J/A+A/607/A48ivo://CDS.VizieR/J/A+A/607/A48doi:10.26093/cds/vizier.36070048CDSRichter P.Nuza S.E.Fox A.J.Wakker B.P.Ben Bekhti N.Fechner C.,Wendt M.Howk J.C.Muzahid S.Ganguly R.Charlton J.2017-11-13T08:02:57Z2017-11-10T07:35:07ZCDS support team

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

cds-question@unistra.frquasarsastrometryspectroscopyline-intensitiesThe Milky Way is surrounded by large amounts of diffuse gaseous matter that connects the stellar body of our Galaxy with its large-scale Local Group (LG) environment. To characterize the absorption properties of this circumgalactic medium (CGM) and its relation to the LG we present the so-far largest survey of metal absorption in Galactic high-velocity clouds (HVCs) using archival ultraviolet (UV) spectra of extragalactic background sources. The UV data are obtained with the Cosmic Origins Spectrograph (COS) onboard the Hubble Space Telescope (HST) and are supplemented by 21cm radio observations of neutral hydrogen. Along 270 sightlines we measure metal absorption in the lines of SiII, SiIII, CII, and CIV and associated HI 21cm emission in HVCs in the velocity range |v_LSR_|=100-500km/s. With this unprecedented large HVC sample we were able to improve the statistics on HVC covering fractions, ionization conditions, small-scale structure, CGM mass, and inflow rate. For the first time, we determine robustly the angular two point correlation function of the high-velocity absorbers, systematically analyze antipodal sightlines on the celestial sphere, and compare the HVC absorption characteristics with that of Damped Lyman alpha absorbers (DLAs) and constrained cosmological simulations of the LG (CLUES project). The overall sky-covering fraction of high-velocity absorption is 77+/-6 percent for the most sensitive ion in our survey, SiIII, and for column densities log N(SiIII)>12.1. This value is 4-5 times higher than the covering fraction of 21 cm neutral hydrogen emission at log N(HI)>18.7 along the same lines of sight, demonstrating that the Milky Way's CGM is multi-phase and predominantly ionized. The measured equivalent-width ratios of SiII, SiIII, CII, and CIV are inhomogeneously distributed on large and small angular scales, suggesting a complex spatial distribution of multi-phase gas that surrounds the neutral 21cm HVCs. We estimate that the total mass and accretion rate of the neutral and ionized CGM traced by HVCs is M_HVC_>3.0x10^9^M_{sun}_ and dM_HVC_/dt>6.1M_{sun}_/yr, where the Magellanic Stream (MS) contributes with more than 90 percent to this mass/mass-flow. If seen from an external vantage point, the Milky Way disk plus CGM would appear as a DLA that would exhibit for most viewing angles an extraordinary large velocity spread of dv=400-800km/s, a result of the complex kinematics of the Milky Way CGM that is dominated by the presence of the MS. We detect a velocity dipole of high-velocity absorption at low/high galactic latitudes that we associate with LG gas that streams to the LG barycenter. This scenario is supported by the gas kinematics predicted from the LG simulations. Our study confirms previous results, indicating that the Milky Way CGM contains sufficient gaseous material to feed the Milky Way disk over the next Gyr at a rate of a few solar masses per year, if the CGM gas can actually reach the MW disk. We demonstrate that the CGM is composed of discrete gaseous structures that exhibit a large-scale kinematics together with small-scale variations in physical conditions. The MS clearly dominates both the cross section and mass flow of high-velocity gas in the Milky Way's CGM. The possible presence of high-velocity LG gas underlines the important role of the local cosmological environment in the large-scale gas-circulation processes in and around the Milky Way.2017A&A...607A..48Rhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/607/A48CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/607/A48https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/607/A48http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/607/A48https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/607/A48https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/607/A48http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/607/A48GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/607/A48/tablea1 (QSO names and Galactic coordinates)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/607/A48/tablea1?