TY - JOUR
T1 - Absorption of Gamma-Ray Burst X-Ray Afterglows by the Missing Baryons
T2 - Confronting Observations with Cosmological Simulations
AU - Grauer, Matan
AU - Behar, Ehud
N1 - Publisher Copyright:
© 2023. The Author(s). Published by the American Astronomical Society.
PY - 2023/8/1
Y1 - 2023/8/1
N2 - A large fraction of the baryons at low redshift are undetected and likely reside in the tenuous, hot intergalactic medium (IGM). One way to probe the missing baryons is through their absorption of bright sources. The anomalous absorption excess in the X-ray afterglows of gamma-ray bursts (GRBs) has been suggested to result from the missing baryons. In order to test this hypothesis, the present paper employs IllustrisTNG simulations to compute the X-ray absorption effect on cosmological distances. The simulation shows that ionization of H and He in the IGM leaves the metals responsible for >60% of the X-ray opacity of high-z sources. The high-z asymptotic optical depth at 0.5 keV in the simulation reaches 0.15 ± 0.07, while the GRB afterglow values tend to ≈0.4, implying that the missing baryons can account for a significant fraction of the observed opacity. The remaining discrepancy is ascribed mainly to the low average metallicity in the simulation, which drops from 0.06 solar at z = 0 to 0.01 at z = 3, and which is below previously measured values.
AB - A large fraction of the baryons at low redshift are undetected and likely reside in the tenuous, hot intergalactic medium (IGM). One way to probe the missing baryons is through their absorption of bright sources. The anomalous absorption excess in the X-ray afterglows of gamma-ray bursts (GRBs) has been suggested to result from the missing baryons. In order to test this hypothesis, the present paper employs IllustrisTNG simulations to compute the X-ray absorption effect on cosmological distances. The simulation shows that ionization of H and He in the IGM leaves the metals responsible for >60% of the X-ray opacity of high-z sources. The high-z asymptotic optical depth at 0.5 keV in the simulation reaches 0.15 ± 0.07, while the GRB afterglow values tend to ≈0.4, implying that the missing baryons can account for a significant fraction of the observed opacity. The remaining discrepancy is ascribed mainly to the low average metallicity in the simulation, which drops from 0.06 solar at z = 0 to 0.01 at z = 3, and which is below previously measured values.
UR - http://www.scopus.com/inward/record.url?scp=85168587398&partnerID=8YFLogxK
U2 - 10.3847/1538-4357/ace1e8
DO - 10.3847/1538-4357/ace1e8
M3 - ???researchoutput.researchoutputtypes.contributiontojournal.article???
AN - SCOPUS:85168587398
SN - 0004-637X
VL - 953
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 2
M1 - 158
ER -