Elliptical galaxies: Chandra helps explain 'red and dead galaxies'

May 30, 2014
Credit: X-ray: NASA/CXC/Stanford Univ/N.Werner et al.

(Phys.org) —NASA's Chandra X-ray Observatory has shed new light on the mystery of why giant elliptical galaxies have few, if any, young stars. This new evidence highlights the important role that supermassive black holes play in the evolution of their host galaxies.

Because star-forming activity in many giant elliptical has shut down to very low levels, these galaxies mostly house long-lived with low masses and red optical colors. Astronomers have therefore called these galaxies "red and dead."

Previously it was thought that these red and dead galaxies do not contain large amounts of —the fuel for star formation—helping to explain the lack of . However, astronomers have used ESA's Herschel Space Observatory to find surprisingly large amounts of cold gas in some giant elliptical galaxies. In a sample of eight galaxies, six contain large reservoirs of cold gas. This is the first time that astronomers have seen large quantities of cold gas in giant that are not located at the center of a massive galaxy cluster.

With lots of cold gas, astronomers would expect many stars to be forming in these galaxies, contrary to what is observed. To try to understand this inconsistency, astronomers studied the galaxies at other wavelengths, including X-rays and radio waves. The Chandra observations map the temperature and density of hot gas in these galaxies. For the six galaxies containing abundant cold gas, including NGC 4636 and NGC 5044 shown here, the X-ray data provide evidence that the hot gas is cooling, providing a source for the cold gas observed with Herschel. However, the cooling process stops before the cold gas condenses to form stars. What prevents the stars from forming?

A strong clue comes from the Chandra images. The hot gas in the center of the six galaxies containing cold gas appears to be much more disturbed than in the cold gas-free systems. This is a sign that material has been ejected from regions close to the central black hole. These outbursts are possibly driven, in part, by clumpy, cold gas that has been pulled onto the black hole. The outbursts dump most of their energy into the center of the galaxy, where the cold gas is located, preventing the cold gas from cooling sufficiently to form stars.

The other galaxies in the sample, NGC 1399 and NGC 4472, are also forming few if any stars, but they have a very different appearance. No cold gas was detected in these galaxies, and the hot gas in their central regions is much smoother. Additionally, they have powerful jets of highly energetic particles, as shown in radio images from the National Science Foundation's Karl G. Jansky Very Large Array. These jets are likely driven by hot gas falling towards the central . By pushing against the hot gas, the jets create enormous cavities that are observed in the Chandra images, and they may heat the hot, X-ray emitting gas, preventing it from cooling and forming cold gas and stars. The centers of NGC 1399 and NGC 4472 look smoother in X-rays than the other galaxies, likely because their more powerful jets produce cavities further away from the center, where the X-ray emission is fainter, leaving their bright cores undisturbed.

Explore further: Pushy black holes stop elliptical galaxies from forming stars

More information: A paper describing these results was published on 24 February 2014 in Monthly Notices of the Royal Astronomical Society: mnras.oxfordjournals.org/content/439/3/2291 , Preprint: arxiv.org/abs/1310.5450

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13 comments

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Tuxford
1 / 5 (6) May 30, 2014
Ah, the merger mania continues. Quick another patch.

Yes, the hot gas near the center is generally disturbed, since it was mostly formed and ejected from the central grey hole supermassive core star. Both energy and matter enter our universe from within the core, some being more stable than others, yielding different appearances of spirals.

Instead, the mania insists that the gas must be recycled somehow.... Gosh, go for the complex answer. That always works...

http://phys.org/n...tml#nRlv

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

http://phys.org/n...tml#nRlv

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

supamark23
5 / 5 (4) May 30, 2014
bahahahahaha, tux that's some seriously funny stuff there. You actually think your model, that requires matter to enter our universe from "outside", is simpler than the generally understood (by rational people) model of the universe? really? okay...
Tuxford
1.7 / 5 (6) May 30, 2014
The outside is actually here and everywhere, just undetectable until the proper conditions initiate the self-sustaining reactions that we call matter, and energy.

Just because you can't understand it, doesn't mean it is complex. Maybe you just don't have the proper rational toolbox? Cheers.
supamark23
5 / 5 (3) May 30, 2014
The outside is actually here and everywhere, just undetectable until the proper conditions initiate the self-sustaining reactions that we call matter, and energy.

Just because you can't understand it, doesn't mean it is complex. Maybe you just don't have the proper rational toolbox? Cheers.


it's not a matter of understanding, it's a matter of your theory being rediculous.
MrPressure
May 31, 2014
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MrPressure
May 31, 2014
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Pejico
May 31, 2014
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Pejico
May 31, 2014
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Pejico
May 31, 2014
This comment has been removed by a moderator.
Pejico
May 31, 2014
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Pejico
May 31, 2014
This comment has been removed by a moderator.
barakn
4 / 5 (4) Jun 07, 2014
Whoah. Pejico was just another Zephir sockpuppet, was it not? I don't think I've ever seen a mod remove every post made by a user before.
Uncle Ira
3.7 / 5 (3) Jun 07, 2014
Whoah. Pejico was just another Zephir sockpuppet, was it not? I don't think I've ever seen a mod remove every post made by a user before.


Usually when ol Zephir-Skippy gets the boot, they take down all his posts, mostly they just disappear without the little note "this has been took down by the moderator". All those old Zephir-Skippy posts get gone whenever they make him get the new name.

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