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Register a new userA far-infrared molecular and atomic line survey of the Orion KL region
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Added by
Mercedes Ramos Lerate
Publication date
2006
fields
Physics
and research's language is
English
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We have carried out a high spectral resolution line survey towards the Orion Kleinmann-Low (KL) cluster from 44-188 um. The observations were taken with the Long Wavelength Spectrometer (LWS) in Fabry-Perot mode, on board the Infrared Space Observatory (ISO). A total of 152 lines are clearly detected and a further 34 features are present as possible detections. The spectrum is dominated by the molecular species H2O, OH and CO, along with [OI] and [CII] lines from PDR or shocked gas and [OIII], [NIII] lines from the foreground M42 HII region. Several isotopic species, as well as NH3, are also detected. HDO and H3O+ are tentatively detected for the first time in the far-infrared range towards Orion-KL. A basic analysis of the line observations is carried out, by comparing with previous measurements and published models and deriving rotational temperatures and column densities in the case of the molecular species. The complexity of the region requires more sophisticated models for the interpretation of all the line observations.
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We present observations towards one of the closest regions of high mass star formation, Orion BN/KL, performed at both low resolution mode (grating mode) and high resolution mode (Fabry-Perot) with the Long Wavelength Spectrometer on board the Infrared Space Observatory. We detected the CO rotational lines from Jup = 15 to Jup = 45. While the lines with Jup<= 32 are spectrally unresolved, the higher lying lines show a broadened profile. Finally, we detected two 13CO lines, namely at Jup = 18 and 24, from which we could derive the opacities of the relative 12CO lines. The LVG analysis of the observed line spectrum allows to distinguish three main physical components with different temperatures, densities and column densities: 1) lines with Jup< 20 originate mainly in the diffuse photodissociation region surrounding the source; 2) lines with Jup between 20 and 30 originate in the high velocity outflow (plateau) emanating from IrC2; 3) lines with Jup > 32 originate in the hot and dense gas of the shocked component of the outflow. We discuss how future observations with HIFI, onboard the Far Infrared Space Telescope (FIRST) will allow to spectrally and spatially disentangle the three components, and, consequently, characterise more precisely the Orion BN/KL star forming region.
Orion KL has served as a benchmark for spectral line searches throughout the (sub)millimeter regime. The main goal is to systematically study spectral characteristics of Orion KL in the 1.3 cm band. We carried out a spectral line survey (17.9 GHz to 26.2 GHz) with the Effelsberg-100 m telescope towards Orion KL. We find 261 spectral lines, yielding an average line density of about 32 spectral features per GHz above 3$sigma$. The identified lines include 164 radio recombination lines (RRLs) and 97 molecular lines. A total of 23 molecular transitions from species known to exist in Orion KL are detected for the first time in the interstellar medium. Non-metastable 15NH3 transitions are detected in Orion KL for the first time. Based on the velocity information of detected lines and the ALMA images, the spatial origins of molecular emission are constrained and discussed. A narrow feature is found in SO2 ($8_{1,7}-7_{2,6}$), possibly suggesting the presence of a maser line. Column densities and fractional abundances relative to H2 are estimated for 12 molecules with LTE methods. Rotational diagrams of non-metastable 14NH3 transitions with J=K+1 to J=K+4 yield different results; metastable 15NH3 is found to have a higher excitation temperature than non-metastable 15NH3, indicating that they may trace different regions. Elemental and isotopic abundance ratios are estimated: 12C/13C=63+-17, 14N/15N=100+-51, D/H=0.0083+-0.0045. The dispersion of the He/H ratios derived from H$alpha$/He$alpha$ pairs to H$delta$/He$delta$ pairs is very small, which is consistent with theoretical predictions that the departure coefficients bn factors for hydrogen and helium are nearly identical. Based on a non-LTE code neglecting excitation by the infrared radiation field and a likelihood analysis, we find that the denser regions have lower kinetic temperature, which favors an external heating of the Hot Core.
We present a 67--93.6 GHz spectral line survey of Orion-KL with the new 4 mm Receiver on the Green Bank Telescope (GBT). The survey reaches unprecedented depths and covers the low-frequency end of the 3 mm atmospheric window which has been relatively unexplored previously. The entire spectral-line survey is published electronically for general use by the astronomical community. The calibration and performance of 4 mm Receiver on the GBT is also summarized.
Orion-KL is a well known high mass star forming region that has long been the target of spectral line surveys and searches for complex molecules. One spectral window where the region had never been surveyed is around wavelengths of $lambda$=1 cm. This is an important window to observe due to the fundamental and low energy transitions of numerous complex molecules that indicate the maximum spatial extent of the molecular species; knowing the spatial distribution of a molecule aids in determining the formation mechanism(s) of that molecule. Additionally, there are fewer transitions in this window, reducing confusion caused by blended lines that can be very problematic at shorter wavelengths ($lambda<$3 mm). In this work, we present the first spectral line survey at $lambda$=1 cm of the Orion-KL region. A total of 89 transitions were detected from 14 molecular species and isotopologues and two atomic species. The observations were conducted with the Combined Array for Research in Millimeter-wave Astronomy in both interferometric and single dish modes.
The degree to which the properties of protostars are affected by environment remains an open question. To investigate this, we look at the Orion A and B molecular clouds, home to most of the protostars within 500 pc. At ~400 pc, Orion is close enough to distinguish individual protostars across a range of environments in terms of both the stellar and gas projected densities. As part of the Herschel Orion Protostar Survey (HOPS), we used the Photodetector Array Camera and Spectrometer (PACS) to map 108 partially overlapping square fields with edge lengths of 5 arcmin or 8 arcmin and measure the 70 micron and 160 micron flux densities of 338 protostars within them. In this paper we examine how these flux densities and their ratio depend on evolutionary state and environment within the Orion complex. We show that Class 0 protostars occupy a region of the 70 micron flux density versus 160 micron to 70 micron flux density ratio diagram that is distinct from their more evolved counterparts. We then present evidence that the Integral-Shaped Filament (ISF) and Orion B contain protostars with more massive envelopes than those in the more sparsely populated LDN 1641 region. This can be interpreted as evidence for increasing star formation rates in the ISF and Orion B or as a tendency for more massive envelopes to be inherited from denser birth environments. We also provide technical details about the map-making and photometric procedures used in the HOPS program.
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