The Top 12 of 2012

12 (Tie with 11). Less Lyman-alpha emission from the oldest galaxies

Why it is important: The farther back in time we look, the closer we get to a point when the first stars and galaxies had only just turned on, and the universe was mostly filled with neutral gas. Here, we see a few hints that observations are approaching this regime.

This paper predicts that, based on the observed distribution of galaxies with Lyman alpha emission at z=6 (dark blue histogram), one should detect a larger number of similar systems at a redshift of 7 (light blue histogram). However, in the observed z=7 sample, only two Ly-alpha emitting galaxies are detected, with an upper limit of four (shaded columns). Despite the small sample size, this is a highly unlikely result that suggests Ly-alpha emitters may be obscured by a higher fraction of neutral gas at redshifts z=7 and greater.

Next: (#11) Dark Matter core, nothing more! How to Mess With the Dark Matter in Dwarf Galaxies

About Betsy Mills

I am a 22nd-grader at UCLA, working with Mark Morris and spending the year at the MPIA in Heidelberg finishing my thesis. I like molecules in space, radio telescopes, the extreme center of our galaxy, getting to look at things no-one else has ever seen before, solving puzzles, and finding creative ways to survive graduate school


  1. Hi Betsy:

    Just a note– it looks like the arXiv link that you have on the first page of this article does not link to the title you provide.

    The link looks like it goes here:

    “How supernova feedback turns dark matter cusps into cores”

    instead of here:

    “Keck Spectroscopy of Faint 3<z<8 Lyman Break Galaxies:- Evidence for a Declining Fraction of Emission Line Sources In the Redshift Range 6<z<8"


    • Ah, actually the links are just switched–


      • Thanks Dave! The links are now fixed.

  2. Fascinating articles! But counting citations seriously distorts what astronomy is about. Because most young astronomers today work in observational cosmology, 10/12 papers are on that topic, the most glamorous frontier. But 10/12 of the most significant new papers of 2012 (selected some other way) paint a certainly much broader canvas, and reflect the amazing scope of astronomical research!
    Only the search for new planets (another glamour topic) and new calculations of the evolution of rotating stars in the HR diagram (a classic issue in stellar astronomy) penetrated the top twelve. So much more was missing!
    Nonetheless, an interesting citation poll.

    • Yes, I had the mass-to-light ratio section entirely backward; this is now corrected (and consistent with the linked astrobite). Thank you!!


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