| 1. |
- Indriolo, Nick, et al.
(författare)
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High Spectral Resolution Observations toward Orion BN at 6 μm: No Evidence for Hot Water
- 2018
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Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 865:2
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Tidskriftsartikel (refereegranskat)abstract
- The Becklin-Neugebauer (BN) object in Orion has a large proper motion and radial velocity with respect to the gas and other stars in the region where it is presumed to have formed. Multiple dynamical interaction scenarios have been proposed to explain this motion. In one case BN is thought to have interacted with stars in the Trapezium cluster, while in another it is thought to have interacted with source I while deeply embedded in molecular gas. If there is dense gas that has been retained in close proximity to BN, it may be evidence that the latter scenario is favored. We observed BN at high spectral resolution in three windows near 6 mu m using the Echelon-Cross-Echelle Spectrograph on board the Stratospheric Observatory for Infrared Astronomy targeting the nu(2) vibrational band of H2O. Absorption from only three transitions of H2O is detected, and through kinematic analysis is associated with cool, dense foreground gas, not BN itself. We find no evidence for H2O absorption or emission at the systemic velocity of BN.
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| 2. |
- Indriolo, Nick, et al.
(författare)
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SOFIA/EXES observations of water absorption in the protostar AFGL 2591 at high spectral resolution
- 2015
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Ingår i: Astrophysical Journal Letters. - 2041-8213. ; 802:2
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Tidskriftsartikel (refereegranskat)abstract
- We present high spectral resolution (similar to 3 km s(-1)) observations of the nu(2) ro-vibrational band of H2O in the 6.086-6.135 mu m range toward the massive protostar AFGL 2591 using the Echelon-Cross-Echelle Spectrograph (EXES) on the Stratospheric Observatory for Infrared Astronomy (SOFIA). Ten absorption features are detected in total, with seven caused by transitions in the nu(2) band of H2O, two by transitions in the first vibrationally excited nu(2) band of H2O, and one by a transition in the nu(2) band of (H2O)-O-18. Among the detected transitions is the nu(2) 1(1,1)-0(0,0) line that probes the lowest-lying rotational level of para-H2O. The stronger transitions appear to be optically thick, but reach maximum absorption at a depth of about 25%, suggesting that the background source is only partially covered by the absorbing gas or that the absorption arises within the 6 mu m emitting photosphere. Assuming a covering fraction of 25%, the H2O column density and rotational temperature that best fit the observed absorption lines are N(H2O) = (1.3 +/- 0.3) x 10(19) cm(-2) and T = 640 +/- 80 K.
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| 3. |
- Neufeld, David A., et al.
(författare)
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HERSCHEL OBSERVATIONS OF INTERSTELLAR CHLORONIUM
- 2012
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 748:1, s. 37-
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Tidskriftsartikel (refereegranskat)abstract
- Using the Herschel Space Observatory's Heterodyne Instrument for the Far-Infrared, we have observed parachloronium (H2Cl+) toward six sources in the Galaxy. We detected interstellar chloronium absorption in foreground molecular clouds along the sight lines to the bright submillimeter continuum sources Sgr A (+50 km s(-1) cloud) and W31C. Both the para-(H2Cl+)-Cl-35 and para-(H2Cl+)-Cl-37 isotopologues were detected, through observations of their 1(11)-0(00) transitions at rest frequencies of 485.42 and 484.23 GHz, respectively. For an assumed ortho-to-para ratio (OPR) of 3, the observed optical depths imply that chloronium accounts for similar to 4%-12% of chlorine nuclei in the gas phase. We detected interstellar chloronium emission from two sources in the Orion Molecular Cloud 1: the Orion Bar photodissociation region and the Orion South condensation. For an assumed OPR of 3 for chloronium, the observed emission line fluxes imply total beam-averaged column densities of similar to 2 x 10(13) cm(-2) and similar to 1.2 x 10(13) cm(-2), respectively, for chloronium in these two sources. We obtained upper limits on the para-(H2Cl+)-Cl-35 line strengths toward H-2 Peak 1 in the Orion Molecular cloud and toward the massive young star AFGL 2591. The chloronium abundances inferred in this study are typically at least a factor similar to 10 larger than the predictions of steady-state theoretical models for the chemistry of interstellar molecules containing chlorine. Several explanations for this discrepancy were investigated, but none has proven satisfactory, and thus the large observed abundances of chloronium remain puzzling.
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