Analysis of Theherschel/Hexos Spectral Survey Toward Orion South: A Massive Protostellar Envelope with Strong External Irradiation (original) (raw)
Related papers
2016
We present a comprehensive analysis of a broad band spectral line survey of the Orion Kleinmann-Low nebula (Orion KL), one of the most chemically rich regions in the Galaxy, using the HIFI instrument on board the Herschel Space Observatory. This survey spans a fre-quency range from 480 to 1907 GHz at a resolution of 1.1 MHz. These observations thus encompass the largest spectral coverage ever obtained toward this high-mass star-forming re-gion in the sub-mm with high spectral resolution, and include frequencies> 1 THz where the Earth’s atmosphere prevents observations from the ground. In all, we detect emission from 39 molecules (79 isotopologues). Combining this dataset with ground based mm spectroscopy ob-tained with the IRAM 30 m telescope, we model the molecular emission from the mm to the far-IR using the XCLASS program which assumes local thermodynamic equilibrium (LTE). Several molecules are also modeled with the MADEX non-LTE code. Because of the wide
The Astrophysical Journal, 2014
We report a detection of the fundamental rotational transition of hydrogen fluoride in absorption towards Orion KL using Herschel/HIFI. After the removal of contaminating features associated with common molecules ("weeds"), the HF spectrum shows a P-Cygni profile, with weak redshifted emission and strong blue-shifted absorption, associated with the low-velocity molecular outflow. We derive an estimate of 2.9 × 10 13 cm −2 for the HF column density responsible for the broad absorption component. Using our best estimate of the H 2 column density within the low-velocity molecular outflow, we obtain a lower limit of ∼ 1.6 × 10 −10 for the HF abundance relative to hydrogen nuclei, corresponding to ∼ 0.6% of the solar abundance of fluorine. This value is close to that inferred from previous ISO observations of HF J=2-1 absorption towards Sgr B2, but is in sharp contrast to the lower limit of 6 × 10 −9 derived by Neufeld et al. (2010) for cold, foreground clouds on the line of sight towards G10.6-0.4.
2010
We present initial results from the Herschel GT key program: Herschel observations of EXtra-Ordinary Sources (HEXOS) and outline the promise and potential of spectral surveys with Herschel/HIFI. The HIFI instrument offers unprecedented sensitivity, as well as continuous spectral coverage across the gaps imposed by the atmosphere, opening up a largely unexplored wavelength regime to high-resolution spectroscopy. We show the spectrum of Orion KL between 480 and 560 GHz and from 1.06 to 1.115 THz. From these data, we confirm that HIFI separately measures the dust continuum and spectrally resolves emission lines in Orion KL. Based on this capability we demonstrate that the line contribution to the broad-band continuum in this molecule-rich source is ∼20−40% below 1 THz and declines to a few percent at higher frequencies. We also tentatively identify multiple transitions of HDO in the spectra. The first detection of this rare isotopologue in the interstellar medium suggests that HDO emis...
A Submillimeter Dust and Gas Study of the Orion B Molecular Cloud
The Astrophysical Journal, 2001
Using SCUBA on the James Clerk Maxwell Telescope, we obtained a map of 850 km continuum emission from the Orion B molecular cloud. The map is 20@ ] 40@ in extent and covers much of the northern half of the giant molecular cloud. A total of 67 discrete continuum sources, or clumps, have been identiÐed, many of which are grouped in three regions, near NGC 2071IR, NGC 2068, and HH 24/25/26. Masses of the sources range from 0.2 to 12 About half of the area of our 850 km map is M _. covered by the current release of the 2MASS infrared survey. Of 40 clumps covered by the 2MASS, 14 have associated infrared sources detected in J, H, and K. Maps of 13CO J \ 2È1 and C18O J \ 2È1 line emission were obtained for two regions in order to Ðnd the gas column density. Formaldehyde spectra were obtained toward eight of the continuum clumps to determine the gas kinetic temperature. Three of the clumps with measured temperature are hot K) while the other Ðve are cold K). (T kin º 80 (T kin ¹ 20 The gas-to-dust ratios di †er substantially between the two regions mapped in CO. In the NGC 2068 region we Ðnd close to constant ratios of dust-togas emission, except in one compact source. However, in the HH 24/25/26 region the dust-togas emission ratio varies substantially with some of the brightest dust continuum sources almost absent in CO emission. One explanation is that CO molecules have frozen onto grains in the dense cores. Why this freeze-out should happen in the HH 24/25/26 cores but not in the NGC 2068 cores remains unexplained. A 12CO J \ 3È2 map of the NGC 2068 region shows patches of high-velocity gas associated with Ðve of the compact continuum sources. The presence of out-Ñows provides strong evidence that the group of sources south of NGC 2068 is actively forming stars.
Astronomy and Astrophysics, 2010
We report a detection of the fundamental rotational transition of hydrogen fluoride in absorption towards Orion KL using Herschel/HIFI. After the removal of contaminating features associated with common molecules ("weeds"), the HF spectrum shows a P-Cygni profile, with weak redshifted emission and strong blue-shifted absorption, associated with the low-velocity molecular outflow. We derive an estimate of 2.9 × 10 13 cm −2 for the HF column density responsible for the broad absorption component. Using our best estimate of the H 2 column density within the low-velocity molecular outflow, we obtain a lower limit of ∼ 1.6 × 10 −10 for the HF abundance relative to hydrogen nuclei, corresponding to ∼ 0.6% of the solar abundance of fluorine. This value is close to that inferred from previous ISO observations of HF J=2-1 absorption towards Sgr B2, but is in sharp contrast to the lower limit of 6 × 10 −9 derived by Neufeld et al. (2010) for cold, foreground clouds on the line of sight towards G10.6-0.4.
