4-8 October 2015
Hans Harnack Haus
Europe/Berlin timezone
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Contribution Contributed Talk

Hans Harnack Haus -
FROM PROTOSTARS TO PROTOPLANETARY DISKS 2

Tracing the evolution of the nitrogen isotopic composition around protostars

Speakers

  • Dr. Susanne WAMPFLER

Primary authors

  • Dr. Susanne WAMPFLER (Centre for Star and Planet Formation and Niels Bohr Institute, Natural History Museum of Denmark, University of Copenhagen)

Co-authors

  • Jes JORGENSEN (Niels Bohr Institute and Centre for Star and Planet Formation, Natural History Museum of Denmark, University of Copenhagen)
  • Martin BIZZARRO (Centre for Star and Planet Formation, Natural History Museum of Denmark, University of Copenhagen)

Content

The volatile elements hydrogen, nitrogen, and oxygen show large isotopic variations among the solar system bodies. These isotopic heterogeneities are peculiar, because the isotopic composition of solar system matter is generally quite homogeneous. Thus, understanding the origin of the volatile stable isotope anomalies will contribute substantially to our understanding when and where the different solar system materials formed.

The Genesis space mission has demonstrated that the solar system solids and the gas reservoir do not share a common nitrogen isotopic composition. The terrestrial planets, comets, and meteorites are significantly enriched in rare ${}^{15}$N compared to the Sun and the gas giants. Two processes have been proposed to explain these variations in the ${}^{14}$N/${}^{15}$N ratio: low-temperature chemical fractionation and isotope-selective photochemistry. However, the relative importance of the two processes is still unclear.

Measurements of the ${}^{14}$N/${}^{15}$N ratio in prestellar cores and protostars can be used to tackle the question what mechanism controls the nitrogen isotope composition during the star formation process. However, such measurements are challenging because of the low abundance of ${}^{15}$N-bearing isotopologues. Thanks to new broad bandwidth receivers at single-dish telescopes and interferometers with unprecedented sensitivity, more comprehensive isotopic studies of star-forming regions can now be carried out.

Different spatial signatures are expected from the chemical fractionation and photochemistry scenarios. Therefore, spatially resolved measurements of the ${}^{14}$N/${}^{15}$N ratio are key to probe these spatial variations and constrain the dominant fractionation mechanism. We will present the first spatially resolved measurement of the ${}^{14}$N/${}^{15}$N ratio around the Class 0 protostar NGC 1333 IRAS 2A with the IRAM Plateau de Bure Interferometer. Early results from high-resolution observations of the young stellar object IRAS 16293-2422 with ALMA can also be expected. In addition, we will present the results from our nitrogen isotope studies of a protostar sample with different single-dish telescopes.

ALMA now offers the possibility to measure isotopic ratios even in protoplanetary disks, so that in the near future we will be able to trace the evolution of the ${}^{14}$N/${}^{15}$N ratio during protostellar evolution and address the origin of the solar system's nitrogen isotope anomaly.