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In previous episodes …..

In previous episodes …. Stars are formed in the spiral arms of the Galaxy, in the densest and coldest regions of the interstellar medium, which are called Molecular Clouds. Image: portion of the galactic plane: darker colours indicate higher extinction regions (due to dust in MCs). 0.1 pc.

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In previous episodes …..

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  1. In previous episodes …..

  2. Stars are formed in the spiral arms of the Galaxy, in the densest and coldest regions of the interstellar medium, which are called Molecular Clouds. Image: portion of the galactic plane: darker colours indicate higher extinction regions (due to dust in MCs).

  3. 0.1 pc 0.1 pc Star Formation • Observationally, two modes of star formation in the Galaxy: • isolated mode, in dark clouds • clustered mode, in giant molecular clouds Taurus Perseus Orion isolated clustered Kandori 2007

  4. Dark clouds(103 Msun, 5 pc, 10 K) • Giant Molecular Clouds(105 Msun, 100 pc, 30 K) • Young stars are associated with the dense cores in molecular clouds • The properties of these dense cores differ for regions of high and low mass star formation Star Formation: must convert dense cores into stars: • temperature ~10—100 K to >107 K -> 6 o. m. • size ~0.5 pc to 2x10-8 (1 Rsun) -> 7 o.m. • density 103-4 cm-3 to ~1026 cm-3 -> 22 o.m.

  5. Low Mass Star Formation ...

  6. Blackbody Spectrum

  7. SPECTRAL ENERGY DISTRIBUTION

  8. Spectral Energy Distribution(SED) a > 0, peak ~100 mm, BB at 10-30 K, Lsmm/Lbol > 0.5%, faint IR cold envelope opt thick in free-fall. powerful and collimated outflows, protostar Class 0 a = d log l Fl / d log l , between 2 and 25 micron

  9. a >~ 0, flat SED, superposition of BB at different T,IR, faint optical envelope part. thick + disk. Moderate outflows, evolvedprotostar Class I

  10. Class II -1.5 <a < 0, mid-IR excess compared to BB, optical envelope being disrupted faint outflow, classical T Tauri, FU Ori

  11. a < -1.5, similar to BB, optical stellar photosphere reddened by circumstellar extinction debris disk, weak-line T Tauri, PMS Class III

  12. Spatial Distribution Class II ~ Class III spatial distribution. Class I: higher density regions Hartmann 2003

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