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.