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/607/A48/tablea1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/607/A48/tablea1?GETtext/xml+votable180.050000true217.45356.73940.0055555555555555565/6930 6/0 134 552 2414 2621 2663 2754 4107 4193 4256 4410 4506 4590 4821 4824 4946 4959 4961 4966 5026 5061 5091 5121 5215 5246 5274 5284 5304-5305 5351 5409 5423 5437 5458 5481 5529 5570 5657 5687 5731 5814 5820-5821 5861 5974 5995 6021 6087 6104 6223 6488 6606 7272 7277 7381 7460 7510 7642 7902-7903 7998 8243 8245 8266 8282 8303 8328 8469 8528 8702 8716 8755 8778 8838 8867 8915 8918 8922 8938-8939 8952 9018 9031 9111 9186 9299 9440 9457 9753 9756 9783 10162 10170 10300 10433 10472 10517 10528 10602 10634 10659 10764 10889 10927 10940 10969 11009 11021 11115 11206 11209 11217 11327 11354 11382 11388 11435 11456 11460 11475 11490 11557 11596 11610 11668 11686 11898 12033 12047 12380 13414 15247 15351 16894 17075 17203 17251 17488 17521 17703 17730 17772 17819 17990 18601 18770 18803 19283 19433 19700 19746 19883 20008 20099 21991 22659 23060 23078 25132 25392 25472 25742 25932 26019 26058 26065 26088 26238 26259 26270 26292 26334 26396 26509 26606 26859 26902 26965 27006 27023 27090 27096 27115 27155 27229 27251 27295 27350 27376 27435 27486 27509 27515-27516 27562 27580 27725 27728 27738 27745 27751 27755 27760 27766 27862 28034 28060 28158 28201 28356 28383 28395 28404 28468 28471 28527 28546 28564 28571 28589 28636 31663 32948 32986 32998 33126 33233 33796 33930 33950 34064 34210 34881 35018 35180 35205 35360 35542 35565 35741 35743 35993 36443 36775 36788 37385 38268 38725 38821 38916 43680 44988 45500 46281 46299 46418 46647 47014 47169 47375 49042https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/607/A48?format=asciiOpticaldefaultJ/A+A/607/A48/tablea1QSO names and Galactic coordinatesSimbadNameSimbad column added by the CDSmeta.idcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNoRow numbermeta.idintNameQSO namemeta.id;meta.maincharGLONGalactic longitudedegpos.galactic.lonGLATGalactic latitudedegpos.galactic.lat_RA.icrsRight ascension (ICRS) (computed by VizieR, not part of the original data)degpos.eq.ranullableindexed_DE.icrsDeclination (ICRS) (computed by VizieR, not part of the original data)degpos.eq.decnullableindexedJ/A+A/607/A48/tablea4Hydrogen column densities in HVCsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNoRow numbermeta.idintNameQSO name (COS)meta.id;meta.maincharvHVCCenter velocity of HVC absorption/emissionkm/sphys.velocintl_logN(HI)Limit flag on logN(HI)meta.code.errorcharlogN(HI)Logarithmic column density (or limit) of HIlog(cm.s**-2)phys.columnDensityfloatl_logN(H)Limit flag on logN(H)meta.code.errorcharlogN(H)Logarithmic column density (or limit) of Hlog(cm.s**-2)phys.columnDensityfloatl_logf(HI)Limit flag on logf(HI)meta.code.errorcharlogf(HI)Logarithmic neutral hydrogen fraction (or limit)log(cm.s**-2)phys.columnDensityfloatJ/A+A/607/A48/tablea2Absorption-line measurements in HVCrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNoRow numbermeta.idintNameQSO name (COS)meta.id;meta.maincharIonIonphys.atmol.ionStagecharlambda0Laboratory wavelength0.1nmem.wlfloatS/NSignal-to-noise per resolution elementstat.snr;pos.angResolutionintvminLower velocity limit of HVC absorptionkm/sspect.dopplerVelocintvmaxUpper velocity limit of HVC absorptionkm/sspect.dopplerVelocintFlag[t] Flag for tentative HVC detectionmeta.code.errorcharW? Equivalent width0.1pmspect.line.eqWidthintnullablee_W? Sigma equivalent width0.1pmstat.error;pos.cartesian.zintnullablel_logNLimit flag on logNmeta.code.errorcharlogN? Logarithmic column density (or limit)phys.columnDensityfloatnullablee_logN? Sigma logarithmic column densitystat.errorfloatnullable