High Spectral Resolution SOFIA/EXES Observations of C2H2 towards Orion-IRc2
Naseem Rangwala, Sean W. J. Colgan, Romane Le Gal, Kinsuk Acharyya, Xinchuan Huang, Timothy J. Lee, Eric Herbst, Curtis deWitt, Matt Richter, Adwin Boogert, Mark McKelvey
备注：
accepted for publication in The Astrophysical Journal
We present high-spectral resolution observations from 12.96 - 13.33 microns towards Orion IRc2 using the mid-infrared spectrograph, EXES, on SOFIA. These observations probe the physical and chemical conditions of the Orion hot core, which is sampled by a bright, compact, mid-infrared background continuum source in the region, IRc2. All ten of the rovibrational C2H2 transitions expected in our spectral coverage, are detected with high S/N, yielding continuous coverage of the R-branch lines from J=9-8 to J=18-17, including both ortho and para species. Eight of these rovibrational transitions are newly reported detections. The isotopologue, 13CCH2, is clearly detected with high signal-to-noise. This enabled a direct measurement of the 12C/13C isotopic ratio for the Orion hot core of 14 +/- 1 and an estimated maximum value of 21. We also detected several HCN rovibrational lines. The ortho and para C2H2 ladders are clearly separate and tracing two different temperatures, 226 K and 164 K, respectively, with a non-equilibrium ortho to para ratio (OPR) of 1.7 +\- 0.1. Additionally, the ortho and para V_LSR values differ by about 1.8 +/- 0.2 km/s, while, the mean line widths differ by 0.7 +/- 0.2 km/s, suggesting that these species are not uniformly mixed along the line of sight to IRc2. We propose that the abnormally low C2H2 OPR could be a remnant from an earlier, colder phase, before the density enhancement (now the hot core) was impacted by shocks generated from an explosive event 500 yrs ago.
Spectrally-resolved observations of three pure rotational lines of H$_2$, conducted with the EXES instrument on SOFIA toward the classic bow shock HH7, reveal systematic velocity shifts between the S(5) line of ortho-H$_2$ and the two para-H$_2$ lines [S(4) and S(6)] lying immediately above and below it on the rotational ladder. These shifts, reported here for the first time, imply that we are witnessing the conversion of para-H$_2$ to ortho-H$_2$ within a shock wave driven by an outflow from a young stellar object. The observations are in good agreement with the predictions of models for non-…
We present high spectral resolution (~3 km/s) observations of the nu_2 ro-vibrational band of H2O in the 6.086--6.135 micron 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 H2{18}O. Among the detected transitions is the nu_2 1(1,1)--0(0,0) line which probes the low…
We have performed a 5-8 $μ$m spectral line survey of the hot molecular core associated with the massive protostar AFGL 2591, using the Echelon-Cross-Echelle Spectrograph (EXES) on the Stratospheric Observatory for Infrared Astronomy (SOFIA). We have supplemented these data with a ground based study in the atmospheric M band around 4.5 $μ$m using the iSHELL instrument on the Infrared Telescope Facility (IRTF), and the full N band window from 8-13 $μ$m using the Texas Echelon Cross Echelle Spectrograph (TEXES) on the IRTF. Here we present the first detection of ro-vibrational transitions of CS i…
Sulfur has been observed to be severely depleted in dense clouds leading to uncertainty in the molecules that contain it and the chemistry behind their evolution. Here, we aim to shed light on the sulfur chemistry in young stellar objects (YSOs) by using high-resolution infrared spectroscopy of absorption by the $ν_3$ rovibrational band of SO$_2$ obtained with the Echelon-Cross-Echelle Spectrograph on the Stratospheric Observatory for Infrared Astronomy. Using local thermodynamic equilibrium models we derive physical parameters for the SO$_2$ gas in the massive YSO MonR2 IRS3. This yields a SO…
High-resolution mid-IR spectroscopy of SVS 13-A with EXES/SOFIA: The surprisingly high CH$_3$OH/H$_2$O ratio in the planet-forming zone of a solar mass protostar
