J/ApJ/764/25ivo://CDS.VizieR/J/ApJ/764/25doi:10.26093/cds/vizier.17640025CDSJenkins E.B.2017-06-01T08:52:31Z2014-11-25T16:13:16ZCDS support team

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

cds-question@unistra.frline-intensitiesspectroscopyultraviolet-astronomyinterstellar-mediumsubdwarf-starsWhen the neutral interstellar medium is exposed to extreme-ultraviolet and soft X-ray radiation, the argon atoms in it are far more susceptible to being ionized than the hydrogen atoms. We make use of this fact to determine the level of ionization in the nearby warm neutral medium. By analyzing Far-Ultraviolet Spectroscopic Explorer observations of ultraviolet spectra of 44 hot subdwarf stars a few hundred parsecs away from the Sun, we can compare column densities of Ar I to those of O I, where the relative ionization of oxygen can be used as a proxy for that of hydrogen. The measured deficiency [ArI/OI]=-0.427+/-0.11dex below the expectation for a fully neutral medium implies that the electron density n(e){approx}0.04/cm3 if n(H)=0.5/cm3. This amount of ionization is considerably larger than what we expect from primary photoionizations resulting from cosmic rays, the diffuse X-ray background, and X-ray emitting sources within the medium, along with the additional ionizations caused by energetic secondary photoelectrons, Auger electrons, and photons from helium recombinations. We favor an explanation that bursts of radiation created by previous, nearby supernova remnants that have faded by now may have elevated the ionization, and the gas has not yet recombined to a quiescent level. A different alternative is that the low-energy portion of the soft X-ray background is poorly shielded by the H I because it is frothy and has internal pockets of very hot, X-ray emitting gases.2013ApJ...764...25Jhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/764/25CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toVI/129 : The FUSE Observation Log (FUSE, 1999-2007)J/AJ/141/50 : White-light flares on Kepler cool stars (Walkowicz+, 2011)J/A+A/533/A62 : Atomic Data for Neutron-Capture Elements. II (Sterling, 2011)J/ApJ/734/65 : CI radial velocities with HST/STIS (Jenkins+, 2011)J/ApJ/711/1236 : Equivalent width of H_2_ from FUSE (Jensen+, 2010)J/A+A/510/A54 : NaI and CaII interstellar absorption (Welsh+, 2010)J/ApJ/700/1299 : Gas-phase element depletions in the ISM (Jenkins, 2009)J/ApJS/176/59 : FUSE survey of OVI in the disk of the Milky Way (Bowen+, 2008)J/ApJ/647/328 : FUSE survey of OVI in ISM (Dixon+, 2006)J/ApJ/647/312 : FUSE survey of OVI in the Milky Way (Otte+, 2006)J/ApJS/163/282 : Molecular hydrogen column densities (Wakker+, 2006)J/ApJS/163/207 : Oscillator and collision strengths in NI (Tayal+, 2006)J/ApJS/147/61 : Interstellar Ca I absorption (Welty+, 2003)J/ApJS/146/1 : O VI absorption in FUSE survey (Wakker+, 2003)J/A+A/346/785 : NaI in Local Bubble (Sfeir+, 1999)J/A+AS/125/149 : CHIANTI: An Atomic Database For Emission Lines I. (Dere+ 1997)J/A+AS/123/159 : IRON Project. XXII. C and O radiative rates (Galavis+ 1997)J/A+AS/109/125 : Photoionisation cross section (Verner+, 1995)J/A+AS/97/443 : Fluorescence for Be to Zn (Kaastra+ 1993)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/764/25https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/764/25http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/764/25https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/764/25https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/764/25http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/764/25GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/764/25/subdwarf (Results for [ArI/OI] and equivalent widths for the 44 targets)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/764/25/subdwarf?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/764/25/subdwarf?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/764/25/subdwarf?GETtext/xml+votable180.050000true231.721028179.69188640.0055555555555555566/2437 4931 5544 5550 5884 5918 8135 9552 9959 10144 10774 11145 12142 12443 12765 12907 12961 13024 13480 18906 19361 24813 26351 27963 31622 33010 33097 33984 34963 35079 35798 38449 38536 39735 40948 42129 43305 45235 45361 45594 47105 47304 47366 47453https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/764/25?format=asciiUVdefaultJ/ApJ/764/25/subdwarfResults for [ArI/OI] and equivalent widths for the 44 targetsSimbadNameSimbad column added by the CDSmeta.idcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintGLONSIMBAD Galactic longitudedegpos.galactic.lonGLATSIMBAD