Hubble and Galaxy Zoo find bars and baby galaxies don't mix

Jan 17, 2014
A Hubble Space Telescope image of the barred spiral galaxy NGC 1300, located 61 million light years away in the constellation of Eridanus. Credit: HST / NASA / ESA.

(Phys.org) —Harnessing the power of both the Hubble Space Telescope and the citizen science project Galaxy Zoo, scientists from the University of Portsmouth have found that bar-shaped features in spiral galaxies accelerate the galaxy aging process.

The astronomers found that the fraction of spiral galaxies with bar features has doubled in the last eight billion years – the latter half of the history of the universe. The scientists publish their results, the first from the Galaxy Zoo: Hubble project, in the journal Monthly Notices of the Royal Astronomical Society.

University of Portsmouth postgraduate researcher Tom Melvin led the new study as part of his thesis work. He and the rest of the Galaxy Zoo science team used classifications provided by citizen scientists to select spiral galaxies across the Universe for the study. Light from the furthest galaxies has taken eight billion years to reach us, so we see them as they appeared eight billion years ago or when the cosmos was a little over half its present age. This allows astronomers to study how the characteristics of galaxies change over this time.

Many galaxies with spiral shapes (like the one we live in, the Milky Way) also have central bar-shaped features. These structures are made up of stars and the extend from the ends of the bar.

Mr Melvin's group studied how the fraction of spiral galaxies with bars changed over time. They found that 8 billion years ago only 11% of spirals had bars, but by 2.5 billion years ago this proportion had doubled. In the present day universe two-thirds of galaxies have bars. And the more massive the galaxy, the more likely this is to be the case.

Mr Melvin comments: "This is a really interesting result which has been made possible by the contributions of citizen scientists, who yet again are helping cutting edge astronomical research when they spend time classifying galaxies at Galaxy Zoo."

The new work also confirms that bars signify maturity for spiral galaxies and may play an important role in switching off the formation of new stars. For some of the most massive spiral galaxies, this happened relatively early in the life of the universe.

Dr Karen Masters, also from Portsmouth University, and Project Scientist for Galaxy Zoo said, "It looks as though bars really are bad for spiral galaxies. As a bar grows in a galaxy, it is less likely to have any new stars being born and the galaxy settles down to a sedate maturity."

Explore further: Hubble view of a special spiral galaxy

More information: Thomas Melvin, Karen Masters, Chris Lintott, Robert C. Nichol, Brooke Simmons, Steven P. Bamford, Kevin R. V. Casteels, Edmond Cheung, Edward M. Edmondson, Lucy Fortson, Kevin Schawinski, Ramin A. Skibba, Arfon M. Smith, and Kyle W. Willett. "Galaxy Zoo: an independent look at the evolution of the bar fraction over the last eight billion years from HST-COSMOS." MNRAS. January 16, 2014 DOI: 10.1093/mnras/stt2397

A preprint is available from arxiv.org/abs/1401.3334

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User comments : 6

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Tuxford
1 / 5 (8) Jan 17, 2014
Just more support for LaViolette's inside-out continuous creation galactic growth model. The core is the source, not the sink, and grows naturally from within overtime. The bigger it gets, the more active it grows and the more it ejects, eventually forming the bars along the polar ejection axes. Gosh, this is really simple. Fortunately, I am not burdened with the anointed intelligence of academics. Otherwise, I might be confused by the Huge Bang fantasy.

http://phys.org/n...ies.html

http://phys.org/n...ter.html

http://phys.org/n...ars.html

http://phys.org/n...022.html

At least, sometimes the simple explanation is the correct explanation.
casualjoe
not rated yet Jan 17, 2014
Wow this has made all that classifying really worth while.
OZGuy
5 / 5 (4) Jan 17, 2014
Fortunately, I am not burdened with the anointed intelligence of academics.


Given your normal protracted rantings on any subject I can assure you most of us do not consider you burdened with any intelligence.
RobertKarlStonjek
3 / 5 (2) Jan 17, 2014
Lenticular galaxies are far brighter than both regular barred and unbarred galaxies thus making barred galaxies ever harder to detect at greater distances.

[Paper: Luminosities of Barred and Unbarred S0 Galaxies]
http://arxiv.org/abs/1205.6183

In the paper they say that bright galaxies existed in the past (at long distances) and dim galaxies are mor prevalant locally.

What they don't mention is that ONLY bright galaxies can be seen at, say 8 billion light years so the decline in dim galaxies with distance would be observed whether there was a decline or not.

But as the model says that bright things Existed in the past and at great distances there is no point in mentioning this obvious problem...

Galaxy Zoo: an independent look at the evolution of the bar fraction over the last eight billion years from HST-COSMOS
http://arxiv.org/...34v1.pdf
IMP-9
not rated yet Jan 18, 2014
What they don't mention is that ONLY bright galaxies can be seen at, say 8 billion light years


The fact that they are dimmer does not mean they are undetectable in the study.
Widdekind
not rated yet Jan 19, 2014
-8Gyr = redshift 1
-2.5Gyr = redshift 0.2

QUOTE:
"the overall bar fraction decreases by a factor of 2, from 22±5% at z = 0.4 (tlb = 4.2 Gyr) to 11±2% at z = 1.0 (tlb = 7.8 Gyr)... the decrease in bar fraction is most prominent in the highest mass bin, while the lower mass discs in our sample show a more modest evolution"

Simplistically stated, "bar" formation is a natural & inevitable outcome, of spiral galaxy evolution... which the most massive galaxies develop first, because they develop fastest (galaxy evolution rate ~ galaxy mass).

Prima facie, spiral "bars" more resemble a "triple dumbbell", with two spheroidal clumps of star-producing gas equally-and-oppositely positioned, about the central bulge. Spiral disks SPIN, because they formed from the merger of many (2+) proto-galactic cloud clumps... if the cores, of those clumps, somewhat survived the merger-and-then-disking-down phase... then gal. evol. could gradually draw them inward, making a "multi-clump" sys. = blg+(2xdmbll)