Query : 2007A&A...475..901K

2007A&A...475..901K - Astronomy and Astrophysics, volume 475, 901-914 (2007/12-1)

OVII and OVIII line emission in the diffuse soft X-ray background: heliospheric and galactic contributions.


Abstract (from CDS):

We study the 0.57keV (O VII triplet) and 0.65keV (O VIII) diffuse emission generated by charge transfer collisions between solar wind (SW) oxygen ions and interstellar H and He neutral atoms in the inner Heliosphere. These lines which dominate the 0.3-1.0keV energy interval are also produced by hot gas in the galactic halo (GH) and possibly the Local Interstellar Bubble (LB). We developed a time-dependent model of the Solar Wind Charge-Exchange (SWCX) X-ray emission, based on the localization of the Solar Wind Parker spiral at each instant. We include input SW conditions affecting three selected fields, as well as shadowing targets observed with XMM-Newton, Chandra and Suzaku satellites and calculate X-ray emission in the oxygen lines O VII and O VIII in order to determine the SWCX contamination and the residual emission to attribute to the galactic soft X-ray background. We obtain ground level intensities and/or simulated lightcurves for each target and compare to X-ray data from the three instruments mentioned. The local 3/4 keV emission (due essentially to O VII and O VIII) detected in front of shadowing clouds is found to be entirely explained by the CX heliospheric emission. No emission from the LB is needed at these energies. The observed and modeled range of the foreground oxygen emission is 0.3-4.6LU (Line Units = photons/cm2/s/sr) for OVII and 0.02-2.1LU for OVIII depending on directions and conditions. Using the model predictions we subtract the heliospheric contribution to the measured emission and derive the halo contribution. We also correct for an error in the preliminary analysis of the Hubble Deep Field North (HDFN). We find intensities of 4.9+1.29–1.04LU, 6.25+0.63–0.98LU, 11.15+2.36–1.41LU for OVII and 1.41+0.60–0.49LU, 1.62+0.35–0.49LU, 1.97+1.11–0.71LU for OVIII towards the Marano Field, the Hubble Deep Field-North, and the Lockman Hole respectively.

Abstract Copyright:

Journal keyword(s): solar wind - X-rays: diffuse background - X-rays: ISM - ISM: general - Galaxy: halo

Simbad objects: 9

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Number of rows : 9
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
1 MBM 12 MoC 02 56 50 +19 32.0           ~ 218 1
2 NAME Marano1 Field reg 03 15.2 -55 14           ~ 20 0
3 NAME Lockman Hole reg 10 45 00.0 +58 00 00           ~ 793 0
4 NAME Hubble Deep Field reg 12 36 49.5 +62 12 58           ~ 1877 1
5 NAME Loop I SR? 15 01 -38.7           ~ 353 2
6 LDN 57 DNe 17 22 38.2 -23 49 34           ~ 300 1
7 NAME NEP reg 18 00 00.000 +66 33 38.55           ~ 304 0
8 NAME Local Group GrG ~ ~           ~ 7726 0
9 NAME Local Bubble ISM ~ ~           ~ 796 0

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