Organic Chemistry in the H2-bearing, CO-rich Interstellar Ice Layer at Temperatures Relevant to Dense Cloud Interiors
Ice chemistry in the dense, cold interstellar medium (ISM) is probably responsible for the formation of interstellar complex organic molecules (COMs). Recent laboratory experiments performed at T ∼ 4 K have shown that irradiation of CO:N _2 ice samples analog to the CO-rich interstellar ice layer ca...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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IOP Publishing
2024-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/ad187e |
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| author | Rafael Martín-Doménech Alexander DelFranco Karin I. Öberg Mahesh Rajappan |
| author_facet | Rafael Martín-Doménech Alexander DelFranco Karin I. Öberg Mahesh Rajappan |
| author_sort | Rafael Martín-Doménech |
| collection | DOAJ |
| description | Ice chemistry in the dense, cold interstellar medium (ISM) is probably responsible for the formation of interstellar complex organic molecules (COMs). Recent laboratory experiments performed at T ∼ 4 K have shown that irradiation of CO:N _2 ice samples analog to the CO-rich interstellar ice layer can contribute to the formation of COMs when H _2 molecules are present. We have tested this organic chemistry under a broader range of conditions relevant to the interior of dense clouds by irradiating CO: ^15 N _2 :H _2 ice samples with 2 keV electrons in the 4–15 K temperature range. The H _2 ice abundance depended on both, the ice formation temperature and the thermal evolution of the samples. Formation of H-bearing organics such as formaldehyde (H _2 CO), ketene (C _2 H _2 O), and isocyanic acid (H ^15 NCO) was observed upon irradiation of ice samples formed at temperatures up to 10 K, and also in ices formed at 6 K and subsequently warmed up and irradiated at temperatures up to 15 K. These results suggest that a fraction of the H _2 molecules in dense cloud interiors might be entrapped in the CO-rich layer of interstellar ice mantles, and that energetic processing of this layer could entail an additional contribution to the formation of COMs in the coldest regions of the ISM. |
| first_indexed | 2024-03-08T03:18:41Z |
| format | Article |
| id | doaj.art-6cff480f9ce34b1d84f9c407b8d01e62 |
| institution | Directory Open Access Journal |
| issn | 1538-4357 |
| language | English |
| last_indexed | 2024-03-08T03:18:41Z |
| publishDate | 2024-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj.art-6cff480f9ce34b1d84f9c407b8d01e622024-02-12T11:49:32ZengIOP PublishingThe Astrophysical Journal1538-43572024-01-01962210710.3847/1538-4357/ad187eOrganic Chemistry in the H2-bearing, CO-rich Interstellar Ice Layer at Temperatures Relevant to Dense Cloud InteriorsRafael Martín-Doménech0https://orcid.org/0000-0001-6496-9791Alexander DelFranco1https://orcid.org/0000-0003-2322-7526Karin I. Öberg2https://orcid.org/0000-0001-8798-1347Mahesh Rajappan3https://orcid.org/0000-0003-2761-4312Centro de Astrobiología (CSIC-INTA) Carretera de Ajalvir , km. 4, Torrejón de Ardoz, E-28850, Madrid, Spain ; rmartin@cab.inta-csic.esCenter for Astrophysics ∣ Harvard & Smithsonian 60 Garden St., Cambridge, MA 02138, USA; Physics and Astronomy Department, Amherst College , 21 Merrill Science Drive, Amherst, MA 01002, USACenter for Astrophysics ∣ Harvard & Smithsonian 60 Garden St., Cambridge, MA 02138, USACenter for Astrophysics ∣ Harvard & Smithsonian 60 Garden St., Cambridge, MA 02138, USAIce chemistry in the dense, cold interstellar medium (ISM) is probably responsible for the formation of interstellar complex organic molecules (COMs). Recent laboratory experiments performed at T ∼ 4 K have shown that irradiation of CO:N _2 ice samples analog to the CO-rich interstellar ice layer can contribute to the formation of COMs when H _2 molecules are present. We have tested this organic chemistry under a broader range of conditions relevant to the interior of dense clouds by irradiating CO: ^15 N _2 :H _2 ice samples with 2 keV electrons in the 4–15 K temperature range. The H _2 ice abundance depended on both, the ice formation temperature and the thermal evolution of the samples. Formation of H-bearing organics such as formaldehyde (H _2 CO), ketene (C _2 H _2 O), and isocyanic acid (H ^15 NCO) was observed upon irradiation of ice samples formed at temperatures up to 10 K, and also in ices formed at 6 K and subsequently warmed up and irradiated at temperatures up to 15 K. These results suggest that a fraction of the H _2 molecules in dense cloud interiors might be entrapped in the CO-rich layer of interstellar ice mantles, and that energetic processing of this layer could entail an additional contribution to the formation of COMs in the coldest regions of the ISM.https://doi.org/10.3847/1538-4357/ad187eInterstellar mediumInterstellar cloudsInterstellar moleculesDense interstellar cloudsIce compositionComplex organic molecules |
| spellingShingle | Rafael Martín-Doménech Alexander DelFranco Karin I. Öberg Mahesh Rajappan Organic Chemistry in the H2-bearing, CO-rich Interstellar Ice Layer at Temperatures Relevant to Dense Cloud Interiors The Astrophysical Journal Interstellar medium Interstellar clouds Interstellar molecules Dense interstellar clouds Ice composition Complex organic molecules |
| title | Organic Chemistry in the H2-bearing, CO-rich Interstellar Ice Layer at Temperatures Relevant to Dense Cloud Interiors |
| title_full | Organic Chemistry in the H2-bearing, CO-rich Interstellar Ice Layer at Temperatures Relevant to Dense Cloud Interiors |
| title_fullStr | Organic Chemistry in the H2-bearing, CO-rich Interstellar Ice Layer at Temperatures Relevant to Dense Cloud Interiors |
| title_full_unstemmed | Organic Chemistry in the H2-bearing, CO-rich Interstellar Ice Layer at Temperatures Relevant to Dense Cloud Interiors |
| title_short | Organic Chemistry in the H2-bearing, CO-rich Interstellar Ice Layer at Temperatures Relevant to Dense Cloud Interiors |
| title_sort | organic chemistry in the h2 bearing co rich interstellar ice layer at temperatures relevant to dense cloud interiors |
| topic | Interstellar medium Interstellar clouds Interstellar molecules Dense interstellar clouds Ice composition Complex organic molecules |
| url | https://doi.org/10.3847/1538-4357/ad187e |
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