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On the origin of halo globular clusters and spheroid stars
Author(s) -
VIETRI MARIO,
PESCE ENRICO
Publication year - 1995
Publication title -
annals of the new york academy of sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.712
H-Index - 248
eISSN - 1749-6632
pISSN - 0077-8923
DOI - 10.1111/j.1749-6632.1995.tb17625.x
Subject(s) - physics , astrophysics , globular cluster , stars , halo , galaxy , metallicity , galactic halo , velocity dispersion , star formation
A scenario is presented for the simultaneous formation of halo globular clusters and spheroid stars, in which shocks occuring in the gaseous, primordial ( Z = 0) Galaxy play the central role. Denser‐than‐average subcondensations are shown to cool quickly and implode. Small condensations ( M < M t = 5 × 10 4 M ⊙ ) are returned to the hot surrounding phase by the reflected shock, large ones ( M > M u = 2 × 10 7 M ⊙ ) fragment into stars in the dense shell behind the implosion shock, thus generating the first spheroid stars. Intermediate clouds, suddenly cooling to 100 K because of collisional H 2 excitation, are compressed and left in approximate pressure equilibrium with the hot medium: they give rise to halo GCs. The dependence of the proposed formation mechanism upon overall galactic metallicity and galaxy rotation velocity is weak, so that a universal upper mass limit is deduced. A mass range for halo GCs (2 × 10 3 – 6 × 10 5 M ⊙ ) and a velocity dispersion for spheroid stars in agreement with observations are predicted.