Modelling the gamma-ray emission from regions adjacent to HESS J1825-137 Tiffany Collins Supervisor: Gavin Rowell 1
HESS J1825-137 (H. E. S. S. Collaboration et al. 2018) 2
HESS J1825-137 (HAWC Collaboration et al. (2019)) ● HAWC observatory observes γ-rays > 100 TeV from this source. ● A TeV halo can be seen around HESS J1825-137. 3 (H. E. S. S. Collaboration et al. 2018)
HESS J1826-130 (H. E. S. S. Collaboration et al. 2018) 14 11 0.4 HESS J1825-137 HESS J1825-137 8 ● Possible PeVatron candidate. 6 Galactic Latitude (deg) 3 HESS J1826-130 0 0.0 ● Originally considered an p TS extension of HESS J1825-137. SNR G18.6-0.2 -0.4 Come back to this later... PSR J1826-1256 PSR J1826-1256 -0.8 -1.2 PWN G18.5-0.4 PWN G18.5-0.4 19.2 18.8 18.4 18.0 17.6 Galactic Longitude (deg) 4
Yama ● A 2019 paper by Araya et al described new GeV emission observed by Fermi-LAT to the south of HESS J1825-137. What particle accelerator accelerates particles to necessary energetics? ● Related to HESS J1825-137 or LS 5039? (Araya et al. 2019) 5
Possible Accelerators of High Energy Particles HESS J1825-137 LS 5039 Impulsive (progenitor SNR) Continuous (PWN) Impulsive (progenitor SNR) Continuous (radio jet) Hadronic Leptonic Hadronic Leptonic Hadronic Leptonic Hadronic Leptonic PWN : Pulsar Wind Nebula 6 SNR: Supernova Remnant
NANTEN 12CO(1-0) data 15-30 km/s (1.6-2.8 kpc) 40-60 km/s (3.5-4.5 kpc) Gamma-ray flux due to proton-proton and bremsstrahlung interactions is proportional to the density of gas 7
Hα data 120 ● Possible SNR rim for HESS J1825- 0° 137 seems to intersect Yama-B 100 ● Hα “hole” towards object B which the Galactic Latitiude (deg) -1° CO cloud seen in the 15-30 km/s 80 range seems to fit into. R -2° A 60 ● Radio jets from LS 5039 seem to B point in the general direction of H rim 40 C -3° Fermi-LAT Object ABC Yama. LS 5039 PSR 1826-1334 HESS J1825-137 20 20° 19° 18° 17° 16° 15° Galactic Longitude (deg) (Finkbeiner 2003) 8
Progenitor SNR for HESS J1825-137 as the accelerator? Successful models: 10 10 p-p Fermi-LAT GeV region ● Hadronic – Impulsive – Yama-B – 21 & 40 kyrs Fermi-LAT Object B W systematic variation E c systematic variation systematic variation ● Assuming constant energy density, the SNR 1 ) 10 11 contains 5x10 50 ergs of energy. 2 s E 2 dN / dE ( ergcm ● BUT the model has to explain Yama-A and Yama-C simultaneously 10 12 ● Yama-A & C requires > 10 51 ergs within SNR. Note: During modelling, only consider the 10 13 object’s (eg Yama-B) contribution to the total 10 6 10 4 10 2 10 0 10 2 10 4 E (TeV) SED. 9
PWN for HESS J1825-137 as the accelerator? 10 10 ● Leptonic – Continuous – 21 & 40 kyrs ● Required injection luminosity of electrons ~ 10 37 1 ) 10 11 ergs/s 2 s E 2 dN / dE ( ergcm ● Spin down power of pulsar ~ 10 36 ergs/s ● May represent an earlier epoch in the PWN 12 10 Bremsstrahlung history where spin down ~ 10 38 ergs/s (braking IC synchrotron index n=3) Fermi-LAT GeV region Fermi-LAT Object B W systematic variation ● Why would the entirety of the spin down power E c systematic variation systematic variation from pulsar be channelled into Yama? 10 13 14 11 5 10 1 10 4 10 10 10 8 10 10 2 E (TeV) 10
