by Ann » Sat Jun 04, 2011 9:17 pm
Interesting. Here is a larger picture of NGC 6744:
http://www.eso.org/public/archives/imag ... o1118a.jpg
Personally I'm mystified by the colors of NGC 6744. According to the ESO Catalog, NGC 6744 has a B-V index of 0.99 and a U-B index of 0.5. This is very red indeed for a galaxy, and redder when it comes to B-V than giant elliptical galaxy M87!
But according to the Principal Galaxy Catalog, NGC 6744 has an effective B-V of 0.86 and an effective U-B of 0.24. That's much bluer than what the ESO Catalog says. And according to James D Wray's Color Atlas of Galaxies, NGC 6744 has a B-V of 0.65 and a U-B of 0.00, which is of course still bluer. How confusing!
Interestingly, James D Wray's book shows NGC 6744 to be completely dominated by a bright yellow center and bar. The arm structure, which in the case of NGC 6744 James D Wray calls plume structure, is full of star formation, but it looks quite faint.
I find it interesting that the galaxy is so yellow. I also find it interesting that NGC 6744 is such a big and bright galaxy. According to Principal Galaxy Catalog, it is 2.4 times brighter than the Milky Way.
In ESO's new image the arm structure appears to dominate the galaxy. Personally I associate a multitude of rather short arms, like the ones seen in NGC 6744, with relatively lightweight and small galaxies, so it is really interesting that NGC 6744 is so big and bright.
(Of course... when I look more closely at the galaxy, I can see that there really are some long elegant arms of the kind that you hardly find anywhere else than in large galaxies.)
Ann
Interesting. Here is a larger picture of NGC 6744:
http://www.eso.org/public/archives/images/large/eso1118a.jpg
Personally I'm mystified by the colors of NGC 6744. According to the ESO Catalog, NGC 6744 has a B-V index of 0.99 and a U-B index of 0.5. This is very red indeed for a galaxy, and redder when it comes to B-V than giant elliptical galaxy M87! :shock:
But according to the Principal Galaxy Catalog, NGC 6744 has an effective B-V of 0.86 and an effective U-B of 0.24. That's much bluer than what the ESO Catalog says. And according to James D Wray's Color Atlas of Galaxies, NGC 6744 has a B-V of 0.65 and a U-B of 0.00, which is of course still bluer. How confusing!
Interestingly, James D Wray's book shows NGC 6744 to be completely dominated by a bright yellow center and bar. The arm structure, which in the case of NGC 6744 James D Wray calls plume structure, is full of star formation, but it looks quite faint.
I find it interesting that the galaxy is so yellow. I also find it interesting that NGC 6744 is such a big and bright galaxy. According to Principal Galaxy Catalog, it is 2.4 times brighter than the Milky Way.
In ESO's new image the arm structure appears to dominate the galaxy. Personally I associate a multitude of rather short arms, like the ones seen in NGC 6744, with relatively lightweight and small galaxies, so it is really interesting that NGC 6744 is so big and bright.
(Of course... when I look more closely at the galaxy, I can see that there really are some long elegant arms of the kind that you hardly find anywhere else than in large galaxies.)
Ann