J/MNRAS/507/5161ivo://CDS.VizieR/J/MNRAS/507/5161doi:10.26093/cds/vizier.75075161CDSSong D.Macias O.Horiuchi S.Crocker R.M.Nataf D.M.2024-11-06T20:34:24Z2024-09-10T15:16:29ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frmilky-way-galaxyglobular-star-clusterspulsarsgamma-ray-astronomymetallicitystellar-massesphotometryinfrared-astronomyvisible-astronomyultraviolet-astronomyx-ray-sourcesstellar-distanceMillisecond pulsars are very likely the main source of gamma-ray emission from globular clusters. However, the relative contributions of two separate emission processes - curvature radiation from millisecond pulsar magnetospheres versus inverse Compton emission from relativistic pairs launched into the globular cluster environment by millisecond pulsars - have long been unclear. To address this, we search for evidence of inverse Compton emission in 8-yr Fermi-LAT data from the directions of 157 Milky Way globular clusters. We find a mildly statistically significant (3.8{sigma}) correlation between the measured globular cluster gamma-ray luminosities and their photon field energy densities. However, this may also be explained by a hidden correlation between the photon field densities and the stellar encounter rates of globular clusters. Analysed in toto, we demonstrate that the gamma-ray emission of globular clusters can be resolved spectrally into two components: (i) an exponentially cut-off power law and (ii) a pure power law. The latter component - which we uncover at a significance of 8.2{sigma} - has a power index of 2.79 +/- 0.25. It is most naturally interpreted as inverse Compton emission by cosmic-ray electrons and positrons injected by millisecond pulsars. We find the luminosity of this power-law component is comparable to, or slightly smaller than, the luminosity of the curved component, suggesting the fraction of millisecond pulsar spin-down luminosity into relativistic leptons is similar to the fraction of the spin-down luminosity into prompt magnetospheric radiation.2021MNRAS.507.5161Shttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/MNRAS/507/5161CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toVII/202 : Globular Clusters in the Milky Way (Harris, 1997)J/ApJ/766/136 : Stellar encounter rates in Galactic GCs (Bahramian+, 2013)J/MNRAS/478/1520 : Milky Way globular clusters data (Baumgardt+, 2018)J/ApJS/247/33 : The Fermi LAT fourth source catalog (4FGL) (Abdollahi+,2020)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/MNRAS/507/5161https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/MNRAS/507/5161http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/MNRAS/507/5161https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/MNRAS/507/5161https://vizier.iucaa.in/viz-bin/votable?-source=J/MNRAS/507/5161http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/MNRAS/507/5161GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/MNRAS/507/5161/tablea1 (Parameters and data analysis results of 127 GCs not detected in the 4FGL data)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/507/5161/tablea1?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/507/5161/tablea1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/507/5161/tablea1?GETtext/xml+votable180.050000true272.4020833-20.77888890.0055555555555555560/https://cdsarc.cds.unistra.fr/viz-bin/moc/J/MNRAS/507/5161?format=asciiGamma-rayX-rayUVOpticalInfraredRadiodefaultJ/MNRAS/507/5161/tablea1Parameters and data analysis results of 127 GCs not detected in the 4FGL datauMWGalactic Milky Way photon field energy density (u_MW_) (4)eV.cm**-3em.energy;obs.fieldfloatl_uTLower limit on uTotal (l_uT)meta.code.errorcharuTTotal photon field energy density (u_Total_) (5)eV.cm**-3phys.energy.densityfloatRDistance from the Sun (R_{sun})kpcpos.distance;pos.heliocentricfloatl_FgammaUpper limit flag on Fgamma (l_Fgamma)meta.code.errorcharFgamma95 per cent confidence level {gamma}-ray upper limits photon flux (F_{gamma}_) (6)1e-08ph.cm**-2.s**-1phot.flux.density;em.gamma.hardfloatl_LgammaUpper limit flag on Lgamma (l_Lgamma)meta.code.errorcharLgamma95 per cent confidence level {gamma}-ray upper limits luminosity (L_{gamma}_) (6)1e+27Wphys.luminosity;em.gammafloat_RApositions from Simbad name (right ascension part)degpos.eq.ra;meta.main_DEpositions from Simbad name (declination part)degpos.eq.dec;meta.mainSimbadNameSimbad column added by the CDSmeta.idcharnullablerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintIDCluster identification number (ID) (1)meta.id;meta.maincharGammac? Integrated stellar encounter rate ({Gamma}_c_) (2)stat.paramfloatnullable[Fe/H]? Iron abundance ([Fe/H])log(Sun)phys.abund.FefloatnullableM*? Stellar mass (M_*_) (3)log(100000solMass)phys.massfloatnullable