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 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