Space Science Institute（空间科学研究所）；ESO（欧洲南方天文台）；INAF, Osservatorio Astrofisico di Arcetri（意大利国家天体物理研究所阿切特里天文台）；Univ. Grenoble Alpes, CNRS, IPAG（格勒诺布尔阿尔卑斯大学、法国国家科学研究中心、行星与地球物理研究所）；Space Science and Astrobiology Division, NASA Ames Research Center（美国宇航局艾姆斯研究中心空间科学与天体生物学部门）；Bay Area Environmental Research Institute（湾区环境研究所）；Jet Propulsion Laboratory, California Institute of Technology（加州理工学院喷气推进实验室）；Universitat Autònoma de Barcelona（巴塞罗那自治大学）；University of Turin（都灵大学）
We present new mid-infrared images of the central region of the Orion Nebula using the newly commissioned SOFIA airborne telescope and its 5 -- 40 micron camera FORCAST. The 37.1 micron images represent the highest resolution observations (<4") ever obtained of this region at these wavelengths. After BN/KL (which is described in a separate letter in this issue), the dominant source at all wavelengths except 37.1 micron is the Ney-Allen Nebula, a crescent-shaped extended source associated with theta 1D. The morphology of the Ney-Allen nebula in our images is consistent with the interpretation t…
Orion BN 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 windo…
We present the first mid-infrared (MIR) detections of HNC and H13CN in the interstellar medium, and numerous, resolved HCN rovibrational transitions. Our observations span 12.8 to 22.9 micron towards the hot core Orion IRc2, obtained with the Echelon-Cross-Echelle Spectrograph aboard the Stratospheric Observatory for Infrared Astronomy (SOFIA). Exceptional, ~5 km/s, resolution distinguishes individual rovibrational transitions of the HNC and HCN P, Q, and R branches; and the H13CN R branch. This allows direct measurement of the species' excitation temperatures, column densities, and relative a…
We present the first high spectral resolution mid-infrared survey in the Orion BN/KL region, covering 7.2 to 28.3 micron. 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 …
We have performed a high resolution 4-13 $μm$ spectral survey of the hot molecular gas associated with the massive protostars AFGL 2591 and AFGL 2136, utilising the Echelon-Cross-Echelle-Spectrograph (EXES) on-board the Stratospheric Observatory for Infrared Astronomy (SOFIA), and the iSHELL instrument and Texas Echelon Cross Echelle Spectrograph (TEXES) on the NASA Infrared Telescope Facility (IRTF). Here we present results of this survey with analysis of CO, HCN, C$_2$H$_2$, NH$_3$ and CS, deriving the physical conditions for each species. Also from the IRTF, iSHELL data at 3 $μm$ for AFGL 2…
Following up on our discovery of terahertz water masers, reported in 2017, we report two further detections of water maser emission at frequencies above 1 THz. Using the GREAT instrument on SOFIA, we have detected emission in the 1.296411 THz $8_{27}-7_{34}$ transition of water toward two additional oxygen-rich evolved stars, omicron Ceti (Mira) and R Crateris, and obtained an upper limit on the 1.296 THz line emission from U Orionis. Toward these three sources, and toward the red supergiant star VY Canis Majorae from which 1.296 THz line emission was reported previously, we have also observed…
We report the SOFIA/HAWC+ band D (154$\,μ$m) and E (214$\,μ$m) polarimetric observations of the filamentary structure OMC-3 that is part of the Orion molecular cloud. The polarization pattern is uniform for both bands and parallel to the filament structure. The polarization degree decreases toward regions with high intensity for both bands, revealing a so called "polarization hole." We identified an optical depth effect in which polarized emission and extinction act as counteracting mechanisms as a potential contributor to this phenomenon. Assuming that the detected polarization is caused by t…
The Orion Molecular Cloud is the nearest massive-star forming region. Massive stars have profound effects on their environment due to their strong radiation fields and stellar winds. Velocity-resolved observations of the [CII] $158\,μ\mathrm{m}$ fine-structure line allow us to study the kinematics of UV-illuminated gas. Here, we present a square-degree-sized map of [CII] emission from the Orion Nebula complex obtained by the upGREAT instrument onboard SOFIA, covering the entire Orion Nebula (M42) plus M43 and the nebulae NGC 1973, 1975, and 1977. We compare the stellar characteristics of these…
