Galaxy-sized peanuts? Astronomers use new imaging software to detect double 'peanut shell' galaxy

Galaxy-sized peanuts? Astronomers use new imaging software to detect double ‘peanut shell’ galaxy
The large (peanut shell)-shaped bulge at the centre of the disc galaxy NGC 128. Credit: Sloan Digital Sky Survey / Aladin Sky Atlas / A.Graham, B.Ciambur (Swinburne University of Technology)

Astronomers at Swinburne University of Technology, Melbourne, have discovered an unusually shaped structure in two nearby disc galaxies. The Swinburne team recently developed new imaging software, making it possible to observe the double "peanut shell shape" formed by the distribution of stars bulging from the centres of these galaxies. The results are published in a new paper in Monthly Notices of the Royal Astronomical Society.

Using data from the Hubble Space Telescope and the Sloan Digital Sky Survey, the researchers realised that two of the galaxies they were studying – NGC 128 and NGC 2549 – were quite exceptional. They are roughly 200 and 60 million light years away respectively, in the constellations of Pisces and Lynx, and they displayed a peanut shell configuration at two separate layers within the galaxies' three-dimensional distribution of stars.

"Ironically, these peanut-shaped structures are far from peanut-sized," says Swinburne's Professor Alister Graham, co-author of the research. "They consist of billions of stars typically spanning up to a quarter of the length of the galaxies."

Although the 'bulges' of both galaxies were already known to display a single peanut shell pattern, astronomers had never before observed the fainter second structure in any galaxy.

"They resemble two peanut shells, with one neatly nested within the other; this is the first time such a phenomenon has been observed," says Bogdan Ciambur, the PhD student who led the investigation.

Galaxy-sized peanuts? Astronomers use new imaging software to detect double ‘peanut shell’ galaxy
A model of the galaxy NGC 128, based on a Hubble Space Telescope image. Credit: B. Ciambur (Swinburne University of Technology)

"We expect the galaxies' surprising anatomy will provide us with a unique view into their pasts. Deciphering their history can tell us about transformations that galaxies like our own Milky Way might experience."

Astronomers believe that peanut shaped bulges are linked to the bar-shaped distribution of stars that is observed across the centres of many rotating galaxy discs. Each of the two galaxies observed contain two such bars, and it is thought that one way the peanut shaped structures may arise is when these bars of stars bend above and below the galaxy's central disc.

"The instability mechanism may be similar to water running through a garden hose: when the water pressure is low, the hose remains still (stars stay on their usual orbits), but when the pressure is high the hose starts to bend (stellar orbits bend outside of the disc plane)," says Mr Ciambur.

Galaxy-sized peanuts? Astronomers use new imaging software to detect double ‘peanut shell’ galaxy
The galaxy NGC 128 is viewed with its disc in an edge-on orientation in this SDSS false-colour image. A (peanut shell)-shaped bulge can be seen around the thin disc. Its inner peanut shell is 5 times smaller.  Credit: Sloan Digital Sky Survey / B.Ciambur (Swinburne University of Technology) / NASA / ESA

"By directly comparing real galaxies with state-of-the-art simulations, we hope to better understand how evolve," says Mr Ciambur. "The discovery is exciting because it will enable us to more fully test the growth of bars over time, including their lengths, rotation speeds, and periods of instability.

The study may also shed new light on the peanut-shaped bulge of our own Milky Way galaxy, which some astronomers suspect contains two stellar bars.

"Thankfully we are too distant from our Galaxy's bulge to get caught up in the dizzying orbits that lead to these interesting peanut shell patterns," adds Professor Graham. "However, this is an ideal vantage point to study our Galaxy's stellar bulge."

The new work appears in "Quantifying the (X/Peanut)-Shaped Structure in Edge-on Disc Galaxies: Length, Strength, and Nested Peanuts", B.C. Ciambur, A.W. Graham, Monthly Notices of the Royal Astronomical Society, Oxford University Press, in press.


Explore further

Image: Hubble captures NGC 4111

More information: A copy of the paper is available from mnras.oxfordjournals.org/content/459/2/1276 , or from the arXiv astronomy preprint server at www.arxiv.org/abs/1603.00019 .
Citation: Galaxy-sized peanuts? Astronomers use new imaging software to detect double 'peanut shell' galaxy (2016, May 6) retrieved 21 August 2019 from https://phys.org/news/2016-05-galaxy-sized-peanuts-astronomers-imaging-software.html
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May 06, 2016
"By directly comparing real galaxies with state-of-the-art simulations, we hope to better understand how galaxies evolve," says Mr Ciambur.


Hope is all that a merger maniac has at this point.

With the galaxy growing from within from the core rather than from without through merger mania, then a symmetric pattern is much more likely to ensue with symmetry about the core.

May 07, 2016
Why still deny the cosmic link? NGC-127 is a daughter of NGC-128; the same way Markarian-205 is a daughter of NGC-4319. The only difference is that Markarian-205 is a much smaller chunk and hence ejected with much higher velocity making it into a quasar form (very high receding velocity and consequent high redshift). http://www.halton...ebuttals

How long will Chip Arp be denied credit for his revolutionary discovery that punctured a "Big Black Hole" into the Big Bang theology and the rest of official cosmology?

May 07, 2016
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The fact that quasars (as opposed to the radio galaxies) appear to be single jet systems, and quasars always appear as red shifted was explained in the 1960s, by Strittmatter (cited in Ref. 16), who suggested that quasars selectively radiate in the backward direction as it is ejected from the galactic centers and an observer therefore, only sees those quasars that are receding from that location and are necessarily red shifted. Kembhavi and Narlikar [16] gave an explanation for this effect in terms of the ram pressure of the intergalactic medium on the light originating from the quasars. According to them, the emission from the quasars is confined to a backward cone; the ram pressure from the intergalactic medium blocks the forward emission, but it does not affect the backward jet. This explains why the quasars unlike radio galaxies are single jet systems and are always redshifted.

May 07, 2016
@FSC: It is a very good question, sorry not to have mentioned you above!

May 07, 2016
How long will Chip Arp be denied credit for his revolutionary discovery


Not until the null result from SDSS have been explained. If Arp's ideas really were correct then the coincidence of high redshift quasars and nearby galaxies should go beyond one or two cherry-picked examples. This can be done with a catalogue of QSOs and galaxies, SDSS high redshift quasars are no more common near galaxies than random. This blew Arp's model out of the water.

http://arxiv.org/.../0506366

His model began as an explanation for redshfit periodicity, an effect which is no longer observed despite the fact redshift surveys are thousands of times larger.

May 11, 2016
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