Why is CMB visible through cosmic 'Dark Ages' ?

[Widdekind]

During the 'Dark Ages', from roughly 400 Kyr to 400 Myr after the Big Bang, space was strewn with neutral primordial gas:

 

in brief, "dark ages" refers to the period after recombination occurred, about 380,000 years after the big bang, creating the cosmic microwave background (CMB), up to and partly including the time that the first stars had formed, perhaps as early as four hundred million years later, and caused the reionization of much of the neutral hydrogen in the universe.

So, if space was strewn with gobs of gas, how can we see through that gas, all the way back to the CMB last scattering surface ??? In the following figure, sight-lines, extending backwards in time, from the present epoch, to the CMB last scattering surface, must first pass through the Dark Ages, and their gobs of gas. How come those clumps of matter don't block LOS ???

 

[John Cuthber]

Hydrogen is transparent.

[Widdekind]

Hydrogen is transparent.

 

Thanks! Does that imply, that there was no dust, nor molecular H₂ ? If all the monoatomic hydrogen atoms, were in their ground states, photons would need at least 3/4 x 13.7eV to excite them into 'level 2' states -- so, when the CMB cooled below ~10eV ~10⁵K, the thermal background 'decoupled' from the now neutral matter. But, would molecular hydrogen or dust have absorbed some spectra, had they been present, thereby proving their absence ??

[alpha2cen]

After dark ages, why we can not see many black holes? The condition is , my guessing, very good to make many black holes. Is the state different what we think?

[John Cuthber]

It's not my field but I believe that the original bang made hydrogen, deuterium, helium and a little lithium. This material went on to form the first stars.

 

"After dark ages, why we can not see many black holes? "

The hint is in the name.

"The condition is , my guessing, very good to make many black holes."

What would your second guess be?

[alpha2cen]

It's not my field but I believe that the original bang made hydrogen, deuterium, helium and a little lithium. This material went on to form the first stars.

 

"After dark ages, why we can not see many black holes? "

The hint is in the name.

"The condition is , my guessing, very good to make many black holes."

What would your second guess be?

 

The energy state is very high. Most of black holes we have seen is created from supernova explosion, i.e., very high energy state.

So, I think, the state after Big Bang was some different high energy state from supernova explosion.

[Widdekind]

Why don't we see that first 'flash' of pan-cosmic star formation, shown on the above figure, but absent from the HDF & HUDF ? We can see quasars, from ~1 Gyr after the big bang -- why can't we see the 'star burst' from about the same time, especially if it was super-bright, including copious quantities of ultra-massive 1^st generation 200 solar-mass stars ??

[Spyman]

This article hints that our technological limit is still to low for such observations, after all Quasars are the most luminous, powerful, and energetic objects known in the universe and first generation stars are still only huge stars.

 

Scientists See Light That May Be From First Objects in Universe 11.02.05

Scientists using NASA's Spitzer Space Telescope say they have detected light that may be from the earliest objects in the universe. If confirmed, the observation provides a glimpse of an era more than 13 billion years ago when, after the fading embers of the theorized Big Bang gave way to millions of years of pervasive darkness, the universe came alive.

...

"This difficult measurement pushes the instrument to performance limits that were not anticipated in its design," said team member Dr. S. Harvey Moseley, instrument scientist for Spitzer. "We have worked very hard to rule out other sources for the signal we observed."

 

The low noise and high resolution of Spitzer's infrared array camera enabled the team to remove the fog of foreground galaxies, made of later stellar populations, until the cumulative light from the first light dominated the signal on large angular scales. The team, which also includes Dr. Richard Arendt, Science Systems and Applications scientist, noted that future missions, such as NASA's James Webb Space Telescope, will find the first individual clumps of these stars or the individual exploding stars that might have made the first black holes.

http://www.nasa.gov/centers/goddard/news/topstory/2005/universe_objects.html

[Widdekind]

This site seemingly says something similar -- somehow, although we can see the CMB, from the Big Bang (t=0), and early quasars/AGN (t=1Gyr), there seems to be some sort of data gap in between, corresponding to a period of chaotic mergers amidst malformed proto-galaxies:

 

The final ACS image, assembled by Anton Koekemoer of the Space Telescope Science Institute, is studded with a wide range of galaxies of various sizes, shapes, and colors. In vibrant contrast to the image's rich harvest of classic spiral and elliptical galaxies, there is a zoo of oddball galaxies littering the field. Some look like toothpicks; others like links on a bracelet. A few appear to be interacting. Their strange shapes are a far cry from the majestic spiral and elliptical galaxies we see today. These oddball galaxies chronicle a period when the universe was more chaotic. Order and structure were just beginning to emerge.

Perhaps the first stars were still shrouded by neutral primordial gas? Perhaps, then, whole Globular Cluster caliber objects formed, hidden in cognito, shrouded in cosmic cocoons, of as-yet-un-re-ionized IGM ??

 

Edited February 15, 2011 by Widdekind

[imatfaal]

I am not sure quite what you are asking; we can see the CMBR because at its origins the entire volume of the galaxy was radiating/absorbing/scattering light - we can still detect the "last hurrah". But after the era of last scattering until now and onwards for many year only a miniscule portion of the volume of the galaxy was/is/willbe radiating; spotting localised events (ie fixed period of time and in certain place) is a hell of a lot more difficult than finding the CMBR