Surprise: Small elliptical galaxy actually a giant disk

July 11, 2016, Carnegie Institution for Science
At left, in optical light, UGC 1382 appears to be a simple elliptical galaxy. But spiral arms emerged when astronomers incorporated ultraviolet and deep optical data (middle). Combining that with a view of low-density hydrogen gas (shown in green at right), scientists discovered that UGC 1382 is gigantic. Credit: NASA/JPL/Caltech/SDSS/NRAO/L. Hagen and M. Seibert

Astronomers have believed since the 1960s that a galaxy dubbed UGC 1382 was a relatively boring, small elliptical galaxy. Ellipticals are the most common type of galaxy and lack the spiral structure of disks like the Milky Way we call home. Now, using a series of multi-wavelength surveys, astronomers, including Carnegie's Mark Seibert, Barry Madore and Jeff Rich, have discovered that it is really a colossal Giant Low Surface Brightness disk galaxy that rivals the champion of this elusive class—a galaxy known as Malin 1. Malin 1 is some 7 times the diameter of the Milky Way. The research is published in the Astrophysical Journal.

Giant Low Surface Brightness galaxies are among the most massive and isolated spiral galaxies known. They are very rare and have two components: what is known as a high surface brightness galaxy, with an extended low disk surrounding it. So why was galaxy UGC1382 so misconstrued before?

Seibert explains: "Although there have been numerous surveys of the now-defunct elliptical since it was first cataloged in the 1960s, the only indication that it may be an unusual system was in 2009 when another survey indicated that there may be a hint of a rotating hydrogen disk, but it was not followed up. UGC 1382 came to our attention while we were looking at star formation in early-type galaxies using NASA's Galaxy Evolution Explorer (GALEX). We saw that in the ultraviolet part of the spectrum spiral arms were visible—something you do not expect to see around elliptical galaxies. Naturally, that finding sent us off on a very different path!"

Further investigation revealed that the hydrogen disk was real and has an enormous width. For comparison, our own Milky Way Galaxy has a width of 30 kiloparsecs (kpc), but UGC1382 is 220 kpc wide-about 7 times as large as the Milky Way. Despite the huge difference in size, the two systems weigh roughly the same. That is, they have very similar amounts of stars and gas.

Lea Hagen the lead author—a graduate student at the Pennsylvania State University and a former Carnegie summer student remarked, "It's unusual and surprising that we would have such a well-studied galaxy and miss its most unique property: a huge set of spiral arms. The fact that the and hydrogen gas extend so far compared to most other galaxies makes this an exciting object for understanding the most extreme examples of galaxy evolution."

"A particularly attractive feature of the newly reclassified UGC 1382 is that it is much closer to us than Malin 1, about a quarter of the distance, in fact," remarked Seibert. "That proximity is what allowed us to conduct the multi-wavelength investigation and it will allow us to start to unravel how these extreme systems form and evolve. We know that such objects need to have a low-density environment without other large galaxies nearby that would disturb it, but they also need a supply of small but gas-rich 'dwarf' galaxies to accrete and build the really large diffuse extended disk. Unlike typical galaxy formation, however, the outer blue spiral disk appears to be older than the inner red disk. That is a big clue about how you get oddball giants like this."

Thus far, there have been about a dozen Giant Low Surface Brightness galaxies found, but none more extreme in size than Malin 1, which now has a rival in UGC 1382. The proximity of UGC 1382 will be a boon to revealing other features of such elusive giants in addition to understanding other seemingly normal early galaxies. The increased sensitivity of future telescopes and instruments may yield yet more discoveries of other misclassified .

Explore further: Hubble sees galaxy hiding in the night sky

More information: "On the Classification of UGC1382 as a Giant Low Surface Brightness Galaxy," Lea M. Z. Hagen et al., 2016, Astrophysical Journal Preprint: arxiv.org/abs/1607.02147

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Tuxford
1.6 / 5 (13) Jul 11, 2016
We know that such objects need to have a low-density environment without other large galaxies nearby that would disturb it, but they also need a supply of small but gas-rich 'dwarf' galaxies to accrete and build the really large diffuse extended disk. Unlike typical galaxy formation, however, the outer blue spiral disk appears to be older than the inner red disk. That is a big clue...

