Observational Evidence Linking Interstellar UV Absorption to PAH Molecules
The 2175 UV extinction feature was discovered in the mid-1960s, yet its physical origin remains poorly understood. One suggestion is absorption by polycyclic aromatic hydrocarbon (PAH) molecules, which is supported by theoretical molecular structure computations and by laboratory experiments. PAHs a...
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description | The 2175 UV extinction feature was discovered in the mid-1960s, yet its physical origin remains poorly understood. One suggestion is absorption by polycyclic aromatic hydrocarbon (PAH) molecules, which is supported by theoretical molecular structure computations and by laboratory experiments. PAHs are positively detected by their 3.3, 6.2, 7.7, 8.6, 11.3, and 12.7 m IR emission bands, which are specified by their modes of vibration. A definitive empirical link between the 2175 UV extinction and the IR PAH emission bands, however, is still missing. We present a new sample of hot stars that have both 2175 absorption and IR PAH emission. We find significant shifts of the central wavelength of the UV absorption feature, up to 2350 , but predominantly in stars that also have IR PAH emission. These UV shifts depend on stellar temperature in a fashion that is similar to the shifts of the 6.2 and 7.7 m IR PAH bands, that is, the features are increasingly more redshifted as the stellar temperature decreases, but only below ∼15 kK. Above 15 kK both UV and IR features retain their nominal values. Moreover, we find a suggestive correlation between the UV and IR shifts. We hypothesize that these similar dependences of both the UV and IR features on stellar temperature hint at a common origin of the two in PAH molecules and may establish the missing link between the UV and IR observations. We further suggest that the shifts depend on molecular size, and that the critical temperature of ∼15 kK above which no shifts are observed is related to the onset of UV-driven hot-star winds and their associated shocks. |
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G. M.</creator><creatorcontrib>Blasberger, Avi ; Behar, Ehud ; Perets, Hagai B. ; Brosch, Noah ; Tielens, Alexander G. G. M.</creatorcontrib><description>The 2175 UV extinction feature was discovered in the mid-1960s, yet its physical origin remains poorly understood. One suggestion is absorption by polycyclic aromatic hydrocarbon (PAH) molecules, which is supported by theoretical molecular structure computations and by laboratory experiments. PAHs are positively detected by their 3.3, 6.2, 7.7, 8.6, 11.3, and 12.7 m IR emission bands, which are specified by their modes of vibration. A definitive empirical link between the 2175 UV extinction and the IR PAH emission bands, however, is still missing. We present a new sample of hot stars that have both 2175 absorption and IR PAH emission. We find significant shifts of the central wavelength of the UV absorption feature, up to 2350 , but predominantly in stars that also have IR PAH emission. These UV shifts depend on stellar temperature in a fashion that is similar to the shifts of the 6.2 and 7.7 m IR PAH bands, that is, the features are increasingly more redshifted as the stellar temperature decreases, but only below ∼15 kK. Above 15 kK both UV and IR features retain their nominal values. Moreover, we find a suggestive correlation between the UV and IR shifts. We hypothesize that these similar dependences of both the UV and IR features on stellar temperature hint at a common origin of the two in PAH molecules and may establish the missing link between the UV and IR observations. We further suggest that the shifts depend on molecular size, and that the critical temperature of ∼15 kK above which no shifts are observed is related to the onset of UV-driven hot-star winds and their associated shocks.