Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

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?

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

    Chalnoth

    User Avatar
    Science Advisor

    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

    marcus

    User Avatar
    Science Advisor
    Gold Member
    Dearly Missed

    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.
     
  5. Nov 24, 2015 #4

    wolram

    User Avatar
    Gold Member

  6. Nov 24, 2015 #5

    PeterDonis

    User Avatar
    2016 Award

    Staff: Mentor

    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.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Ancient Galaxies twice the size of the Milky Way
  1. The Milky Way (Replies: 2)

Loading...