Issue |
A&A
Volume 397, Number 2, January II 2003
|
|
---|---|---|
Page(s) | 635 - 643 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361:20021527 | |
Published online | 17 December 2002 |
Models for the positive latitude e-e+ annihilation feature
1
Centre d'Étude Spatiale des Rayonnements, 9 Av. du Colonel Roche, 31028 Toulouse Cedex, France
2
American University of Sharjah, College of Arts & Sciences, Physics Unit, Sharjah, UAE
Corresponding author: P. von Ballmoos, pvb@cesr.fr
Received:
2
August
2002
Accepted:
10
October
2002
Galactic maps of e-e+ annihilation radiation based on
CGRO-OSSE, SMM and TGRS data have indicated the existence of an
extended component at positive Galactic latitudes (,
), in addition to the emission from the galactic
bulge and disk (Purcell et al. [CITE]; Cheng et al. [CITE];
Milne et al. [CITE]; Milne et al. [CITE]). This Positive
Latitude Enhancement (PLE) was first attributed to an “annihilation
fountain" in the Galactic center (Dermer & Skibo [CITE]) but has since
been the object of several models.
After discussing the observational evidence for the PLE, we
investigate various models for the PLE: besides the scenarios
proposed in the literature, we have introduced a number of models
requiring relatively modest positron rates due to a local origin of
the e-e+ emission (local galactic-, solar system-, earth-
and spacecraft-environment origins). The various scenarios for the
PLE are constrained in the light of the latest OSSE-SMM-TGRS data
analysis results: we have looked at the possible positron production
mechanisms as well as the annihilation conditions in the different
physical environments (temperature and dust grain content) proposed
for the positive-latitude region. By constraining those parameters,
based on the recent limits for the line width and the positronium
fraction, we found that some of the models can essentially be
discarded. A number of other scenarios will have to await further
measurements and maps, such as will be possible with INTEGRAL's SPI
and IBIS instruments. We present a table/checklist of
model-falsification criteria.
Key words: elementary particles / ISM: bubbles / ISM: clouds / ISM: supernova remnants
© ESO, 2003
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