J/ApJS/146/125 O VI in the galactic halo (Savage+, 2003)
Distribution and kinematics of O VI in the Galactic halo.
Savage B.D., Sembach K.R., Wakker B.P., Richter P., Meade M., Jenkins E.B.,
Shull J.M., Moos H.W., Sonneborn G.
<Astrophys. J. Suppl. Ser. 146, 125 (2003)>
=2003ApJS..146..125S 2003ApJS..146..125S
ADC_Keywords: Interstellar medium ; Molecular clouds ; Ultraviolet ;
Radial velocities ; Velocity dispersion
Keywords: Galaxy: halo - ISM: abundances - ISM: clouds - ultraviolet: ISM
Abstract:
Far-Ultraviolet Spectroscopic Explorer (FUSE) spectra of 100
extragalactic objects and two distant halo stars are analyzed to
obtain measures of O VI λλ1031.93, 1037.62 absorption
along paths through the Milky Way thick disk/halo.
Description:
The FUSE O VI catalog paper (Wakker et al., 2003, Cat. J/ApJS/146/1)
contains the full details of the FUSE observations, the data handling,
the basic ISM measurements, and plots of the O VI absorption line
profiles for all of the objects in our study. Here we review the most
essential aspects of the observations and reductions of the spectra
for the 100 extragalactic objects and two stars.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 97 104 *Results for O VI in the Thick Disk of the Milky Way
table7.dat 86 103 *Measures of H I, Hα, and 0.25keV Diffuse
X-Rays toward Each Survey Object
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Note on table2.dat: 102 studied objects plus the mean values of LMC and SMC
Note on table7.dat: 102 studied objects plus PG 1011-040
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See also:
J/ApJS/146/1 : O VI absorption in FUSE survey (Wakker+, 2003)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 14 A14 --- Name Object name
15 A1 --- n_Name [b] Note on Name (1)
17- 22 F6.2 deg GLON Galactic longitude
24- 29 F6.2 deg GLAT Galactic latitude
31- 34 I4 km/s RV ? Radial velocity
36- 41 F6.4 --- z ? Redshift
43 I1 --- Q Data quality (2)
45- 48 I4 km/s V- Negative velocity integration limit
49 A1 --- u_V- Uncertainty flag on V-
51- 53 I3 km/s V+ Positive velocity integration limit
54 A1 --- u_V+ Uncertainty flag on V+
56- 58 I3 km/s exp ? Expected average velocity of the
O VI absorption (3)
60- 62 I3 km/s obs ? Average observed LSR velocity of the
O VI absorption
64- 65 I2 km/s e_obs ? 1 σ random error in the observed
velocity (4)
67- 68 I2 km/s b ? Observed O VI velocity dispersion
69 A1 --- u_b Uncertainty flag on b
71- 72 I2 km/s e_b ? 1σ random error in the velocity
dispersion
74 A1 --- l_logN(OVI) Limit flag on logN(OVI)
75- 79 F5.2 [cm-2] logN(OVI) log of O VI column density for the velocity
range V- to V+ based on the strong line of
the doublet
80 A1 --- n_logN(OVI) Note on logN(OVI) (1)
82- 85 F4.2 --- e_sc ? 1 σ combined statistical and
continuum placement errors in log N(O VI)
86 A1 --- n_sc [b] Note on e_sc (1)
87- 90 F4.2 --- e_sys ? Systematic error in log N(O VI)
92 A1 --- l_logNsin|b| Limit flag on logNsin|b|
93- 97 F5.2 [cm-2] logNsin|b| log of projected O VI column density
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Note (1): Notes as follows:
a = Wakker et al. (2003, Cat. J/ApJS/146/1) summarize the results
of measures of N(OVI)W/N(OVI)S for objects with S/N>6.5
(Q=3 or 4) for which the continuum near O VI λ1037.62 is
reliable. Here, N(OVI)W and N(OVI)S refer to values of
Na(OVI) derived from the weak and strong component of the O VI
doublet, respectively. The integrations extend over a limited
velocity range to avoid the contamination problems affecting the
O VI λ1037.62 line. If there is little or no unresolved
line saturation the value of N(OVI)W/N(OVI)S should be close
to 1.0 (Savage & Sembach, 1991ApJ...379..245S 1991ApJ...379..245S). Wakker et al.
