Context. Sites of massive star formation have complex internal structures. Local heating by young stars and kinematic processes, such as outflows and stellar winds, generate large temperature and ...velocity gradients. Complex cloud structures lead to intricate emission line shapes. CO lines from high mass star forming regions are rarely Gaussian and show often multiple peaks. Furthermore, the line shapes vary significantly with the quantum number Jup, due to the different probed physical conditions and opacities. Aims. The goal of this paper is to show that the complex line shapes of 12CO and 13CO in NGC 2024 showing multiple emission and absorption features, which vary with rotational quantum number J can be explained consistently with a model, whose temperature and velocity structure are based on the well-established scenario of a PDR and the “Blister model”. Methods. We present velocity-resolved spectra of seven 12CO and 13CO lines ranging from $J_{\rm up}=3$ to $J _{\rm up}=13$. We combined these data with 12CO high-frequency data from the ISO satellite and analyzed the full set of CO lines using an escape probability code and a one-dimensional full radiative transfer code. Results. We find that the bulk of the molecular cloud associated with NGC 2024 consists of warm (75 K) and dense ($9\times 10^5$ cm-3) gas. An additional hot (~300 K) component, located at the interface of the HII region and the molecular cloud, is needed to explain the emission of the high-J CO lines. Deep absorption notches indicate that very cold material (~20 K) exists in front of the warm material, too. Conclusions. A temperature and column density structure consistent with those predicted by PDR models, combined with the velocity structure of a “Blister model”, appropriately describes the observed emission line profiles of this massive star forming region. This case study of NGC 2024 shows that, with physical insights into these complex regions and careful modeling, multi-line observations of 12CO and 13CO can be used to derive detailed physical conditions in massive star forming regions.
Context.The THz atmospheric “windows”, centered at roughly 1.3 and 1.5 THz, contain numerous spectral lines of astronomical importance, including three high-J CO lines, the N II line at 205 μm, and ...the ground transition of para-H2D+. The CO lines are tracers of hot (several 100 K), dense gas; N II is a cooling line of diffuse, ionized gas; the H2D+ line is a non-depleting tracer of cold (~20 K), dense gas. Aims.As the THz lines benefit the study of diverse phenomena (from high-mass star-forming regions to the WIM to cold prestellar cores), we have built the CO N+ Deuterium Observations Receiver (CONDOR) to further explore the THz windows by ground-based observations. Methods.CONDOR was designed to be used at the Atacama Pathfinder EXperiment (APEX) and Stratospheric Observatory For Infrared Astronomy (SOFIA). CONDOR was installed at the APEX telescope and test observations were made to characterize the instrument. Results.The combination of CONDOR on APEX successfully detected THz radiation from astronomical sources. CONDOR operated with typical $T_{\rm rec}=1600$ K and spectral Allan variance times of ~30 s. CONDOR's “first light” observations of CO 13-12 emission from the hot core Orion FIR 4 (= OMC1 South) revealed a narrow line with $T_{\rm MB}\approx 210$ K and $\Delta V\approx 5.4$ km s-1. A search for N II emission from the ionization front of the Orion Bar resulted in a non-detection. Conclusions.The successful deployment of CONDOR at APEX demonstrates the potential for making observations at THz frequencies from ground-based facilities.
CONDOR, the CO, N+, Deuterium Observations Receiver, is designed to make velocity-resolved observations of the CO, NII, and p-H2D+ lines in the 1.4 THz (200-240μm) atmospheric windows. CONDOR's first ...light observations were made with the APEX telescope in November 2005. The CONDOR beam on APEX (at ν = 1.5 THz) was expected to consist of a 4.3″ main beam and a 73″ error beam; this beam structure was verified from scans of Mars. The pointing accuracy, also determined from Mars scans, was better than 7″. The average atmospheric transmission during our Orion observations (elev~57°) was 19 ± 4% along the line-of-sight. A forward efficiency of Feff = 0.8 was determined from sky dips, and observations of the Moon and Mars were used to couple the CONDOR beam to sources of different sizes (ηc = 0.40 and ~0.10, respectively). For more information, see Wiedner et al. 2006.
CONDOR – A heterodyne receiver at 1.25-1.5 THz Wiedner, M. C.; Wieching, G.; Bielau, F. ...
Proceedings of the International Astronomical Union,
08/2006, Letnik:
2, Številka:
S237
Journal Article
Recenzirano
Odprti dostop
The CON+Deuterium Observations Receiver (CONDOR) is a heterodyne receiver that operates between 1250–1530 GHz. Its primary goal is to observe star-forming regions in CO, N+, and H2D+ emission.
