A Maximum Entropy Map of the 511 [CLC]ke[/CLC]V Positron Annihilation Line Emission Distribution Near the Galactic Center

Liu, Cheng; Leventhal, M.; Smith, David M.; Purcell, W. R.; Tueller, J.; Connors, A.; Dixon, David; Kinzer, R. L.; Skibo, J. G.

doi:10.1086/310638

Cited by 40 publications

(21 citation statements)

References 23 publications

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“…The OSSE instrument that flew during 1991−2000 on-board CGRO accumulated so far the largest database for studying the 511 keV line intensity distribution. The observations of the Gamma-Ray Spectrometer onboard the Solar Maximum Mission (SMM) (1980−1988) and of the Transient Gamma-Ray Spectrometer (TGRS) on-board the WIND mission (1995−1997) have also been used to estimate the overall 511 keV line flux and maximum emission size (Purcell et al 1994;Kinzer et al 1996;Tueller et al 1996;Cheng et al 1997;Purcell et al 1997;Harris et al 1998;Milne et al 2000;Kinzer et al 2001). …”

Section: Comparison With Earlier Measurementsmentioning

confidence: 99%

“…The celestial 511 keV intensity distribution should be tied to the spatial source distribution, although positron diffusion and effects associated with the annihilation physics may to some extent blur this link. First estimations of the 511 keV emission morphology were obtained by the Oriented Scintillation Spectrometer Experiment (OSSE) on-board the Compton Gamma-Ray Observatory (CGRO) satellite (Purcell et al 1994;Cheng et al 1997;Purcell et al 1997;Milne et al 2000;Milne et al 2001), but observations were restricted to the inner Galaxy, giving only a limited view of the 511 keV emission distribution. With the launch of ESA's INTEGRAL satellite in October 2002, a new gamma-ray observatory is available that allows a detailed study of positron annihilation signatures.…”

Section: Introductionmentioning

confidence: 99%

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The all-sky distribution of 511 keV electron-positron annihilation emission

Knödlseder¹,

Jean²,

Lonjou³

et al. 2005

A&A

313

394

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Abstract. We present a map of 511 keV electron-positron annihilation emission, based on data accumulated with the SPI spectrometer aboard ESA's INTEGRAL gamma-ray observatory, that covers approximately ∼95% of the celestial sphere. Within the exposed sky area, 511 keV line emission is significantly detected towards the galactic bulge region and, at a very low level, from the galactic disk. The bulge emission is highly symmetric and is centred on the galactic centre with an extension of ∼8• (FWHM). The emission is equally well described by models that represent the stellar bulge or halo populations. The detection significance of the bulge emission is ∼50σ, that of the galactic disk is ∼4σ. The disk morphology is only weakly constrained by the present data, being compatible with both the distribution of young and old stellar populations. The 511 keV line flux from the bulge and disk components is (1.05 ± 0.06) × 10 −3 ph cm −2 s −1 and (0.7 ± 0.4) × 10 −3 ph cm −2 s −1 , respectively, corresponding to a bulge-to-disk flux ratio in the range 1−3. Assuming a positronium fraction of f p = 0.93 this translates into annihilation rates of (1.5 ± 0.1) × 10 43 s −1 and (0.3 ± 0.2) × 10 43 s −1 , respectively. The ratio of the bulge luminosity to that of the disk is in the range 3−9. We find no evidence for a point-like source in addition to the diffuse emission, down to a typical flux limit of ∼10 −4 ph cm −2 s −1 . We also find no evidence for the positive latitude enhancement that has been reported from OSSE measurements; our 3σ upper flux limit for this feature is 1.5 × 10 −4 ph cm −2 s −1 . The disk emission can be attributed to the β + -decay of the radioactive species 26Al and 44 Ti. The bulge emission arises from a different source which has only a weak or no disk component. We suggest that Type Ia supernovae and/or low-mass X-ray binaries are the prime candidates for the source of the galactic bulge positrons. Light dark matter annihilation could also explain the observed 511 keV bulge emission characteristics.

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Section: Comparison With Earlier Measurementsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The all-sky distribution of 511 keV electron-positron annihilation emission

Knödlseder¹,

Jean²,

Lonjou³

et al. 2005

A&A

313

394

View full text Add to dashboard Cite

show abstract

“…Recent data have allowed a determination of the physical conditions in the interstellar medium where the positrons annihilate (Guessoum et al 2004;Churazov et al 2005;Jean et al 2006), based on an improved understanding of the various physical processes involved (Guessoum et al 2005). In parallel, considerable progress has been made in mapping the Galaxy at 511 keV, first by CGRO-OSSE (Purcell et al 1994;Cheng et al 1997;Purcell et al 1997;Milne et al 2000;Milne et al 2001) and, in particular, recently by INTEGRAL-SPI (Knödlseder et al 2005).…”

Section: Introduction: Galactic Positron Sourcesmentioning

confidence: 99%

Microquasars as sources of positron annihilation radiation

Guessoum¹,

Jean²,

Prantzos³

2006

A&A

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We consider the production of positrons in microquasars, i.e. X-ray binary systems that exhibit jets frequently, but not continuously. We estimate the production rate of positrons in microquasars, both by simple energy considerations and in the framework of various proposed models. We then evaluate the collective emissivity of the annihilation radiation produced by Galactic microquasars and we find that it might constitute a substantial contribution to the annihilation flux measured by INTEGRAL/SPI. We also discuss the possible spatial distribution of Galactic microquasars, on the basis of the (scarce) available data and the resulting morphology of the flux received on Earth. Finally, we consider nearby "misaligned" microquasars, with jets occasionally hitting the atmosphere of the companion star; these would represent interesting point sources, for which we determine the annihilation flux and the corresponding light curve, as well as the line's spectral profile. We discuss the possibility of detection of such point sources by future instruments.

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“…• , b ≈ 7 • ), in addition to the emission from the galactic bulge and disk (Purcell et al 1997;Cheng et al 1997;Milne et al 2000;Milne et al 2001). This Positive Latitude Enhancement (PLE) was first attributed to an "annihilation fountain" in the Galactic center (Dermer & Skibo 1997) but has since been the object of several models.…”

Section: Abstract Galactic Maps Of Ementioning

confidence: 99%

Models for the positive latitude e^-e⁺annihilation feature

Ballmoos

Guessoum

Jean

et al. 2002

A&A

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Abstract. 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 (l ≈ −2• , b ≈ 7 • ), in addition to the emission from the galactic bulge and disk (Purcell et al. 1997;Cheng et al. 1997;Milne et al. 2000;Milne et al. 2001). This Positive Latitude Enhancement (PLE) was first attributed to an "annihilation fountain" in the Galactic center (Dermer & Skibo 1997) 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.

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A Maximum Entropy Map of the 511 [CLC]ke[/CLC]V Positron Annihilation Line Emission Distribution Near the Galactic Center

Cited by 40 publications

References 23 publications

The all-sky distribution of 511 keV electron-positron annihilation emission

The all-sky distribution of 511 keV electron-positron annihilation emission

Microquasars as sources of positron annihilation radiation

Models for the positive latitude e^-e⁺annihilation feature

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A Maximum Entropy Map of the 511 [CLC]ke[/CLC]V Positron Annihilation Line Emission Distribution Near the Galactic Center

Cited by 40 publications

References 23 publications

The all-sky distribution of 511 keV electron-positron annihilation emission

The all-sky distribution of 511 keV electron-positron annihilation emission

Microquasars as sources of positron annihilation radiation

Models for the positive latitude e-e+annihilation feature

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Product

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Models for the positive latitude e^-e⁺annihilation feature