Photoevaporation Flows in Blister H<scp>ii</scp>Regions. I. Smooth Ionization Fronts and Application to the Orion Nebula

Henney, W. J.; Arthur, S. J.; García-Díaz, Ma. T.

doi:10.1086/430593

Cited by 56 publications

(93 citation statements)

References 59 publications

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“…This additional contribution to the overall kinematical disorder is not surprising since it was already established that velocity gradients alone, in ordered flows, cannot reproduce the typical non‐thermal linewidths observed (e.g. Henney et al 2005; García‐Díaz et al 2008).…”

Section: Discussionmentioning

confidence: 80%

Origins and interpretation of the tridimensional kinematical disorder in H ii regions

Lagrois¹,

Joncas²,

Drissen³

et al. 2011

Monthly Notices of the Royal Astronomical Society

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Classical spectro‐interferometry allowed us to obtain a large‐scale Hα survey of the central portions of the late‐type Sc galaxy M33. A series of 28 small‐to‐intermediate size H ii regions, kinematically dominated by Champagne flows, quiescent wind effects, potentially embedded globules and filaments, and photoablation flows, are identified and delimited. The main goal of this work is to compare and check for an eventual correlation between two statistical parameters obtained for each targeted object, namely the standard deviation of the velocity centroid distribution (σc) and the mean non‐thermal linewidth (〈σi, kin〉). These parameters, by definition, allow for a comparison between the kinematical disorder on the plane of the sky and along the line‐of‐sight. The slope of the σc versus 〈σi, kin〉 diagram, approaching unity, indicates that variations of the kinematical disorder are roughly equivalent on all spatial axes. H ii regions should therefore be regarded as strictly tridimensional objects. We attempt to reproduce the observed relation using non‐turbulent, hydrodynamical models of expanding H ii regions. Simulations indicate that the two parameters are generally correlated, as observed, in a monotonically increasing trend although the areas populated in the theoretical σc−〈σi, kin〉 space diagram do not match the observations. A certain reconciliation between models and observations is reached if one allows turbulent motions to have a sizeable kinematical impact in the ionized medium, i.e. confirming that all H ii regions in the survey have a strong turbulent component. This could apply to all optical nebulae hence in agreement with high Reynolds numbers typically found in the ionized interstellar medium. A photometric investigation of bright stars found in our nebula sample indicates that Champagne‐like objects coexist with wind‐blown bubbles in the σc versus 〈σi, kin〉 diagram. This suggests that objects characterized by multiple Champagne flows and those that are wind‐dominated can develop turbulent velocity motions of comparable amplitudes.

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Section: Discussionmentioning

confidence: 80%

Origins and interpretation of the tridimensional kinematical disorder in H ii regions

Lagrois¹,

Joncas²,

Drissen³

et al. 2011

Monthly Notices of the Royal Astronomical Society

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“…From the ratio of the surface brightness in the radio continuum with that expected from ionization by θ 1 Ori C, both Wen & O'Dell (1995) and Henney et al (2005) derived a model of a concave surface with ridges (e.g. the one producing the Bright Bar).…”

Section: Location Of the Samples Along The Line Of Sightmentioning

confidence: 99%

Which Stars Are Ionizing the Orion Nebula?

O’Dell

Kollatschny

Ferland

2017

ApJ

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The common assumption that θ 1 Ori C is the dominant ionizing source for the Orion Nebula is critically examined. This assumption underlies much of the existing analysis of the nebula. In this paper we establish through comparison of the relative strengths of emission lines with expectations from Cloudy models and through the direction of the bright edges of proplyds that θ 2 Ori A, which lies beyond the Bright Bar, also plays an important role. θ 1 Ori C does dominate ionization in the inner part of the Orion Nebula, but outside of the Bright Bar as far as the southeast boundary of the Extended Orion Nebula, θ 2 Ori A is the dominant source. In addition to identifying the ionizing star in sample regions, we were able to locate those portions of the nebula in 3-D. This analysis illustrates the power of MUSE spectral imaging observations in identifying sources of ionization in extended regions.

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“…1 and above, the density contrast between the tenuous H II region and the dense A65, page 4 of 16 molecular cloud L1630 sets up a champagne flow streaming into the H II region (Tenorio-Tagle 1979). Strictly speaking, on a large scale the surface of the L1630 cloud will be convex, which will lead to a photo-evaporation flow following the nomenclature described in Henney et al (2005). However, as the radius of curvature of the ionization front is much larger than the distance to the ionizing source and as we are focussing on the material passing close to the star (which will originate from a small part of L1630), the analysis of Henney et al (2005) suggest that we can approximate the structure of the flow as a champagne flow in a plane-parallel geometry.…”

Section: Photo-evaporation Flowmentioning

confidence: 99%

Blowing in the wind: The dust wave aroundσOrionis AB

Ochsendorf

Cox

Krijt

et al. 2014

A&A

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Observations obtained with the Spitzer Space Telescope and the WISE satellite have revealed a prominent arc-like structure at 50 ( 0.1 pc) from the O9.5V/B0.5V system σ Ori AB. We measure a total dust mass of 2.3±1.5×10−5 M . The derived dust-to-gas mass ratio is 0.29 ± 0.20. We attribute this dust structure to the interaction of radiation pressure from the star with dust carried along by the IC 434 photo-evaporative flow of ionized gas from the dark cloud L1630. We have developed a quantitative model for the interaction of a dusty ionized flow with nearby (massive) stars where radiation pressure stalls dust, piling it up at an appreciable distance (>0.1 pc), and force it to flow around the star. The model demonstrates that for the conditions in IC 434, the gas will decouple from the dust and will keep its original flow lines. Hence, we argue that this dust structure is the first example of a dust wave created by a massive star moving through the interstellar medium. Our model shows that for higher gas densities, coupling is more efficient and a bow wave will form, containing both dust and gas. Our model describes the physics of dust waves and bow waves and quantitatively reproduces the optical depth profile at 70 µm. Dust waves (and bow waves) stratify dust grains according to their radiation pressure opacity, which reflects the size distribution and composition of the grain material. It is found that in the particular case of σ Ori AB, dust is able to survive inside the ionized region. Comparison of our model results with observations implies that dust-gas coupling through Coulomb interaction is less important than previously thought, challenging our understanding of grain dynamics in hot, ionized regions of space. We describe the difference between dust (and bow) waves and classical bow shocks created by the interaction of a stellar wind with the interstellar medium. The results show that for late O-type stars with weak stellar winds, the stand-off distance of the resulting bow shock is very close to the star, well within the location of the dust wave. In general, we conclude that dust waves and bow waves should be common around stars showing the weak-wind phenomenon, i.e., stars with log(L/L ) < 5.2, and that these structures are best observed at mid-IR to FIR wavelengths, depending on the stellar spectral type. In particular, dust waves and bow waves are most efficiently formed around weak-wind stars moving through a high density medium. Moreover, they provide a unique opportunity to study the direct interaction between a (massive) star and its immediate surroundings.

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Photoevaporation Flows in Blister HiiRegions. I. Smooth Ionization Fronts and Application to the Orion Nebula

Cited by 56 publications

References 59 publications

Origins and interpretation of the tridimensional kinematical disorder in H ii regions

Origins and interpretation of the tridimensional kinematical disorder in H ii regions

Which Stars Are Ionizing the Orion Nebula?

Blowing in the wind: The dust wave aroundσOrionis AB

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