J/ApJ/862/34 X-ray spectral analysis of 107 MW sight lines (Nakashima+, 2018)
Spatial distribution of the Milky Way hot gaseous halo constrained by Suzaku
X-ray observations.
Nakashima S., Inoue Y., Yamasaki N., Sofue Y., Kataoka J., Sakai K.
<Astrophys. J., 862, 34 (2018)>
=2018ApJ...862...34N 2018ApJ...862...34N
ADC_Keywords: Milky Way; X-ray sources; Interstellar medium
Keywords: Galaxy: halo ; ISM: structure ; X-rays: ISM
Abstract:
The formation mechanism of the hot gaseous halo associated with the
Milky Way is still under debate. We report new observational
constraints on the gaseous halo using 107 lines of sight of the Suzaku
X-ray observations at 75°<l<285° and |b|>15° with a total
exposure of 6.4Ms. The gaseous halo spectra are represented by a
single-temperature plasma model in collisional ionization equilibrium.
The median temperature of the observed fields is 0.26keV (3.0x106K)
with a typical fluctuation of ∼30%. The emission measure varies by an
order of magnitude and marginally correlates with the Galactic
latitude. Despite the large scatter of the data, the emission measure
distribution is roughly reproduced by a disk-like density distribution
with a scale length of ∼7kpc, a scale height of ∼2kpc, and a total
mass of ∼5x107M☉. In addition, we found that a spherical hot
gas with the β-model profile hardly contributes to the observed
X-rays but that its total mass might reach ≳109M☉. Combined
with indirect evidence of an extended gaseous halo from other
observations, the hot gaseous halo likely consists of a dense
disk-like component and a rarefied spherical component; the X-ray
emissions primarily come from the former, but the mass is dominated by
the latter. The disk-like component likely originates from stellar
feedback in the Galactic disk due to the low scale height and the
large scatter of the emission measures. The median [O/Fe] of ∼0.25
shows the contribution of the core-collapse supernovae and supports
the stellar feedback origin.
Description:
We used archival data of the Suzaku/XIS, which is sensitive to
0.2-12.0keV X-rays. The field of view (FOV) is ∼18'x18' with a spatial
resolution of ∼2' in a half-power diameter.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 168 122 Observations and fitting results
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See also:
VIII/76 : Leiden/Argentine/Bonn (LAB) Survey of Gal. HI (Kalberla+ 2005)
J/MNRAS/430/60 : Suzaku view of highly ionized outflows in AGN (Gofford+, 2013)
J/ApJ/773/92 : XMM survey of soft background. III. Gal. halo (Henley+, 2013)
J/A+A/553/A12 : XMM SSC survey of Galactic Plane (Nebot Gomez-Moran+, 2013)
J/A+A/627/A100 : HESS and Suzaku observations of Vela X (HESS Coll+, 2019)
https://heasarc.gsfc.nasa.gov/W3Browse/all/xray.html/ : Master X-ray catalog
on Heasarc
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Reg [1/107] Region number
5- 13 I9 --- Seq [100018010/904001010] Sequence
identifier in Suzaku archive
15- 34 A20 --- Name Target name in event header
36- 41 F6.2 deg GLON Galactic longitude of aim point
43- 48 F6.2 deg GLAT Galactic latitude of aim point
50- 54 F5.1 ks Exp [10.8/167] Effective exposure time
after screening
56 A1 --- l_DYE Limit flag on DYE
57- 58 I2 deg DYE [20/90] Screening criteria
for DYE_ELV cut
60- 63 F4.1 10+20cm-2 NH [0.6/27.6] Fixed H I column density (1)
65- 68 F4.2 keV kThalo [0.1/0.8]? Hot gaseous halo temperature
70- 73 F4.2 keV e_kThalo [0/0.3]? Lower uncertainty in kThalo
75- 78 F4.2 keV E_kThalo [0/0.2]? Upper uncertainty in kThalo
80 A1 --- l_EMhalo Limit flag on EMhalo
81- 86 F6.1 10-2pc/cm6 EMhalo [0.6/327]? Hot gaseous halo
emission measure
88- 90 F3.1 10-2pc/cm6 e_EMhalo [0.1/6.3]? Lower uncertainty in EMhalo
92- 94 F3.1 10-2pc/cm6 E_EMhalo [0.1/4.8]? Upper uncertainty in EMhalo
96 A1 --- l_[O/Fe] Limit flag on [O/Fe]
97-101 F5.2 [-] [O/Fe] [-1/1]? Hot gaseous halo O/Fe
abundance ratio
103 A1 --- f_[O/Fe] [f] Flag on [O/Fe] (2)
105-108 F4.2 [-] e_[O/Fe] [0.04/0.8]? Lower uncertainty in [O/Fe]
110-113 F4.2 [-] E_[O/Fe] [0.04/2.7]? Upper uncertainty in [O/Fe]
115 I1 [Sun] Zhalo [1]? Hot gaseous metal abundance except
for Fe
117-120 F4.1 10-15W/m2.deg2 Shalo [0.5/11.7]? Gasous halo unabsorbed
surface brightness (3)
122-124 F3.1 keV kTlocal [0.1]? Local component fixed temperature
126 A1 --- l_EMlocal Limit flag on EMlocal
127-131 F5.1 10-2pc/cm6 EMlocal [6.4/38.8]? Local component
emission measure
133-135 F3.1 10-2pc/cm6 e_EMlocal [0.6/6.4]? Lower uncertainty in EMlocal
137-139 F3.1 10-2pc/cm6 E_EMlocal [0.7/5.3]? Upper uncertainty in EMlocal
141 I1 [Sun] Zlocal [1]? Fixed metal abundance
143-146 F4.1 ph/cm2/s/sr NCXB [7.5/14.1]? CXB component normalization
at 1keV
148-150 F3.1 ph/cm2/s/sr e_NCXB [0.1/0.6]? Uncertainty in NCXB
152-154 F3.1 ph/cm2/s/sr E_NCXB [0.1/0.6]? Uncertainty in NCXB
156-168 A13 --- C/dof Best-fit C-statistics/degree of freedom
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Note (1): Calculated according to Willingale+ (2013MNRAS.431..394W 2013MNRAS.431..394W)
Note (2):
f = [O/Fe] fixed at 0.
Note (3): In the 0.4-1.0keV band. Units are 1e-12erg/cm2/s.deg2.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 22-Jul-2019