Sorry merger maniacs, but I simply must explain:

The maniacs are caught in a riddle - just like the photon - how can it be both? How can it be undisturbed, and yet grow so big requiring that it be disturbed often?

No, the galaxy grows from new matter entering our observable subset of the universe in the fertile conditions inside the galactic core grey star. The core grows unstable periodically and ejected the matter, growing the galaxy from the inside out. This one has been growing for a while. So the core is the older part. Merger, merger, merger...
cantdrive85
1.9 / 5 (13) Jul 11, 2016
So if it grows from the inside out, wouldn't the inside be younger? The new pushes the old out?
antiantigoracle
Jul 11, 2016
This comment has been removed by a moderator.
Tuxford
1.3 / 5 (13) Jul 11, 2016
So if it grows from the inside out, wouldn't the inside be younger? The new pushes the old out?

Good point. The core star itself is older, but the surrounding region would then be populated by younger stars. However, the core region is more fertile than the outer regions, being more concentrated with matter, which helps spur faster growth of the stars therein. So it is complex.

The stars in the outer regions have had plenty of time to grow big and hot blue, or more populous with red stars, making the region appear younger or older depending on your model. And often the blue stars concentrate in the arms, where matter is more concentrated, spurring more rapid growth thereof.

Thanks for asking.

http://phys.org/n...ays.html
cantdrive85
1.9 / 5 (13) Jul 11, 2016
Looks more like the cranks pushing the serious commentators out. I do thank y'all for all the info you've given me in PMs at Thunderdolts. Which one am I? You'll find out soon enough.

Are you suggesting we've had discussions? Which one am I? I'm the same guy, my handle is the same there as here. But alas, I haven't even been on the forum for almost a year. You know, preaching to the choir and all... So you're promoting that you're going to come out of the closet and you're basing it entirely on fabrications and lies. I can only imagine the extreme lengths with which you'll reach with even more fabrications and lies. As a matter of fact, there was another poster in these threads who claimed to do such "research". I'd wager to say if you gave me 5 minute perusing the EU forum and I could find your dumbass there Cap'n. But that would be boring, looking for Stoopid when he's already ignored here. BTW, you're ignored too.
Tektrix
5 / 5 (13) Jul 11, 2016
Looks more like the cranks pushing the serious commentators out.

All the white space I see speaks volumes. ; )
Whydening Gyre
4.7 / 5 (13) Jul 11, 2016
So if it grows from the inside out, wouldn't the inside be younger? The new pushes the old out?

Article did not say it was "growing" from the inside out. Just that the densest portion was in the center and also appeared to be the highest in new star formation.
Additionally, it only appears to "grow" because of the different methods used to observe it. (Read the article to understand that little bit o' info)
cantdrive85
2 / 5 (8) Jul 12, 2016
My comment was regarding Tuxford's.

It's fairly clear from observational evidence that quasars are ejected from galactic cores, just as plasmoids are ejected across all scales of plasma processes. That being the first stage in the life cycle galaxies, which do grow from within from the matter fed to it via the intergalactic Birkeland currents in which the galaxies reside.
harmonograms
4.2 / 5 (10) Jul 12, 2016
No, the galaxy grows from new matter entering our observable subset of the universe in the fertile conditions inside the galactic core grey star. The core grows unstable periodically and ejected the matter, growing the galaxy from the inside out.


Galaxies are not observed to create new matter (and the associated new gravity) as you suggest; please refer to the First Law of Thermodynamics.
Solon
3 / 5 (2) Jul 13, 2016
Both standard model and EU models are incorrect. Whether galactic cores or Suns, the energy is primarily gamma radiation, and everything around that core is the result of Gamma attenuation. Matter IS created, by pair production.

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