The Star-formation Law in Galactic High-mass Star-forming Molecular Clouds
We study the star-formation (SF) law in 12 Galactic molecular clouds with ongoing high-mass star-formation (HMSF) activity, as traced by the presence of a bright IRAS source and other HMSF tracers. We define the molecular cloud (MC) associated with each IRAS source using {sup 13}CO line emission, and count the young stellar objects (YSOs) within these clouds using GLIMPSE and MIPSGAL 24 μm Spitzer databases. The masses for high-luminosity YSOs (L {sub bol} > 10 L {sub ⊙}) are determined individually using pre-main-sequence evolutionary tracks and the evolutionary stages of the sources, whereas a mean mass of 0.5 M {sub ⊙} was adopted to determine the masses in the low-luminosity YSO population. The star-formation rate surface density (Σ{sub SFR}) corresponding to a gas surface density (Σ{sub gas}) in each MC is obtained by counting the number of the YSOs within successive contours of {sup 13}CO line emission. We find a break in the relation between Σ{sub SFR} and Σ{sub gas}, with the relation being a power law (Σ{sub SFR}∝Σ{sub gas}{sup N}) with the index N varying between 1.4 and 3.6 above the break. The Σ{sub gas} at the break is between 150–360 M {sub ⊙} pc{sup −2} for the sample clouds, which compares well with the threshold gas density found in recent studies of Galactic star-forming regions. Our clouds treated as a whole lie between the Kennicutt relation and the linear relation for Galactic and extra-galactic dense star-forming regions. We find a tendency for the high-mass YSOs to be found preferentially in dense regions at densities higher than 1200 M {sub ⊙} pc{sup −2} (∼0.25 g cm{sup −2}).
- OSTI ID:
- 22872771
- Journal Information:
- Astrophysical Journal, Vol. 839, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
Similar Records
A wide-field near- and mid-infrared Census of young stars in NGC 6334
THE DEPENDENCE OF STAR FORMATION EFFICIENCY ON GAS SURFACE DENSITY