4.7-THz Local Oscillator for the GREAT Heterodyne Spectrometer on SOFIA

Richter, Heiko; Wienold, Martin; Schrottke, L.; Biermann, K.; Grahn, H. T.; Hübers, Heinz‐Wilhelm

doi:10.1109/tthz.2015.2442155

Cited by 99 publications

(75 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For the tuning to the [OI] 63 µm line, a quantum-cascade laser was used as local oscillator (Richter et al 2015). At the Cep E-mm position, the zerolevel width observed for example by Lefloch et al (2011) For OH and CO observations of all three positions, the lower frequency, L2 channel was connected to 4 GHz wide digital back-ends described in Risacher et al (2016), providing respective spectral resolutions of 1.00 and 0.99 km s −1 (given in Table 2).…”

Section: Observationsmentioning

confidence: 99%

Nature of shocks revealed by SOFIA OI observations in the Cepheus E protostellar outflow

Gusdorf

Anderl

Leflóch

et al. 2017

A&A

View full text Add to dashboard Cite

Context. Protostellar jets and outflows are key features of the star-formation process, and primary processes of the feedback of young stars on the interstellar medium. Understanding the underlying shocks is necessary to explain how jet and outflow systems are launched, and to quantify their chemical and energetic impacts on the surrounding medium. Aims. We performed a high-spectral resolution study of the [OI] 63 µm emission in the outflow of the intermediate-mass Class 0 protostar Cep E-mm. The goal is to determine the structure of the outflow, to constrain the chemical conditions in the various components, and to understand the nature of the underlying shocks, thus probing the origin of the mass-loss phenomenon.Methods. We present observations of the O i 3 P 1 → 3 P 2 , OH between 2 Π 1/2 J = 3/2 and J = 1/2 at 1837.8 GHz, and CO (16-15) lines with the GREAT receiver onboard SOFIA towards three positions in the Cep E protostellar outflow: Cep E-mm (the driving protostar), Cep E-BI (in the southern lobe), and Cep E-BII (the terminal position in the southern lobe). Results. The line is detected at all three positions. The [OI] 63 µm line is detected in Cep E-BI and BII, whereas the OH line is not detected. In Cep E-BII, we identify three kinematical components in O i and CO. These were already detected in CO transitions and relate to spatial components: the jet, the HH377 terminal bow-shock, and the outflow cavity. We measure line temperature and line integrated intensity ratios for all components. The O i column density is higher in the outflow cavity than in the jet, which itself is higher than in the terminal shock. The terminal shock is the region where the abundance ratio of O i to CO is the lowest (about 0.2), whereas the jet component is atomic (N(O i) / N(CO) ∼ 2.7). In the jet, we compare the [OI] 63 µm observations with shock models that successfully fit the integrated intensity of 10 CO lines. We find that these models most likely do not fit the [OI] 63 µm data.Conclusions. The high intensity of O i emission points towards the propagation of additional dissociative or alternative FUV-irradiated shocks, where the illumination comes from the shock itself. A picture emerges from the sample of low-to-high mass protostellar outflows, where similar observations have been performed, with the effects of illumination increasing with the mass of the protostar. These findings need confirmation with more observational constraints and a larger sample.

show abstract

Section: Observationsmentioning

confidence: 99%

Nature of shocks revealed by SOFIA OI observations in the Cepheus E protostellar outflow

Gusdorf

Anderl

Leflóch

et al. 2017

A&A

View full text Add to dashboard Cite

show abstract

“…With the successful commissioning of GREAT's H channel in May 2014, the fine-structure line of atomic oxygen became accessible for spectrally resolved studies. A novel NbN HEB waveguide mixer (Büchel et al 2015) was pumped by a quantum cascade laser as local oscillator (Richter et al 2015); the Doppler correction was applied offline. The southern deployment flights offered excellent observing conditions.…”

