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J/ApJ/749/157  Far-UV spectra of Galactic corona sight lines     (Wakker+, 2012)

Characterizing transition temperature gas in the Galactic corona. Wakker B.P., Savage B.D., Fox A.J., Benjamin R.A., Shapiro P.R. <Astrophys. J., 749, 157 (2012)> =2012ApJ...749..157W
ADC_Keywords: Spectra, ultraviolet ; Interstellar medium ; Milky Way ; Line Profiles Keywords: Galaxy: halo - ISM: clouds - ISM: general - ultraviolet: ISM Abstract: We present a study of the properties of the transition temperature (T∼105K) gas in the Milky Way corona, based on the measurements of OVI, NV, CIV, SiIV, and FeIII absorption lines seen in the far-ultraviolet spectra of 58 sight lines to extragalactic targets, obtained with the Far-Ultraviolet Spectroscopic Explorer and the Space Telescope Imaging Spectrograph. In many sight lines the Galactic absorption profiles show multiple components, which are analyzed separately. We find that the highly ionized atoms are distributed irregularly in a layer with a scale height of about 3 kpc, which rotates along with the gas in the disk, without an obvious gradient in the rotation velocity away from the Galactic plane. Within this layer the gas has randomly oriented velocities with a dispersion of 40-60km/s. On average the integrated column densities are logN(OVI)=14.3, logN(NV)=13.5, logN(CIV)=14.2, logN(SiIV)=13.6, and logN(FeIII)=14.2, with a dispersion of just 0.2 dex in each case. In sight lines around the Galactic center and Galactic north pole, all column densities are enhanced by a factor ∼2, while at intermediate latitudes in the southern sky there is a deficit in N(O VI) of about a factor of two, but no deficit for the other ions. Description: In Table 1, we give observational information for the HST Goddard High Resolution (R>10000) GHRS, STIS-G140M, or STIS-E140M spectra that were taken before 2007 and for which the S/N per 20km/s near either the NV or CIV line is larger than 7. Of the set of observations, 9 targets were only observed using the GHRS, 18 were only observed using STIS-G140M, and 31 were observed using STIS-E140M. Of the 58 targets used in our analysis, 43 also have FUSE data with S/N near OVI greater than 7. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 98 154 Observational data (for 69 targets) table2.dat 165 1089 Measurements (for 57 targets)
See also: B/hst : HST Archived Exposures Catalog (STScI, 2007) VI/129 : The FUSE Observation Log (FUSE, 1999-2007) VIII/76 : Leiden/Argentine/Bonn (LAB) Survey of Galactic HI (Kalberla+ 2005) J/ApJS/182/378 : HI and OVI absorbers in nearby Universe (Wakker+, 2009) J/ApJ/702/1472 : Column densities for HI, AlIII, SiIV, CIV, OVI (Savage+, 2009) J/ApJS/176/59 : FUSE survey of OVI in the disk of the Milky Way (Bowen+, 2008) J/ApJS/168/213 : Ionization states and cooling efficiencies (Gnat+, 2007) 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/146/125 : O VI in the galactic halo (Savage+, 2003) J/ApJS/146/1 : O VI absorption in FUSE survey (Wakker+, 2003) J/ApJS/136/631 : IUE absorption toward 164 early-type stars (Savage+, 2001) J/ApJS/136/463 : Distances and metallicities of HVCs and IVCs (Wakker, 2001) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 15 A15 --- Name Object name 17- 22 F6.2 deg GLON Galactic longitude 24- 29 F6.2 deg GLAT Galactic latitude 31- 36 A6 --- Status Status (1) 38- 47 A10 --- Inst Instrument (2) 49- 50 I2 km/s Res [6/30] Resolution (3) 52- 56 F5.1 ks Exp [1/529] Exposure time 58- 59 I2 --- S/NO [1/44]? OVI signal-to-noise ratio 61- 62 I2 --- S/NN [2/67]? NV signal-to-noise ratio 64- 65 I2 --- S/NC [2/35]? CIV signal-to-noise ratio 67- 68 I2 --- S/NSi [3/43]? SiIV signal-to-noise ratio 70- 98 A29 --- ObsID Observational ID number
Note (1): Status of the analysis as follows: Ratios = this sight line is used to analyze ionic ratios; Meas. = only one or two of the four ions were measured; Skip = the S/N of the data is sufficient, but the measurement is impossible or ambiguous. Note (2): FUSE or HST spectrograph, with in the case of GHRS data the central wavelength of the grating setting added; an added central wavelength for STIS data means that the G140M grating was used, otherwise the spectrum was obtained using the E140M echelle. Note (3): Approximate size of resolution element.
