Astrophysical charge exchange Liyi Gu (SRON → RIKEN, Japan) Jelle Kaastra (SRON) SPEX: collisional, photoionized, charge exchange plasma https://www.sron.nl/astrophysics-spex AtomDB workshop, University of Georgia, 2017/11/02
Astrophysical chargeexchange
Liyi Gu (SRON→ RIKEN,Japan)Jelle Kaastra (SRON)
SPEX:collisional,photoionized,chargeexchangeplasmahttps://www.sron.nl/astrophysics-spex
AtomDB workshop,UniversityofGeorgia,2017/11/02
Heavy ionH atom
ground-state
ElectronPotentialEnergy radialdistance(a.u.)
Barrier Excitedstate
ground-state
Targetatom
Projectileion
• atom-ioncollision• fallontoahighlyexcitedlevel• cascadetothegroundstatebyemittingphoton
• newCXcode(n,l,v-resolved)inSPEX byGu+2016,incorporatinglatestcrosssectioncalculations(kronos,Mullen+2017)
• Bothsingle-v andMaxwellianoptions
Chargeexchangeinanutshell
Chargeexchangeastrophysics
• Firstintroducedincomets(Lisse+1996)
• SolarwindCXinheliosphereandplanets(Dennerl+2006,Branduardi-Raymont+2007,Smith+2014)
• Supernovaremnants(Katsuda+2011,Cumbee+2014),starburstgalaxies(Tsuru+2007,Cumbee+2016).
• Clustersofgalaxies(Fabian+2011,Walker+2015)
Cygnusloop
Heliosphere
opticalimageonX-raybackgroundDennerl etal.2003
RGSspectrum(Gu etal.2016,Mullenetal.2017)
X-ray comets:3-Ddiagnostic ofsolar winds
SNRinour Galaxy:CXorionized absorption
• Spectrumbestdescribedbyionizedabsorptionwithcolumndensity/temperaturewellmatchingtheGalactichalomodel.NPSisinthehalo!
• Solvethe‘toohighN-to-Oabundance’problem(Miller+2008).
Northpolarspur(Gu+2016)
AGNwindCXlurking inUVNGC1275(Gu+2017)
• Offsetvelocity~3000km/s
• agreewithLyaabsorbers
• AGNoutflow
HubbleSTIS
• Bulbul+2014andBoyarsky+2014claima3.5keVlineinstackedclusterspectra,notassociatedwithanyknownatomicline.
• Interpretedaspossibledecayofdarkmattercandidate(so-calledsterileneutrino)
• >300citations,mostofthemarepureparticlesciencediscussingpossibledecaymodel.
• Controversial:instrumentaleffects,afewclaimsofdetectionandmanynon-detectionafterwards,includinganegativeresultwith1.6Ms XMMdataofadwarfgalaxy.
Bulbul+2014
Boyarsky+2014
3.5keV linefrom galaxy clusters
• Chargeexchangeoffullyionizedsulfurwithhydrogenatomproducesalineatnearly3.5keV
• Clustershavesufficientingredientsforchargeexchange at3.5keV.
• Hitomi datasupports.
Gu+2015
Possible atomic origin
CXbetter explains 3.5keV dilemmaColdgas? 3.5keV?
Perseuscluster Massive> 1010𝑀𝑠𝑢𝑛 Yes
Virgocluster(M87) Little~106𝑀𝑠𝑢𝑛 No
Coma cluster Little No
Ophiuchuscluster Little No?
M31 Yes Yes
Galacticcenter Yes Yes?
Dwarfgalaxies No No(1.6Ms)
21clusters,XMM/RGS(Gu+2017)
• 2.8𝜎 featureatOVIIILy𝛿• Cannotbeironlines• Cannotbeastrophysicaleffects• inlinewiththesulfurmodelfor3.5keV
ColorsfordifferentCXvelocities
Newsupports:O8+CXwith H
AffectingOabundance
100km/s
800km/s400km/s
• OabundanceofhotICM(mostlymeasuredbyOVIIILya)mightbeoverestimatedby8 − 22%(for𝑣 = 100 − 800 km/s).
• Accurateabundancemeasurementisakeyscience• Hitomi datashowsFemightbeoverestimatedby5 − 10% forCX• CXlineintensity~𝑁678v𝑞678,thermallineintensity~𝑁6𝑅<=> −differentz-scaling• CrosssectionfromJanev+1993,updateneeded
Conclusion• CXiscommonly regarded only asasystematics inastrophysics
• Can be apotentially importantsystematics for chemical compositionofclusters(hence starforming history)
• High resolutionUV/X-rayspectroscopyneededtomakeCXaserioustopic:Ø 3-DsolarwindsØ AGNwinds/feedbackØ FormationofHafilamentsinclusters
• What’s next:WHIMaccretion?CXwhite paperfor XARM/Athena?
• Accuratecrosssection calculationand labdatasupportfrom H- to Ne- like.