Observing H2 emission in forming galaxies

Kazuyuki Omukai, Tetsu Kitayama

Research output: Contribution to journalArticlepeer-review

11 Citations (Scopus)


We study the H2 cooling emission of forming galaxies and discuss their observability using the future infrared facility Single Aperture Far-Infrared Observatory (SAFIR). Forming galaxies with mass ≲, 10 11 M⊙ emit most of their gravitational energy liberated by contraction in molecular hydrogen line radiation, although a large part of thermal energy at virialization is radiated away by the hydrogen Lyα emission. For more massive objects, the degree of heating due to dissipation of kinetic energy is so great that the temperature does not drop below 10 4 K, and the gravitational energy is emitted mainly by the Lyα emission. Therefore, the total H2 luminosity attains the peak value of LH2 ∼ 1042 ergs s-1 for forming galaxies whose total mass Mtot ∼ 1011 M⊙. If these sources are situated at redshift z ∼ 8, they can be detected by rotational lines of 0-0 S(3) at 9.7 μm and 0-0 S(1) at 17 μm by SAFIR. An efficient way to find such H2 emitters is to look at the Lyα emitters, since the brightest H2 emitters are also luminous in Lyα emission.

Original languageEnglish
Pages (from-to)738-745
Number of pages8
JournalAstrophysical Journal
Issue number2 I
Publication statusPublished - 2003 Dec 20
Externally publishedYes


  • Cosmology: theory
  • Galaxies: formation
  • Infrared: galaxies

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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