Galactic latitudedegpos.galactic.latfloatBmag[9.3/16.3]? SIMBAD B-band magnitudemagphot.mag;em.opt.BfloatnullableVmag[9.6/15.2]? SIMBAD V-band magnitudemagphot.mag;em.opt.Vfloatnullableb_[ArI/OI][-3.8/-0.01] Lower limit of [ArI/OI] (3)log(Sun)phys.abund;stat.minfloat[ArI/OI][-1.9/0.3] Best value of [ArI/OI] (3)log(Sun)phys.abundfloatB_[ArI/OI][-1/0.7] Upper limit of [ArI/OI] (3)log(Sun)phys.abund;stat.maxfloatErr[2.2/11.1] Denominator (c_1_) Value/Error (4)stat.fit.goodnessfloatProb[0.01/1] Probability of worse fitstat.probability;meta.modelledfloatSimbadSimbad column added by the CDSmeta.ref.urlcharNameStar namemeta.id;meta.maincharn_Name[def] Other star identifications in the note (1)meta.notecharW1048[-21/179] Equivalent width for ArI 1048.220 line log(f{lambda})=2.440 in m{AA} (2)0.1pmspect.line.eqWidthinte_W1048[3/27] W1048 uncertainty0.1pmstat.errorintf_W919[(] (: W919 not used in the linear fitmeta.codecharW919[-3/58]? Equivalent width for OI 919.917 line log(f{lambda})=-0.788, ew6=11.6 in m{AA} (2)0.1pmspect.line.eqWidthintnullablee_W919[3/39]? W919 uncertainty0.1pmstat.errorintnullablef_W922[(] (: W922 not used in the linear fitmeta.codecharW922[-4/86]? Equivalent width for OI 922.200 line log(f{lambda})=-0.645, ew6=15.3 in m{AA} (2)0.1pmspect.line.eqWidthintnullablee_W922[5/31]? W922 uncertainty0.1pmstat.errorintnullablef_W925[(] (: W925 not used in the linear fitmeta.codecharW925[13/107] Equivalent width for OI 925.446 line log(f{lambda})=-0.484, ew6=20.6 in m{AA} (2)0.1pmspect.line.eqWidthinte_W925[3/39] W925 uncertainty0.1pmstat.errorintf_W916[(] (: W916 not used in the linear fitmeta.codecharW916[25/101]? Equivalent width for OI 916.815 line log(f{lambda})=-0.362, ew6=25.0 in m{AA} (2)0.1pmspect.line.eqWidthintnullablee_W916[4/38]? W916 uncertainty0.1pmstat.errorintnullablef_W930[(] (: W930 not used in the linear fitmeta.codecharW930[20/134]? Equivalent width for OI 930.257 line log(f{lambda})=-0.301, ew6=27.8 in m{AA} (2)0.1pmspect.line.eqWidthintnullablee_W930[4/59]? W930 uncertainty0.1pmstat.errorintnullableW920[-2/99]? Equivalent width for OI 919.658 line log(f{lambda})=-0.137, ew6=34.5 in m{AA} (2)0.1pmspect.line.eqWidthintnullablee_W920[4/46]? W920 uncertainty0.1pmstat.errorintnullablef_W921[(] (: W921 not used in the linear fitmeta.codecharW921[30/166]? Equivalent width for OI 921.857 line log(f{lambda})=-0.001, ew6=40.4 in m{AA} (2)0.1pmspect.line.eqWidthintnullablee_W921[4/34]? W921 uncertainty0.1pmstat.errorintnullablef_W924[(] (: W924 not used in the linear fitmeta.codecharW924[15/152] Equivalent width for OI 924.950 line log(f{lambda})=0.155, ew6=46.9 in m{AA} (2)0.1pmspect.line.eqWidthinte_W924[3/38] W924 uncertainty0.1pmstat.errorintf_W950[(] (: W950 not used in the linear fitmeta.codecharW950[28/175]? Equivalent width for OI 950.885 line log(f{lambda})=0.176, ew6=49.0 in m{AA} (2)0.1pmspect.line.eqWidthintnullablee_W950[3/38]? W950 uncertainty0.1pmstat.errorintnullablef_W976[(] (: W976 not used in the linear fitmeta.codecharW976[41/256]? Equivalent width for OI 976.448 line log(f{lambda})=0.509 in m{AA} (2)0.1pmspect.line.eqWidthintnullablee_W976[4/39]? W976 uncertainty0.1pmstat.errorintnullablef_W948[(] (: W948 not used in the linear fitmeta.codecharW948[68/180]? Equivalent width for OI 948.686 line log(f{lambda})=0.778 in m{AA} (2)0.1pmspect.line.eqWidthintnullablee_W948[4/22]? W948 uncertainty0.1pmstat.errorintnullablef_W971[(] (: W971 not used in the linear fitmeta.codecharW971[62/228]? Equivalent width for OI 971.738 line log(f{lambda})=1.052 in m{AA} (2)0.1pmspect.line.eqWidthintnullablee_W971[3/39]? W971 uncertainty0.1pmstat.errorintnullable_RARight Ascension (J2000) from SIMBAD (not part of the original data)degpos.eq.ra;meta.main_DEDeclination (J2000) from SIMBAD (not part of the original data)degpos.eq.dec;meta.mainJ/ApJ/764/25/fig6*Figure 6 data used for the figureE[24/3995] Photon energyeVem.energydoublerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintobs[69/281900] External observed background (4{pi}E.F(obs)) (upper panel)ph.cm**-2.s**-1phot.flux;em.X-raydoubleSNR[0.09/215900] External flux from supernova remnant(s) (4{pi}E.F(SNR)) (upper panel)ph.cm**-2.s**-1phot.flux;em.X-raydoubleE.F(MS)Internal flux for the injection of ionizing photons from main sequence starsph.cm**-3.s**-1phot.flux;em.X-raydoubleE.F(AB)Internal flux for the injection of ionizing photons from active binariesph.cm**-3.s**-1phot.flux;em.X-raydoubleE.F(WD)Internal flux for the injection of ionizing photons from white dwarfsph.cm**-3.s**-1phot.flux;em.X-raydouble