TY - JOUR
T1 - H2 line emission associated with the formation of the first stars
AU - Mizusawa, Hiromi
AU - Nishi, Ryoichi
AU - Omukai, Kazuyuki
PY - 2004
Y1 - 2004
N2 - Molecular hydrogen (H2) line radiation emitted in the formation events of first-generation stars is evaluated in a discussion of its detectability by future observational facilities. H2 luminosity evolution from the onset of prestellar collapse until the formation of a ∼ 100 M⊙ protostar is followed. Calculations are extended not only to the early phase of the runaway collapse, but also to the later phase of accretion, whose observational features have not been studied before. Contrary to the runaway collapse phase, where the pure-rotational lines are always dominant, in the accretion phase rovibrational line emission becomes prominent. The maximum luminosity is also attained in the accretion phase for strong emission lines. The peak intensity of the strongest rovibrational line reaches ∼ 10-29 W m-2, corresponding to the flux density of 10-5 μJy, for a source at the typical redshift of first-generation star formation, 1 + z = 20. Although the redshifted rovibrational H2 emission from such an epoch falls in the wavelength range of the next-generation infrared satellite, Space Infrared Telescope for Cosmology and Astrophysics, for exceeding the detection threshold, 107 such protostars are required to reach the maximum luminosity simultaneously in a pregalactic cloud. It is improbable that this condition is satisfied in a realistic scenario of early structure formation.
AB - Molecular hydrogen (H2) line radiation emitted in the formation events of first-generation stars is evaluated in a discussion of its detectability by future observational facilities. H2 luminosity evolution from the onset of prestellar collapse until the formation of a ∼ 100 M⊙ protostar is followed. Calculations are extended not only to the early phase of the runaway collapse, but also to the later phase of accretion, whose observational features have not been studied before. Contrary to the runaway collapse phase, where the pure-rotational lines are always dominant, in the accretion phase rovibrational line emission becomes prominent. The maximum luminosity is also attained in the accretion phase for strong emission lines. The peak intensity of the strongest rovibrational line reaches ∼ 10-29 W m-2, corresponding to the flux density of 10-5 μJy, for a source at the typical redshift of first-generation star formation, 1 + z = 20. Although the redshifted rovibrational H2 emission from such an epoch falls in the wavelength range of the next-generation infrared satellite, Space Infrared Telescope for Cosmology and Astrophysics, for exceeding the detection threshold, 107 such protostars are required to reach the maximum luminosity simultaneously in a pregalactic cloud. It is improbable that this condition is satisfied in a realistic scenario of early structure formation.
KW - Cosmology: early universe
KW - Galaxies: high-redshift
KW - Infrared: galaxies
KW - Stars: formation
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U2 - 10.1093/pasj/56.3.487
DO - 10.1093/pasj/56.3.487
M3 - Article
AN - SCOPUS:3142741183
VL - 56
SP - 487
EP - 495
JO - Publications of the Astronomical Society of Japan
JF - Publications of the Astronomical Society of Japan
SN - 0004-6264
IS - 3
ER -