 5101 have a big black hole which has quenched star formation in this galaxy? Yes, I think that is quite possible. There appears to be quite a strong link between the mass of the black hole at the center of a galaxy and the galaxy's rate of star formation: the bigger and more massive the hole, the fewer new stars will be born. The reason for this appears to be that massive black holes are often associated with jets that blow a lot of the star forming gas and dust clear out of a galaxy, and when the gas that falls back onto the galaxy it is either swallowed by the black hole, or else it is kept turbulent, so that it becomes useless for star formation.
My software classifies NGC 5101 as SB0-a. That means that it is midway between a barred lenticular galaxy with no gas, dust or star formation and an Sa-type spiral. Sa spirals have large yellow centers and arms with some, but not a lot of, star formation.
My software classifies NGC 5078, on the other hand, as an Sa spiral. So my software thinks that NGC 5078 has more dust and gas than NGC 5101 and probably also more star formation. I think that may well be true. In most cases, a thick dust lane like the one we see in NGC 5078 will be associated with [i]some[/i] star formation. Interestingly, my software tells me that NGC 5078 is more ultraviolet than NGC 5101, which fits in with the idea that NGC 5079 has more star formation than NGC 5101. Admittedly, when I checked out images of NGC 5078 on the net, I couldn't find a single image that showed any obvious sign of star formation anywhere in this galaxy. Actually I think your image is doing the best job of it, because there are brightenings in the dust lane in your image which might be evidence of some star formation.
You also said:
[quote]While edge on Ngc5078 exhibits a huge amount of dust, gas and galactic building matter, (said to be from the remnants of a spirals interaction with it billions ?? of years prior), but now, tidal forces that the 'S' shaped companion IC879 are exerting on it, pulling the perhaps, already settled core (after the collision) of Ngc5078 apart. And at the same time, IC879 is in a death struggle that you would think it surely can't win![/quote]
You are right that IC879 is doomed!
You are also right that IC879 is creating tidal forces that are pulling at NGC 5078. You are also right, I'm sure, that NGC 5078 has undergone mergers during its many billion year old lifetime. These mergers have undoubtedly made NGC 5078 grow, and they have influenced its spiral shape. I don't think, however, that there is any chance or risk that the nucleus of NGC 5078 will be torn apart, certainly not by a small galaxy like IC 879. In a galaxy as large as NGC 5078, with as little star formation as this one has, chances are that the nucleus of this galaxy contains a really big black hole. You don't tear such objects apart.
You are right that these two galaxies are a fascinating old couple! Imagine, they may have been "married" for a really long time!
Ann