Dense and Disrupted Gas towards Galactic TeV Gamma-Ray Sources - - PowerPoint PPT Presentation

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Dense and Disrupted Gas towards Galactic TeV Gamma-Ray Sources - - PowerPoint PPT Presentation

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Dense and Disrupted Gas towards Galactic TeV Gamma-Ray Sources Phoebe de Wilt The University of Adelaide Phoebe de Wilt NANTEN2 meeting, UWS, 5-6 Feb 2015 The TeV Gamma-Ray Sky Image credit: tevcat.uchicago.edu ~50% of Galactic TeV sources

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Phoebe de Wilt NANTEN2 meeting, UWS, 5-6 Feb 2015

Dense and Disrupted Gas towards Galactic TeV Gamma-Ray Sources

Phoebe de Wilt The University of Adelaide

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HOW DO WE IDENTIFY ALL OF THESE GAMMA-RAY SOURCES? (i) spatial and ideally also morphological coincidence with a counterpart (ii) a viable γ-ray emission mechanism for the object, and (iii) a consistent multiwavelength behaviour matching the suggested identification and the particle distribution within the source.

The TeV Gamma-Ray Sky

Image credit: tevcat.uchicago.edu

~50% of Galactic TeV sources are Unidentified!

Phoebe de Wilt NANTEN2 meeting, UWS, 5-6 Feb 2015

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HOPS overlap Dedicated 12mm observations

Image from Gast et al 2011 (For the HESS Collaboration), H2O southern Galactic Plane Survey (HOPS, Walsh et al 2011) data used

The H.E.S.S. Sky and 12 mm Mopra mapping coverage

Molecular clumps initially identified by NH3 (1,1) emission within 5σ of TeV centroid Additional transitions searched for NH3 (2,2), NH3 (3,3), H2O maser, HC3N (3-2), H69α

Phoebe de Wilt NANTEN2 meeting, UWS, 5-6 Feb 2015

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SLIDE 4

HOPS overlap Dedicated 12mm observations

Image from Gast et al 2011 (For the HESS Collaboration), H2O southern Galactic Plane Survey (HOPS, Walsh et al 2011) data used

The H.E.S.S. Sky and 12 mm Mopra mapping coverage

Molecular clumps initially identified by NH3 (1,1) emission within 5σ of TeV centroid Additional transitions searched for NH3 (2,2), NH3 (3,3), H2O maser, HC3N (3-2), H69α

Phoebe de Wilt

  • NH3 (1,1), NH3 (2,2), NH3 (3,3)

– used to estimate optical depth, density and mass – used to search for interesting gas dynamics (e.g. line broadening due to shocks) – have found some unexpected emission (e.g. enhanced ortho-to-para

NH3 abundance) NANTEN2 meeting, UWS, 5-6 Feb 2015

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Preliminary results from this study

  • Of 43 Galactic TeV sources covered, NH3 (1,1) emission is detected within

the region of 34 of them. H2O maser emission within ~1/3 of these molecular clumps H69α emission is detected towards < 1/5 of them

  • Mass and density has been estimated for all MCs displaying NH3 (2,2)

emission

Phoebe de Wilt NANTEN2 meeting, UWS, 5-6 Feb 2015 NANTEN2 meeting, UWS, 5-6 Feb 2015

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SLIDE 6

HESS J1729-345

  • Several HII regions towards

HESS J1729-345

  • 22 GHz H2O masers detected

nearby (Walsh et al 2011)

  • TeV emission offset from nearby

TeV SNR (HESS J1731-347) Phoebe de Wilt

  • Cool, dense cloud cores detected in NH3 study coincident with IRDC at same distance as
  • SNR. Basic diffusion studies show, if cosmic rays from SNR are responsible for TeV

emission, the SNR must be ~ 104 years old. The SNR age is not known.

image from de Wilt et al in prep Angular resolution ~ 1 arcmin

NANTEN2 meeting, UWS, 5-6 Feb 2015

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ASA ASM Monash, 8-12 July 2013

