High-precision analyses of Lyα damping wing of gamma-ray bursts in the reionization era: On the controversial results from GRB 130606A at z = 5.91

Publications of the Astronomical Society of Japan

Hattori, Takashi¹  Aoki, Kentaro¹  Totani, Tomonori²  Kawai, Nobuyuki³ 

[1] Subaru Telescope, National Astronomical Observatory of Japan, 650 North A'ohoku Place, Hilo, HI 96720, USA;Department of Astronomy, The University of Tokyo, Hongo, Tokyo 113-0033, Japan;Department of Physics, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551, Japan

关键词: "dark ages;    reionization;    first stars";    "gamma-ray burst: individual: GRB 130606A";    "techniques: spectroscopic";   

DOI  :  10.1093/pasj/psv123

学科分类：天文学(综合)

来源: Oxford University Press

【 摘 要 】

TheunprecedentedlybrightafterglowofSwiftGRB130606Aatz=5.91gaveusauniqueopportunitytoprobethereionizationerathroughhigh-precisionanalysesoftheredwarddampingwingofLyαabsorption,butthereportedconstraintsontheneutralhydrogenfraction$$(!f_{mH,{smallI}})$$inintergalacticmedium(IGM)derivedfromspectratakenbydifferenttelescopesareincontradictiontoeachother.HereweexaminetheoriginofthisdiscrepancybyanalyzingthespectrumtakenbytheVeryLargeTelescope(VLT)withourownanalysiscodepreviouslyusedtofittheSubaruspectrum.ThoughtheVLTteamreportednoevidenceforIGMH iusingtheVLTspectrum,weconfirmourpreviousresultofpreferringnon-zeroIGMH i(thebestfit$$f_{mH,{smallI}}sim0.06$$,whenIGMH iextendstotheGRBredshift).ThefitresidualsoftheVLTspectrumusingthemodelwithoutIGMH ishowthesamesystematictrendastheSubaruspectrum.Weconsiderthatthelikelyoriginofthediscrepancybetweenthetwoteamsisthedifferenceofthewavelengthrangesadoptedinthefittings;ourwavelengthrangeiswiderthanthatoftheVLTteam,andalsoweavoidedtheshortestwavelengthrangeofdeepLyαabsorption(λobslt;8426 Å),becausethisregionisdominatedbyH iinthehostgalaxyandthesystematicuncertaintyabouthostH ivelocitydistributionislarge.WealsostudythesensitivityoftheseresultstotheadoptedLyαcross-sectionformulae,rangingfromtheclassicalLorentzianfunctiontothemostrecentonetakingintoaccountfullyquantummechanicalscattering.Itisfoundthatthepreferencefornon-zeroIGMH iisrobustagainstthechoiceofthecross-sectionformulae,butitisquantitativelynotnegligibleandhenceoneshouldbecarefulinfutureanalyses.

【 授权许可】

Unknown