H3+ chemistry network (trac #357)

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reported by: @CloudyLex

We should compare our H3+ network with that discussed in this paper.

Title:  
Physical conditions in the central molecular zone inferred by H3+
Authors:    
Le Petit, Franck; Ruaud, Maxime; Bron, Emeric; Godard, Benjamin; Roueff, Evelyne; Languignon, David; Le Bourlot, Jacques
Affiliation:    
AA(LERMA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Université, UPMC Paris 06, 92190, Meudon, France Franck.LePetit@obspm.fr), AB(Université Bordeaux, LAB, UMR 5804, 33270, Floirac, France; CNRS, LAB, UMR 5804, 33270, Floirac, France), AC(LERMA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Université, UPMC Paris 06, 92190, Meudon, France), AD(LERMA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Université, UPMC Paris 06, 92190, Meudon, France), AE(LERMA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Université, UPMC Paris 06, 92190, Meudon, France), AF(LERMA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Université, UPMC Paris 06, 92190, Meudon, France), AG(LERMA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Université, UPMC Paris 06, 92190, Meudon, France; Université Paris-Diderot Paris 07, 75013, Paris, France)
Publication:    
Astronomy & Astrophysics, Volume 585, id.A105, 16 pp. (A&A Homepage)
Publication Date:   
01/2016
Origin: 
EDP Sciences
Astronomy Keywords: 
astrochemistry, ISM: molecules, cosmic rays, ISM: clouds, Galaxy: nucleus
DOI:    
10.1051/0004-6361/201526658
Bibliographic Code: 
2016A&A...585A.105L
Abstract

Context. The H3+ molecule has been detected in many lines of sight within 
the central molecular zone (CMZ) with exceptionally large column densities 
and unusual excitation properties compared to diffuse local clouds. The 
detection of the (3, 3) metastable level has been suggested to be the 
signature of warm and diffuse gas in the CMZ. 

Aims: We aim to determine the physical conditions and processes in the 
CMZ that explain the ubiquitous properties of H3+ in this medium and to 
constrain the value of the cosmic-ray ionization rate. 

Methods: We use the Meudon photodissociation region (PDR) code in 
which H3+ excitation has been implemented. We re-examine the 
relationship between the column density of H3+ and the cosmic-ray 
ionization rate, ?, up to large values of ? in the frame of this full chemical 
model. We study the impact of the various mechanisms that can excite H3+ 
in its metastable state. We produce grids of PDR models exploring different 
parameters (?, size of clouds, metallicity) and infer the physical conditions 
that best match the observations toward ten lines of sight in the CMZ. For 
one of them, Herschel observations of HF, OH+, H2O+, and H3O+ can be 
used as additional constraints. We check that the results found for H3+ 
also account for the observations of these molecules. 

Results: We find that the linear relationship between N(H3+) and ? only 
holds up to a certain value of the cosmic-ray ionization rate, which depends 
on the proton density. A value ? ~ 1-11 × 10-14 s-1 explains both the large 
observed H3+ column density and its excitation in the metastable level (3, 
3). This ? value agrees with that derived from synchrotron emission and Fe 
K? line. It also reproduces N(OH+), N(H2O+) and N(H3O+) detected toward 
Sgr B2(N). We confirm that the CMZ probed by H3+ is diffuse, nH? 100 cm-
3 and warm, T ~ 212-505 K. This warm medium is due to cosmic-ray 
heating. We also find that the diffuse component probed by H3+ must fill a 
large fraction of the CMZ. Finally, we suggest the warm gas in the CMZ 
enables efficient H2 formation via chemisorption sites as in PDRs. This 
contributes to enhance the abundance of H3+ in this high cosmic-ray flux 
environment.

