What is the highest redshift (Z number) a galaxy can have?

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    Galaxy Redshift
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Discussion Overview

The discussion revolves around the highest redshift (Z number) that a galaxy can have, exploring the epoch at which galaxy formation becomes impossible. Participants consider theoretical limits, the timeline of atomic and star formation, and the implications of redshift measurements.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants suggest that galaxies are being discovered at increasingly higher redshifts, prompting questions about the epoch at which galaxy formation ceases to be possible.
  • One participant references a Wikipedia article that discusses the highest redshifts and lists distant astronomical objects, indicating that there is existing literature on the topic.
  • Another participant posits that atoms formed around Z=20, implying that galaxies would form sometime after that, although this claim is questioned regarding the timing of star formation.
  • A later reply clarifies that atoms formed before Z=1089, which corresponds to the redshift of the Cosmic Microwave Background (CMB), and suggests that the first stars, rather than atoms, would have initiated reionization.
  • One participant states that the current limit on redshift is believed to be between Z=22 and Z=23, theorizing that star formation could not have begun before this period, while also suggesting the possibility of supermassive black hole seeds forming earlier.

Areas of Agreement / Disagreement

Participants express varying views on the timeline of atomic and star formation, with some uncertainty regarding the exact redshift values and the implications for galaxy formation. No consensus is reached on the highest redshift at which galaxies can exist.

Contextual Notes

Limitations include the dependence on definitions of redshift and the unresolved nature of the timeline for star and galaxy formation. The discussion reflects ongoing debates in astrophysics regarding early universe conditions.

Who May Find This Useful

Readers interested in cosmology, astrophysics, and the formation of galaxies in the early universe may find this discussion relevant.

wolram
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Galaxies seem to being found further and further back to the BB, At what epoch is it going to be impossible for galaxies to form?
https://arxiv.org/abs/0912.4263
 
Last edited:
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Thank you for the reply, as I can make out atoms formed about
Z=20 at the latest, so I expect galaxies to form some time after that.?
 
wolram said:
Thank you for the reply, as I can make out atoms formed about
Z=20 at the latest, so I expect galaxies to form some time after that.?
Atoms formed sometime before z=1089 (the redshift of the CMB). Perhaps you meant stars?

The formation of the first stars and galaxies would have been the event which kicked off the process of reionization:
https://en.wikipedia.org/wiki/Reionization

The basic process is that as the first stars formed, they put out a lot of photons that were high enough in energy to ionize the gas that was spread throughout the universe. These stars would have formed in the most dense regions first, forming the first galaxies.
 
The current tlimit on redshift is believed to be beteen z=22 and z=23. which corresponds to the so-called dark ages which lasted until the universe was about 150,000,000 years old Star formation should theoretically not have begun any earlier than that. It is, however, considered theoretically possible the seeds of what would become supermassive black holes black holes could have fromed before the first stars lit up. Thes JWST could possibly detects these as discussed here; https://arxiv.org/abs/1203.6075, The Formation of the First Massive Black Holes.
 
Thank you for replies.
 

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