GREAT/SOFIA atmospheric calibration

Guan, Xin; Stutzki, J.; Graf, U. U.; Güsten, R.; Okada, Yoko; Requeña-Torres, M. A.; Simon, R.; Wiesemeyer, H.

doi:10.1051/0004-6361/201218925

Cited by 96 publications

(105 citation statements)

References 16 publications

Supporting

Mentioning

103

Contrasting

Order By: Relevance

“…To improve the signal-to-noise ratio (S/N) the [C ii] and [N ii] data were smoothed to a velocity resolution of 1.20 km s −1 and 1.57 km s −1 per channel, respectively. The spectra were calibrated using the procedure outlined in Guan et al (2012).…”

Section: Sofia [C Ii] and [N Ii] Datamentioning

confidence: 99%

“…Moreover, the position switching observing mode made the presence of this feature a significant issue that needed to be addressed in the data reduction. The standard atmospheric calibration was not sufficient to produce a satisfactory fit to the water feature, and we had to use a set of non-standard parameters in the atmospheric model (Guan et al 2012) to fit the width and the peak of the water line. The main change to the normal procedure was to reduce the contribution from the Dry atmosphere in steps, allowing the Wet part (water) to fit the atmospheric feature.…”

Section: Sofia [C Ii] and [N Ii] Datamentioning

confidence: 99%

See 1 more Smart Citation

Ionized gas at the edge of the central molecular zone

Langer

Goldsmith

Pineda

et al. 2015

A&A

Self Cite

View full text Add to dashboard Cite

Context. The edge of the central molecular zone (CMZ) is the location where massive dense molecular clouds with large internal velocity dispersions transition to the surrounding more quiescent and lower CO emissivity region of the Galaxy. Little is known about the ionized gas surrounding the molecular clouds and in the transition region. Aims. We determine the properties of the ionized gas at the edge of the CMZ near Sgr E using observations of N + and C + .Methods. We observed a small portion of the edge of the CMZ near Sgr E with spectrally resolved [C ii] 158 μm and [N ii] 205 μm fine structure lines at six positions with the GREAT instrument on SOFIA and in [C ii] using Herschel HIFI on-the-fly strip maps. We use the [N ii] spectra along with a radiative transfer model to calculate the electron density of the gas and the [C ii] maps to illuminate the morphology of the ionized gas and model the column density of CO-dark H 2 .Results. We detect two [C ii] and [N ii] velocity components, one along the line of sight to a CO molecular cloud at −207 km s −1 associated with Sgr E and the other at −174 km s −1 outside the edge of another CO cloud. From the [N ii] emission we find that the average electron density is in the range of ∼5 to 21 cm −3 for these features. This electron density is much higher than that of the disk's warm ionized medium, but is consistent with densities determined for bright diffuse H ii nebula. The column density of the CO-dark H 2 layer in the −207 km s −1 cloud is ∼1−2× 10 21 cm −2 in agreement with theoretical models. The CMZ extends further out in Galactic radius by ∼7 to 14 pc in ionized gas than it does in molecular gas traced by CO. Conclusions. The edge of the CMZ likely contains dense hot ionized gas surrounding the neutral molecular material. The high fractional abundance of N + and high electron density require an intense EUV field with a photon flux of order 10 6 to 10 7 photons cm −2 s −1 , and/or efficient proton charge exchange with nitrogen, at temperatures of order 10 4 K, and/or a large flux of X-rays. Sgr E is a region of massive star formation as indicated by the presence of numerous compact H ii regions. The massive stars are potential sources of the EUV radiation that ionizes and heat the gas. In addition, X-ray sources and the diffuse X-ray emission in the CMZ are candidates for ionizing nitrogen.

show abstract

Section: Sofia [C Ii] and [N Ii] Datamentioning

confidence: 99%

Section: Sofia [C Ii] and [N Ii] Datamentioning

confidence: 99%

Ionized gas at the edge of the central molecular zone

Langer

Goldsmith

Pineda

et al. 2015

A&A

Self Cite

View full text Add to dashboard Cite

show abstract

“…The data were calibrated using standard procedures based on the KOSMA/GREAT calibrator (Guan et al 2012), for the data analysis the GILDAS 2 software was used. The forward efficiency was set to 95% and the data were converted to a RayleighJeans equivalent T mb,RJ scale using a beam efficiency of 51% for the L2 and 58% for the M band, respectively.…”

Section: Observation and Data Reductionmentioning

confidence: 99%

SOFIA observations of far-infrared hydroxyl emission toward classical ultracompact HII/OH maser regions

