On the Possibility of Observing H2 Emission from Primordial Molecular Cloud Kernels

Abstract

We study the prospects for observing H${}_2$ emission during the assembly of primordial molecular cloud kernels. The primordial molecular cloud cores, which resemble those at the present epoch, can emerge around $1+z=20$ according to recent numerical simulations. The kernels form inside the cores, and the first stars will appear inside the kernels. A kernel typically contracts to form one of the first generation stars with an accretion rate that is as large as $\sim 0.01M_{\odot }$ year${}^{-1}$. This occurs due to the primordial abundances that result in a kernel temperature of order 1000K, and the collapsing kernel emits H${}_2$ line radiation at a rate $\sim 10^{35}$ erg sec${}^{-1}$. Principally $J=5-3$ (v=0) rotational emission of H${}_2$ is expected. At redshift $1+z=20$, the expected flux is $\sim 0.01\mu$Jy for a single kernel. While an individual object is not observable by any facilities available in the near future, the expected assembly of primordial star clusters on sub-galactic scales can result in fluxes at the sub-mJy level. This is marginally observable with ASTRO-F. We also examine the rotational $J=2-0$ (v=0) and vibrational $\delta v=1$ emission lines. The former may possibly be detectable with ALMA.

15 pages, 1 figure. MNRAS (Submitted)

References in corpus (2)

• The Formation of the First Stars. I. The Primordial Star Forming Cloud
• Impact of Future Submillimeter and Millimeter Large Facilities on the Studies of Galaxy Formation and Evolution

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