</description><identifier>ISSN: 0004-637X</identifier><identifier>EISSN: 1538-4357</identifier><identifier>DOI: 10.3847/1538-4357/aa5b8a</identifier><language>eng</language><publisher>Philadelphia: The American Astronomical Society</publisher><subject>ABSORPTION ; Aromatic hydrocarbons ; astrochemistry ; Astrophysics ; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY ; CORRELATIONS ; CRITICAL TEMPERATURE ; dust, extinction ; EMISSION ; Extinction ; Hot stars ; Interstellar chemistry ; INTERSTELLAR SPACE ; ISM: molecules ; Laboratory experiments ; MOLECULAR STRUCTURE ; MOLECULES ; Observational studies ; POLYCYCLIC AROMATIC HYDROCARBONS ; RED SHIFT ; STARS ; Stellar temperature ; Stellar winds ; Ultraviolet absorption ; ULTRAVIOLET RADIATION ; Vibration mode ; WAVELENGTHS</subject><ispartof>The Astrophysical journal, 2017-02, Vol.836 (2), p.173</ispartof><rights>2017. 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All rights reserved.</rights><rights>Copyright IOP Publishing Feb 20, 2017</rights><lds50>peer_reviewed</lds50><oa>free_for_read</oa><woscitedreferencessubscribed>false</woscitedreferencessubscribed><citedby>FETCH-LOGICAL-c366t-28cfd352ded757c4b52b8ea3035ac1e5af647e2e23682b6b3b1f57ea81dbdafa3</citedby><cites>FETCH-LOGICAL-c366t-28cfd352ded757c4b52b8ea3035ac1e5af647e2e23682b6b3b1f57ea81dbdafa3</cites><orcidid>0000-0002-5004-199X</orcidid></display><links><openurl>$$Topenurl_article</openurl><openurlfulltext>$$Topenurlfull_article</openurlfulltext><thumbnail>$$Tsyndetics_thumb_exl</thumbnail><linktopdf>$$Uhttps://iopscience.iop.org/article/10.3847/1538-4357/aa5b8a/pdf$$EPDF$$P50$$Giop$$H</linktopdf><link.rule.ids>230,314,776,780,881,27903,27904,38869,53845</link.rule.ids><linktorsrc>$$Uhttps://iopscience.iop.org/article/10.3847/1538-4357/aa5b8a$$EView_record_in_IOP_Publishing$$FView_record_in_$$GIOP_Publishing</linktorsrc><backlink>$$Uhttps://www.osti.gov/biblio/22663786$$D View this record in Osti.gov$$Hfree_for_read</backlink></links><search><creatorcontrib>Blasberger, Avi</creatorcontrib><creatorcontrib>Behar, Ehud</creatorcontrib><creatorcontrib>Perets, Hagai B.</creatorcontrib><creatorcontrib>Brosch, Noah</creatorcontrib><creatorcontrib>Tielens, Alexander G. G. M.</creatorcontrib><title>Observational Evidence Linking Interstellar UV Absorption to PAH Molecules</title><title>The Astrophysical journal</title><addtitle>APJ</addtitle><addtitle>Astrophys. J</addtitle><description>The 2175 UV extinction feature was discovered in the mid-1960s, yet its physical origin remains poorly understood. One suggestion is absorption by polycyclic aromatic hydrocarbon (PAH) molecules, which is supported by theoretical molecular structure computations and by laboratory experiments. PAHs are positively detected by their 3.3, 6.2, 7.7, 8.6, 11.3, and 12.7 m IR emission bands, which are specified by their modes of vibration. A definitive empirical link between the 2175 UV extinction and the IR PAH emission bands, however, is still missing. We present a new sample of hot stars that have both 2175 absorption and IR PAH emission. We find significant shifts of the central wavelength of the UV absorption feature, up to 2350 , but predominantly in stars that also have IR PAH emission. These UV shifts depend on stellar temperature in a fashion that is similar to the shifts of the 6.2 and 7.7 m IR PAH bands, that is, the features are increasingly more redshifted as the stellar temperature decreases, but only below ∼15 kK. Above 15 kK both UV and IR features retain their nominal values. Moreover, we find a suggestive correlation between the UV and IR shifts. We hypothesize that these similar dependences of both the UV and IR features on stellar temperature hint at a common origin of the two in PAH molecules and may establish the missing link between the UV and IR observations. We further suggest that the shifts depend on molecular size, and that the critical temperature of ∼15 kK above which no shifts are observed is related to the onset of UV-driven hot-star winds and their associated shocks.