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| EPoS Contribution |
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The Star-formation Rate of the Central Molecular Zone determined from Young Stellar Objects
Christine Koepferl MPIA, Heidelberg, DE | |
| In contrast to most other galaxies, star-formation rates in the Milky Way can be estimated directly from Young Stellar Objects (YSOs). In the Central Molecular Zone (CMZ) the star-formation rate calculated from the number of YSOs with 24 micron emission differs by a factor of ten from traditional methods that are based on diffuse emission (e.g. free-free). Whether this effect is real or due to incorrect estimates has not been previously understood. On one hand, the different methods may trace different time-scales and would disagree if the star-formation was episodic. On the other hand the estimate based on YSOs could for example be heavily contaminated by more evolved objects. Many of the YSOs selected at 24 microns and used to measure the star-formation rate do not have counterparts in Herschel observations, suggesting they may not be as young as previously assumed. In this talk I will present radiative transfer modeling results which suggests that, indeed, main-sequence O and B stars in a constant ambient medium can mimic YSOs at 24 microns, while being faint or undetected at Herschel wavelengths. Using these modeling results we estimate the fraction of misclassified "YSOs" and derive a corrected star-formation rate for the CMZ. | |
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| Caption: A patch of the CMZ observed by MIPS at 24 microns (left) and PACS at 70 microns (right). The yellow circle indicates an object detected in MIPS and classified as a YSO but with no counterpart in the Herschel observations. Our radiative transfer model of an embedded YSOs (white circle) matches the observation in MIPS (yellow circle) but also produces a source detected in PACS. On the other hand, our model of a more evolved source (here a main-sequence star) has no strong counterpart in PACS (blue circle) in better agreement with the observed source. | |
| Collaborators: T. Robitaille, MPIA, Germany E. Morales, MPIA, Germany |
Suggested Session:
Massive Star Formation and Feedback |