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Ancient Galaxies twice the size of the Milky Way

  1. Nov 23, 2015 #1
    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?


    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?
  2. jcsd
  3. Nov 23, 2015 #2


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    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.
  4. Nov 23, 2015 #3


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    Here is the technical paper the the popular journalism refers to:
    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.
  5. Nov 24, 2015 #4


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  6. Nov 24, 2015 #5


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    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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