Shaken or Stirred: The Diffuse Interstellar Medium with Exceptionally High SiO Abundance
Interstellar shocks, a key element of stellar feedback processes, shape the structure of the interstellar medium (ISM) and are essential for the chemistry, thermodynamics, and kinematics of interstellar gas. Powerful, high-velocity shocks are driven by stellar winds, young supernova explosions, more...
| 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 |
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| Online Access: | https://doi.org/10.3847/1538-4357/accba1 |
| _version_ | 1797700036714299392 |
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| author | Daniel R. Rybarczyk Snežana Stanimirović Antoine Gusdorf |
| author_facet | Daniel R. Rybarczyk Snežana Stanimirović Antoine Gusdorf |
| author_sort | Daniel R. Rybarczyk |
| collection | DOAJ |
| description | Interstellar shocks, a key element of stellar feedback processes, shape the structure of the interstellar medium (ISM) and are essential for the chemistry, thermodynamics, and kinematics of interstellar gas. Powerful, high-velocity shocks are driven by stellar winds, young supernova explosions, more evolved supernova remnants, cloud–cloud collisions, and protostellar outflows, whereas the existence and origin of much-lower-velocity shocks (≲10 km s ^−1 ) are not understood. Direct observational evidence for interstellar shocks in diffuse and translucent ISM environments has been especially lacking. We present the most sensitive survey to date of SiO—often considered an unambiguous tracer of interstellar shocks—in absorption, obtained with the Northern Extended Millimeter Array interferometer. We detect SiO in five of eight directions probing diffuse and translucent environments without ongoing star formation. Our results demonstrate that SiO formation in the diffuse ISM (i.e., in the absence of significant star formation and stellar feedback) is more widespread and effective than previously reported. The observed SiO line widths are all ≲4 km s ^−1 , excluding high-velocity shocks as a formation mechanism. Yet, the SiO abundances we detect are mostly 1–2 orders of magnitude higher than those typically assumed in quiescent environments and are often accompanied by other molecular transitions whose column densities cannot be explained with UV-dominated chemical models. Our results challenge the traditional view of SiO production via stellar feedback sources and emphasize the need for observational constraints on the distribution of Si in the gas phase and grain mantles, which are crucial for understanding the physics of grain processing and the diffuse interstellar chemistry. |
| first_indexed | 2024-03-12T04:17:19Z |
| format | Article |
| id | doaj.art-b3989ce45c52434bb64e4c7d5c303de2 |
| institution | Directory Open Access Journal |
| issn | 1538-4357 |
| language | English |
| last_indexed | 2024-03-12T04:17:19Z |
| publishDate | 2023-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj.art-b3989ce45c52434bb64e4c7d5c303de22023-09-03T10:35:55ZengIOP PublishingThe Astrophysical Journal1538-43572023-01-0195015210.3847/1538-4357/accba1Shaken or Stirred: The Diffuse Interstellar Medium with Exceptionally High SiO AbundanceDaniel R. Rybarczyk0https://orcid.org/0000-0003-3351-6831Snežana Stanimirović1https://orcid.org/0000-0002-3418-7817Antoine Gusdorf2https://orcid.org/0000-0002-0354-1684University of Wisconsin–Madison , Department of Astronomy, 475 N. Charter St., Madison, WI 53703, USA ; rybarczyk@astro.wisc.eduUniversity of Wisconsin–Madison , Department of Astronomy, 475 N. Charter St., Madison, WI 53703, USA ; rybarczyk@astro.wisc.eduLaboratoire de Physique de l’École Normale Supérieure, ENS, Université PSL, CNRS, Sorbonne Université , Université de Paris, F-75005 Paris, France; Observatoire de Paris, PSL University , Sorbonne Université, LERMA, F-75014 Paris, FranceInterstellar shocks, a key element of stellar feedback processes, shape the structure of the interstellar medium (ISM) and are essential for the chemistry, thermodynamics, and kinematics of interstellar gas. Powerful, high-velocity shocks are driven by stellar winds, young supernova explosions, more evolved supernova remnants, cloud–cloud collisions, and protostellar outflows, whereas the existence and origin of much-lower-velocity shocks (≲10 km s ^−1 ) are not understood. Direct observational evidence for interstellar shocks in diffuse and translucent ISM environments has been especially lacking. We present the most sensitive survey to date of SiO—often considered an unambiguous tracer of interstellar shocks—in absorption, obtained with the Northern Extended Millimeter Array interferometer. We detect SiO in five of eight directions probing diffuse and translucent environments without ongoing star formation. Our results demonstrate that SiO formation in the diffuse ISM (i.e., in the absence of significant star formation and stellar feedback) is more widespread and effective than previously reported. The observed SiO line widths are all ≲4 km s ^−1 , excluding high-velocity shocks as a formation mechanism. Yet, the SiO abundances we detect are mostly 1–2 orders of magnitude higher than those typically assumed in quiescent environments and are often accompanied by other molecular transitions whose column densities cannot be explained with UV-dominated chemical models. Our results challenge the traditional view of SiO production via stellar feedback sources and emphasize the need for observational constraints on the distribution of Si in the gas phase and grain mantles, which are crucial for understanding the physics of grain processing and the diffuse interstellar chemistry.https://doi.org/10.3847/1538-4357/accba1Diffuse molecular cloudsInterstellar line absorptionShocks |
| spellingShingle | Daniel R. Rybarczyk Snežana Stanimirović Antoine Gusdorf Shaken or Stirred: The Diffuse Interstellar Medium with Exceptionally High SiO Abundance The Astrophysical Journal Diffuse molecular clouds Interstellar line absorption Shocks |
| title | Shaken or Stirred: The Diffuse Interstellar Medium with Exceptionally High SiO Abundance |
| title_full | Shaken or Stirred: The Diffuse Interstellar Medium with Exceptionally High SiO Abundance |
| title_fullStr | Shaken or Stirred: The Diffuse Interstellar Medium with Exceptionally High SiO Abundance |
| title_full_unstemmed | Shaken or Stirred: The Diffuse Interstellar Medium with Exceptionally High SiO Abundance |
| title_short | Shaken or Stirred: The Diffuse Interstellar Medium with Exceptionally High SiO Abundance |
| title_sort | shaken or stirred the diffuse interstellar medium with exceptionally high sio abundance |
| topic | Diffuse molecular clouds Interstellar line absorption Shocks |
| url | https://doi.org/10.3847/1538-4357/accba1 |
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