Infrared spectroscopy of substellar objects in Orion
Monthly Notices of the Royal Astronomical Society, 2001
We present broad band spectra of a sample of 21 low luminosity sources in the Trapezium Cluster, with masses in the range 0.008 -0.10 M ⊙ (assuming an age of 1 Myr). These were selected for low extinction in most cases and are located west of the brighter nebulosity. The spectra are in the H bandpass (1.4-1.95 µm) and K bandpass (1.9-2.5 µm) also for most of the brighter sources, with a resolution of 50 nm. They were taken with the United Kingdom Infrared Telescope (UKIRT) using the CGS4 spectrometer. Absorption by water vapour bands is detected in all the substellar candidates except one, which is a highly reddened object with strong H 2 emission and an anomalously blue (I-J) colour, implying that it is a very young cluster member with circumstellar matter. The observation of prominent water vapour bands confirms the low Effective Temperatures implied by our (I-J) colour measurements in an earlier paper and would imply late M or L spectral types if these were older field dwarfs. However, the profiles of the H bandpass spectra are very different from those of field dwarfs with similar water absorption strength, demonstrating that they are not foreground or background objects. In addition, the CO absorption bands at 2.3 µm and the NaI absorption feature at 2.21 µm are very weak for such cool sources. All these features are quite well reproduced by the AMES-Dusty-1999 model atmospheres of , and arise from the much lower gravities predicted for the Trapezium sources (3.5 < log(g) < 4.0) compared to evolved objects (log g ∼ 5.5), This represents a new proof of the substellar status of our sources, independent of the statistical arguments for low contamination, which are reexamined here. The very late spectral types of the planetary mass objects and very low mass brown dwarfs demonstrate that they are cluster members, since they are too luminous to be field dwarfs in the background. We also present additional UKIRT photometry of a small region in the south of the Trapezium cluster where the extinction and nebular brightness are low, which permitted the detection of objects with 1 Myr masses slightly lower than our previous least massive source at 8 M Jup . Following a minor update to our previous J band photometry, due to a new UKIRT filter calibration, there are ∼ 15 planetary mass candidates in the full dataset.
Disentangling the Environment of the Fu Orionis Candidate HBC 722 with Herschel
The Astrophysical Journal, 2011
We analyze the submillimeter emission surrounding the new FU Orionis-type object, HBC 722. We present the first epoch of observations of the active environs of HBC 722, with imaging and spectroscopy from PACS, SPIRE, and HIFI aboard the Herschel Space Observatory, as well as CO J= 2-1 and 350 µm imaging (SHARC-II) with the Caltech Submillimeter Observatory. The primary source of submillimeter continuum emission in the region -2MASS 20581767+4353310 -is located 16 ′′ south-southeast of the optical flaring source while the optical and near-IR emission is dominated by HBC 722. A bipolar outflow extends over HBC 722; the most likely driver is the submillimeter source. We detect warm -2 -(100 K) and hot (246 K) CO emission in the surrounding region, evidence of outflow-driven heating in the vicinity. The region around HBC 722 itself shows little evidence of heating driven by the new outbursting source itself.
Low-resolution spectroscopy and spectral energy distributions of selected sources towards σ Orionis
Astronomy and Astrophysics, 2008
Aims. We study in detail nine sources in the direction of the young σ Orionis cluster, which is considered to be a unique site for studying stellar and substellar formation. The nine sources were selected because of their peculiar properties, such as extremely-red infrared colours or excessively strong Hα emission for their blue optical colours. Methods. We acquired high-quality, low-resolution spectroscopy (R ∼ 500) of the nine targets with ALFOSC at the Nordic Optical Telescope. We also re-analysed [24]-band photometry from MIPS/Spitzer and compiled the highest quality photometric dataset available at the ViJHK s passbands and the four IRAC/Spitzer channels, for constructing accurate spectral energy distributions between 0.55 and 24 μm. Results. The nine targets were classified into: one Herbig Ae/Be star with a scattering edge-on disc; two G-type stars; one X-ray flaring, early-M, young star with chromospheric Hα emission; one very low-mass, accreting, young spectroscopic binary; two young objects at the brown-dwarf boundary with the characteristics of classical T Tauri stars; and two emission-line galaxies, one undergoing star formation, and another whose spectral energy distribution is dominated by an active galactic nucleus. We also discovered three infrared sources associated with overdensities in a cold cloud of the cluster centre. Conclusions. Low-resolution spectroscopy and spectral energy distributions are a vital tool for measuring the physical properties and evolution of young stars and candidates in the σ Orionis cluster.
Diffuse Gamma-ray Observations of the Orion Molecular Clouds
2009
We report on a preliminary analysis of the diffuse gamma-ray observations of local giant molecular clouds Orion A and B with the Large Area Telescope onboard the Fermi Gamma-ray Space Telescope. The gamma-ray emission of the clouds is well explained by hadronic and electromagnetic interactions between cosmic rays and nuclei in the clouds. In consequence, we obtain the total masses of the Orion A and B clouds to be (80.6 +/- 7.5 +/- 4.8) x 10^3 Msun and (39.5 +/- 5.2 +/- 2.6) x 10^3 Msun, respectively, for the distance to the clouds of 400 pc and the Galactic CR spectrum predicted by GALPROP on the local observations of CRs. The structure of molecular clouds have been extensively studied by radio telescopes, especially using the line intensity of CO molecules (WCO) and a constant conversion factor from Wco to N (H_2) (= Xco). However, this factor is found to be significantly different for Orion A and B: 1.76 +/- 0.04 +/- 0.02 and 1.27 +/- 0.06 +/- 0.01, respectively.