The Mid-infrared Molecular Inventory toward Orion IRc2

Abstract

We present the first high spectral resolution mid-infrared survey in the Orion BN/KL region, covering 7.2–28.3 μm. With SOFIA/EXES, we target the enigmatic source Orion IRc2. While this is in the most prolifically studied massive star-forming region, longer wavelengths and molecular emission lines dominated previous spectral surveys. The mid-infrared observations in this work access different components and molecular species in unprecedented detail. We unambiguously identify two new kinematic components, both chemically rich with multiple molecular absorption lines. The “blue clump” has v LSR = −7.1 ± 0.7 km s−1, and the “red clump” has 1.4 ± 0.5 km s−1. While the blue and red clumps have similar temperatures and line widths, molecular species in the blue clump have higher column densities. They are both likely linked to pure rotational H2 emission also covered by this survey. This work provides evidence for the scenario that the blue and red clumps are distinct components unrelated to the classic components in the Orion BN/KL region. Comparison to spectroscopic surveys toward other infrared targets in the region show that the blue clump is clearly extended. We analyze, compare, and present in-depth findings on the physical conditions of C2H2, 13CCH2, CH4, CS, H2O, HCN, H 13 CN , HNC, NH3, and SO2 absorption lines and an H2 emission line associated with the blue and red clumps. We also provide limited analysis of H2O and SiO molecular emission lines toward Orion IRc2 and the atomic forbidden transitions [Fe ii], [S i], [S iii], and [Ne ii].

Potential energy surfaces and dynamic properties via ab initio composite and density functional approaches

“…Alternative methods for analyzing anharmonic corrections for vibrational spectroscopy include using quartic force fields combined with vibrational perturbation theory 41,42 and re-parameterized semiempirical methods 43 targeting molecules relevant in astrochemistry. [42][43][44][45] While local vibrational model theory is a powerful theory to describe CNM, vibrational self-consistent field (VSCF) theory, which was developed in the late 1970s, fully accounts for anharmonicity by considering the vibrational Schrödinger Equation. Approximations are made that make VSCF theory analogous to Hartree-Fock theory.…”

High-resolution SOFIA/EXES Spectroscopy of Water Absorption Lines in the Massive Young Binary W3 IRS 5

“…Previous studies of the MIR water absorption spectrum toward massive protostars have revealed a rich spectral content. High spectral resolution observations can provide much insight into the characteristics of these regions (e.g., Knez et al 2009;Indriolo et al 2015;Barr et al 2018;Dungee et al 2018;Indriolo et al 2018;Rangwala et al 2018;Goto et al 2019;Barr et al 2020;Indriolo et al 2020;Nickerson et al 2021;Barr et al 2022aBarr et al , 2022bLi et al 2022;Nickerson et al 2023). Water has also been studied at high spectral resolution via pure rotational transitions, using the heterodyne instruments on board SWAS, Odin, and Herschel Space Observatory (e.g., Snell et al 2000;Wilson et al 2003;Chavarría et al 2010;Karska et al 2014).…”