by Ann » Tue Nov 05, 2019 6:35 am
Tully-Fisher relation. The more luminous a galaxy is,
the faster it spins. Illustration: Astro533Fa10
These super-fast spinning galaxies are so fascinating!
I'm strongly reminded of the Tully-Fischer relation:
Wikipedia wrote:
In astronomy, the Tully–Fisher relation (TFR) is an empirical relationship between the mass or intrinsic luminosity of a spiral galaxy and its asymptotic rotation velocity or emission line width. It was first published in 1977 by astronomers R. Brent Tully and J. Richard Fisher.[1] The luminosity is calculated by multiplying the galaxy's apparent brightness by {\displaystyle 4\pi d^{2}}{\displaystyle 4\pi d^{2}}, where {\displaystyle d}d is its distance from us, and the spectral-line width is measured using long-slit spectroscopy.
So the more luminous a galaxy is, the faster it spins, which results in broad and smeared spectral lines. Presumably, too, a luminous galaxy is also a massive galaxy. So we can assume that fast-spinning galaxies are massive.
Super fast spinning galaxies.
APOD Robot wrote:
It is therefore further hypothesized that their dark matter halos are so massive -- and their spins so fast -- that it is harder for them to form stars than regular spirals.
I get the idea of the massive dark matter halos, and I agree that the most massive galaxies rarely form a lot of stars. All right, but take a look at the middle galaxy in the bottom row, OGC 1304! This galaxy is among the fastest spinning galaxies known, and presumably it is very very massive, so it is not "allowed" to form a lot of stars. Well, OGC 1304 couldn't care less. Look at all the blue stuff all around it!
Click to play embedded YouTube video.
The middle galaxy in the top row is also relatively blue, but I agree that the other four galaxies are not churning out too many new stars. The two "end galaxies in the top row" are extremely elegant and beautiful. Why are they black and white? Were they photographed in (near) infrared light?
(By the way, I think the crazy kids in the carousel video are Danish.)
Ann
[float=right][img2]https://upload.wikimedia.org/wikipedia/commons/b/bb/OffsetTF.png[/img2][c][size=85]Tully-Fisher relation. The more luminous a galaxy is,
the faster it spins. Illustration: Astro533Fa10 [/size][/c][/float]
These super-fast spinning galaxies are so fascinating! :D
I'm strongly reminded of the Tully-Fischer relation:
[quote][url=https://en.wikipedia.org/wiki/Tully–Fisher_relation]Wikipedia[/url] wrote:
In astronomy, the Tully–Fisher relation (TFR) is an empirical relationship between the mass or intrinsic luminosity of a spiral galaxy and its asymptotic rotation velocity or emission line width. It was first published in 1977 by astronomers R. Brent Tully and J. Richard Fisher.[1] The luminosity is calculated by multiplying the galaxy's apparent brightness by {\displaystyle 4\pi d^{2}}{\displaystyle 4\pi d^{2}}, where {\displaystyle d}d is its distance from us, and the spectral-line width is measured using long-slit spectroscopy.[/quote]
So the more luminous a galaxy is, the faster it spins, which results in broad and smeared spectral lines. Presumably, too, a luminous galaxy is also a massive galaxy. So we can assume that fast-spinning galaxies are massive.
[float=left][img2]https://apod.nasa.gov/apod/image/1911/SuperSpirals_HubbleSDSS_1080.jpg[/img2][c][size=85]Super fast spinning galaxies.[/size][/c][/float]
[quote]APOD Robot wrote:
It is therefore further hypothesized that their dark matter halos are so massive -- and their spins so fast -- that it is harder for them to form stars than regular spirals.[/quote]
I get the idea of the massive dark matter halos, and I agree that the most massive galaxies rarely form a lot of stars. All right, but take a look at the middle galaxy in the bottom row, OGC 1304! This galaxy is among the fastest spinning galaxies known, and presumably it is very very massive, so it is not "allowed" to form a lot of stars. Well, OGC 1304 couldn't care less. Look at all the blue stuff all around it!
[float=right][youtube]https://www.youtube.com/watch?v=B2F38hqsAM0[/youtube][/float]
The middle galaxy in the top row is also relatively blue, but I agree that the other four galaxies are not churning out too many new stars. The two "end galaxies in the top row" are extremely elegant and beautiful. Why are they black and white? Were they photographed in (near) infrared light?
(By the way, I think the crazy kids in the carousel video are Danish.) :mrgreen:
Ann