SpringerLink
Forum Springer Astron. Astrophys.
Forum Whats New Search Orders


Astron. Astrophys. 358, 514-520 (2000)

Previous Section Next Section Title Page Table of Contents

7. Conclusions

We have constructed the FIR luminosity function for IRAS point sources with colours of UCH II regions and CS(2-1) detections, for different sectors in the galactic disk. The LFs are reliable above a luminosity of [FORMULA], and extend to [FORMULA] in the high luminosity end, with a peak at [FORMULA]. We analysed the trends in the LF of IRAS/CS sources in terms of an ensemble of massive star forming regions, and two free parameters suffice to provide a remarkably good fit to the shape of the LF. The fits required a maximum for the number of stars born in a given MSFR with [FORMULA]. The best results were obtained setting [FORMULA] for [FORMULA], and [FORMULA] for [FORMULA]. A few conclusions can be summarised:

  1. The LFs inside and outside the solar circle are different at 96% confidence level. The LF within the solar circle, built with 413 sources, peaks at [FORMULA], while the LF outside the solar circle, built with 142 sources, peaks at [FORMULA].

  2. The IMF index we obtain is [FORMULA] and constant with galactocentric radius. At 50% cumulative probability for the goodness of fit, and keeping [FORMULA] fixed at the best fit value, [FORMULA] in the inner Galaxy, and [FORMULA] in the outer Galaxy.

  3. A power law distribution for the number of stars per MSFR has an exponent [FORMULA] in the inner Galaxy. But in the outer Galaxy the best fit model corresponds to [FORMULA]. Thus, the expectation value for the number of stars per MSFR with [FORMULA] decreases from 225 for [FORMULA] to 120 for [FORMULA].

The results of our analysis show that the observed luminosity functions for UCH II regions can be traced to the underlying young population. The differences within and outside the solar circle reflect a decrease in the average number of stars per massive star forming region towards the outer Galaxy, rather than a steeper IMF.

Previous Section Next Section Title Page Table of Contents

© European Southern Observatory (ESO) 2000

Online publication: June 8, 2000
helpdesk.link@springer.de