OH+ Formation in the Low-temperature O+(4S) + H2 Reaction

Kovalenko, Artem; Tran, Thuy Dung; Rednyk, Serhiy; Roučka, Štěpán; Dohnal, Petr; Plašil, R.; Gerlich, D.; Glosı́k, J.

doi:10.3847/1538-4357/aab106

Cited by 14 publications

(8 citation statements)

References 47 publications

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“…Four of our sightlines have data for T 01 (Rachford et al 2002(Rachford et al , 2009Sheffer et al 2008) which range from 59 K for HD 41117 and 101 K for HD 185418, and these correspond to cosmic ray ionization rates which may vary by about a factor of four. Moreover, reactions between molecular hydrogen and O + /OH + have also been recently studied in ion trap experiments at low temperatures (Kovalenko et al 2018;Tran et al 2018). The derived rate coefficients corresponding to k 3 and k 4 are within the same order of magnitude as with previous values, which give differences in the calculated ζ p by at most 20 percent.…”

Section: Discussionsupporting

confidence: 63%

The EDIBLES survey IV. Cosmic ray ionization rates in diffuse clouds from near-ultraviolet observations of interstellar OH$^+$

Bacalla,

Linnartz,

Cox

et al. 2018

Preprint

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We report cosmic ray ionization rates towards ten reddened stars studied within the framework of the EDIBLES (ESO Diffuse Interstellar Bands Large Exploration Survey) program, using the VLT-UVES. For each sightline, between 2 and 10 individual rotational lines of OH + have been detected in its (0,0) and (1,0) A 3 Π − X 3 Σ − electronic band system. This allows constraining of OH + column densities towards different objects. Results are also presented for 28 additional sightlines for which only one or rather weak signals are found. An analysis of these data makes it possible to derive the primary cosmic ray ionization rate ζ p in the targeted diffuse interstellar clouds. For the ten selected targets, we obtain a range of values for ζ p equal to (3.9 − 16.4) × 10 −16 s −1 . These values are higher than the numbers derived in previous detections of interstellar OH + in the far-infrared / sub-millimeter-wave regions and in other near-ultraviolet studies. This difference is a result of using new OH + oscillator strength values and a more complete picture of all relevant OH + formation and destruction routes (including the effect of proton recombinations on PAHs), and the relatively high N(OH + ) seen toward those ten targets.

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Section: Discussionsupporting

confidence: 63%

The EDIBLES survey IV. Cosmic ray ionization rates in diffuse clouds from near-ultraviolet observations of interstellar OH$^+$

Bacalla,

Linnartz,

Cox

et al. 2018

Preprint

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“…More recently, we updated the photorates to those from Heays et al ( 2017) and adopted the exponential integral formalism for the depth dependence due to dust. Additional changes to the chemical rates include oxygen chemistry rates from Kovalenko et al (2018) and Tran et al (2018), and carbon chemistry rates from Dagdigian (2019). In order to compute synthetic line emission intensities we assume a Doppler line width of ∆v = 1.5 km s −1 .…”

Section: Edge-on Pdr Modelsmentioning

confidence: 99%

[CII] 158$μ$m emission from Orion A. II. Photodissociation region physics

Pabst,

Goicoechea,

Hacar

et al. 2021

Preprint

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Context. The [C ii] 158 µm fine-structure line is the dominant cooling line of moderate-density photodissociation regions (PDRs) illuminated by moderately bright far-ultraviolet (FUV) radiation fields. This makes this line a prime diagnostic for extended regions illuminated by massive stars. Aims. We aim to understand the origin of [C ii] emission and its relation to other tracers of gas and dust in PDRs. One focus is a study of the heating efficiency of interstellar gas as traced by the [C ii] line to test models of the photoelectric heating of neutral gas by polycyclic aromatic hydrocarbon (PAH) molecules and very small grains. Methods. We make use of a one-square-degree map of velocity-resolved [C ii] line emission toward the Orion Nebula complex, and split this out into the individual spatial components, the expanding Veil Shell, the surface of OMC4, and the PDRs associated with the compact H ii region of M43 and the reflection nebula NGC 1977. We employed Herschel far-infrared photometric images to determine dust properties. Moreover, we compared with Spitzer midinfrared photometry to trace hot dust and large molecules, and velocity-resolved IRAM 30m CO(2-1) observations of the molecular gas.Results. The [C ii] intensity is tightly correlated with PAH emission in the IRAC 8 µm band and far-infrared emission from warm dust, with small variations between the four studied subregions (Veil Shell, OMC4, M43, and NGC 1977). The correlation between [C ii] and CO(2-1) is very different in the four subregions and is very sensitive to the detailed geometry of the respective regions. Constant-density PDR models are able to reproduce the observed [C ii], CO(2-1), and integrated far-infrared (FIR) intensities. The physical conditions in the Veil Shell of the Orion Nebula, M43, and NGC 1977 reveal a constant ratio of thermal pressure p th over incident FUV radiation field measured by G0. We observe strong variations in the photoelectric heating efficiency in the Veil Shell behind the Orion Bar and these variations are seemingly not related to the spectral properties of the PAHs. Conclusions. The [C ii] emission from the Orion Nebula complex stems mainly from moderately illuminated PDR surfaces. The correlations of the different tracers ([C ii], FIR, CO, 70 µm, and 8 µm emission) show small variations that are not yet understood. Future observations with the James Webb Space Telescope can shine light on the PAH properties that may be linked to these variations.

