What can spectroscopy of this distant galaxy reveal about the universe at z~10?

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Discussion Overview

The discussion revolves around the implications of spectroscopy for a candidate young galaxy observed at a redshift of approximately 10, focusing on its age, formation, and the challenges of acquiring spectroscopic data. The scope includes theoretical considerations, observational techniques, and the potential for future studies with the James Webb Space Telescope (JWST).

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants highlight that the galaxy is identified as a candidate at redshift z = 9.6, suggesting it is among the first galaxies observable at such an early cosmic time.
  • There is confusion regarding the age of the galaxy, with some participants noting the discrepancy between the stated age of 500 million years and the later mention of an age less than 200 million years, which is derived from spectroscopic constraints.
  • One participant references existing models that suggest galaxies should not form until around 300 million years after the Big Bang, raising questions about the implications for this candidate galaxy.
  • Another participant interprets the data to suggest that if the galaxy's light was emitted at 490 million years, its formation must have occurred at a cosmic age of at least 290 million years, implying a formation redshift of less than 14.
  • Concerns are raised about the difficulty of obtaining spectroscopic data at such high redshifts without the aid of gravitational lensing, emphasizing the unique opportunity this galaxy presents for studying the early universe.

Areas of Agreement / Disagreement

Participants express confusion and seek clarification on the age of the galaxy, indicating a lack of consensus on the interpretation of the data. There are competing views regarding the implications of the redshift and the feasibility of spectroscopic observations.

Contextual Notes

There are limitations in the discussion regarding the assumptions made about the galaxy's age and formation, as well as the dependence on the definitions of redshift and cosmic time. The mathematical steps leading to the conclusions about the galaxy's formation redshift remain unresolved.

Chronos
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A highly magnified candidate for a young galaxy seen when the Universe was 500 Myrs old
http://arxiv.org/abs/1204.2305

"... We derive a robust photometric redshift of z = 9.6 ±0.2, corresponding to a cosmic age of 490 ±15Myr (i.e., 3.6% of the age of the Universe). ... The object is the first z>9 candidate that is bright enough for detailed spectroscopic studies with JWST"

Spectroscopy of such an ancient galaxy would be very interesting.
 
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Very cool. Thanks for posting.

Do you know what they mean by "If the galaxy is indeed at such a large redshift, then its age is less than 200 Myr" ?

They start off saying it is probably 500 million years old (dating from the singularity) and SEEM to use "Myr" with that, so I'm confused by the later use of "200 Myr"
 
Based on existing models, the earliest galaxies should not develop until around 300 million years after the BB.
 
phinds said:
Very cool. Thanks for posting.

Do you know what they mean by "If the galaxy is indeed at such a large redshift, then its age is less than 200 Myr" ?

They start off saying it is probably 500 million years old (dating from the singularity) and SEEM to use "Myr" with that, so I'm confused by the later use of "200 Myr"

In the paper they say
The significant magnification by cluster lensing
(a factor of ∼15) allows us to analyze the object’s ultra-violet and optical luminosity in its rest-2 frame, thus enabling us to constrain on its stellar mass, star-formation rate and age.. If the galaxy
is indeed at such a large redshift, then its age is less than 200 Myr (at the 95% confidence level),
implying a formation redshift of zf <∼ 14

I think what they're saying is that the image they have is of a galaxy which is 'now' 500 million years old and which first formed at 200 million yrs.
 
alexg said:
In the paper they say

..enabling us to constrain on its stellar mass, star-formation rate and age.. If the galaxy is indeed at such a large redshift, then its age is less than 200 Myr (at the 95% confidence level), implying a formation redshift of zf <∼ 14

I think what they're saying is that the image they have is of a galaxy which is 'now' 500 million years old and which first formed at 200 million yrs.

If the light was emitted at 490Myr and they have constrained the age to be less than 200Myr from the spectrum, they deduce its formation would have been at a cosmic age of at least 290 Myr. That implies its formation was at z<14 and implies we will be able to observe the period of formation with JWST which is designed to work to z=15 or higher.
 
Spectroscopic data will be difficult to acquire at z~14, even with JWST, without gravitational lensing. This little gal offers a unique [so far] opportunity to probe the composition of the universe near z~10.
 

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