J/ApJ/871/35ivo://CDS.VizieR/J/ApJ/871/35doi:10.26093/cds/vizier.18710035CDSZheng Y.Peek J.E.G.Putman M.E.Werk J.K.2021-05-27T14:33:27Z2020-08-10T07:51:40ZCDS support team

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

cds-question@unistra.fractive-galactic-nucleiquasarsspectroscopyultraviolet-astronomyredshiftedEvery quasar (quasi-stellar object; QSO) spectrum contains absorption-line signatures from the interstellar medium, disk-halo interface, and circumgalactic medium (CGM) of the Milky Way (MW). We analyze Hubble Space Telescope/Cosmic Origins Spectrograph (COS) spectra of 132 QSOs to study the significance and origin of SiIV absorption at |v_LSR_|<=100km/s in the Galactic halo. The gas in the north predominantly falls in at -50<~v_LSR_<~0km/s, whereas in the south, no such pattern is observed. The SiIV column density has an average and a standard deviation of <N_SiIV_>=(3.8+/-1.4)x10^13^cm^-2^. At |b|>~30{deg}, N_SiIV_ does not significantly correlate with b, which cannot be explained by a commonly adopted flat-slab geometry. We propose a two-component model to reconstruct the N_SiIV_-b distribution: a plane-parallel component N_DH_^{perp}^ to account for the MW's disk-halo interface and a global component N_G_ to reproduce the weak dependence on b. We find N_DH_^{perp}^=1.3_-0.7_^+4.7^x10^12^cm^-2^ and N_G_=3.4+/-0.3)x10^13^cm^-2^ on the basis of Bayesian analyses and block bootstrapping. The global component is most likely to have a Galactic origin, although its exact location is uncertain. If it were associated with the MW's CGM, we would find M_gas,all_>~ 4.7x10^9^M_{sun}_(C_f_/1)(R/75kpc)^2^(f_SiIV_/0.3)^-1^(Z/0.3Z_{sun}_)^-1^ for the cool gas at all velocities in the Galactic halo. Our analyses show that there is likely a considerable amount of gas at |v_LSR_|<=100km/s hidden in the MW's CGM.2019ApJ...871...35Zhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/871/35CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toB/hst : HST Archived Exposures Catalog (STScI, 2007)J/ApJS/97/1 : HST Quasar Absorption Line Key Project. X. (Lockman+ 1995)J/ApJS/122/355 : Low z QSO absorption systems (Vanden Berk+, 1999)J/ApJ/729/87 : SiIV absorption systems (Cooksey+, 2011)J/ApJ/736/42 : HST QSO Catalog (Ribaudo+, 2011)J/ApJ/804/79 : HST/COS obs. of QSOs within 600kpc of M31 (Lehner+, 2015)J/ApJ/818/113 : HST observations of QSOs with medium spectra (Neeleman+, 2016)J/ApJS/230/6 : HST/COS & /STIS absorption-line spectrosc. II. (Keeney+, 2017)J/ApJS/243/2 : SiIV and NV absorption line SDSS quasar systems (Chen+, 2019)https://media.stsci.edu/hlsp/cos-gal : the COS Quasar Database for Galactichttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/871/35https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/871/35http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/871/35https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/871/35https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/871/35http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/871/35GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/871/35/table1 (Si IV data sample)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/871/35/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/871/35/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/871/35/table1?GETtext/xml+votable180.050000true214.498083925.13683330.005555555555555556Associated datahttps://cdsarc.cds.unistra.fr/assocdata/?obs_collection=J/ApJ/871/356/2245 2414 2584 2610 2621 2733 2764 4506 4821 5203 5244 5262 5274 5355 5409 5481 5570 5731 5821 7277 7508 7642 7896 7998 8071 8216 8299 8528 8641 8755 8845 8918 8922 8952 9031 9194 10162 10624 10659 10691 10927 11217 11388 11490 11668 12380 15247 16447 17075 17186 17203 17488 17730 17990 18601 18769 18786 19147 19283 19433 19700 19730 19746 19767 19883 19909 19932 20079 20269 20290 22659 25132 25472 25932 26270 26292 26453 26509 26859 26902 27155 27349 27562 27580 27720 27862 28060 28083 28356 28517 29398 31663 33126 33233 33796 33930 33950 34065 34210 34881 35018 35180 35205 35360 35542 35741 35743 36313 36443 36775 36786 38268 38916 40213 44988 45341 45500 46143 46281 46299 46418 46444 46647 46795 47014 47169 47375 47510 49042https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/871/35?format=asciiUVdefaultJ/ApJ/871/35/table1Si IV data samplee_N1402N1402 uncertaintycm**-2stat.errordoublerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSeq[1/132] Running sequence numbermeta.idintIDHSLA-V1 identifier (1)meta.id;meta.filecharz[0.002/3]? SIMBAD redshiftsrc.redshiftfloatnullableSNRSiIV[12.5/154.2] S/N per resolution element for the absorption-free region between 1394{AA} and 1401{AA} (2)stat.snrfloatQ[-1/1] Quality flag (3)meta.code.qualintlogN1393[13.2/14.3] Log of apparent column density for SiIV 1393{AA} integrated from -100 to 100km/sphys.columnDensityfloate_logN1393[0.002/0.07] logN1393 uncertaintystat.errorfloatN1393Apparent column density for SiIV 1393{AA} integrated from -100 to 100km/scm**-2phys.columnDensitydoublee_N1393N1393 uncertaintycm**-2stat.errordoubleV1393[-51.4/40.1] Centroid velocity for SiIV 1393{AA} integrated from -100 to 100km/skm/sspect.dopplerVelocfloate_V1393[0.3/9]? V1393 uncertaintykm/sstat.errorfloatnullablelogN1402[13.2/14.1] Log of apparent column density for SiIV 1402{AA} integrated from -100 to 100km/sphys.columnDensityfloate_logN1402[0.003/0.2] logN1402 uncertaintystat.errorfloatN1402Apparent column density for SiIV 1402{AA} integrated from -100 to 100km/scm**-2phys.columnDensitydoubleV1402[-50.5/42.7] Centroid velocity for SiIV 1402{AA} integrated from -100 to 100km/skm/sspect.dopplerVelocfloate_V1402[0.5/17]? V1402 uncertaintykm/sstat.errorfloatnullableONameSIMBAD namemeta.id;meta.mainchar_RAPositions from SIMBAD (right ascension part)degpos.eq.ra;meta.main_DEPositions from SIMBAD (declination part)degpos.eq.dec;meta.mainGrism1Grism(s) used for the HST/COS spectrum; column added by CDSmeta.id;obscharGrism2Grism used for the second HST/COS spectrum if any; column added by CDSmeta.id;obscharImgPreview of the spectrum (stacked)meta.ref.urlchar