Section: Terahertz Spectroscopy Of Oh and Oi With Greatmentioning

confidence: 99%

Far-infrared study of tracers of oxygen chemistry in diffuse clouds

Wiesemeyer

Güsten

Heyminck

et al. 2015

A&A

View full text Add to dashboard Cite

Context. The chemistry of the diffuse interstellar medium rests upon three pillars: exothermic ion-neutral reactions ("cold chemistry"), endothermic neutral-neutral reactions with significant activation barriers ("warm chemistry"), and reactions on the surfaces of dust grains. While warm chemistry becomes important in the shocks associated with turbulent dissipation regions, the main path for the formation of interstellar OH and H 2 O is that of cold chemistry. Aims. The aim of this study is to observationally confirm the association of atomic oxygen with both atomic and molecular gas phases, and to understand the measured abundances of OH and OH + as a function of the available reservoir of H 2 . Methods. We obtained absorption spectra of the ground states of OH, OH + and O i with high-velocity resolution, with GREAT onboard SOFIA, and with the THz receiver at the APEX. We analyzed them along with ancillary spectra of HF and CH from HIFI. To deconvolve them from the hyperfine structure and to separate the blend that is due to various velocity components on the sightline, we fit model spectra consisting of an appropriate number of Gaussian profiles using a method combining simulated annealing with downhill simplex minimization. Together with HF and/or CH as a surrogate for H 2 , and H i λ21 cm data, the molecular hydrogen Results. The column density of O i is correlated at a high significance with the amount of available molecular and atomic hydrogen, with an atomic oxygen abundance of 3 × 10 −4 relative to H nuclei. While the velocities of the absorption features of OH and OH + are loosely correlated and reflect the spiral arm crossings on the sightline, upon closer inspection they display an anticorrespondence. The arm-to-interarm density contrast is found to be higher in OH than in OH + . While both species can coexist, with a higher abundance in OH than in OH + , the latter is found less frequently in absence of OH than the other way around, which is a direct consequence of the rapid destruction of OH + by dissociative recombination when not enough H 2 is available. This conjecture has been substantiated by a comparison between the OH/OH + ratio with f, showing a clear correlation. The hydrogen abstraction reaction chain+ is confirmed as the pathway for the production of OH and H 2 O. Our estimate of the branching ratio of the dissociative recombination of H 3 O + to OH and H 2 O is confined within the interval of 84 to 91%, which matches laboratory measurements (74 to 83%). -A correlation between the linewidths and column densities of OH + features is found to be significant with a false-alarm probability below 5%. Such a correlation is predicted by models of interstellar MHD turbulence. For OH the same correlation is found to be insignificant because there are more narrow absorption features. Conclusions. While it is difficult to assess the contributions of warm neutral-neutral chemistry to the observed abundances, it seems fair to conclude that the predictions of cold ion-neutral chemistry match t...

show abstract

“…3,[9][10][11] Initial works in this research field have been carried out exploiting either first order or third order distributed feedback (DFB) cavities, [12][13][14] which has also lead to device that has been applied in astrophysics measurements. 15 However, compared to these devices, we propose an approach that has the advantage of avoiding any risky cleaving, preserving a surface emission with a single-lobe far field pattern, peak output power of almost 2 mW, low dissipation and single modality with high reliability on the yield of the fabrication process.…”

mentioning

confidence: 99%

A patch-array antenna single-mode low electrical dissipation continuous wave terahertz quantum cascade laser

Bosco

Bonzon

Ohtani

et al. 2016

Applied Physics Letters

View full text Add to dashboard Cite

We introduce a double metal terahertz quantum cascade laser meant for astrophysical heterodyne measurements. The laser ridge is embedded in benzocyclobutene, and the device exhibits single mode, continuous wave operation around 4.745 THz with a peak power of almost 1.8 mW at 10 K and a power consumption of ≈1.6 W. Moreover, thanks to the integration of a top metal contact with a patch array antenna for light out-coupling the beam of the emitted light has a low-divergence single-lobe profile and an FWHM of ≈30°.

show abstract

4.7-THz Local Oscillator for the GREAT Heterodyne Spectrometer on SOFIA

Cited by 99 publications

References 23 publications

Nature of shocks revealed by SOFIA OI observations in the Cepheus E protostellar outflow

Nature of shocks revealed by SOFIA OI observations in the Cepheus E protostellar outflow

Far-infrared study of tracers of oxygen chemistry in diffuse clouds

A patch-array antenna single-mode low electrical dissipation continuous wave terahertz quantum cascade laser

Contact Info

Product

Resources

About