JHU: Leaky star-forming galaxies

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MargaritaMc
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JHU: Leaky star-forming galaxies

Post by MargaritaMc » Mon Oct 13, 2014 1:58 pm

John Hopkins University
Leaky, Star-Forming Galaxies Lead Johns Hopkins Researchers to Better Understand the Universe

October 9, 2014
By focusing on large, star-forming galaxies in the universe, researchers at Johns Hopkins University were able to measure its radiation leaks in an effort to better understand how the universe evolved as the first stars were formed.
Sanchayeeta Borthakur, an assistant research scientist in the university’s Department of Physics and Astronomy in the Krieger School of Arts and Sciences, reports in a paper published online Oct. 9, in the journal Science, that an indicator used for studying star-forming galaxies that leak radiation, is an effective measurement tool for other scientists to use.

The researchers used the radiation leak measurement method to help find the ideal star-forming galaxy that contained holes in its cold gas cover. Studying the radiation that seeps through these holes has been an ongoing conundrum for scientists for years.
... Borthakur said scientists know that these leaky galaxies exist, but finding one has been a problem. This, in turn, makes it difficult for researchers to have a clearer understanding of how the reionization process works.
... reionization is core to the history of the cosmos as it marks the birth of the very first stars and galaxies....

Using observations made with the Cosmic Origin Spectrograph onboard the Hubble Space Telescope, the research team found the right galaxy to study. In the study, the researchers credit a combination of unusually strong winds, intense radiation and a massive, highly star-forming galaxy for proving the validity of the indicator.
This method first created by Heckman in 2001, can sort out what gas is present and also accurately measure the percentage of holes in the gas cover, said Borthakur.
“The confirmation of the indicator is key,” she said. “The implications are now people can use this indicator to study distant galaxies at longer wavelengths.”
This research was funded by NASA with grant number #12886.*
* But this article is behind a paywall, and there isn't a preprint in arXiv, so I haven't been able to find which galaxy they have used in this research. The article, using this press release, in Science Daily has an image of NGC 300. So that might be a hint.
S. Borthakur, T. M. Heckman, C. Leitherer, R. A. Overzier. A local clue to the reionization of the universe. Science, 2014; 346 (6206): 216 DOI: 10.1126/science.1254214

Editor's Summary:

A light leak to transform the universe

After the universe had cooled into an expanse of neutral gas after the Big Bang, how did the first starlight emerge from the dark? Borthakur et al. found a local starburst galaxy that leaks continuum radiation, which may provide some clues. Wind-generated gaps in the neutral gas enable large fractions of ionizing radiation to escape, possibly mimicking processes in the early universe.
Margarita
"In those rare moments of total quiet with a dark sky, I again feel the awe that struck me as a child. The feeling is utterly overwhelming as my mind races out across the stars. I feel peaceful and serene."
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Ann
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Re: John Hopkins U: Leaky star-forming galaxies

Post by Ann » Mon Oct 13, 2014 3:19 pm

Thanks, Margarita, very interesting!

However, the galaxy in question certainly isn't NGC 300. According to the link you provided, the galaxy that was studied was characterized by
unusually strong winds, intense radiation
and it was also
a massive, highly star-forming galaxy
That is not a characterization of NGC 300. This galaxy is considerably smaller than the Milky Way, and it is relatively faint in the far infrared, suggesting that its rate of star formation isn't all that impressive.

Ann
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MargaritaMc
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Re: John Hopkins U: Leaky star-forming galaxies

Post by MargaritaMc » Tue Oct 14, 2014 7:48 pm

Ann wrote:
However, the galaxy in question certainly isn't NGC 300.
Ann
Curiouser and curiouser!” Cried Alice (she was so much surprised, that for the moment she quite forgot how to speak good English).”

― Lewis Carroll, Alice's Adventures in Wonderland
I must see if I can find someone with a subscription to the ScienceMag! :lol2:
"In those rare moments of total quiet with a dark sky, I again feel the awe that struck me as a child. The feeling is utterly overwhelming as my mind races out across the stars. I feel peaceful and serene."
— Dr Debra M. Elmegreen, Fellow of the AAAS

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MargaritaMc
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Re: JHU: Leaky star-forming galaxies

Post by MargaritaMc » Tue Oct 14, 2014 8:46 pm

Got it!

The galaxy is J0921+4509 About three billion light years away, in the direction of the constellation Ursa Major.

As the research paper was behind a paywall, it didn't occur to me that the figures wouldn't be! :roll:
But they are freely available at Science Mag here.

And there is a useful article here...
Space.com
The nearby compact galaxy named J0921+4509, which is rapidly producing stars, has many of the characteristics that would have been required to light up the early universe. Located approximately 3 billion light-years from the Milky Way, the star-forming regions of the tightly bound galaxy are surrounded by dense clouds of gas. Holes in the gas allow radiation to leak out, mimicking events that would have broken through the darkness that followed the birth of the universe.

J0921+4509 produces approximately 50 solar-masses' worth of stars each year, more than 33 times the number of stars created by the Milky Way every year.
Margarita
"In those rare moments of total quiet with a dark sky, I again feel the awe that struck me as a child. The feeling is utterly overwhelming as my mind races out across the stars. I feel peaceful and serene."
— Dr Debra M. Elmegreen, Fellow of the AAAS

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