NGC 2024, a sites of massive star formation, have complex internal structures caused by cal heating by young stars, outflows, and stellar winds. These complex cloud structures lead to intricate ...emission line shapes. The goal of this paper is to show that the complex line shapes of 12 CO lines in NGC 2024 can be explained consistently with a model, whose temperature and velocity structure are based on the well-established scenario of a PDR and the Blister model. We present velocity-resolved spectra of seven CO lines ranging from J=3 to J=13, and we combined these data with CO high-frequency data from the ISO satellite. We find that the bulk of the molecular cloud associated with NGC 2024 consists of warm (75 K) and dense (9e5 cm-3) gas. An additional hot (~ 300 K) component, located at the interface of the HII region and the molecular cloud, is needed to explain the emission of the high-J CO lines. Deep absorption notches indicate that very cold material (20 K) exists in front of the warm material, too. A temperature and column density structure consistent with those predicted by PDR models, combined with the velocity structure of a Blister model, appropriately describes the observed emission line profiles of this massive star forming region. This case study of NGC 2024 shows that, with physical insights into these complex regions and careful modeling, multi-line observations of CO can be used to derive detailed physical conditions in massive star forming regions.
The THz atmospheric windows centered at roughly 1.3 and 1.5~THz, contain
numerous spectral lines of astronomical importance, including three high-J CO
lines, the N+ line at 205 microns, and the ...ground transition of para-H2D+. The
CO lines are tracers of hot (several 100K), dense gas; N+ is a cooling line of
diffuse, ionized gas; the H2D+ line is a non-depleting tracer of cold (~20K),
dense gas. As the THz lines benefit the study of diverse phenomena (from
high-mass star-forming regions to the WIM to cold prestellar cores), we have
built the CO N+ Deuterium Observations Receiver (CONDOR) to further explore the
THz windows by ground-based observations. CONDOR was designed to be used at the
Atacama Pathfinder EXperiment (APEX) and Stratospheric Observatory For Infrared
Astronomy (SOFIA). CONDOR was installed at the APEX telescope and test
observations were made to characterize the instrument. The combination of
CONDOR on APEX successfully detected THz radiation from astronomical sources.
CONDOR operated with typical Trec=1600K and spectral Allan variance times of
30s. CONDOR's first light observations of CO 13-12 emission from the hot core
Orion FIR4 (= OMC1 South) revealed a narrow line with T(MB) = 210K and
delta(V)=5.4km/s. A search for N+ emission from the ionization front of the
Orion Bar resulted in a non-detection. The successful deployment of CONDOR at
APEX demonstrates the potential for making observations at THz frequencies from
ground-based facilities.
The THz atmospheric windows centered at roughly 1.3 and 1.5~THz, contain numerous spectral lines of astronomical importance, including three high-J CO lines, the N+ line at 205 microns, and the ...ground transition of para-H2D+. The CO lines are tracers of hot (several 100K), dense gas; N+ is a cooling line of diffuse, ionized gas; the H2D+ line is a non-depleting tracer of cold (~20K), dense gas. As the THz lines benefit the study of diverse phenomena (from high-mass star-forming regions to the WIM to cold prestellar cores), we have built the CO N+ Deuterium Observations Receiver (CONDOR) to further explore the THz windows by ground-based observations. CONDOR was designed to be used at the Atacama Pathfinder EXperiment (APEX) and Stratospheric Observatory For Infrared Astronomy (SOFIA). CONDOR was installed at the APEX telescope and test observations were made to characterize the instrument. The combination of CONDOR on APEX successfully detected THz radiation from astronomical sources. CONDOR operated with typical Trec=1600K and spectral Allan variance times of 30s. CONDOR's first light observations of CO 13-12 emission from the hot core Orion FIR4 (= OMC1 South) revealed a narrow line with T(MB) = 210K and delta(V)=5.4km/s. A search for N+ emission from the ionization front of the Orion Bar resulted in a non-detection. The successful deployment of CONDOR at APEX demonstrates the potential for making observations at THz frequencies from ground-based facilities.
Here we describe a novel microarray platform that integrates all functions needed to perform any array‐based experiment in a compact instrument on the researcher’s laboratory benchtop. Oligonucle ...otide probes are synthesized in situ via a light‐ activated process within the channels of a three‐dimensional microfluidic reaction carrier. Arrays can be designed and produced within hours according to the user’s requirements. They are processed in a fully automatic workflow. We have characterized this new platform with regard to dynamic range, discrimination power, reproducibility and accuracy of biological results. The instrument detects sample RNAs present at a frequency of 1:100 000. Detection is quantitative over more than two orders of magnitude. Experiments on four identical arrays with 6398 features each revealed a mean coefficient of variation (CV) value of 0.09 for the 6398 unprocessed raw intensities indicating high reproducibility. In a more elaborate experiment targeting 1125 yeast genes from an unbiased selection, a mean CV of 0.11 on the fold change level was found. Analyzing the transcriptional response of yeast to osmotic shock, we found that biological data acquired on our platform are in good agreement with data from Affymetrix GeneChips, quantitative real‐time PCR and—albeit somewhat less clearly—to data from spotted cDNA arrays obtained from the literature.
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