title: No high-mass protostars in the silhouette young stellar object M17-SO1.
abstract: The birth of very massive stars is not well understood, in contrast to the formation process of low-mass stars like our Sun. It is not even clear that massive stars can form as single entities; rather, they might form through the mergers of smaller ones born in tight groups. The recent claim of the discovery of a massive protostar in M17 (a nearby giant ionized region) forming through the same mechanism as low-mass stars has therefore generated considerable interest. Here we show that this protostar has an intermediate mass of only 2.5 to 8 solar masses (M(o), contrary to the earlier claim of 20M(o) (ref. 8). The surrounding circumstellar envelope contains only 0.09M(o) and a much more extended local molecular cloud has 4-9M(o).
authors.affiliation: Department of Astronomy, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan. sako@ioa.s.u-tokyo.ac.jp
authors.forename: Shigeyuki
authors.initials: S
authors.lastname: Sako
authors.forename: Takuya
authors.initials: T
authors.lastname: Yamashita
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Kataza
authors.forename: Takashi
authors.initials: T
authors.lastname: Miyata
authors.forename: Yoshiko K
authors.initials: YK
authors.lastname: Okamoto
authors.forename: Mitsuhiko
authors.initials: M
authors.lastname: Honda
authors.forename: Takuya
authors.initials: T
authors.lastname: Fujiyoshi
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Terada
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kamazaki
authors.forename: Zhibo
authors.initials: Z
authors.lastname: Jiang
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Hanawa
authors.forename: Takashi
authors.initials: T
authors.lastname: Onaka