OUTFLOW VERSUS INFALL IN SPIRAL GALAXIES: METAL ABSORPTION IN THE HALO OF NGC 891
Gas accreting onto a galaxy will be of low metallicity while halo gas due to a galactic fountain will be of near-solar metallicity. We test these predictions by measuring the metal absorption line properties of halo gas 5 kpc above the plane of the edge-on galaxy NGC 891, using observations taken wi...
| Main Authors: | , , , , |
|---|---|
| Other Authors: | |
| Format: | Article |
| Language: | en_US |
| Published: |
IOP Publishing
2015
|
| Online Access: | http://hdl.handle.net/1721.1/94577 |
| _version_ | 1826203310559854592 |
|---|---|
| author | Bregman, Joel N. Seitzer, Patrick Cowley, C. R. Miller, Matthew J. Miller, Eric D |
| author2 | MIT Kavli Institute for Astrophysics and Space Research |
| author_facet | MIT Kavli Institute for Astrophysics and Space Research Bregman, Joel N. Seitzer, Patrick Cowley, C. R. Miller, Matthew J. Miller, Eric D |
| author_sort | Bregman, Joel N. |
| collection | MIT |
| description | Gas accreting onto a galaxy will be of low metallicity while halo gas due to a galactic fountain will be of near-solar metallicity. We test these predictions by measuring the metal absorption line properties of halo gas 5 kpc above the plane of the edge-on galaxy NGC 891, using observations taken with HST/STIS toward a bright background quasar. Metal absorption lines of Fe II, Mg II, and Mg I in the halo of NGC 891 are clearly seen, and when combined with recent deep H I observations, we are able to place constraints on the metallicity of the halo gas for the first time. The H I line width defines the line broadening, from which we model opacity effects in these metal lines, assuming that the absorbing gas is continuously distributed in the halo. The gas-phase metallicities are [Fe/H] = –1.18 ± 0.07 and [Mg/H] = –0.23 + 0.36/ – 0.27 (statistical errors) and this difference is probably due to differential depletion onto grains. When corrected for such depletion using Galactic gas as a guide, both elements have approximately solar or even supersolar abundances. This suggests that the gas is from the galaxy disk, probably expelled into the halo by a galactic fountain, rather than from accretion of intergalactic gas, which would have a low metallicity. The abundances would be raised by significant amounts if the absorbing gas lies in a few clouds with thermal widths smaller than the rotational velocity of the halo. If this is the case, both the abundances and [Mg/Fe] would be supersolar. |
| first_indexed | 2024-09-23T12:34:55Z |
| format | Article |
| id | mit-1721.1/94577 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T12:34:55Z |
| publishDate | 2015 |
| publisher | IOP Publishing |
| record_format | dspace |
| spelling | mit-1721.1/945772022-10-01T09:51:26Z OUTFLOW VERSUS INFALL IN SPIRAL GALAXIES: METAL ABSORPTION IN THE HALO OF NGC 891 Bregman, Joel N. Seitzer, Patrick Cowley, C. R. Miller, Matthew J. Miller, Eric D MIT Kavli Institute for Astrophysics and Space Research Miller, Eric D. Gas accreting onto a galaxy will be of low metallicity while halo gas due to a galactic fountain will be of near-solar metallicity. We test these predictions by measuring the metal absorption line properties of halo gas 5 kpc above the plane of the edge-on galaxy NGC 891, using observations taken with HST/STIS toward a bright background quasar. Metal absorption lines of Fe II, Mg II, and Mg I in the halo of NGC 891 are clearly seen, and when combined with recent deep H I observations, we are able to place constraints on the metallicity of the halo gas for the first time. The H I line width defines the line broadening, from which we model opacity effects in these metal lines, assuming that the absorbing gas is continuously distributed in the halo. The gas-phase metallicities are [Fe/H] = –1.18 ± 0.07 and [Mg/H] = –0.23 + 0.36/ – 0.27 (statistical errors) and this difference is probably due to differential depletion onto grains. When corrected for such depletion using Galactic gas as a guide, both elements have approximately solar or even supersolar abundances. This suggests that the gas is from the galaxy disk, probably expelled into the halo by a galactic fountain, rather than from accretion of intergalactic gas, which would have a low metallicity. The abundances would be raised by significant amounts if the absorbing gas lies in a few clouds with thermal widths smaller than the rotational velocity of the halo. If this is the case, both the abundances and [Mg/Fe] would be supersolar. United States. National Aeronautics and Space Administration (Hubble Space Telescope Grant) United States. National Aeronautics and Space Administration (Long Term Space Astrophysics Grant) United States. National Aeronautics and Space Administration (Astrophysics Data Analysis Program Grant) 2015-02-18T14:26:22Z 2015-02-18T14:26:22Z 2013-03 2010-07 Article http://purl.org/eprint/type/JournalArticle 0004-637X 1538-4357 http://hdl.handle.net/1721.1/94577 Bregman, Joel N., Eric D. Miller, Patrick Seitzer, C. R. Cowley, and Matthew J. Miller. “OUTFLOW VERSUS INFALL IN SPIRAL GALAXIES: METAL ABSORPTION IN THE HALO OF NGC 891.” The Astrophysical Journal 766, no. 1 (March 7, 2013): 57. © 2013 The American Astronomical Society en_US http://dx.doi.org/10.1088/0004-637x/766/1/57 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 American Astronomical Society |
| spellingShingle | Bregman, Joel N. Seitzer, Patrick Cowley, C. R. Miller, Matthew J. Miller, Eric D OUTFLOW VERSUS INFALL IN SPIRAL GALAXIES: METAL ABSORPTION IN THE HALO OF NGC 891 |
| title | OUTFLOW VERSUS INFALL IN SPIRAL GALAXIES: METAL ABSORPTION IN THE HALO OF NGC 891 |
| title_full | OUTFLOW VERSUS INFALL IN SPIRAL GALAXIES: METAL ABSORPTION IN THE HALO OF NGC 891 |
| title_fullStr | OUTFLOW VERSUS INFALL IN SPIRAL GALAXIES: METAL ABSORPTION IN THE HALO OF NGC 891 |
| title_full_unstemmed | OUTFLOW VERSUS INFALL IN SPIRAL GALAXIES: METAL ABSORPTION IN THE HALO OF NGC 891 |
| title_short | OUTFLOW VERSUS INFALL IN SPIRAL GALAXIES: METAL ABSORPTION IN THE HALO OF NGC 891 |
| title_sort | outflow versus infall in spiral galaxies metal absorption in the halo of ngc 891 |
| url | http://hdl.handle.net/1721.1/94577 |
| work_keys_str_mv | AT bregmanjoeln outflowversusinfallinspiralgalaxiesmetalabsorptioninthehaloofngc891 AT seitzerpatrick outflowversusinfallinspiralgalaxiesmetalabsorptioninthehaloofngc891 AT cowleycr outflowversusinfallinspiralgalaxiesmetalabsorptioninthehaloofngc891 AT millermatthewj outflowversusinfallinspiralgalaxiesmetalabsorptioninthehaloofngc891 AT millerericd outflowversusinfallinspiralgalaxiesmetalabsorptioninthehaloofngc891 |