Schmidt's conjecture and star formation in molecular clouds
Por:
Lada C.J., Lombardi M., Roman-Zuniga C., Forbrich J., Alves J.F.
Publicada:
1 dic 2013
Resumen:
We investigate Schmidt's conjecture (i.e., that the star formation rate (SFR) scales in a power-law fashion with the gas density) for four well-studied local molecular clouds (giant molecular clouds, GMCs). Using the Bayesian methodology, we show that a local Schmidt scaling relation of the form (protostars pc-2) exists within (but not between) GMCs. Further, we find that the Schmidt scaling law does not by itself provide an adequate description of star formation activity in GMCs. Because the total number of protostars produced by a cloud is given by the product of S *(A K) and S'(> A K), the differential surface area distribution function, integrated over the entire cloud, the cloud's structure plays a fundamental role in setting the level of its star formation activity. For clouds with similar functional forms of S*(A K), observed differences in their total SFRs are primarily due to the differences in S'(> A K) between the clouds. The coupling of S*(A K) with the measured S'(> A K) in these clouds also produces a steep jump in the SFR and protostellar production above AK ~ 0.8 mag. Finally, we show that there is no global Schmidt law that relates the SFR and gas mass surface densities between GMCs. Consequently, the observed Kennicutt-Schmidt scaling relation for disk galaxies is likely an artifact of unresolved measurements of GMCs and not a result of any underlying physical law of star formation characterizing the molecular gas. © 2013. The American Astronomical Society. All rights reserved.
Filiaciones:
Lada C.J.:
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, United States
Lombardi M.:
Department of Physics, University of Milan, via Celoria 16, I-20133 Milan, Italy
Roman-Zuniga C.:
Univ Nacl Autonoma Mexico, Inst Astron, Unidad Acad Ensenada, Ensenada 22860, Baja California, Mexico
Forbrich J.:
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, United States
Institute for Astronomy, University of Vienna, Türkenschanzstrasse 17, A-1180 Vienna, Austria
Alves J.F.:
Institute for Astronomy, University of Vienna, Türkenschanzstrasse 17, A-1180 Vienna, Austria
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