Csengeri

Menten

Wyrowski

et al. 2012

A&A

Self Cite

View full text Add to dashboard Cite

Context. The hydroxyl radical (OH) is found in various environments within the interstellar medium (ISM) of the Milky Way and external galaxies, mostly either in diffuse interstellar clouds or in the warm, dense environments of newly formed low-mass and high-mass stars, i.e., in the dense shells of compact and ultracompact HII regions (UCHIIRs). Until today, most studies of interstellar OH involved the molecule's radio wavelength hyperfine structure (hfs) transitions. These lines are generally not in local thermodynamical equilibrium (LTE) and either masing or over-cooling complicates their interpretation. In the past, observations of transitions between different rotational levels of OH, which are at far-infrared (FIR) wavelengths, have suffered from limited spectral and angular resolution. Since these lines have critical densities many orders of magnitude higher than the radio wavelength ground state hfs lines and are emitted from levels with more than 100 K above the ground state, when observed in emission, they probe very dense and warm material. Aims. We aim to probe the warm and dense molecular material surrounding the UCHIIR/OH maser sources W3(OH), G10.62−0.39 and NGC 7538 IRS1 by studying the 2 Π 1/2 , J = 3/2−1/2 rotational transition of OH in emission and, toward the last source also the molecule's 2 Π 3/2 , J = 5/2−3/2 ground-state transition in absorption. Methods. We used the Stratospheric Observatory For Infrared Astronomy (SOFIA) to observe these OH lines, which are near 1.84 THz (163 μm) and 2.51 THz (119.3 μm), with high angular (∼16 /11 ) and spectral resolution (better than 1 km s −1 ). Results. We clearly detect the OH lines, some of which are blended with each other. Employing non-LTE radiative transfer calculations we predict line intensities using models of a low OH abundance envelope versus a compact, high-abundance source corresponding to the origin of the radio OH lines. From the observed velocities and line-widths we can place constraints on the origin of the emission, and with detailed modeling we show for instance that the OH emission of W3(OH) comes from the UCHIIR and not from the envelope of the nearby hot-core. Conclusions. The FIR lines of the OH molecule provide important information on the density and temperature structure of UCHIIRs. Taking a low-abundance envelope component is not sufficient to reproduce the spectra for W3(OH) and G10.62−0.39, a compact, high OH column density source -corresponding to the OH radio emitting sources is definitively required.

show abstract

“…Calibration was performed with the standard pipeline (Guan et al 2012). Using the beam efficiency η c ≈ 0.51 and the forward efficiency (η f ) of 0.95 (Heyminck et al 2012), we converted all data to line brightness temperature scale, T B = η f × T * A /η c .…”

Section: Observationsmentioning

confidence: 99%

[CII] gas in IC 342

Röllig

Simon

Güsten

et al. 2012

A&A

Self Cite

View full text Add to dashboard Cite

We used the dual-band receiver GREAT on board the SOFIA airborne telescope to perform observations of the [C II] 158 μm finestructure line at the postitions of two giant molecular clouds (GMC) in the center of IC 342 (GMCs C and E) and compared the spectra with corresponding ground-based data for low-and mid-J CO and [C I]. We performed model calculations assuming a clumpy photodissociation region (PDR) environment using the KOSMA-τ PDR model code to derive physical parameters of the local medium. The [C II] 158 μm emission resembles the spectral signature of ground-based atomic and molecular lines, which indicates a common origin. The emission from GMC E can be decomposed into a cool, molecular component with weak far-ultraviolet (FUV) fields and low, mean densities of 10 3 cm −3 and a strongly excited starburst/PDR region with higher densities of 10 4 cm −3 and FUV intensities of 250-300 Draine fields. The emission from GMC C is consistent with gas densities of 5000 cm −3 , FUV intensities of a few Draine fields and total gas masses of 20 × 10 6 M . The high spectral resolution of the GREAT receiver allowed us to decompose the [C II] emission of the GMC E into a strongly excited gas component resembling a PDR/starburst environment and a quieter, less excited gas component and to analyze the different components within a single beam individually.

show abstract

GREAT/SOFIA atmospheric calibration

Cited by 96 publications

References 16 publications

Ionized gas at the edge of the central molecular zone

Ionized gas at the edge of the central molecular zone

SOFIA observations of far-infrared hydroxyl emission toward classical ultracompact HII/OH maser regions

[CII] gas in IC 342

Contact Info

Product

Resources

About