by Ann » Mon Nov 01, 2010 3:03 am
I found this information about NGC 7727 on the net:
Paper: Star Cluster Population in NGC 7727
Volume: 322, The Formation and Evolution of Massive Young Star Clusters
Page: 219
Authors: Trancho, G.; Miller, B.W.; Schweizer, F.; Whitmore, B.
Abstract: We present observations of the merger NGC7727 taken in the optical with HST and in the K-band with Gemini South in excellent seeing. Comparing the optical data with Monte-Carlo simulations (Whitmore et al. 1997) suggests the presence of an intermediate-age population, but this is not conclusive due to the age/metallicity degeneracy in optical colours. Therefore, we have obtained images in Ks with FLAMINGOS-I on Gemini South since the V-I vs. V-Ks diagram is an excellent separator of age and metallicity. Comparing the data with Bruzual & Charlot (2001) models confirms the presence of an intermediate-age population (between 1-2 Gyr) and, surprisingly, a lack of old, metal-poor clusters.
So there is an intermediate population here, 1-2 billion years old, which says something about when the merger stopped generating new stars. Clearly NGC 7727 is an elliptical galaxy in the making.
It is a fascinating picture. I like the subtle colors: the bulge is yellow-orange, the arms are mostly greyish-neutral (made up of intermediate-aged stars, no doubt) and there is a hint of blue in two arcs on opposite sides of the bulge. That is probably where we find the youngest stars in this galaxy. Fascinatingly, though, "above" the bulge there is what looks like a large cluster or an association, but it isn't really bluish in color - perhaps it is a background galaxy?
There really does seem to be a double nucleus in this galaxy!
This is a very interesting picture, Kent. Thank you for posting it!
Ann
I found this information about NGC 7727 on the net:
[quote]Paper: Star Cluster Population in NGC 7727
Volume: 322, The Formation and Evolution of Massive Young Star Clusters
Page: 219
Authors: Trancho, G.; Miller, B.W.; Schweizer, F.; Whitmore, B.
Abstract: We present observations of the merger NGC7727 taken in the optical with HST and in the K-band with Gemini South in excellent seeing. Comparing the optical data with Monte-Carlo simulations (Whitmore et al. 1997) suggests the presence of an intermediate-age population, but this is not conclusive due to the age/metallicity degeneracy in optical colours. Therefore, we have obtained images in Ks with FLAMINGOS-I on Gemini South since the V-I vs. V-Ks diagram is an excellent separator of age and metallicity. Comparing the data with Bruzual & Charlot (2001) models confirms the presence of an intermediate-age population (between 1-2 Gyr) and, surprisingly, a lack of old, metal-poor clusters.[/quote]
So there is an intermediate population here, 1-2 billion years old, which says something about when the merger stopped generating new stars. Clearly NGC 7727 is an elliptical galaxy in the making.
It is a fascinating picture. I like the subtle colors: the bulge is yellow-orange, the arms are mostly greyish-neutral (made up of intermediate-aged stars, no doubt) and there is a hint of blue in two arcs on opposite sides of the bulge. That is probably where we find the youngest stars in this galaxy. Fascinatingly, though, "above" the bulge there is what looks like a large cluster or an association, but it isn't really bluish in color - perhaps it is a background galaxy?
There really does seem to be a double nucleus in this galaxy!
This is a very interesting picture, Kent. Thank you for posting it!
Ann