APOD: UGC 12591: The Fastest Rotating... (2017 Mar 07)

[MrE]

Not visible in the cropped image but in the enlargement when fully sized, in the upper right corner is a very nice bright galaxy. to the left of it is a very red (faint) galaxy with what appears to be a brightly shining supernova

[neufer]

Numerous galaxies, is this gravational lensing or reality?

Gravitational lensing is reality! But I don't see any obvious lensing in this image. (And the object in this image is much too close to be an effective lens.)

If the brightest object below UGC 12591 is, in fact, a distant galaxy then I calculate that gravitational lensing is probably making it appear to be ~34" away (off towards the bottom) when it should otherwise have appeared to be just ~32" away (off towards the bottom). This qualifies as significant though not "obvious lensing." In fact, all those distant galaxies appear ~2" (i.e., 4,000 light years) further away from the center of UGC 12591 than they would otherwise. And if there had been a distant galaxy or quasar sitting directly behind UGC 12591 it would probably have formed a noticeable ring (or Einstein cross) with a diameter of ~2-3" (i.e., 4 to 6 thousand light years)...but there isn't.

[Ann]

To return to fast-rotating galaxy UGC 12591, other galaxies rotate fast, too. NGC 488 is a particularly whirligig-like specimen.

Click to view full size image

[c]NGC 488. Photo: Adam Block/Caelum Observatory.[/c]

Charles J. Peterson (a relative, Chris?) wrote in Astronomical Journal, vol. 85, Mar. 1980, p. 226-229:

The rotation curve of NGC 488 has been measured out to a radius of 20 kpc, at which point the velocity is 363 km⁻¹ and continuing to increase with radius. This rotational velocity is the largest known for an Sb galaxy. For a mass model based on the thin-disk approximation of Kuzmin [Publ. Tartu Astron. Obs. 32, 211 (1952)], we find the mass and mass-luminosity interior to 20 kpc are M ⪆ 4.0 X 10¹¹ M_☉ and <M/L>_B ⪆ 3.6. Exterior to the nuclear region, the mass-luminosity relation shows only a gentle increase with radius.

Phew! I couldn't copy that from the page, so I had to write it all in by hand, including all those pesky mathematical symbols and signs!

Ann

[sillyworm]

All these wondrous beautiful elusive mysterious mind-bending exotic Galaxies....and we may never even get to explore Andromeda.Imagining WHY & HOW are two of the most exiting mind journeys.

[douglas]

"Classified as an S0/Sa galaxy, UGC 12591 sits somewhere between a lenticular and a spiral galaxy.

Also known as LEDA 71392 and 2MASX J23252175+2829425, UGC 12591 lies just under 400 million light-years away from us in the westernmost region of the Pisces-Perseus Supercluster, a chain of galaxy clusters that stretches out for hundreds of millions of light-years — one of the largest known structures in the cosmos."

http://www.sci-news.com/astronomy/hubbl ... 04653.html

http://space.wikia.com/wiki/Lenticular_galaxy

I'm going to go with the collision growth scenario. Those spiral arms look disconnected from the core, and circularized.

[MartinNi]

The orbits of earth satellites are at altitudes defined by their velocity ... higher velocity to maintain higher altitudes. As their velocity decays they eventually fall back to earth. If galaxy objects are at the same linear velocity, they would be "falling" towards the center. Does this explain arms spiraling inward towards the center black hole of galaxies?

The (~circular) orbits of earth satellites are at altitudes defined by their velocity
... higher velocities are needed to maintain lower altitudes:

Centrifugal force = mv²/r = gravitational force = GmM/r²

Hence: v² = GM/r : or v = sqrt (GM/r)

For (~circular) orbital velocity to be constant
the gravitational force of galaxies must drop off more slowly as 1/r not 1/r².

Centrifugal force = mv²/r = gravitational force = Cm/r (; i.e., total dark mass M grows as Cr/G)

Hence: v² = C : or v = sqrt (C)

(; i.e., UGC 12591's dark mass density is ~4 times that of the Milky Way.)

Hi Art,
isn't this simple formalism for point masses (or masses with radial symmetric distibution, when located "outsite" of them) rather inadequate (and so the estimated "dark mass density" wrong) for a much more non-spherical mass distribution, which a flat disk like UGC 12591 represents ?
What about a correct formalism for spiral galaxies ?

Kind regards
Martin

[neufer]

The orbits of earth satellites are at altitudes defined by their velocity ... higher velocity to maintain higher altitudes. As their velocity decays they eventually fall back to earth. If galaxy objects are at the same linear velocity, they would be "falling" towards the center. Does this explain arms spiraling inward towards the center black hole of galaxies?

The (~circular) orbits of earth satellites are at altitudes defined by their velocity
... higher velocities are needed to maintain lower altitudes:

Centrifugal force = mv²/r = gravitational force = GmM/r²

Hence: v² = GM/r : or v = sqrt (GM/r)

For (~circular) orbital velocity to be constant
the gravitational force of galaxies must drop off more slowly as 1/r not 1/r².

Centrifugal force = mv²/r = gravitational force = Cm/r (; i.e., total dark mass M grows as Cr/G)

Hence: v² = C : or v = sqrt (C)

(; i.e., UGC 12591's dark mass density is ~4 times that of the Milky Way.)

Hi Art, isn't this simple formalism for point masses (or masses with radial symmetric distibution, when located "outsite" of them) rather inadequate (and so the estimated "dark mass density" wrong) for a much more non-spherical mass distribution, which a flat disk like UGC 12591 represents ?

What about a correct formalism for spiral galaxies ?

Hi, Martin.

I refer you to: http://physics.stackexchange.com/questi ... e-spheroid

However, to first order what I wrote still stands...
the main difference being the vertical oscillation vis-a-vis the galactic disk
(which involves the, as yet, unknown flatness of the dark matter galactic disk).

[john_erickson]

The quoted spin rate as a linear velocity, km/sec. What is the angular rate of spin or is the quoted km/sec at baseline distance from center of rotation?

[Chris Peterson]

The quoted spin rate as a linear velocity, km/sec. What is the angular rate of spin or is the quoted km/sec at baseline distance from center of rotation?

As Art pointed out in response to that question, galaxies typically have a near constant linear (tangential) velocity, independent of radius. So this is the measured velocity anywhere you look, not at any particular distance from the center. (That also means that the angular velocity varies with radius.)

[douglas]

Here you go: collisional mass accretion.

"To appreciate this galaxy, its optical-IR luminosity is nine times that of M31."

"This halo accretion rate is two orders of magnitude too low to assemble the stellar mass of this galaxy within a Hubble time.
Therefore, significant accretion must have occurred via some other mode, such as cold flows
or mergers, to produce the stellar mass seen in this galaxy today, confirming the conclusion
drew in NGC 1961 (Anderson & Bregman 2011)."

XMM-Newton Detects a Hot Gaseous Halo in the Fastest Rotating Spiral Galaxy UGC 12591
https://arxiv.org/PS_cache/arxiv/pdf/11 ... 0324v1.pdf

[douglas]

NGC 1961/Arp 184

http://asterisk.apod.com/viewtopic.php? ... 61#p232436

Extremely disrupted "spiral arms" with star formation at arms' extremity:
http://cseligman.com/text/atlas/ngc19a.htm#1961
"NGC 1961 is about 185 million light years away. Given that and the brighter central galaxy's apparent size of 4.1 by 2.2 arcmin, it spans about 220 thousand light years; while the 4.9 by 4.2 arcmin wide region that includes the very faint northern arms spans about 260 thousand light years."

http://sleshin.startlogic.com/stargazer ... itemId=728