Patchy reionization and the oldest galaxy in the visible universe

[PB666]

http://abcnews.go.com/Technology/discovery-farthest-galaxy-brings-questions-early-universe/story?id=33583326

This is actually an intesting article and suggests there might be older galaxies enshrouded in plasma left over from the opaque epoch.

[UmbralRaptor]

Found the actual paper!

http://abcnews.go.com/Technology/discovery-farthest-galaxy-brings-questions-early-universe/story?id=33583326

This is actually an intesting[sic] article and suggests there might be older galaxies enshrouded in plasma left over from the opaque epoch.

Er...? Recombination happened clear back at z~1100. The only absorption by low density neutral hydrogen clouds would be at specific wavelengths (eg: lyman alpha), messing with spectroscopic (though not photometric) distance measurements. This particular galaxy is in the middle of reionization, so finding galaxies somewhat farther out (especially if they're lensed) is to be expected.

As best I can tell from the paper, this is the most distant spectroscopically-confirmed galaxy. (Hence why it's now in a bunch of Wikipedia lists). They appear to have found a luminosity and color cut that shows high redshift galaxies (if not clusters) that have substantially ionized their surroundings.

[PB666]

Found the actual paper!

Er...? Recombination happened clear back at z~1100.

≃11776 {\AA}?

The only absorption by low density neutral hydrogen clouds would be at specific wavelengths (eg: lyman alpha), messing with spectroscopic (though not photometric) distance measurements. This particular galaxy is in the middle of reionization, so finding galaxies somewhat farther out (especially if they're lensed) is to be expected.

As best I can tell from the paper, this is the most distant spectroscopically-confirmed galaxy. (Hence why it's now in a bunch of Wikipedia lists). They appear to have found a luminosity and color cut that shows high redshift galaxies (if not clusters) that have substantially ionized their surroundings.

The first generation of stars are rather large, and short-lived. So you have the higher temperature photosphere producing Ionizing UV, leftover heat from the big-bang, and nova ejecting highly ionized particles and energetic EM, so this ionizing effect is expected. Even intergalactic gas is currently quite hot, but due to another reason, the very low density means that the gas is traveling from 'whatever' mass millions or billions of kilometers outside of its initial space-time into space where gas derived from other space-time are traveling, it does not take much to have a collision at a couple thousand meters per second, clearly enough to ionize electrons. Add to this GBH emmitting X-ray into the space over the poles.

Of course the other articles indicate their is probably a desire to detect the cold neutrinos from before the opaque period. So the could potentially see further back but with a rather myopic view.

ty for the ref.

Edited September 9, 2015 by PB666

[UmbralRaptor]

≃11776 {\AA}?

Looks like it's supposed to be 11776 â„«, so a near-IR detection of rest-frame mid-UV!

[PB666]

Is this actually peer-reviewed or is it a university hype page? looks like a meeting abstract or something.

[UmbralRaptor]

Is this actually peer-reviewed or is it a university hype page? looks like a meeting abstract or something.

The entire article is available in the arXiv link (click pdf). And it was published in ApJL.

The Astrophysical Journal Letters is a peer-reviewed express scientific journal that allows astrophysicists to rapidly publish short notices of significant original research. The American Astronomical Society has chosen IOP Publishing to publish The Astrophysical Journal.

https://iopscience.iop.org/2041-8205

[PB666]

The entire article is available in the arXiv link (click pdf). And it was published in ApJL.

https://iopscience.iop.org/2041-8205

thanks again

I will synopse this a bit. The lyman series of are the UV emmission spectrum of hydrogen. In the lab alpha is 1216 Ang which translates into 121.6 nm, which approaching the vacuum UV, this stuff not the good UV but is the stuff that will give you a sunburn. They found what the think is this ly alpha at 1177.6 nm. The degree of redshift is a 8.6 (calibrated) fold factor which is the highest degree of redshift for any celestial object in the visible universe. This means that it is moving away from us faster than most other galaxies and possibly all other known galaxies. Because we assume inflation was uniform and because this object should be comoving better relative to surrounding mass, we then have to assume this galaxy is farther away than galaxies with lower redshifts or z

As the universe cooled plasma hydrogen in form of proton and free electrons, deionizing the universe permitting CMBR. This produces nonionizing radiation. The theta between comoving gas is relatively large which means that the light is rather quickly redshifted relative to the gas it moves through that gas at greater distances. In quickly redshifting it is less suceptible to absorbtion from gas or plasma.

