CEA: Extremely Young Stellar Clump in the Distant Universe

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CEA: Extremely Young Stellar Clump in the Distant Universe

Post by bystander » Fri May 15, 2015 3:33 pm

Discovery of an Extremely Young Stellar Clump in the Distant Universe
Institute of Research into the Fundamental Laws of the Universe
Alternative Energies and Atomic Energy Commission (CEA)
Subaru Telescope | NAOJ | 2015 May 14
[img3="Discovery of a giant star-forming clump less than 10 million years old in a galaxy of the distant Universe. Observations were obtained using the WFC3 wide field camera on-board Hubble. ... (Credit: CEA/HST)"]http://subarutelescope.org/Pressrelease ... /fig1e.png[/img3][hr][/hr]
A Key for Understanding Galaxy Evolution

As part of an observing program carried out with the Subaru Telescope and the Hubble Space Telescope, a group of researchers from the Service d’Astrophysique- Laboratoire AIM of CEA-IRFU led by Anita Zanella discovered the birth cry of a massive star-forming clump in the disk of a very distant galaxy. This giant clump is less than 10 million years old, and it is the very first time that such a young star-forming region is observed in the distant universe. This discovery sheds new light on how stars were born within distant galaxies. The physical properties of this object reveal that newly-born clumps in such galaxies survive from stellar winds and supernovae feedback, and can thus live for a few hundred million years unlike the predictions from several theoretical models. Their long lifetime could enable their migration toward the inner regions of the galaxy, hence contributing to the total mass of the galactic bulge and the growth of the central black hole. These results are published in the journal Nature on 7 May 2015.

A Burst of Star Formation in a Galaxy of the Distant Universe

When the universe was only 3 billion years old, galaxies had very different properties than those they exhibit nowadays. Their shapes were more irregular and their disks were much more gas-rich. We actually know that the latter formed their stars more rapidly, within gigantic, much more massive and luminous star-forming regions than those typically observed in local galaxies. However, the way these large stellar clumps formed is not yet understood, and their evolution along cosmic history is still highly debated. To clarify these open issues, astrophysicists from SAp carried out their own observing campaign with the Hubble Space Telescope (in imaging and spectroscopic mode) and the Subaru telescope (in spectroscopic mode) installed in Hawaii. Indeed, the apparent faintness of distant galaxies requires the use of powerful observing facilities. They discovered the signature of a giant clump made of very young stars and caught while just forming, within a galaxy located at a distance of 11 billion light-years.

Less than 10 million years old, this clump has not yet evolved enough for its stars to be directly detected. Therefore it is thanks to the radiations from the gas ionized by these young stars that it was revealed. This giant clump has a gas mass of about one billion times that of the Sun. Forming its stars at a rate of 30 solar masses per year, it contributes up to 50% of the total star formation of the galaxy. Besides, its growth rate in mass and its efficiency in converting molecular gas into new stars are 10 times higher than the typical values observed at this epoch of cosmic history. This confirms the presence of a prodigious burst of star formation in this region. ...

A Massive Clump of Stars Detected at its Birth in the Distant Universe
Alternative Energies and Atomic Energy Commission (CEA) | 2015 May 08

An extremely young massive clump forming by gravitational collapse in a primordial galaxy - A. Zanella et al
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Re: CEA: Extremely Young Stellar Clump in the Distant Univer

Post by Ann » Sat May 16, 2015 4:24 am

Can anyone help me with this? In the six images illustrating this article, we can see the levels of ionization of this stellar clump in different wavelengths. Panel number tree is OII. I realized that I had no idea what wavelength OII is, so I searched for it on the web. I came up absolutely empty, except for an utterly confusing paper cataloging what seemed like hundreds of lines of ionization for OII, ranging from lines in the far ultraviolet (if not X-rays) to lines in the far infrared (if not microwaves).

I guess that in the article which bystander quoted, OII must refer to a very specific line and a very specific wavelength. Which one? Can anyone help me?

Ann
Last edited by Ann on Sat May 16, 2015 8:17 am, edited 1 time in total.
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Re: CEA: Extremely Young Stellar Clump in the Distant Univer

Post by bystander » Sat May 16, 2015 4:45 am

Ann wrote:...
I guess that in the article which bystander quoted, OII must refer to a very specific line and a very specific wavelength. Which one? Can anyone help me?

According to the paper, they were using [O II] at 372.7 nm.
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Re: CEA: Extremely Young Stellar Clump in the Distant Univer

Post by Ann » Sat May 16, 2015 5:04 am

Thank you, bystander.

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Re: CEA: Extremely Young Stellar Clump in the Distant Univer

Post by geckzilla » Sat May 16, 2015 5:18 am

Since that galaxy's OII lines are redshifted, I think what you may want are the non-redshifted values. Here is a table of persistent lines of singly ionized oxygen [OII]
http://physics.nist.gov/PhysRefData/Han ... table4.htm

Compare with the table for hydrogen which has that familiar line at 656 nm...
http://physics.nist.gov/PhysRefData/Han ... table3.htm

It's rather confusing for me as well. It would probably be easier if it were all in graph form. I also don't understand why the 658nm is missing for singly ionized nitrogen.
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