X-Ray Spectroscopy of Interstellar Carbon: Evidence for Scattering by Carbon-bearing Material in the Spectrum of 1ES 1553+113
Molecules and particles make up ∼40%–70% of carbon in the interstellar medium, yet the exact chemical structure of these constituents remains unknown. We present carbon K-shell absorption spectroscopy of the Galactic interstellar medium obtained with the Low Energy Transmission Grating Spectrometer...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
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IOP Publishing
2023-01-01
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| Series: | The Astrophysical Journal |
| Subjects: | |
| Online Access: | https://doi.org/10.3847/1538-4357/acd0ab |
| _version_ | 1797698914534555648 |
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| author | John Staunton Frits Paerels |
| author_facet | John Staunton Frits Paerels |
| author_sort | John Staunton |
| collection | DOAJ |
| description | Molecules and particles make up ∼40%–70% of carbon in the interstellar medium, yet the exact chemical structure of these constituents remains unknown. We present carbon K-shell absorption spectroscopy of the Galactic interstellar medium obtained with the Low Energy Transmission Grating Spectrometer on board the Chandra Observatory that directly addresses this question. We probe several lines of sight, using bright active galactic nuclei as backlighters. We make our measurements differentially with respect to the bright source Mrk 421, in order to take the significant carbon K absorption in the instrument into account. In the spectrum of the blazar 1ES 1553+113 we find evidence for a novel feature: strong extinction on the low-energy side of the neutral C 1 s −2 p resonance, which is indicative of scattering by graphite particles. We find evidence for characteristic particle radii of order 0.1–0.15 μ m. If this explanation for the feature is correct, limits on the mass of the available carbon along the line of sight may imply that the grains are partially aligned, and the X-rays from the source may have intrinsic polarization. |
| first_indexed | 2024-03-12T04:00:59Z |
| format | Article |
| id | doaj.art-c9c76f4cbfb34746800823cd569bc2b1 |
| institution | Directory Open Access Journal |
| issn | 1538-4357 |
| language | English |
| last_indexed | 2024-03-12T04:00:59Z |
| publishDate | 2023-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj.art-c9c76f4cbfb34746800823cd569bc2b12023-09-03T11:41:29ZengIOP PublishingThe Astrophysical Journal1538-43572023-01-0194912610.3847/1538-4357/acd0abX-Ray Spectroscopy of Interstellar Carbon: Evidence for Scattering by Carbon-bearing Material in the Spectrum of 1ES 1553+113John Staunton0Frits Paerels1Columbia Astrophysics Laboratory, Columbia University , 538 W. 120th St., New York, NY 10027, USA ; frits@astro.columbia.eduColumbia Astrophysics Laboratory, Columbia University , 538 W. 120th St., New York, NY 10027, USA ; frits@astro.columbia.eduMolecules and particles make up ∼40%–70% of carbon in the interstellar medium, yet the exact chemical structure of these constituents remains unknown. We present carbon K-shell absorption spectroscopy of the Galactic interstellar medium obtained with the Low Energy Transmission Grating Spectrometer on board the Chandra Observatory that directly addresses this question. We probe several lines of sight, using bright active galactic nuclei as backlighters. We make our measurements differentially with respect to the bright source Mrk 421, in order to take the significant carbon K absorption in the instrument into account. In the spectrum of the blazar 1ES 1553+113 we find evidence for a novel feature: strong extinction on the low-energy side of the neutral C 1 s −2 p resonance, which is indicative of scattering by graphite particles. We find evidence for characteristic particle radii of order 0.1–0.15 μ m. If this explanation for the feature is correct, limits on the mass of the available carbon along the line of sight may imply that the grains are partially aligned, and the X-rays from the source may have intrinsic polarization.https://doi.org/10.3847/1538-4357/acd0abActive galactic nucleiSpectroscopyCarbonaceous grainsInterstellar medium |
| spellingShingle | John Staunton Frits Paerels X-Ray Spectroscopy of Interstellar Carbon: Evidence for Scattering by Carbon-bearing Material in the Spectrum of 1ES 1553+113 The Astrophysical Journal Active galactic nuclei Spectroscopy Carbonaceous grains Interstellar medium |
| title | X-Ray Spectroscopy of Interstellar Carbon: Evidence for Scattering by Carbon-bearing Material in the Spectrum of 1ES 1553+113 |
| title_full | X-Ray Spectroscopy of Interstellar Carbon: Evidence for Scattering by Carbon-bearing Material in the Spectrum of 1ES 1553+113 |
| title_fullStr | X-Ray Spectroscopy of Interstellar Carbon: Evidence for Scattering by Carbon-bearing Material in the Spectrum of 1ES 1553+113 |
| title_full_unstemmed | X-Ray Spectroscopy of Interstellar Carbon: Evidence for Scattering by Carbon-bearing Material in the Spectrum of 1ES 1553+113 |
| title_short | X-Ray Spectroscopy of Interstellar Carbon: Evidence for Scattering by Carbon-bearing Material in the Spectrum of 1ES 1553+113 |
| title_sort | x ray spectroscopy of interstellar carbon evidence for scattering by carbon bearing material in the spectrum of 1es 1553 113 |
| topic | Active galactic nuclei Spectroscopy Carbonaceous grains Interstellar medium |
| url | https://doi.org/10.3847/1538-4357/acd0ab |
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