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EPoS |
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EPoS Contribution
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Evidence of Enhanced Ionization in Protostellar Envelopes
Kamber Schwarz MPIA, Heidelberg, DE | |
| Ionization is a major driver of chemical evolution in protostellar systems. Recent observations reveal protoplanetary disks to be chemically distinct from the interstellar medium by the Class I Iphase. Thus, physical conditions during the proceeding phase, when aninfalling envelope of material is still present, are important for determining the extent of chemical processing at early stages. We use observations of H13CO+ and C18O from the Northern Extended Millimeter Array to constrain the ionization rate in the envelopes ofthree Class 0 protostars. We find ionization rates in the range 10-15 to 10-11 s-1,several orders of magnitude above the ionization rate of 10-17 s-1 in the interstellar medium. One implication of this result is that ionization driven chemistry is likely more efficient at earlier stages of protostellar evolution. | |
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| Caption: Top: NOEMA observations of H13CO+ 1-0 (background), and C18O 2-1 (contours) envelope emission toward three protostars: NGC 1333-IRAS4A (left), L1157 (center), and L1448C (right). Bottom: Cosmic ray ionization rate derived from the abundance ratio of HCO+ and CO assuming an electron abundance 1-3 times the HCO+ abundance. All three sources show ionization rates above those in the dense ISM. | |
| Collaborators: M. Wells, MPIA, DE S. Maret, UGrenoble, FR P. Andre, CEA, FR A. Belloche, MPIfR, DE E. Bergin, U Michigan, US C. Corella, INAF, IT |
Relevant topic(s): Chemistry Cosmic Rays Disks |
| Relevant Big Question: What are the physical conditions during the early stages of protostellar evolution? | |