</description><subject>ABSORPTION</subject><subject>Aromatic hydrocarbons</subject><subject>astrochemistry</subject><subject>Astrophysics</subject><subject>ASTROPHYSICS, COSMOLOGY AND ASTRONOMY</subject><subject>CORRELATIONS</subject><subject>CRITICAL TEMPERATURE</subject><subject>dust, extinction</subject><subject>EMISSION</subject><subject>Extinction</subject><subject>Hot stars</subject><subject>Interstellar chemistry</subject><subject>INTERSTELLAR SPACE</subject><subject>ISM: molecules</subject><subject>Laboratory experiments</subject><subject>MOLECULAR STRUCTURE</subject><subject>MOLECULES</subject><subject>Observational studies</subject><subject>POLYCYCLIC AROMATIC HYDROCARBONS</subject><subject>RED SHIFT</subject><subject>STARS</subject><subject>Stellar temperature</subject><subject>Stellar winds</subject><subject>Ultraviolet absorption</subject><subject>ULTRAVIOLET RADIATION</subject><subject>Vibration mode</subject><subject>WAVELENGTHS</subject><issn>0004-637X</issn><issn>1538-4357</issn><fulltext>true</fulltext><rsrctype>article</rsrctype><creationdate>2017</creationdate><recordtype>article</recordtype><recordid>eNp9kM9LwzAUx4MoOKd3jwXxZl2bND92HEPdZDIPTryFJH3VzNrUJBv439sycRfx9HiPz_cL74PQeZ5dE1HwUU6JSAtC-UgpqoU6QIPf0yEaZFlWpIzwl2N0EsK6X_F4PED3Sx3Ab1W0rlF1crO1JTQGkoVt3m3zmsybCD5EqGvlk9VzMtHB-bank-iSx8kseXA1mE0N4RQdVaoOcPYzh2h1e_M0naWL5d18OlmkhjAWUyxMVRKKSyg55abQFGsBimSEKpMDVRUrOGDAhAmsmSY6rygHJfJSl6pSZIgudr0uRCuDsRHMm3FNAyZKjFn3pWB7qvXucwMhyrXb-O7HILtmKhguxj2V7SjjXQgeKtl6-6H8l8wz2XuVvUTZS5Q7r13kahexrt13_oNf_oGrdi0FYRLLnBPZlhX5Bl1ehms</recordid><startdate>20170220</startdate><enddate>20170220</enddate><creator>Blasberger, Avi</creator><creator>Behar, Ehud</creator><creator>Perets, Hagai B.</creator><creator>Brosch, Noah</creator><creator>Tielens, Alexander G. G. M.</creator><general>The American Astronomical Society</general><general>IOP Publishing</general><scope>AAYXX</scope><scope>CITATION</scope><scope>7TG</scope><scope>8FD</scope><scope>H8D</scope><scope>KL.</scope><scope>L7M</scope><scope>OTOTI</scope><orcidid>https://orcid.org/0000-0002-5004-199X</orcidid></search><sort><creationdate>20170220</creationdate><title>Observational Evidence Linking Interstellar UV Absorption to PAH Molecules</title><author>Blasberger, Avi ; Behar, Ehud ; Perets, Hagai B. ; Brosch, Noah ; Tielens, Alexander G. G. M.</author></sort><facets><frbrtype>5</frbrtype><frbrgroupid>cdi_FETCH-LOGICAL-c366t-28cfd352ded757c4b52b8ea3035ac1e5af647e2e23682b6b3b1f57ea81dbdafa3</frbrgroupid><rsrctype>articles</rsrctype><prefilter>articles</prefilter><language>eng</language><creationdate>2017</creationdate><topic>ABSORPTION</topic><topic>Aromatic hydrocarbons</topic><topic>astrochemistry</topic><topic>Astrophysics</topic><topic>ASTROPHYSICS, COSMOLOGY AND ASTRONOMY</topic><topic>CORRELATIONS</topic><topic>CRITICAL TEMPERATURE</topic><topic>dust, extinction</topic><topic>EMISSION</topic><topic>Extinction</topic><topic>Hot stars</topic><topic>Interstellar chemistry</topic><topic>INTERSTELLAR SPACE</topic><topic>ISM: molecules</topic><topic>Laboratory experiments</topic><topic>MOLECULAR STRUCTURE</topic><topic>MOLECULES</topic><topic>Observational studies</topic><topic>POLYCYCLIC AROMATIC HYDROCARBONS</topic><topic>RED SHIFT</topic><topic>STARS</topic><topic>Stellar temperature</topic><topic>Stellar winds</topic><topic>Ultraviolet absorption</topic><topic>ULTRAVIOLET RADIATION</topic><topic>Vibration mode</topic><topic>WAVELENGTHS</topic><toplevel>peer_reviewed</toplevel><toplevel>online_resources</toplevel><creatorcontrib>Blasberger, Avi</creatorcontrib><creatorcontrib>Behar, Ehud</creatorcontrib><creatorcontrib>Perets, Hagai B.