We report new polarimetric and photometric maps of the massive star-forming region OMC-1 using the HAWC+ instrument on the Stratospheric Observatory for Infrared Astronomy (SOFIA). We present continuum polarimetric and photometric measurements of this region at 53, 89, 154, and 214 microns at angular resolutions of 5.1, 7.9, 14.0, and 18.7 arcseconds for the four bands, respectively. The photometric maps enable the computation of improved SEDs for the region. We find that at the longer wavelengths, the inferred magnetic field configuration matches the `hourglass' configuration seen in previous…
Multiline observations of hydrogen, helium, and carbon radio-recombination lines toward Orion A: A detailed dynamical study and direct determination of physical conditions
Context. The combined use of carbon radio recombination lines (CRRLs) and the 158 $μ$m-[CII] line is a powerful tool for the study of the energetics and physical conditions (e.g., temperature and density) of photodissociation regions (PDRs). However, there are few observational studies that exploit this synergy. Aims. Here we explore the relation between CRRLs and the 158 $μ$m-[CII] line in light of new observations and models. Methods. We present new and existing observations of CRRLs in the frequency range 0.15--230 GHz with ALMA, VLA, the GBT, Effelsberg 100m, and LOFAR towards Orion~A (M42…
We report the first detection of the S(1) pure rotational line of ortho-H2 at 17.04 um in an asymptotic giant branch star, using observations of IRC+10216 with the Echelon-cross-echelle Spectrograph (EXES) mounted on the Stratospheric Observatory for Infrared Astronomy (SOFIA). This line, which was observed in a very high sensitivity spectrum (RMS noise ~0.04% of the continuum), was detected in the wing of a strong telluric line and displayed a P Cygni profile. The spectral ranges around the frequencies of the S(5) and S(7) ortho-H2 transitions were observed as well but no feature was detected…
Velocity-resolved [O I] 63,145 um, [C II] 158 um, and OH mapping along the Orion BN/KL explosive outflow and irradiated shocks
Instituto de Física Fundamental (CSIC)（基础物理研究所（西班牙科学理事会））；Max-Planck Institut für Radioastronomie（马克斯·普朗克射电天文研究所）；Observatoire de Paris, Université PSL, Sorbonne Université, LUX（巴黎天文台，巴黎文理研究大学，索邦大学，LUX）；Ecole Normale Supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université de Paris（法兰西高等师范学校，巴黎文理研究大学，法国国家科学研究中心，索邦大学，巴黎大学）；Physikalisches Institut der Universität zu Köln（科隆大学物理学院）
We have observed the massive protostar AFGL 2136 IRS 1 in multiple wavelength windows in the near-to-mid-infrared at high ($\sim3$ km s$^{-1}$) spectral resolution using VLT+CRIRES, SOFIA+EXES, and Gemini North+TEXES. There is an abundance of H$_2$O absorption lines from the $ν_1$ and $ν_3$ vibrational bands at 2.7 $μ$m, from the $ν_2$ vibrational band at 6.1 $μ$m, and from pure rotational transitions near 10-13 $μ$m. Analysis of state-specific column densities derived from the resolved absorption features reveals that an isothermal absorbing slab model is incapable of explaining the relative …
High spectral resolution observations toward the low mass-loss rate C-rich, J-type AGB star Y CVn have been carried out at 7.5, 13.1 and 14.0 um with SOFIA/EXES and IRTF/TEXES. Around 130 HCN and H13CN lines of bands v2, 2v2, 2v2-v2, 3v2-2v2, 3v2-v2, and 4v2-2v2 have been identified involving lower levels with energies up to ~3900 K. These lines have been complemented with the pure rotational lines J=1-0 and 3-2 of the vibrational states up to 2v2 acquired with the IRAM 30 m telescope, and with the continuum taken with ISO. We have analyzed the data with a ro-vibrational diagram and a code whi…
Max-Planck-Institut für extraterrestrische Physik（马克斯·普朗克地外物理研究所）；University of Helsinki（赫尔辛基大学）；Max-Planck-Institut für Radioastronomie（马克斯·普朗克射电天文研究所）；Radboud University（拉布德大学）；Universität zu Köln（科隆大学）
