J/A+A/643/A36ivo://CDS.VizieR/J/A+A/643/A36doi:10.26093/cds/vizier.36430036CDSBellomi E.Godard B.Hennebelle P.Valdivia V.Pineau Des Forets G.,Lesaffre P.Perault M.2021-07-05T07:31:06Z2021-02-10T14:13:40ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frinterstellar-mediumThe amount of data collected by spectrometers from radio to ultraviolet (UV) wavelengths opens a new era where the statistical and chemical information contained in the observations can be used concomitantly to investigate the thermodynamical state and the evolution of the interstellar medium (ISM). In this paper, we study the statistical properties of the HI-to-H_2_ transition observed in absorption in the local diffuse and multiphase ISM. Our goal is to identify the physical processes that control the probability of occurrence of any line of sight and the origins of the variations of the integrated molecular fraction from one line of sight to another. The turbulent diffuse ISM is modeled using the RAMSES code, which includes detailed treatments of the magnetohydrodynamics, the thermal evolution of the gas, and the chemistry of H_2_. The impacts of the UV radiation field, the mean density, the turbulent forcing, the integral scale, the magnetic field, and the gravity on the molecular content of the gas are explored through a parametric study that covers a wide range of physical conditions. The statistics of the HI-to-H_2_ transition are interpreted through analytical prescriptions and compared with the observations using a modified and robust version of the Kolmogorov-Smirnov test. The analysis of the observed background sources shows that the lengths of the lines of sight follow a flat distribution in logarithmic scale from ~100pc to ~3kpc. Without taking into account any variation of the parameters along a line of sight or from one line of sight to another, the results of one simulation, convolved with the distribution of distances of the observational sample, are able to simultaneously explain the position, the width, the dispersion, and most of the statistical properties of the HI-to-H_2_ transition observed in the local ISM. The tightest agreement is obtained for a neutral diffuse gas modeled over ~200pc, with a mean density n_H_=1-2cm^-3^, illuminated by the standard interstellar UV radiation field, and stirred up by a large-scale compressive turbulent forcing. Within this configuration, the 2D probability histogram of the column densities of H and H_2_, poetically called the kingfisher diagram, is remarkably stable and is almost unaltered by gravity, the strength of the turbulent forcing, the resolution of the simulation, or the strength of the magnetic field B_x_, as long as B_x_<4{mu}G. The weak effect of the resolution and our analytical prescription suggest that the column densities of HI are likely built up in large-scale warm neutral medium and cold neutral medium (CNM) structures correlated in density over ~20pc and ~10pc, respectively, while those of H_2_ are built up in CNM structures between ~3 and ~10pc. Combining the chemical and statistical information contained in the observations of HI and H_2_ sheds new light on the study of the diffuse matter. Applying this new tool to several atomic and molecular species is a promising perspective to understanding the effects of turbulence, magnetic field, thermal instability, and gravity on the formation and evolution of molecular clouds.2020A&A...643A..36Bhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/643/A36CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/ApJS/199/8 : Interstellar column densities compilation (Gudennavar+, 2012)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/643/A36https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/643/A36http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/643/A36https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/643/A36https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/643/A36http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/643/A36GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/643/A36/tablea1 (Observational dataset used in this work)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/643/A36/tablea1?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/643/A36/tablea1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/643/A36/tablea1?GETtext/xml+votable180.050000true311.5541335.54280.0055555555555555566/375 463 474 859 1044 1055 1060 1196 1198 1293 1539 1550 1554 1558 1577 1633 1766 2409 2884 2909 3030 3053 3060 3136 3214 3245 3247 3256 3307 3430 3585 5091 5423 5506 5731 7277 7281 7713 7814-7815 7859 8017 8071 9194 9433 9612 10731 10912 10970 11217 11388 11490 11668 12025 12380 13001 13255 13268 13289 13454 13557 13721 13729 13953 14008 14015 14062 14167 14179 14197 14220 14240 14249 14263 14305 14311 14630-14631 14643 14653 14777 14805 14810 14824-14825 15351 15369 15375-15376 15392 15406 15478-15479 15580 15611 15626 15631 15656-15657 15660 15662-15663 15672 15682-15683 15747-15748 16046 16131 16671 17075 17754 18439 18928 19009 19283 19676 19883 20423 20546 20613 20764 20915 21233 21401 21438-21439 21635 21646-21647 21655-21656 22039 22249 22253 22258 22579 22659 22772 22854-22855 22862 22884 22890 22892 22904 22966 22992 22994 23637 23714 23717 23780 23851 23979 24179 24338 24340 24370 24463 24513 25182 25659 25742 25965 25988 26292 27498 27574 27862 28147 28356 28687 28700 28796 28890-28891 28915 28944 29040 29089 29162 29463 29513 29522 29600 29876 29893 30709 30722 30818 31705 31756 31759 33984 34065 35180 35741 36468 36786 36942 36944 36959 37128 37145 37209 37231 37323 37331-37334 37339 37662 37676 37732 37822 37841 37870-37871 37877 37893 37897 37900 37930 37963 38016 38019 38024 38110 38248 38780 39170 39201-39202 39209 39216 39281 39327 39334 39374 39775 39803 39853 39907 39916 39931 40068 40521 41103 41129 41510 41528 41598 41614 41630 41637 41646 41653 41655 41689 41692 41696 41698 41750 42080 42116 42126 42214 42221 42236 42335 42366 42383 42394 42405 42408 42416-42417 42428 42449 42470 42483 42609 42652 42672 42748 42791 42947-42948 42959 42977 42980-42982 42994 43014 43023-43024 43028 43040-43041 43045 43062 43099 43130 43137 43308 43365 43407 44100 44305 44312 44360 44366 44378 44389 44903 45105 45964 46186 46615 47014 47169 47375 47648 47828 48497 49042https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/643/A36?format=asciidefaultJ/A+A/643/A36/tablea1Observational dataset used in this workSimbadNameSimbad column added by the CDSmeta.idcharNameSource IDmeta.id;meta.maincharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintGLONGalactic longitudedegpos.galactic.lonGLATGalactic latitudedegpos.galactic.latDist? Distance (1)kpcpos.distancefloatnullableE(B-V)? Extinctionmagphot.color.excessfloatnullabler_E(B-V)? Reference for extinction, in refs.dat filemeta.ref;pos.frameintnullablel_logN(HI)Limit flag on logN(HI)meta.code.errorcharlogN(HI)? HI column densitylog(cm**-2)phys.columnDensityfloatnullabler_logN(HI)? Reference for logN(HI), in refs.dat filemeta.ref;pos.frameintnullablel_logN(H2)Limit flag on logN(H2)meta.code.errorcharlogN(H2)? H_2_ column densitylog(cm**-2)phys.columnDensityfloatnullabler_logN(H2)? Reference for logN(H2), in refs.dat filemeta.ref;pos.frameintnullablelogNHTotal proton column density (2)log(cm**-2)phys.columnDensityfloat_RA.icrsRight ascension (ICRS) (computed by VizieR, not part of the original data. The format may include more digits than the original data because of internal accuracy requirements in VizieR and across other CDS services)degpos.eq.ranullableindexed_DE.icrsDeclination (ICRS) (computed by VizieR, not part of the original data. The format may include more digits than the original data because of internal accuracy requirements in VizieR and across other CDS services)degpos.eq.decnullableindexedJ/A+A/643/A36/refsReferencesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRefReference codemeta.noteintBibCodeBibCodemeta.bib.bibcodecharAutAuthor's namemeta.bib.authorcharComCommentsmeta.notechar