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- Privon, G., et al.
(författare)
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The Dense Molecular Gas and Nuclear Activity in the ULIRG IRAS 13120-5453
- 2017
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 835:2, s. Article Number: 213-
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Tidskriftsartikel (refereegranskat)abstract
- We present new Atacama Large Millimeter/submillimeter Array Band 7 (?340 GHz) observations of the dense gas tracers HCN, HCO+, and CS in the local, single-nucleus, ultraluminous infrared galaxy IRAS 13120-5453. We find centrally enhanced HCN (4-3) emission, relative to HCO+ (4-3), but do not find evidence for radiative pumping of HCN. Considering the size of the starburst (0.5 kpc) and the estimated supernovae rate of ?1.2 yr-1, the high HCN/HCO+ ratio can be explained by an enhanced HCN abundance as a result of mechanical heating by the supernovae, though the active galactic nucleus and winds may also contribute additional mechanical heating. The starburst size implies a high ?IR of 4.7 × 1012 L? kpc-2, slightly below predictions of radiation-pressure limited starbursts. The HCN line profile has low-level wings, which we tentatively interpret as evidence for outflowing dense molecular gas. However, the dense molecular outflow seen in the HCN line wings is unlikely to escape the Galaxy and is destined to return to the nucleus and fuel future star formation. We also present modeling of Herschel observations of the H2O lines and find a nuclear dust temperature of ?40 K. IRAS 13120-5453 has a lower dust temperature and ?IR than is inferred for the systems termed "compact obscured nuclei (CONs)" (such as Arp 220 and Mrk 231). If IRAS 13120-5453 has undergone a CON phase, we are likely witnessing it at a time when the feedback has already inflated the nuclear ISM and diluted star formation in the starburst/active galactic nucleus core.
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| 2. |
- Sliwa, Kazimierz, et al.
(författare)
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Extreme CO Isotopic Abundances in the ULIRG IRAS 13120-5453: An Extremely Young Starburst or Top-heavy Initial Mass Function
- 2017
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Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 840:2
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Tidskriftsartikel (refereegranskat)abstract
- We present ALMA 12CO (J = 1-0, 3-2 and 6-5), 13CO (J = 1-0), and C18O (J = 1-0) observations of the local ultraluminous infrared galaxy (ULIRG) IRAS 13120-5453. The morphologies of the three isotopic species differ, as 13CO shows a hole in emission toward the center. We measure integrated brightness temperature line ratios of 12CO/13CO ? 60 (exceeding 200) and 13CO/C18O ? 1 in the central region. Assuming optical thin emission, C18O is more abundant than 13CO in several regions. The abundances within the central 500 pc are consistent with the enrichment of the interstellar medium via a young starburst (>7 Myr), a top-heavy initial mass function, or a combination of both.
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