A clumpy-cloud photon-dominated regions model of the global far-infrared line emission of the Milky Way

Cubick, M.; Stutzki, J.; Ossenkopf, V.; Krämer, C.; Röllig, M.

doi:10.1051/0004-6361:20079270

Cited by 54 publications

(74 citation statements)

References 66 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…and x(N) = 1.0 × 10 −4 (see also Cubick et al 2008 , Table 3), the model computes the equilibrium chemistry and temperature of the cloud using reaction rates from the UMIST database (Woodall et al 2007). Based on the geometry in Fig.…”

Section: Discussionmentioning

confidence: 99%

Chemical stratification in the Orion Bar: JCMT Spectral Legacy Survey observations

Wiel

Tak

Ossenkopf

et al. 2009

A&A

Self Cite

View full text Add to dashboard Cite

Context. Photon-dominated regions (PDRs) are expected to show a layered structure in molecular abundances and emerging line emission, which is sensitive to the physical structure of the region as well as the UV radiation illuminating it. Aims. We aim to study this layering in the Orion Bar, a prototypical nearby PDR with a favorable edge-on geometry.Methods. We present new maps of 2 × 2 fields at 14 -23 resolution toward the Orion Bar in the SO 8 8 -9 9 , H 2 CO 5 15 -4 14 , 13 CO 3-2, C 2 H 4 9/2 -3 7/2 and 4 7/2 -3 5/2 , C 18 O 2-1 and HCN 3-2 transitions. Results. The data reveal a clear chemical stratification pattern. The C 2 H emission peaks close to the ionization front, followed by H 2 CO and SO, while C 18 O, HCN and 13 CO peak deeper into the cloud. A simple PDR model reproduces the observed stratification, although the SO emission is predicted to peak much deeper into the cloud than observed while the H 2 CO peak is predicted to peak closer to the ionization front than observed. In addition, the predicted SO abundance is higher than observed while the H 2 CO abundance is lower than observed. Conclusions. The discrepancies between the models and observations indicate that more sophisticated models, including production of H 2 CO through grain surface chemistry, are needed to quantitatively match the observations of this region.

show abstract

Section: Discussionmentioning

confidence: 99%

Chemical stratification in the Orion Bar: JCMT Spectral Legacy Survey observations

Wiel

Tak

Ossenkopf

et al. 2009

A&A

Self Cite

View full text Add to dashboard Cite

show abstract

“…We use the KOSMA-τ PDR code (Störzer et al 1996;Röllig et al 2006) 2 to numerically solve the coupled equations of energy balance (heating and cooling), chemical equilibrium, and radiative transfer. The main features of the KOSMA-τ PDR model are: a) spherical model symmetry, i.e finite model clouds; b) modular chemistry, which means, that chemical species can easily be added or removed from the network and the network will rebuild dynamically; c) isotope chemistry including 13 C and 18 O; and d) optimization toward large model grids in parameter space, allowing for example to build up any composition of individual clouds in order to simulate clumpy material (for details see Cubick et al 2008). The KOSMA-τ results can be accessed on-line at: http://www.…”

Section: The Kosma-τ Pdr Modelmentioning

confidence: 99%

Carbon fractionation in photo-dissociation regions

Röllig

Ossenkopf

2013

A&A

Self Cite

View full text Add to dashboard Cite

We upgraded the chemical network from the UMIST Database for Astrochemistry 2006 to include isotopes such as 13 C and 18 O. This includes all corresponding isotopologues, their chemical reactions and the properly scaled reaction rate coefficients. We study the fractionation behavior of astrochemically relevant species over a wide range of model parameters, relevant for modelling of photo-dissociation regions (PDRs). We separately analyze the fractionation of the local abundances, fractionation of the total column densities, and fractionation visible in the emission line ratios. We find that strong C + fractionation is possible in cool C + gas. Optical thickness as well as excitation effects produce intensity ratios between 40 and 400. The fractionation of CO in PDRs is significantly different from the diffuse interstellar medium. PDR model results never show a fractionation ratio of the CO column density larger than the elemental ratio. Isotope-selective photo-dissociation is always dominated by the isotope-selective chemistry in dense PDR gas. The fractionation of C, CH, CH + and HCO + is studied in detail, showing that the fractionation of C, CH and CH + is dominated by the fractionation of their parental species. The light hydrides chemically derive from C + , and, consequently, their fractionation state is coupled to that of C + . The fractionation of C is a mixed case depending on whether formation from CO or HCO + dominates. Ratios of the emission lines of [C ii], [C i], 13 CO, and H 13 CO + provide individual diagnostics to the fractionation status of C + , C, and CO.

show abstract

“…Israel & Baas (2003) give comparable central masses of IC 342 of 5−7 × 10 6 M , given the uncertainties in the relative abundance of ionized carbon, filling factors, and distance. To confine the local gas parameters we used the KOSMA-τ PDR model code (Störzer et al 1996;Röllig et al 2006) to model the emission of an ensemble of clumpy PDRs in a beam of 15 (Cubick et al 2008). We fitted the model to the absolute intensities therefore making the total model gas mass sensitive to the distance of the PDR.…”

Section: Discussionmentioning

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

A clumpy-cloud photon-dominated regions model of the global far-infrared line emission of the Milky Way

Cited by 54 publications

References 66 publications

Chemical stratification in the Orion Bar: JCMT Spectral Legacy Survey observations

Chemical stratification in the Orion Bar: JCMT Spectral Legacy Survey observations

Carbon fractionation in photo-dissociation regions

[CII] gas in IC 342

Contact Info

Product

Resources

About