The ionization of intergalactic gas is not over. Hydrogen stars are very hard to form because they lack nuclei, but dense pockets gas kept apart by motion are begiining to cool, and friction of swirls is causing circular motion to abate and hydrogen collapses into large first generation stars. These stars, because of their inherant size have a very hot light producing surface which translates into much more blue and UV light than our sun. The galaxy EGSY8p7 falls into this catagory. When these stars formed they send large amounts of high velocity plasma and UV, and x-rays into the surrounding media, which cause a reionization and this process prevents us from seeing the very oldest stars, because at frequencies higher than CNBR much of the universe is becomes opaque.

Except an area between our galaxies comoving reference frame and this ancient galaxy, EGSY8p7, that for some reason has not greatly reionized or is less dense in gas. It is more or less looking down into a pit in a media composed of plasma. So the question why is this area less ionized and other areas more ionized.

Previous reports last year claimed that polarized light in CNBR indicate structure, possibly as a consequence of imperfect inflation. Critques argue that this is either not true or that the signal to noise was to low for the conclusions the authors drew. So this paper suggests in a different way that long range gas densities were not uniform. EM in the universe should have been uniform and thus piar production should also have been uniform. However this paper indicates the may been non-uniformity.

So what are the critiques,

could this galaxy not be closer and moving in the comoving frame and away from us.

Absorption spectrum of skyline molecules. They use another spectra IRAC[3.6]-[4.5] to suugest a redshift of 8, making it older than other galaxies at the previous limit of 7.

The 11776 Ang value they claim is sigma =7 which using the monte carlo markov chaim seems reasoable given the distribution and signal to noise. The critque is that the signal is on a rather limited number of pixels, and one cannot claim at that level independency between adjacent pixels. Non-independcy can tend to amplify statistical diiferences by making power look greater than it is. So they did randomly sample 1500 spots looking for a similar line and found none, so the background values i hoped are the basis for their monte carlo seem reasonable, the issue then is how independent can 11 clustered pixels be, given that this is a keck ground based telescope observation.

Another critique is that previous researchers got it wrong, taking in adequate measures to find emmision spectrum bands in galaxies potentially more redshifted than 7.

The range of equivilent width values of. 17-42 Ang makes this not only one of the oldest but one of the brightest Z>7 galaxies and is comparble to galaxies younger than the reionization < 6.5. but studies of redshift 2 galaxies shows a higher range of EW suggesting that light from the most distant galaxies is somewhat attenuated.

I suppose this opens the door with space telescopes, better infrared equipment in a cooler environemnt better signal to noise and even more red shifted galaxies. Some of the physics for deionization and reionization is likely to change.

Technical critique, the paper lacked an abbreviation list, but they use a rather large number of obscure abbreviations, its actually the first time i have seen references abbreviated in this style and was a bit disconcerting. The lyman alpha wave length was not given, for a broader audiance relavent spectral lines should have been illustrated, this may seem trivial, but they specifically select certain bands over others because of post emmision contamination and absoption potentials. It would have been nice to see a table or figure detailing what those were. The z-value calibration method was only breifly detailed. The skyline contribution while specifically defined, generally was not well defined. Figure 1 legend marginally explains the figure.

[PB666]

http://www.csmonitor.com/Science/2015/0909/At-13.2-billion-years-this-galaxy-is-almost-as-old-as-the-universe-itself

This source is a little bit better written.

[PB666]

http://phys.org/news/2016-08-stars-previously-thought.html

New article out on the matter.