</creatorcontrib><creatorcontrib>Brosch, Noah</creatorcontrib><creatorcontrib>Tielens, Alexander G. G. M.</creatorcontrib><collection>CrossRef</collection><collection>Meteorological & Geoastrophysical Abstracts</collection><collection>Technology Research Database</collection><collection>Aerospace Database</collection><collection>Meteorological & Geoastrophysical Abstracts - Academic</collection><collection>Advanced Technologies Database with Aerospace</collection><collection>OSTI.GOV</collection><jtitle>The Astrophysical journal</jtitle></facets><delivery><delcategory>Remote Search Resource</delcategory><fulltext>fulltext_linktorsrc</fulltext></delivery><addata><au>Blasberger, Avi</au><au>Behar, Ehud</au><au>Perets, Hagai B.</au><au>Brosch, Noah</au><au>Tielens, Alexander G. G. M.</au><format>journal</format><genre>article</genre><ristype>JOUR</ristype><atitle>Observational Evidence Linking Interstellar UV Absorption to PAH Molecules</atitle><jtitle>The Astrophysical journal</jtitle><stitle>APJ</stitle><addtitle>Astrophys. J</addtitle><date>2017-02-20</date><risdate>2017</risdate><volume>836</volume><issue>2</issue><spage>173</spage><pages>173-</pages><issn>0004-637X</issn><eissn>1538-4357</eissn><abstract>The 2175 UV extinction feature was discovered in the mid-1960s, yet its physical origin remains poorly understood. One suggestion is absorption by polycyclic aromatic hydrocarbon (PAH) molecules, which is supported by theoretical molecular structure computations and by laboratory experiments. PAHs are positively detected by their 3.3, 6.2, 7.7, 8.6, 11.3, and 12.7 m IR emission bands, which are specified by their modes of vibration. A definitive empirical link between the 2175 UV extinction and the IR PAH emission bands, however, is still missing. We present a new sample of hot stars that have both 2175 absorption and IR PAH emission. We find significant shifts of the central wavelength of the UV absorption feature, up to 2350 , but predominantly in stars that also have IR PAH emission. These UV shifts depend on stellar temperature in a fashion that is similar to the shifts of the 6.2 and 7.7 m IR PAH bands, that is, the features are increasingly more redshifted as the stellar temperature decreases, but only below ∼15 kK. Above 15 kK both UV and IR features retain their nominal values. Moreover, we find a suggestive correlation between the UV and IR shifts. We hypothesize that these similar dependences of both the UV and IR features on stellar temperature hint at a common origin of the two in PAH molecules and may establish the missing link between the UV and IR observations. We further suggest that the shifts depend on molecular size, and that the critical temperature of ∼15 kK above which no shifts are observed is related to the onset of UV-driven hot-star winds and their associated shocks.</abstract><cop>Philadelphia</cop><pub>The American Astronomical Society</pub><doi>10.3847/1538-4357/aa5b8a</doi><tpages>8</tpages><orcidid>https://orcid.org/0000-0002-5004-199X</orcidid><oa>free_for_read</oa></addata></record> |
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subjects | ABSORPTION Aromatic hydrocarbons astrochemistry Astrophysics ASTROPHYSICS, COSMOLOGY AND ASTRONOMY CORRELATIONS CRITICAL TEMPERATURE dust, extinction EMISSION Extinction Hot stars Interstellar chemistry INTERSTELLAR SPACE ISM: molecules Laboratory experiments MOLECULAR STRUCTURE MOLECULES Observational studies POLYCYCLIC AROMATIC HYDROCARBONS RED SHIFT STARS Stellar temperature Stellar winds Ultraviolet absorption ULTRAVIOLET RADIATION Vibration mode WAVELENGTHS |
title | Observational Evidence Linking Interstellar UV Absorption to PAH Molecules |
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