<i>Herschel </i>survey and modelling of externally-illuminated photoevaporating protoplanetary disks

Champion, Jason; Berné, O.; Vicente, S.; Kamp, I.; Petit, Franck; Joblin, C.; Goicoechea, J. R.

doi:10.1051/0004-6361/201629404

Cited by 22 publications

(21 citation statements)

References 72 publications

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“…In the atomic layer of the high thermal pressure model by Joblin et al (2018), FUV-pumped H 2 followed by collisional deexcitation is an important heating process, but its rate is three times lower than the photoelectric heating rate. Only in very bright and dense PDRs can FUV-pumped H 2 followed by collisional deexcitation dominate (e.g., Burton et al 1990;Champion et al 2017). In the successive layers, as soon as H 2 is self-shielding, collisional deexcitation of H 2 leads to cooling and the photoelectric heating dominates widely.…”

Section: Heating Processesmentioning

confidence: 99%

High-J CO emission spatial distribution and excitation in the Orion Bar

Parikka

Habart

Bernard─Salas

et al. 2018

A&A

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Context. With Herschel, we can for the first time observe a wealth of high-J CO lines in the interstellar medium with a high angular resolution. These lines are specifically useful for tracing the warm and dense gas and are therefore very appropriate for a study of strongly irradiated dense photodissocation regions (PDRs). Aims. We characterize the morphology of CO J = 19-18 emission and study the high-J CO excitation in a highly UV-irradiated prototypical PDR, the Orion Bar. Methods. We used fully sampled maps of CO J = 19-18 emission with the Photoconductor Array Camera and Spectrometer (PACS) on board the Herschel Space Observatory over an area of ∼110 × 110 with an angular resolution of 9 . We studied the morphology of this high-J CO line in the Orion Bar and in the region in front and behind the Bar, and compared it with lower-J lines of CO from J = 5-4 to J = 13-12 and 13 CO from J = 5-4 to J = 11-10 emission observed with the Herschel Spectral and Photometric Imaging Receiver (SPIRE). In addition, we compared the high-J CO to polycyclic aromatic hydrocarbon (PAH) emission and vibrationally excited H 2 . We used the CO and 13 CO observations and the RADEX model to derive the physical conditions in the warm molecular gas layers. Results. The CO J = 19-18 line is detected unambiguously everywhere in the observed region, in the Bar, and in front and behind of it. In the Bar, the most striking features are several knots of enhanced emission that probably result from column and/or volume density enhancements. The corresponding structures are most likely even smaller than what PACS is able to resolve. The high-J CO line mostly arises from the warm edge of the Orion Bar PDR, while the lower-J lines arise from a colder region farther inside the molecular cloud. Even if it is slightly shifted farther into the PDR, the high-J CO emission peaks are very close to the H/H 2 dissociation front, as traced by the peaks of H 2 vibrational emission. Our results also suggest that the high-J CO emitting gas is mainly excited by photoelectric heating. The CO J = 19-18/J = 12-11 line intensity ratio peaks in front of the CO J = 19-18 emission between the dissociation and ionization fronts, where the PAH emission also peak. A warm or hot molecular gas could thus be present in the atomic region where the intense UV radiation is mostly unshielded. In agreement with recent ALMA detections, low column densities of hot molecular gas seem to exist between the ionization and dissociation fronts. As found in other studies, the best fit with RADEX modeling for beam-averaged physical conditions is for a density of 10 6 cm −3 and a high thermal pressure (P/k = n H × T ) of ∼1-2 × 10 8 K cm −3 . Conclusions. The high-J CO emission is concentrated close to the dissociation front in the Orion Bar. Hot CO may also lie in the atomic PDR between the ionization and dissociation fronts, which is consistent with the dynamical and photoevaporation effects.

