Philipp Richter, Benjamin Winkel, Bart P. Wakker, N. M. Pingel, Andrew J. Fox, G. Heald, Rene A. M. Walterbos, C. Fechner, N. Ben Bekhti, G. Gentile, Laura Zschaechner
- We present a detailed analysis of the absorption properties of one of the tidal gas streams around the "Whale" galaxy NGC 4631 in the direction of the quasar 2MASS J12421031+3214268. Our study is based on ultraviolet spectral data obtained with the Cosmic Origins Spectrograph (COS) on board the Hubble Space Telescope (HST) and 21cm-data from the HALOGAS project and the Green Bank Telescope (GBT). We detect strong H I Ly alpha absorption in the velocity range +550 to +800 km s(-1) related to gas from a NGC 4631 tidal stream known as Spur 2. We measure a column density of log (N(H I/cm(-2))) = 18.68 +/- 0.15, indicating that the quasar sightline traces the outer boundary of Spur 2 as seen in the 21 cm data. Metal absorption in Spur 2 is detected in the lines of O I, C II, Si II, and Si III in a complex absorption pattern that reflects the multiphase nature of the gas. We find that the average neutral gas fraction in Spur 2 toward 2MASS J12421031+3214268 is only 14%. This implies that ionized gas dominates the total mass of Spur 2, whichWe present a detailed analysis of the absorption properties of one of the tidal gas streams around the "Whale" galaxy NGC 4631 in the direction of the quasar 2MASS J12421031+3214268. Our study is based on ultraviolet spectral data obtained with the Cosmic Origins Spectrograph (COS) on board the Hubble Space Telescope (HST) and 21cm-data from the HALOGAS project and the Green Bank Telescope (GBT). We detect strong H I Ly alpha absorption in the velocity range +550 to +800 km s(-1) related to gas from a NGC 4631 tidal stream known as Spur 2. We measure a column density of log (N(H I/cm(-2))) = 18.68 +/- 0.15, indicating that the quasar sightline traces the outer boundary of Spur 2 as seen in the 21 cm data. Metal absorption in Spur 2 is detected in the lines of O I, C II, Si II, and Si III in a complex absorption pattern that reflects the multiphase nature of the gas. We find that the average neutral gas fraction in Spur 2 toward 2MASS J12421031+3214268 is only 14%. This implies that ionized gas dominates the total mass of Spur 2, which then may comprise more than 10(9)M(circle dot). No significant depletion of Si is observed, showing that Spur 2 does not contain significant amounts of dust. From the measured O I/H I column density ratio, we determine an alpha abundance in Spur 2 of 0.131(-0.05)(+0.07) solar ([alpha/H] = -0.90 +/- 0.16), which is substantially lower than what is observed in the NGC 4631 disk. The low metallicity and low dust content suggest that Spur 2 represents metal-deficient gas stripped off a gas-rich satellite galaxy during a recent encounter with NGC 4631.…
MetadatenAuthor details: | Philipp RichterORCiDGND, Benjamin WinkelORCiD, Bart P. WakkerORCiD, N. M. Pingel, Andrew J. FoxORCiD, G. Heald, Rene A. M. WalterbosORCiD, C. Fechner, N. Ben Bekhti, G. Gentile, Laura ZschaechnerORCiD |
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DOI: | https://doi.org/10.3847/1538-4357/aae838 |
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ISSN: | 0004-637X |
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ISSN: | 1538-4357 |
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Title of parent work (English): | The astrophysical journal : an international review of spectroscopy and astronomical physics |
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Subtitle (English): | Tidal Gas Streams around the Whale Galaxy NGC 4631 Explored with HST/COS |
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Publisher: | IOP Publ. Ltd. |
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Place of publishing: | Bristol |
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Publication type: | Article |
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Language: | English |
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Date of first publication: | 2018/11/29 |
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Publication year: | 2018 |
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Release date: | 2021/06/15 |
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Tag: | ISM: abundances; galaxies: evolution; galaxies: halos; galaxies: interactions; quasars: absorption lines |
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Volume: | 868 |
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Issue: | 2 |
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Number of pages: | 12 |
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Funding institution: | NASA/ESA Hubble Space TelescopeNational Aeronautics & Space Administration (NASA) [14085]; NASANational Aeronautics & Space Administration (NASA) [NAS5D26555] |
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Organizational units: | Mathematisch-Naturwissenschaftliche Fakultät / Institut für Physik und Astronomie |
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DDC classification: | 5 Naturwissenschaften und Mathematik / 52 Astronomie / 520 Astronomie und zugeordnete Wissenschaften |
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Peer review: | Referiert |
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Publishing method: | Open Access / Green Open-Access |
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