Interstellar gas towards the VHE gamma-ray sources Interstellar gas - - PowerPoint PPT Presentation

Interstellar gas towards the VHE gamma-ray sources Interstellar gas towards the VHE gamma-ray sources HESS J1640-465 & HESS J1641-463 HESS J1640-465 & HESS J1641-463

James Lau, Gavin Rowell, Gary Hill University of Adelaide 2015 Nanten2 Workshop

Introduction Introduction

• HESS J1640-465 & HESS J1641-463

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Luminous TeV gamma-ray sources discovered by H.E.S.S.

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True nature of the sources are still being debated

• Hadronic, leptonic or combination of both?
• HESS group at the University of Adelaide - Radeladio

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Using molecular lines to probe the interstellar medium towards VHE gamma-ray sources

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Help reveal the environment theses sources exist in

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Morphological matches with TeV emission?

• Hadronic interaction between cosmic-rays and ambient medium

HESS observations HESS observations

• HESS J1640-465

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Discovered as part of a HESS survey of the galactic plane (2006)

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Located at l = 338.2, b=-0.02 degrees (Galactic coordinates)

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Intrinsic extended with a Gaussian width of 4.3 ± 0.2' (2014)

Aharonian et al. (2005) HESS Collaboration (2014)

HESS observations HESS observations

• HESS J1641-463

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HESS observations towards HESS J1640-465 during 2004-2011 revealed a new TEV source, HESS J1641-463

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Source is revealed at high energies

• Significance of 8.5 sigma above 4 TeV

Oya et al. (2013)

Projected gamma-ray flux All events E > 1 T eV E > 2 T eV E > 3 T eV E > 4 T eV E > 5 T eV

HESS J1640-465 in X-rays HESS J1640-465 in X-rays

Funk et al. (2007) Gotthelf et al. (2014)

• XMM Newton

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Slightly asymmetric X-ray source

• NuSTAR – recent pulsar detection!

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Pulse X-ray emission detected with a period of 206 ms

HESS J1641-463 in X-rays HESS J1641-463 in X-rays

XMM-Newton and Chandra

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Collection of many weak X-ray sources Oya et al. (2014)

Fermi-LAT observations Fermi-LAT observations

Initially found one Fermi source coincident with HESS J1640-465

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Reanalysis after discovery of HESS J1641-463 led to discovery of 2 distinct Fermi sources (coincident with the HESS sources) Lemoine-Goumard et al. (2014)

Low-energy wavelength observations Low-energy wavelength observations

Blue: 610 MHz radio continuum emission Green: 8 μm infrared emission Red: 24 μm infrared emission Castelletti et al. (2011) Colour: Radio view (MOST 843 MHz) Oya et al. (2013)

Supernova remnants and distances Supernova remnants and distances

• HESS J1640-465 & HESS J1641-463 are

seen towards supernova remnants

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SNR G338.3-0.0 and SNR G338.5+0.1 respectively

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Distance to the SNRs is ~ 10-11 kpc (via HI observations) in the Norma II spiral arm

• 11 kpc along this line of sight

corresponds to a Vlsr of ~ -45 km/s Kothes and Dougherty, 2007

Right: 12CO (1-0) spectra in regions towards HESS J1640-465 and HESS J1641-463

Nanten CO survey data

Left: Integrated 12CO(1-0) between

• 68 and -12 km/s

MopraCO survey data MopraCO survey data

• 12CO(1-0) data from the

Mopra Galactic Plane CO survey.

• First-look data cubes

courtesy of Burton et al. Above: Integrated 12CO(1-0) between

• 68 and -12 km/s

Right: 12CO(1-0) spectra of

regions towards HESS J1640-465 and HESS J1641-463

MopraCO data MopraCO data

Integrated 12CO(1-0) slices

• 60 to -55 km/s
• 55 to -50 km/s
• 50 to -45 km/s
• 45 to -40 km/s
• 40 to -35 km/s
• 35 to -30 km/s

Mopra 7mm data - CS(1-0) Mopra 7mm data - CS(1-0)

Integrated CS(1-0) slices

• 60 to -55 km/s
• 55 to -50 km/s
• 50 to -45 km/s
• 45 to -40 km/s
• 40 to -35 km/s
• 35 to -30 km/s

Mopra 7mm data - CS(1-0) Mopra 7mm data - CS(1-0)

Integrated image of CS(1-0) emission between -56 and -16 km/s CS(1-0) spectra of the grided regions indicated in red in the image opposite.

Detections in HC3N(5-4), CH3OH and SiO(1-0)

Mopra 7mm data Mopra 7mm data

Background: Integrated CS(1-0) emission between -56 and -16 km/s

Origin scenario – HESS J1640-465 Origin scenario – HESS J1640-465

• Hadronic

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Significant overlap between TeV emission and north-western part of SNR G338.3-0.0

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Spectral shape similar to other VHE gamma-rays sources identified as SNRs interacting with molecular clouds

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Hadronic production model assuming gas density of 150 cm-3 (Lemoine-Goumard et al. 2014)

• Leptonic

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Newly discovered pulsar suggests that PWN could be in part powering the TeV source Gamma-ray spectra of HESS J1640-465 Red – Fermi data points Blue – HESS data points Dashed line - Hadronic production model Lemoine-Goumard et al. (2014)

Origin scenario – HESS J1641-463 Origin scenario – HESS J1641-463

• Connection between VHE gamma-ray

spectra & HE gamma-ray spectrum is unclear

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2 mechanisms/sources producing photons in each energy band?

• VHE hadronic origin

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If SNR G338.5+0.1 were young, could accelerate particles to required energies. Would require a very hard proton energy spectrum.

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CRs from SNR G338.3-0.0 could have diffusively reached 1641.

• Would explain the relative

brightness of J1641 at high energies compared to J1640 Gamma-ray spectra of HESS J1641-463 Red – Fermi data points Blue – HESS data points Solid lines are best spectral fits to the respective flux points Lemoine-Goumard et al. (2014)

Current & Future work Current & Future work

CS(1-0) peak velocity map from

• 150 to 0 km/s (clipped)
• Mopra observations

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More complete picture of the gas and its properties towards HESS J1640-465 and HESS J1641-463

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Understanding dense gas “bridge” important for diffusion origin scenario

• Objective

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Paper detailing all the information we have gleaned from our Mopra

• bservations.

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Using this to model & constrain

• rigin scenarios for both VHE

sources

Thanks for your attention Thanks for your attention