A three-dimensional map of the hot Local Bubble using diffuse interstellar bands
Abstract: The Solar System is located within a low-density cavity, known as the Local Bubble, which appears to be filled with an X-ray emitting gas at a temperature of 10$^6$ K. Such conditions are too harsh for typical interstellar atoms and molecules to survive. There exists an enigmatic tracer of interstellar gas, known as Diffuse Interstellar Bands (DIB), which often appears as absorption features in stellar spectra. The carriers of these bands remain largely unidentified. Here we report the three-dimensional structure of the Local Bubble using two different DIB tracers ($\lambda$5780 and $\lambda$5797), which reveals that DIB carriers are present within the Bubble. The map shows low ratios of $\lambda$5797/$\lambda$5780 inside the Bubble compared to the outside. This finding proves that the carrier of the $\lambda$5780 DIB can withstand X-ray photo-dissociation and sputtering by fast ions, where the carrier of the $\lambda$5797 DIB succumbs. This would mean that DIB carriers can be more stable than hitherto thought and that the carrier of the $\lambda$5780 DIB must be larger than that of the $\lambda$5797 DIB. Alternatively, small-scale denser (and cooler) structures that shield some of the DIB carriers must be prevalent within the Bubble, implying that such structures may be an intrinsic feature of supernova-driven bubbles.
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A three-dimensional map of the hot Local Bubble using
- Such conditions are too harsh for typical interstellar atoms and molecules to survive2, 3.
- In the 2nd quadrant (upper-left sector) DIB carriers are abundant in the direction of the Taurus dark clouds and molecular.
- H. Gh. Khosroshahi - Present address: Institude in research in fundamental science, Tehran, Iran.
- To map DIB absorption in and around the LB, the authors conducted a high signal-to-noise (S/N) survey of 637 nearby early-type stars in both hemispheres (see Supplementary Fig. 4).
- This error was estimated based on fitting three different continuum lines in ±2 Å range around the peak (linear fit, quadratic fit, and simultaneous fit to the DIB and a linear continuum33).
- All distances to the target stars are measured from parallaxes from the second Gaia data re- lease (GDR2)34, 35.
- The lack of constraints as a result of empty voxels renders the inversion method unable to accurately determine the shape of the clouds especially at the cloud edges (See Supplementary Fig. 6).
- Λ5780 DIB vertical slices, also known as Supplementary Figure 2.
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...6 the comparison with the data from Bailey et al. (2016) and the recent work by Farhang et al. (2019) who studied mostly objects within 200 pc. Data from this work complete our picture of the map within 100 pc radius area where data from Table 1 is lacking in the number of observations....
...Finally, it is possible to compare our results from the wide-minimum region with the data from Bailey et al. (2016) and Farhang et al. (2019) which show basically the same result....
"A three-dimensional map of the hot ..." refers methods in this paper
...Therefore we used the catalog of Bailer-Jones et al. (2018)36 who provide purely geometric distance estimates for GDR2 sources....
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