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“…The PDR code used to generate its underlying database of line intensities has improved physics and chemistry. Critical updates include those discussed in Neufeld & Wolfire (2016), plus photorates from Heays et al (2017), oxygen chemistry rates from Kovalenko et al (2018), andTran et al (2018), and carbon chemistry rates from Dagdigian (2019). We have also implemented new collisional excitation rates for [O I] from Lique et al (2018) (and Lique private communication) and have included 13 C chemistry along with the emitted line intensities for [ 13 C II] and 13 CO.…”

Section: Photodissociation Regionsmentioning

confidence: 99%

FEEDBACK: a SOFIA Legacy Program to Study Stellar Feedback in Regions of Massive Star Formation

Schneider,

Simon,

Guevara

et al. 2020

Preprint

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FEEDBACK is a SOFIA (Stratospheric Observatory for Infrared Astronomy) legacy program dedicated to study the interaction of massive stars with their environment. It performs a survey of 11 galactic high mass star forming regions in the 158 µm (1.9 THz) line of [C II] and the 63 µm (4.7 THz) line of [O I]. We employ the 14 pixel Low Frequency Array (LFA) and 7 pixel High Frequency Array (HFA) upGREAT heterodyne instrument to spectrally resolve (0.24 MHz) these far-infrared fine structure lines. With a total observing time of 96h, we will cover ∼6700 arcmin 2 at 14.1 angular resolution for the [C II] line and 6.3 for the [O I] line. The observations started in spring 2019 (Cycle 7). Our aim is to understand the dynamics in regions dominated by different feedback processes from massive stars such as stellar winds, thermal expansion, and radiation pressure, and to quantify the mechanical energy injection and radiative heating efficiency. This is an important science topic because feedback of massive stars on their environment regulates the physical conditions and sets the emission characteristics in the interstellar medium (ISM), influences the star formation activity through molecular cloud dissolution and compression processes, and drives the evolution of the ISM in galaxies. The [C II] line provides the kinematics of the gas and is one of the dominant cooling lines of gas for low to moderate densities and UV fields. The [O I] line traces warm and highdensity gas, excited in photodissociations regions with a strong UV field or by shocks. The source sample spans a broad range in stellar characteristics from single OB stars, to small groups of O stars, to rich young stellar clusters, to ministarburst complexes. It contains wellknown targets such as Aquila, the Cygnus X region, M16, M17, NGC7538, NGC6334, Vela, and W43 as well as a selection of H II region bubbles, namely RCW49, RCW79, and RCW120. These [C II] maps, together with the less explored [O I] 63 µm line, provide an outstanding database for the community. They will be made publically available and will trigger further studies and follow-up observations.

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OH⁺ Formation in the Low-temperature O⁺(⁴S) + H₂ Reaction

Cited by 14 publications

References 47 publications

The EDIBLES survey IV. Cosmic ray ionization rates in diffuse clouds from near-ultraviolet observations of interstellar OH$^+$

The EDIBLES survey IV. Cosmic ray ionization rates in diffuse clouds from near-ultraviolet observations of interstellar OH$^+$

[CII] 158$μ$m emission from Orion A. II. Photodissociation region physics

FEEDBACK: a SOFIA Legacy Program to Study Stellar Feedback in Regions of Massive Star Formation

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