HESS J1825-137 particle transport ● Model electron diffusion vs cooling time between PWN and Yama-B ● Assuming basic diffusion R ( E,t )= √ 2 D ( E ,t ) B E / TeV D ( E,t )= χ D 0 √ B / 3 μ G ● Requires fast diffusion (χ>0.1) for electrons to reach Yama in the age of HESS J1825-137 ● OR requires a more powerful pulsar (Araya et al. 2019) 11
Progenitor SNR for LS 5039 10 10 ● Using ages between 10 3 – 10 6 yr. p-p data points data points (1/3) Energy Range ● No impulsive model meets necessary conditions Cutoff Range Index Range to be successful (energetics ~ 10 51-52 ergs) 1 ) 10 11 2 s ● The SNR associated with the compact object E 2 dN / dE ( ergcm within LS 5039 would be fading or already apart of the ISM. 10 12 10 13 4 10 4 10 6 10 10 2 10 0 10 2 E (TeV) 12
Continuous injection of particles from LS 5039 via accretion 10 10 ● Leptonic – Continuous – 1x10 6 yrs ● Accretion power of matter onto compact object 1 ) 10 11 from companion star = 8 x 10 35 ergs/s (Casares 2 s et al. 2005) E 2 dN / dE ( ergcm ● Requires injection luminosity ~ 10 36 ergs 10 12 Bremsstrahlung ● Possible within systematic variation. IC synchrotron Fermi-LAT GeV region Fermi-LAT Object A ● LS 5039 ~ 0.1 million years old (Moldón et al. W systematic variation E c systematic variation 2012) systematic variation 13 10 10 14 10 11 10 8 10 5 10 2 10 1 10 4 E (TeV) 13
HESS J1825-137 & LS 5039 combination A combination of processes from LS 5039 & HESS J1825- 137 is still possible (Araya et al. 2019) 14
What’s next? MULTIZONE MODELLING! 0.1-1 TeV 1-5 TeV 5-10 TeV ● Multizone Modelling involves solving the particle transport equation over a 3D grid of varying ISM density and B-field. 15
Yama 16
HESS J1826-130 OR Python package gamma-py can predict what CTA will see. 17
Outline ● Attempted to model the GeV Fermi-LAT emission towards the south of HESS J1825- 137. ● The source of acceleration of high energy particles resulting in this emission was assumed to be either an accelerator linked to HESS J1825-137 or LS 5309. ● Neither model alone could explain the GeV gamma-rays. A combination of the two sources may still be possible. ● The next step is Multizone Modelling towards the Fermi-LAT emission. ● Multizone Modelling towards HESS J182-130 will attempt to predict CTA observations. References for single and multizone modelling: ● Sano, H., Yamane, Y., Voisin, F., et al. 2017a, ApJ, 843, 61 ● Voisin, Fabien. “Environment Studies of Pulsar Wind Nebulae and Their Interactions with the Interstellar Medium.” 2017. 18
Backup – Equations governing SED Hadronic (proton-proton): p+p → π 0 + π + + π - π 0 → γ + γ ∞ dN = ∫ A max ( T p ) F ( E γ ,T p ) dE p dE γ E p = E γ Multiplicity of neutral pions Parameterisation Function 19
Backup – Equations governing SED Leptonic (Inverse Compton): e -* +γ * → e - + γ n ( ϵ ) d ϵ dN = 3 4 σ T c ∫ F KN ( E e , E γ , ϵ ) ϵ dE γ (Bremsstrahlung): e -* + Z → e - + Z + γ dN = nc ∫ d σ ( E e , E γ ,Z ) dE e dE γ 20
Backup – Equations governing SED (Synchrotron): e -* + B → e - 3 B ∞ P ( ν )= √ 3 e ν ν c ∫ K 5 ( x ) dx 2 mc ν 3 ν c 21
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