Astronomy and Astrophysics – Astrophysics
Scientific paper
2001-04-30
Astronomy and Astrophysics
Astrophysics
12pages, no figure. PASJ (Accepted; tex-file is replaced)
Scientific paper
A possible formation mechanism of hydrogen molecules on a galactic scale is examined. We are interested especially in the role of hydrogen molecules for formation and evolution of primordial galaxies. Then, formation process of hydrogen molecules in a very low-metallicity galaxy (I Zw 18; the most typical metal-deficient galaxy) is studied. Adopting a recent observational result of absorption lines of hydrogen molecule in I Zw 18, we obtain the upper limit for the ionization degree in the case where hydrogen molecules can form via the H$^{-}$-process, although they are generally believed to form on the surface of dust grains. Furthermore, we present a critical ionization degree, above which H$^{-}$-process can be dominant over the formation process on the surface of grains. Interestingly, this critical ionization degree is comparable to the upper limit of the ionization degree for I Zw 18. For determination of the formation process of hydrogen molecules, future observational facilities can be useful. Thus, we examine the detectability in some wavelengths for the metal deficient galaxies. According to our estimate, near-infrared line emission of hydrogen molecule is observable in the level of 10 $\mu$Jy, the free-free radio emission is in the level of mJy, and the far-infrared emission from the dust on which hydrogen molecules form can also be detected with 10-mJy level with its temperature of 16 K. The near-infrared line and the far-infrared continuum are feasible for ASTRO-F observations.
Hirashita Hiroyuki
Kamaya Hideyuki
No associations
LandOfFree
H2 Formation in Low Metallicity Galaxies does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with H2 Formation in Low Metallicity Galaxies, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and H2 Formation in Low Metallicity Galaxies will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-287612