THE BOLOCAM GALACTIC PLANE SURVEY. XIV. PHYSICAL PROPERTIES OF MASSIVE STARLESS AND STAR-FORMING CLUMPS
- Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States)
- Department of Physics, 4-181 CCIS, University of Alberta, Edmonton AB T6G 2E1 (Canada)
- CASA, University of Colorado, 389-UCB, Boulder, CO 80309 (United States)
- European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching bei München (Germany)
- University of Gothenburg, SE-412 96 Gothenburg (Sweden)
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
- Department of Astronomy, Yale University, P.O. Box 208101, New Haven, CT 06520 (United States)
We sort 4683 molecular clouds between 10° < ℓ < 65° from the Bolocam Galactic Plane Survey based on observational diagnostics of star formation activity: compact 70 μm sources, mid-IR color-selected YSOs, H{sub 2}O and CH{sub 3}OH masers, and UCH ii regions. We also present a combined NH{sub 3}-derived gas kinetic temperature and H{sub 2}O maser catalog for 1788 clumps from our own GBT 100 m observations and from the literature. We identify a subsample of 2223 (47.5%) starless clump candidates (SCCs), the largest and most robust sample identified from a blind survey to date. Distributions of flux density, flux concentration, solid angle, kinetic temperature, column density, radius, and mass show strong (>1 dex) progressions when sorted by star formation indicator. The median SCC is marginally subvirial (α ∼ 0.7) with >75% of clumps with known distance being gravitationally bound (α < 2). These samples show a statistically significant increase in the median clump mass of ΔM ∼ 170–370 M {sub ⊙} from the starless candidates to clumps associated with protostars. This trend could be due to (i) mass growth of the clumps at M-dot ∼200--440 M {sub ⊙} Myr{sup −1} for an average freefall 0.8 Myr timescale, (ii) a systematic factor of two increase in dust opacity from starless to protostellar phases, and/or (iii) a variation in the ratio of starless to protostellar clump lifetime that scales as ∼M {sup −0.4}. By comparing to the observed number of CH{sub 3}OH maser containing clumps, we estimate the phase lifetime of massive (M > 10{sup 3} M {sub ⊙}) starless clumps to be 0.37 ± 0.08 Myr (M/10{sup 3} M {sub ⊙}){sup −1}; the majority (M < 450 M {sub ⊙}) have phase lifetimes longer than their average freefall time.
- OSTI ID:
- 22863147
- Journal Information:
- Astrophysical Journal, Vol. 822, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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