Open AccessOn the possibility of observing H 2 emission from primordial molecular cloud kernels
Author(s) -
Kamaya Hideyuki,
Silk Joseph
Publication year - 2002
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2002.05301.x
Subject(s) - physics , astrophysics , observable , stars , molecular cloud , redshift , flux (metallurgy) , emission spectrum , astronomy , spectral line , galaxy , materials science , quantum mechanics , metallurgy
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 ∼0.01 M ⊙ yr −1 . This occurs owing to the primordial abundances, which result in a kernel temperature of order 1000 K, and the collapsing kernel emits H 2 line radiation at a rate ∼10 35 erg s −1 . Predominantly J =5‐3 ( v =0) rotational emission of H 2 is expected. At redshift 1+ z ∼20 , the expected flux is ∼0.01 μJy 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 subgalactic scales can result in fluxes at the sub‐mJy level. This is marginally observable with ASTRO‐F and ALMA. We also examine the rotational J =2‐0 ( v =0) and vibrational δv =1 emission lines. The former may possibly be detectable with ALMA.