X-RAY SCATTERING ECHOES AND GHOST HALOS FROM THE INTERGALACTIC MEDIUM: RELATION TO THE NATURE OF AGN VARIABILITY
X-ray bright quasars might be used to trace dust in the circumgalactic and intergalactic medium through the phenomenon of X-ray scattering, which is observed around Galactic objects whose light passes through a sufficient column of interstellar gas and dust. Of particular interest is the abundance o...
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| Format: | Article |
| Language: | en_US |
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IOP Publishing
2015
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| Online Access: | http://hdl.handle.net/1721.1/98313 |
| _version_ | 1826194441113698304 |
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| author | Corrales, Lia |
| author2 | MIT Kavli Institute for Astrophysics and Space Research |
| author_facet | MIT Kavli Institute for Astrophysics and Space Research Corrales, Lia |
| author_sort | Corrales, Lia |
| collection | MIT |
| description | X-ray bright quasars might be used to trace dust in the circumgalactic and intergalactic medium through the phenomenon of X-ray scattering, which is observed around Galactic objects whose light passes through a sufficient column of interstellar gas and dust. Of particular interest is the abundance of gray dust larger than 0.1 µm, which is difficult to detect at other wavelengths. To calculate X-ray scattering from large grains, one must abandon the traditional Rayleigh-Gans approximation. The Mie solution for the X-ray scattering optical depth of the universe is ~1%. This presents a great difficulty for distinguishing dust scattered photons from the point source image of Chandra, which is currently unsurpassed in imaging resolution. The variable nature of AGNs offers a solution to this problem, as scattered light takes a longer path and thus experiences a time delay with respect to non-scattered light. If an AGN dims significantly ([> over ~]3 dex) due to a major feedback event, the Chandra point source image will be suppressed relative to the scattering halo, and an X-ray echo or ghost halo may become visible. I estimate the total number of scattering echoes visible by Chandra over the entire sky: N[subscript ech] ~ 10[superscript 3](ν[subscript fb]/yr[superscript -1]), where ν[subscript fb] is the characteristic frequency of feedback events capable of dimming an AGN quickly. |
| first_indexed | 2024-09-23T09:55:51Z |
| format | Article |
| id | mit-1721.1/98313 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T09:55:51Z |
| publishDate | 2015 |
| publisher | IOP Publishing |
| record_format | dspace |
| spelling | mit-1721.1/983132022-09-26T14:38:15Z X-RAY SCATTERING ECHOES AND GHOST HALOS FROM THE INTERGALACTIC MEDIUM: RELATION TO THE NATURE OF AGN VARIABILITY Corrales, Lia MIT Kavli Institute for Astrophysics and Space Research Corrales, Lia X-ray bright quasars might be used to trace dust in the circumgalactic and intergalactic medium through the phenomenon of X-ray scattering, which is observed around Galactic objects whose light passes through a sufficient column of interstellar gas and dust. Of particular interest is the abundance of gray dust larger than 0.1 µm, which is difficult to detect at other wavelengths. To calculate X-ray scattering from large grains, one must abandon the traditional Rayleigh-Gans approximation. The Mie solution for the X-ray scattering optical depth of the universe is ~1%. This presents a great difficulty for distinguishing dust scattered photons from the point source image of Chandra, which is currently unsurpassed in imaging resolution. The variable nature of AGNs offers a solution to this problem, as scattered light takes a longer path and thus experiences a time delay with respect to non-scattered light. If an AGN dims significantly ([> over ~]3 dex) due to a major feedback event, the Chandra point source image will be suppressed relative to the scattering halo, and an X-ray echo or ghost halo may become visible. I estimate the total number of scattering echoes visible by Chandra over the entire sky: N[subscript ech] ~ 10[superscript 3](ν[subscript fb]/yr[superscript -1]), where ν[subscript fb] is the characteristic frequency of feedback events capable of dimming an AGN quickly. United States. National Aeronautics and Space Administration (Earth and Space Science Fellowship Program Grant NNX11AO09H) 2015-09-01T20:43:10Z 2015-09-01T20:43:10Z 2015-05 2014-12 Article http://purl.org/eprint/type/JournalArticle 1538-4357 0004-637X http://hdl.handle.net/1721.1/98313 Corrales, Lia. “X-RAY SCATTERING ECHOES AND GHOST HALOS FROM THE INTERGALACTIC MEDIUM: RELATION TO THE NATURE OF AGN VARIABILITY.” The Astrophysical Journal 805, no. 1 (May 15, 2015): 23. © 2015 The American Astronomical Society en_US http://dx.doi.org/10.1088/0004-637x/805/1/23 The Astrophysical Journal Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. application/pdf IOP Publishing IOP Publishing |
| spellingShingle | Corrales, Lia X-RAY SCATTERING ECHOES AND GHOST HALOS FROM THE INTERGALACTIC MEDIUM: RELATION TO THE NATURE OF AGN VARIABILITY |
| title | X-RAY SCATTERING ECHOES AND GHOST HALOS FROM THE INTERGALACTIC MEDIUM: RELATION TO THE NATURE OF AGN VARIABILITY |
| title_full | X-RAY SCATTERING ECHOES AND GHOST HALOS FROM THE INTERGALACTIC MEDIUM: RELATION TO THE NATURE OF AGN VARIABILITY |
| title_fullStr | X-RAY SCATTERING ECHOES AND GHOST HALOS FROM THE INTERGALACTIC MEDIUM: RELATION TO THE NATURE OF AGN VARIABILITY |
| title_full_unstemmed | X-RAY SCATTERING ECHOES AND GHOST HALOS FROM THE INTERGALACTIC MEDIUM: RELATION TO THE NATURE OF AGN VARIABILITY |
| title_short | X-RAY SCATTERING ECHOES AND GHOST HALOS FROM THE INTERGALACTIC MEDIUM: RELATION TO THE NATURE OF AGN VARIABILITY |
| title_sort | x ray scattering echoes and ghost halos from the intergalactic medium relation to the nature of agn variability |
| url | http://hdl.handle.net/1721.1/98313 |
| work_keys_str_mv | AT corraleslia xrayscatteringechoesandghosthalosfromtheintergalacticmediumrelationtothenatureofagnvariability |