Ancient Galaxies twice the size of the Milky Way

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Discussion Overview

The discussion revolves around the observation of ancient galaxies that are reportedly twice the size of the Milky Way, particularly in the context of their formation shortly after the Big Bang (BB). Participants explore the implications of these findings for the Big Bang theory, the complexities of galaxy formation, and the nature of the universe's early structure.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether the existence of these large galaxies is consistent with the timing of the Big Bang theory.
  • Another participant notes the complexity of galaxy formation and the natural variation in local matter density, suggesting that definitive conclusions may be difficult to reach.
  • A technical paper is referenced, detailing a study of massive galaxies at high redshifts, which indicates that a significant portion of these galaxies may have formed earlier than previously thought, but the implications for the galaxy stellar mass function (GSMF) remain uncertain.
  • Some participants express amazement at the discovery of galaxies increasingly closer to the Big Bang, while also noting that the most distant galaxies still represent a small fraction of the universe's early expansion.
  • There is mention of the redshift values associated with these galaxies, which are crucial for understanding their distance and the expansion of the universe.

Areas of Agreement / Disagreement

Participants express a mix of wonder and skepticism regarding the implications of these findings for the Big Bang theory and galaxy formation. There is no consensus on how these observations should be interpreted or their significance in the broader context of cosmology.

Contextual Notes

The discussion highlights the limitations in understanding galaxy formation and the dependence on various assumptions regarding mass estimates and redshift interpretations. The complexity of translating observed brightness into stellar mass estimates is also noted as a potential area for adjustment in future studies.

Tanelorn
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I saw this news about galaxies twice the size of the milky way observed a relativity short time after the BB and wondered if this is still consistent with the BB theory or its timing?

http://news.yahoo.com/ancient-monster-galaxies-scientists-perplexed-122353576.html
I also wanted to ask if there are many Cosmologists who support the theory of a Universe from nothing to explain how the U began?
 
Space news on Phys.org
It's always going to be hard to say, because the physics of galaxy formation are extremely complicated, and because there's quite a lot of natural variation in local matter density.
 
Here is the technical paper the the popular journalism refers to:
http://arxiv.org/abs/1505.05721
Spitzer bright, UltraVISTA faint sources in COSMOS: the contribution to the overall population of massive galaxies at z=3-7
K. I. Caputi, O. Ilbert, C. Laigle, H. J. McCracken, O. Le Fevre, J. Fynbo, B. Milvang-Jensen, P. Capak, M. Salvato, Y. Taniguchi
(Submitted on 21 May 2015)
We have analysed a sample of 574 Spitzer 4.5 micron-selected galaxies with [4.5]<23 and Ks_auto>24 (AB) over the UltraVISTA ultra-deep COSMOS field. Our aim is to investigate whether these mid-IR bright, near-IR faint sources contribute significantly to the overall population of massive galaxies at redshifts z>=3. By performing a spectral energy distribution (SED) analysis using up to 30 photometric bands, we have determined that the redshift distribution of our sample peaks at redshifts z~2.5-3.0, and ~32% of the galaxies lie at z>=3. We have studied the contribution of these sources to the galaxy stellar mass function (GSMF) at high redshifts. We found that the [4.5]<23, Ks_auto>24 galaxies produce a negligible change to the GSMF previously determined for Ks_auto<24 sources at 3=<z<4, but their contribution is more important at 4=<z<5, accounting for >~50% of the galaxies with stellar masses Mst>~6 x 10^10 Msun. We also constrained the GSMF at the highest-mass end (Mst>~2 x 10^11 Msun) at z>=5. From their presence at 5=<z<6, and virtual absence at higher redshifts, we can pinpoint quite precisely the moment of appearance of the first most massive galaxies as taking place in the ~0.2 Gyr of elapsed time between z~6 and z~5. Alternatively, if very massive galaxies existed earlier in cosmic time, they should have been significantly dust-obscured to lie beyond the detection limits of current, large-area, deep near-IR surveys.
18 pages, 15 figures, 4 tables. Updated to match version in press at the ApJ

You can see Karina Caputi and Henry McCracken ( both quoted in the Yahoo account) listed among the authors.
You can see the stellar mass estimates 60 billion and 200 billion solar masses. You can also see the redshift z estimate of between 5 and 6.
How one compares this to the Milky Way depends on how one rates the constituents of our galaxy: how much is stars, gas, dust, etc.
At issue is the "GSMF" the galaxy stellar mass function. How one translates the observed brightness of a galaxy into an estimate of the overall mass of stars in it. Results like this may not be earth-shaking but they might eventually result in some adjustment of the way the GSMF is calculated for galaxies with redshifts like z = 5 and z = 6.
 
wolram said:
It is amazing astronomers keep finding galaxies closer and closer to the big bang

But still not very close, if you think in terms of redshift, which is a measure of how much the universe has expanded since the light was emitted. The largest redshift on the list is z = 8.68, which corresponds to the universe expanding by a factor of 1 + z, or almost 10, since that light was emitted. But the CMB is at a redshift of z = 1000, so the universe expanded by a factor of about 100 between the CMB being emitted and the oldest galaxy on the list emitting the light we now see.
 

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