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Section: Heating Processesmentioning

confidence: 99%

High-J CO emission spatial distribution and excitation in the Orion Bar

Parikka

Habart

Bernard─Salas

et al. 2018

A&A

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“…This does however mean that we cannot model things like infrared emission, to which the proplyd envelope makes an important contribution (e.g. Champion et al 2017).…”

Section: Disc Density Distribution and Dust Propertiesmentioning

confidence: 99%

“…Cleeves et al 2013;Cleeves 2016) rather than the dust radiative equilibrium temperature. Champion et al (2017) undertook 1D PDR models of proplyds using the code, however in those they compute the dust temperature in the surface layers and the disc temperature is assumed to be uniformly 19.5 K. Robberto et al (2002) also took a similar approach semi-analytically, considering the proplyd to be a spherical system with non-spherical external irradiation and internal heating by the host star, but again the focus was on the layers external to the circumstellar disc and their infrared emission. Sellek et al (2020) studied the dynamical evolution of dust in discs with an external photoevaporative wind.…”

Section: Introductionmentioning

confidence: 99%

Warm millimetre dust in protoplanetary discs near massive stars

Haworth

2021

Preprint

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Dust plays a key role in the formation of planets and its emission also provides one of our most accessible views of protoplanetary discs. If set by radiative equilibrium with the central star, the temperature of dust in the disc plateaus at around 10 − 20 K in the outer regions. However sufficiently nearby massive stars can heat the outer disc to substantially higher temperatures.In this paper we study the radiative equilibrium temperature of discs in the presence of massive external sources and gauge the effect that it has on millimetre dust mass estimates. Since millimetre grains are not entrained in any wind we focus on geometrically simple 2Daxisymmetric disc models using radiative transfer calculations with both the host star and an external source. Recent surveys have searched for evidence of massive stars influencing disc evolution using disc properties as a function of projected separation. In assuming a disc temperature of 20 K for a disc a distance 𝐷 from a strong radiation source, disc masses are overestimated by a factor that scales with 𝐷 −1/2 interior to the separation that external heating becomes important. This could significantly alter dust mass estimates of discs in close proximity to 𝜃 1 C in the Orion Nebular Cluster. We also make an initial assessment of the effect upon snow lines. Within a parsec of an O star like 𝜃 1 C a CO snow line no longer exists, though the water snow line is virtually unaffected except for very close separations of ≤ 0.01 pc.

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“…Transition regions between molecular clouds and ionized regions (H II) are referred to as PDRs (Tielens & Hollenbach 1985). This concept of PDRs is applicable to many regions in the universe, such as the surface of protoplanetary disks (Adams et al 2004;Gorti & Hollenbach 2008;Champion et al 2017), as well as planetary nebulae (see, e.g., Bernard-Salas & Tielens 2005;Cox et al 2016). More broadly, star-forming and planetforming regions can be studied as PDRs (see, e.g., Tielens 2005;Goicoechea et al 2016;Joblin et al 2018), or even starburst galaxies (Fuente et al 2005).…”

Section: Photodissociation Regionsmentioning

confidence: 99%

Simulated JWST Data Sets for Multispectral and Hyperspectral Image Fusion

Guilloteau

Oberlin

Berné

et al. 2020

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The James Webb Space Telescope (JWST) will provide multispectral and hyperspectral infrared images of a large number of astrophysical scenes. Multispectral images will have the highest angular resolution, while hyperspectral images (e.g., with integral field unit spectrometers) will provide the best spectral resolution. This paper aims at providing a comprehensive framework to generate an astrophysical scene and to simulate realistic hyperspectral and multispectral data acquired by two JWST instruments, namely, NIRCam Imager and NIRSpec IFU. We want to show that this simulation framework can be resorted to assess the benefits of fusing these images to recover an image of high spatial and spectral resolutions. To do so, we make a synthetic scene associated with a canonical infrared source, the Orion Bar. We develop forward models including corresponding noises for the two JWST instruments based on their physical features. JWST observations are then simulated by applying the forward models to the aforementioned synthetic scene. We test a dedicated fusion algorithm we developed on these simulated observations. We show that the fusion process reconstructs the high spatio-spectral resolution scene with a good accuracy on most areas, and we identify some limitations of the method to be tackled in future works. The synthetic scene and observations presented in the paper can be used, for instance, to evaluate instrument models, pipelines, or more sophisticated algorithms dedicated to JWST data analysis. Besides, fusion methods such as the one presented in this paper are shown to be promising tools to fully exploit the unprecedented capabilities of the JWST.

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Herschel survey and modelling of externally-illuminated photoevaporating protoplanetary disks

Cited by 22 publications

References 72 publications

High-J CO emission spatial distribution and excitation in the Orion Bar

High-J CO emission spatial distribution and excitation in the Orion Bar

Warm millimetre dust in protoplanetary discs near massive stars

Simulated JWST Data Sets for Multispectral and Hyperspectral Image Fusion

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