The Galactic Positron Annihilation Radiation \amp The Propagation of Positrons in the Interstellar Medium Export

@article{citeulike:2487184, abstract = {The ratio of the luminosity of 511 keV positron annihilation radiation, measured by INTEGRAL, from the Galactic positron bulge (\<1.5 kpc) compared to that of the disk is \~{}2. This ratio is roughly a factor of 5 larger than that expected simply from the bulge/disk ratio of \~{}0.3 of the Galactic supernovae, which are thought to be the principal source of the annihilating positrons through the decay of radionuclei made by explosive nucleosynthesis in the supernovae. We show that the measured 511 keV luminosity ratio can be understood in the context of a Galactic supernova origin, if the detailed propagation of these \~{}MeV positrons in the various phases of the interstellar medium is also taken into consideration, since these relativistic positrons must first slow down to energies \<10 eV before they can annihilate. From this we find that roughly 50\% of the positrons produced in the disk escape from it into the halo and bulge before they slow down and annihilate. This escape accounts for the very low observed annihilation radiation luminosity of the disk. We also show that the expected annihilation sites of the propagating positrons in both the bulge and the disk are almost entirely in the warm phases of the interstellar medium. Such annihilation is quite consistent with both the observed fraction (\~{}93+/-7\%) of annihilation via Positronium and the observed ratio (\~{}0.5) of broad (\~{}5.4 keV) to narrow (\~{}1.3 keV) components of the bulge 511 keV line emission.}, archivePrefix = {arXiv}, author = {Higdon, J. C. and Lingenfelter, R. E. and Rothschild, R. E.}, citeulike-article-id = {2487184}, citeulike-linkout-0 = {http://arxiv.org/abs/0711.3008}, citeulike-linkout-1 = {http://arxiv.org/pdf/0711.3008}, citeulike-linkout-2 = {http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2007arXiv0711.3008H}, eprint = {0711.3008}, journal = {ArXiv e-prints}, keywords = {bibtex, cited, galactic-center, integral, positrons, uncited}, month = {November}, posted-at = {2009-04-07 10:04:45}, priority = {2}, title = {The Galactic Positron Annihilation Radiation {\amp The Propagation of Positrons in the Interstellar Medium}}, url = {http://arxiv.org/abs/0711.3008}, volume = {711}, year = {2007} }

TY - JOUR ID - citeulike:2487184 L3 - citeulike-article-id:2487184 N2 - The ratio of the luminosity of 511 keV positron annihilation radiation, measured by INTEGRAL, from the Galactic positron bulge (<1.5 kpc) compared to that of the disk is ~2. This ratio is roughly a factor of 5 larger than that expected simply from the bulge/disk ratio of ~0.3 of the Galactic supernovae, which are thought to be the principal source of the annihilating positrons through the decay of radionuclei made by explosive nucleosynthesis in the supernovae. We show that the measured 511 keV luminosity ratio can be understood in the context of a Galactic supernova origin, if the detailed propagation of these ~MeV positrons in the various phases of the interstellar medium is also taken into consideration, since these relativistic positrons must first slow down to energies <10 eV before they can annihilate. From this we find that roughly 50% of the positrons produced in the disk escape from it into the halo and bulge before they slow down and annihilate. This escape accounts for the very low observed annihilation radiation luminosity of the disk. We also show that the expected annihilation sites of the propagating positrons in both the bulge and the disk are almost entirely in the warm phases of the interstellar medium. Such annihilation is quite consistent with both the observed fraction (~93+/-7%) of annihilation via Positronium and the observed ratio (~0.5) of broad (~5.4 keV) to narrow (~1.3 keV) components of the bulge 511 keV line emission. JF - ArXiv e-prints TI - The Galactic Positron Annihilation Radiation {\amp The Propagation of Positrons in the Interstellar Medium} VL - 711 KW - bibtex KW - cited KW - galactic-center KW - integral KW - positrons KW - uncited AU - Higdon, JC AU - Lingenfelter, RE AU - Rothschild, RE PY - 2007/November// UR - http://arxiv.org/abs/0711.3008 ER -