STScI: Super Spirals Spin Super Fast

[bystander]

Super Spirals Spin Super Fast
NASA | STScI | HubbleSite | 2019 Oct 17

Dark matter tugs the most massive spiral galaxies to breakneck speeds

Credit: NASA, ESA, SDSS, P. Ogle and J. DePasquale (STScI)

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You’ve probably never noticed it, but our solar system is moving along at quite a clip. Stars in the outer reaches of the Milky Way, including our Sun, orbit at an average speed of 130 miles per second. But that’s nothing compared to the most massive spiral galaxies. “Super spirals,” which are larger, brighter, and more massive than the Milky Way, spin even faster than expected for their mass, at speeds up to 350 miles per second.

Their rapid spin is a result of sitting within an extraordinarily massive cloud, or halo, of dark matter – invisible matter detectable only through its gravity. The largest “super spiral” studied here resides in a dark matter halo weighing at least 40 trillion times the mass of our Sun. The existence of super spirals provides more evidence that an alternative theory of gravity known as Modified Newtonian Dynamics, or MOND, is incorrect.

A Break in Spiral Galaxy Scaling Relations at the Upper Limit of Galaxy Mass ~ Patrick M. Ogle et al

• Astrophysical Journal Letters 884(1):L11 (2019 Oct 10) DOI: 10.3847/2041-8213/ab459e
• arXiv.org > astro-ph > arXiv:1909.09080 > 19 Sep 2019

[Ann]

That's the old Tully-Fisher relation, isn't it?

Ann

[neufer]

That's the old Tully-Fisher relation, isn't it?

• OLD

Hey... Tully & Fisher were fellow Astronomy grad students with me at the University of Maryland!

• (They both got PhDs & I got a draft notice from Nixon. )

[Ann]

That's the old Tully-Fisher relation, isn't it?

• OLD

Hey... Tully & Fisher were fellow Astronomy grad students with me at the University of Maryland!

• (They both got PhDs & I got a draft notice from Nixon. )

They were fellow Astronomy grad students with you, Art? I'm impressed!

Oh, and... that draft note? Is that why you never became a professional astronomer? I'm sorry.

Why I called it the OLD Tully-Fisher relation is because I first read about it and got a (brief) explanation for it perhaps 25 years ago. I thought it sounded like a splendid idea to use the rotational velocity of spiral galaxies to get a (rough) idea about their mass. But even though it sounded like such a good idea, the method never seemed to be implemented. And no one seemed to talk about it. But now its usefulness has been proved! Success, and justice, for Tully and Fisher!

Ann

P.S. The face-on galaxy at the upper left of the six that are used as examples of very massive spirals sure looks splendid. It's a Hubble type Sa, I guess. Not that the galaxy in the upper right corner doesn't look superb, too! I would love to know more about their properties, such as their mass, luminosity, U-B and B-V indexes, as well as their far infrared magnitude. And, of course, their rotational velocity!

[neufer]

That's the old Tully-Fisher relation, isn't it?

• OLD!

Hey... Tully & Fisher were fellow Astronomy grad students with me at the University of Maryland!

• (They both got PhDs & I got a draft notice from Nixon. )

They were fellow Astronomy grad students with you, Art? I'm impressed!

Oh, and... that draft note? Is that why you never became a professional astronomer? I'm sorry.

• It all turned out OK.

I didn't go to Vietnam and I got to use my Physics/Astronomy knowledge to practical
advantage in analyzing the weather and the ozone hole with infrared remote sensing.

Why I called it the OLD Tully-Fisher relation is because I first read about it and got a (brief) explanation for it perhaps 25 years ago. I thought it sounded like a splendid idea to use the rotational velocity of spiral galaxies to get a (rough) idea about their mass. But even though it sounded like such a good idea, the method never seemed to be implemented. And no one seemed to talk about it. But now its usefulness has been proved! Success, and justice, for Tully and Fisher!

I got seriously involved in the Shakespeare authorship question about 25 years ago.

It has proved to be a nice transition into a fascinating mystery that is far less explored
than Physics & Astronomy and hence full of new discoveries for amateurs like myself.