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 15 A15 --- Name Target name 17- 20 I4 km/s Vmin [-125/50] Lower velocity of integration (1) 22- 25 I4 km/s Vmax [-65/120] Upper velocity of integration (1) 27- 31 A5 --- Ion Ion (CIII, CIIIN, CIV, FeIII, NV, OVI, SIII, SiIII or SiIV) 35 A1 --- l_Ns [≤?x] Flag on strong line (2) 37- 41 F5.2 [cm-2] Ns [0/15]?=0 log column density of strong line (3) 43- 46 F4.2 [cm-2] e_Ns ?=0 Statistical error in Ns 48- 51 F4.2 [cm-2] E_Ns ?=0 Systematic error in Ns 55- 57 I3 km/s <Vs> [-79/76]? Centroid velocity (1st moment) of strong line 59- 60 I2 km/s e_<Vs> [0/28]? Uncertainty in <Vs> 63- 65 I3 km/s Ws [0/118]?=0 FWHM of strong line (1.661*2nd moment) (4) 67- 68 I2 km/s e_Ws ?=0 Uncertainty in Ws 71- 86 A16 --- info.s Information flag on strong line (5) 90 A1 --- l_Nw [≤?x] Flag on weak line (2) 92- 96 F5.2 [cm-2] Nw [0/15]?=0 log column density of weak line (3) 98-101 F4.2 [cm-2] e_Nw ?=0 Statistical error in Nw 103-106 F4.2 [cm-2] E_Nw ?=0 Systematic error in Nw 110-112 I3 km/s <Vw> [-69/74]? Centroid velocity (1st moment) of weak line 114-115 I2 km/s e_<Vw> [0/13]? Uncertainty in <vW> 118-120 I3 km/s Ww [0/116]?=0 FWHM of strong line (1.661 * 2nd moment) (4) 122-123 I2 km/s e_Ww ?=0 Uncertainty in WW 126-142 A17 --- info.w Information flag on weak line (5) 144-152 A9 --- Ion2 Ion pair ratio 154 A1 --- l_logR [<≥x] Flag on ion pair ratio (2) 156-160 F5.2 [-] logR [-1.3/0.8]? Log of ion ratio 162-165 F4.2 [-] e_logR [0/0.3]? Uncertainty in logR
Note (1): Velocity range of integration for either all Milky Way Disk/Halo absorption or for individual components. Note (2): Flag indicating whether the following values represent a measurement (=), an upper limit (<) or the absence of data (x). Note (3): For OVI, NV, CIV and SiIV separate values are given for the strong and weak line of the doublet, while for CIII, SiIII, FeIII and SIII only one value is given, in the 'strong line' slot. Note (4): The listed widths are corrected for instrumental broadening (FWHMcorr=sqrt(FWHMobs2-Res2). Instrumental widths are 19 km/s for GHRS-G160M spectra, 30 km/s for STIS-G140M spectra, 6.5 km/s for STIS-E140M spectra, and ∼20 km/s for FUSE spectra. Note (5): String providing extra information on the quality of a measurement or the reason for the absence of a measurement. Possible values are: NODATA = No spectrum exists covering this line NOFLUX = There is no flux at the wavelength of this line; which happens for 3C351.0, PHL1811 and PKS0312-77 for lines blueward of the Lyman limit break in their spectra. GOOD = Listed column density, centroid and linewidth are all deemed to be OK. ULIM = Column density value is an upper limit. SAT = Absorption is saturated. BADWID = Column density measurement is OK, but the given measured linewidth probably is unreliable. UNREL = Column density measurement is probably not too reliable. CONT:lll = Measurement contaminated by another absorption line, with the following possibilities: SINGLET = Not really contaminated, but used in the weak line slot for CIII, SiIII, FeIII and SIII. H2 = OVI by H_2 J=3 lambda 1031.1 or H_2 J=4 lambda 1032.3 SIII by H_2 J=2 lambda 1012.1 or H_2 J=3 lambda 1012.7 Lya = NV and SiIV in 12 sightlines by redshifted Lyα Lyb = OVI and CIV in 5 sightlines by redshifted Lyβ Lyg = OVI lambda 1031.9 toward HE0226-4110 by Lyγ at z=0.071 Lyk = FeIII toward 3C351.0 by Lyκ at z=0.221 FeII = FeIII in 4 sightlines by high-velocity FeII-1121.9 CIII = NV lambda 1242.8 toward PG1206+069 by CIII lambda 977.0 at z=0.274 OVI = CIV lambda 1031.9 toward HE0226-4110 by OVI lambda 1031.9 at z=0.495 CII* = OVI lambda 1037.6 toward NGC1705 and VIIZw118 by CII* lambda 1037.0 CII*-GC = OVI lambda 1037.6 toward PKS2005-489 by CII* lambda 1037.0 in globular cluster STELLAR = SIII by stellar lines toward NGC1705 UNK = unidentified contamination in 7 sightlines BADCONT = NV and CIV continuum fit is unreliable for NGC1705 EM = NV by apparent emission feature toward Mrk290 OVI-NGC3516 = OVI by OVI in NGC3516 NV-NGC1705 = NV by NV in NGC1705 CIV-NGC1705 = CIV by CIV in NGC1705
History: From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 02-Dec-2013
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