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.