Migrated from https://www.nublado.org/ticket/357

{
    "status": "new",
    "changetime": "2019-02-04T13:02:49Z",
    "_ts": "1549285369825011",
    "description": "We should compare our H3+ network with that discussed in this paper.\n\n{{{\nTitle:\t\nPhysical conditions in the central molecular zone inferred by H3+\nAuthors:\t\nLe Petit, Franck; Ruaud, Maxime; Bron, Emeric; Godard, Benjamin; Roueff, Evelyne; Languignon, David; Le Bourlot, Jacques\nAffiliation:\t\nAA(LERMA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universit\u00e9, UPMC Paris 06, 92190, Meudon, France Franck.LePetit@obspm.fr), AB(Universit\u00e9 Bordeaux, LAB, UMR 5804, 33270, Floirac, France; CNRS, LAB, UMR 5804, 33270, Floirac, France), AC(LERMA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universit\u00e9, UPMC Paris 06, 92190, Meudon, France), AD(LERMA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universit\u00e9, UPMC Paris 06, 92190, Meudon, France), AE(LERMA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universit\u00e9, UPMC Paris 06, 92190, Meudon, France), AF(LERMA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universit\u00e9, UPMC Paris 06, 92190, Meudon, France), AG(LERMA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universit\u00e9, UPMC Paris 06, 92190, Meudon, France; Universit\u00e9 Paris-Diderot Paris 07, 75013, Paris, France)\nPublication:\t\nAstronomy & Astrophysics, Volume 585, id.A105, 16 pp. (A&A Homepage)\nPublication Date:\t\n01/2016\nOrigin:\t\nEDP Sciences\nAstronomy Keywords:\t\nastrochemistry, ISM: molecules, cosmic rays, ISM: clouds, Galaxy: nucleus\nDOI:\t\n10.1051/0004-6361/201526658\nBibliographic Code:\t\n2016A&A...585A.105L\nAbstract\n\nContext. The H3+ molecule has been detected in many lines of sight within \nthe central molecular zone (CMZ) with exceptionally large column densities \nand unusual excitation properties compared to diffuse local clouds. The \ndetection of the (3, 3) metastable level has been suggested to be the \nsignature of warm and diffuse gas in the CMZ. \n\nAims: We aim to determine the physical conditions and processes in the \nCMZ that explain the ubiquitous properties of H3+ in this medium and to \nconstrain the value of the cosmic-ray ionization rate. \n\nMethods: We use the Meudon photodissociation region (PDR) code in \nwhich H3+ excitation has been implemented. We re-examine the \nrelationship between the column density of H3+ and the cosmic-ray \nionization rate, ?, up to large values of ? in the frame of this full chemical \nmodel. We study the impact of the various mechanisms that can excite H3+ \nin its metastable state. We produce grids of PDR models exploring different \nparameters (?, size of clouds, metallicity) and infer the physical conditions \nthat best match the observations toward ten lines of sight in the CMZ. For \none of them, Herschel observations of HF, OH+, H2O+, and H3O+ can be \nused as additional constraints. We check that the results found for H3+ \nalso account for the observations of these molecules. \n\nResults: We find that the linear relationship between N(H3+) and ? only \nholds up to a certain value of the cosmic-ray ionization rate, which depends \non the proton density. A value ? ~ 1-11 \u00d7 10-14 s-1 explains both the large \nobserved H3+ column density and its excitation in the metastable level (3, \n3). This ? value agrees with that derived from synchrotron emission and Fe \nK? line. It also reproduces N(OH+), N(H2O+) and N(H3O+) detected toward \nSgr B2(N). We confirm that the CMZ probed by H3+ is diffuse, nH? 100 cm-\n3 and warm, T ~ 212-505 K. This warm medium is due to cosmic-ray \nheating. We also find that the diffuse component probed by H3+ must fill a \nlarge fraction of the CMZ. Finally, we suggest the warm gas in the CMZ \nenables efficient H2 formation via chemisorption sites as in PDRs. This \ncontributes to enhance the abundance of H3+ in this high cosmic-ray flux \nenvironment.\n}}}",
    "reporter": "gary",
    "cc": "",
    "resolution": "",
    "time": "2016-01-13T21:09:36Z",
    "component": "atomic/molecular data base",
    "summary": "H3+ chemistry network",
    "priority": "good to do",
    "keywords": "",
    "version": "trunk",
    "milestone": "no milestone",
    "owner": "nobody",
    "type": "physics"
}

[cloudy-bot]

@peter-van-hoof-noaccount changed milestone from "" to "no milestone"