(2003, Cat. J/ApJS/146/1) find that for 15 of 20 objects
N(OVI)W/N(OVI)S is within 1σ of 1.0 implying little or
no line saturation. For five objects the values of
N(OVI)W/N(OVI)S suggest some saturation. The results for
those five cases are listed below:
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Object N(OVI)W/N(OVI)S ΔlogN(corr)
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Mrk 421 1.60±0.18 0.57
PG 1259+593 1.29±0.11 0.24
Mrk 817 1.28±0.07 0.23
Mrk 1383 1.23±0.08 0.19
3C 273 1.13±0.04 0.11
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b = Average values of log N(O VI) in the Milky Way halo in the
directions of the LMC and SMC are listed along with the standard
deviations. The measurements are from Howk et al.
(2002ApJ...572..264H 2002ApJ...572..264H, 2002ApJ...569..214H 2002ApJ...569..214H), and Hoopes et al.
(2002ApJ...569..233H 2002ApJ...569..233H). For the direction to the LMC, values of
logN(OVI) toward 12 LMC stars range from 14.22 to 14.67 for
integrations extending over the LSR velocity range averaging from
-36 to 175km/s. For a narrower velocity range averaging from
-50 to 50km/s, the values of logN(OVI) range from 13.61 to 14.23
with an average of 14.02 and a standard deviation of 0.18.
logN(OVI) in the Milky Way toward 11 SMC stars ranges from 13.77
to 14.39 and the velocity range of the Milky Way halo absorption
on average extends from -45 to 63km/s. The substantial dispersion
in the observed values of logN(OVI) of 0.13 and 0.17dex for Milky
Way halo gas toward the LMC and SMC, respectively, shows that the
irregularity in the distribution of Milky Way O VI extends to
angular scales as small as 5° to 0.05° (Howk et al.,
2002ApJ...572..264H 2002ApJ...572..264H).
Note (2): Quality flag as follows:
4 = excellent data with the observed S/N>14 in the continuum adjacent
to the O VI 1031.93 line in a 10 pixel bin which is equivalent
to one resolution element
3 = good data with S/N=9 to 14
2 = fair data with S/N=5 to 9
1 = poor data with S/N=3 to 5
Note (3): Expected average velocity of the O VI absorption assuming a
corotating halo with an exponential scale height of 2.5kpc and
a turbulent velocity of 60km/s
Note (4): The systematic velocity error is ∼10km/s
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Byte-by-byte Description of file: table7.dat
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Bytes Format Units Label Explanations
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1- 14 A14 --- Name Object name
17- 22 F6.2 deg GLON Galactic longitude
25- 30 F6.2 deg GLAT Galactic latitude
33 A1 --- l_logN(OVI) Limit flag on logN(OVI)
34- 38 F5.2 [cm-2] logN(OVI) log of O VI column density
41- 44 F4.2 [cm-2] e_logN(OVI) ? random error in log N(O VI)
46- 53 E8.2 cm-2 N(HI) Values of log N(HI) integrated over the
O VI velocity range from V- to V+ using
the H I observations displayed in
Wakker et al. 2003, Cat. J/ApJS/146/1
56- 63 E8.2 cm-2 e_N(HI) Error in N(HI)
65- 69 F5.2 Ry I(Ha) ? Intensity of Hα emission (1)
70 A1 --- u_I(Ha) [a] Uncertainty of I(Ha) (2)
72- 76 F5.3 Ry e_I(Ha) ? Error in I(Ha)
77 A1 --- n_I(Ha) [a] Uncertainty of e_I(Ha) (2)
79- 82 I4 ct/s/arcmin+2 I(X) Intensity of the ROSAT (R1+R2 band)
0.25keV soft X-ray diffuse background (3)
84- 86 I3 ct/s/arcmin+2 e_I(X) Error in I(X)
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Note (1): Intensity of Hα emission, in the 1° field containing
the survey object from the Wisconsun Hα Survey
(Haffner et al., 2001AAS...199.1609O 2001AAS...199.1609O)
Note (2): 'a' indicates a very uncertain Hα measurement because
of starlight contamination of the observation for the survey
direction. The listed intensity is an average over the survey
measurements for adjacent directions (see Haffner et al.,
2001AAS...199.1609O 2001AAS...199.1609O). Errors are not listed in these cases.
Note (3): Intensity averaged over a 36'x36' region centered on the survey object
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History:
From electronic version of the journal
(End) James Marcout, Patricia Bauer [CDS] 06-Jun-2003