STAR FORMATION IN MASSIVE CLUSTERS VIA BONDI ACCRETION

Journal Article · Fri Feb 10 04:00:00 EST 2012 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/746/1/75· OSTI ID:22011797

Murray, Norman; Chang, Philip ^[1]

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1. Canadian Institute for Theoretical Astrophysics, 60 St. George Street, University of Toronto, Toronto, ON M5S 3H8 (Canada)

Essentially all stars form in giant molecular clouds (GMCs). However, inside GMCs, most of the gas does not participate in star formation; rather, denser gas accumulates in clumps in the GMC, with the bulk of the stars in a given GMC forming in a few of the most massive clumps. In the Milky Way, these clumps have masses M{sub cl} {approx}< 5 Multiplication-Sign 10{sup -2} of the GMC, radii r{sub cl} {approx} 1 pc, and free-fall times {tau}{sub cl} {approx} 2 Multiplication-Sign 10{sup 5} yr. We show that clumps inside GMCs should accrete at a modified Bondi accretion rate, which depends on clump mass as M-dot{sub cl}{approx}M{sub cl}{sup 5/4}. This rate is initially rather slow, usually slower than the initial star formation rate inside the clump (we adopt the common assumption that inside the clump, M-dot{sub *}={epsilon}{sub ff}M{sub cl}/{tau}{sub cl}, with {epsilon}{sub ff} Almost-Equal-To 0.017). However, after {approx}2 GMC free-fall times {tau}{sub GMC}, the clump accretion rate accelerates rapidly; formally, the clump can accrete the entire GMC in {approx}3{tau}{sub GMC}. At the same time, the star formation rate accelerates, tracking the Bondi accretion rate. If the GMC is disrupted by feedback from the largest clump, half the stars in that clump form in the final {tau}{sub GMC} before the GMC is disrupted. The theory predicts that the distribution of effective star formation rates, measured per GMC free-fall time, is broad, ranging from {approx}0.001 up to 0.1 or larger and that the mass spectrum of star clusters is flatter than that of clumps, consistent with observations.

• OSTI ID: 22011797
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 746; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
GALACTIC EVOLUTION
MASS SPECTRA
MILKY WAY
STAR ACCRETION
STAR CLUSTERS
STARS