HESS J1640-465

  • High energy data makes it

difficult to discriminate between leptonic and hadronic emission

  • Recent PSR detected (Gotthelf

at al 2014)

  • Known TeV PWNe have

Apparent efficiency, ε 0.01% < ε < 7%

(Gallant et al. 2007 – for the HESS Collaboration)

  • More diffuse gas

e.g. CO (1-0) is being investigated

(see James' talk)

Apparent Efficiency≡4 D

2F / ˙

E

γ

π Dense gas adjacent to TeV emission Leptonic source?

HESS J1640-465 TeV emission

ε = 0.01%

ε = 7% de Wilt et al. (in prep)

ATNF PSR catalogue sources

(Manchester et al. 2005)

PSRs associated with TeV PWNe

(de Oña-Wilhelmi et al. for the CTA Collaboration 2012) de Wilt et al. (in prep) Aharonian et al. (2006) H.E.S.S. TeV excess contours

Phoebe de Wilt

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HESS J1848-018 / W43

Image from de Wilt et al (in prep)

  • High Mass stellar cluster

which contains Colliding Wind Binary WR121a

(Anderson et al 2013)

  • Widespread broadline

SiO (1-0) emission

(de Wilt et al – in prep)

  • IRDC and NH3 emission

coincident with TeV centroid

  • More TeV data available.

TeV morphology studies currently being undertaken – may give clues to source of TeV emission Phoebe de Wilt

Angular resolution ~ 1 arcmin

NANTEN2 meeting, UWS, 5-6 Feb 2015

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Ortho-Para NH3 abundance ratio – Looking for shocks

  • NH3 is classified as ortho or para depending on whether the nuclear

spins of the hydrogen atoms are aligned or not (ortho = aligned, para = not aligned)

  • In gas phase formation of NH3, the ortho-para NH3 abundance ratio

(OPR) is expected to be < 1 (e.g. Faure et al. 2013)

  • Theory and limited observations suggest that OPR > 1 indicates

previous shock activity which has released NH3 from dust grains into the gas phase (e.g. Faure et al. 2013, Umemoto et al 1999)

  • With NH3 (J,K) J=K=1,2,3,4,5,6 observations we can estimate the OPR

Para NH3 Ortho NH3 (1,1) (2,2) (4,4) (5,5) (J,K) K=3n (3,3) (6,6) (J,K) K=3n /

NANTEN2 meeting, UWS, 5-6 Feb 2015 Phoebe de Wilt

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HESS J1745-303

NH3 emission

– Morphological coincidence with SiO (1-0) emission (de Wilt et al in prep) – Nearby SNR/MC interaction evidenced by 1720MHz OH masers – Gas outside of SNR boundary... another shock responsible? – Masers at velocities -6 to -2 km/s (Yusef-Zadeh et al 1995) – Not at same velocity as this gas which also supports the hypothesis of a second shock

  • rigin

– Previous shock...? Wind blown bubble?

NH (3,3)-to-(1,1) Tmb ratio

3

Aharonian et al. (2008) : H.E.S.S. TeV excess contours

NANTEN2 meeting, UWS, 5-6 Feb 2015

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HESS J1745-303

NH3 emission

– Morphological coincidence with SiO (1-0) emission (de Wilt et al in prep) – Nearby SNR/MC interaction evidenced by 1720MHz OH masers – Gas outside of SNR boundary... another shock responsible? – Masers at velocities -6 to -2 km/s (Yusef-Zadeh et al 1995) – Not at same velocity as this gas which also supports the hypothesis of a second shock

  • rigin

– Previous shock...? Wind blown bubble?

NH (3,3)-to-(1,1) Tmb ratio

3

Aharonian et al. (2008) : H.E.S.S. TeV excess contours

NANTEN2 meeting, UWS, 5-6 Feb 2015

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  • W28 NH3 emission

– Extended with spatial coincidence with SiO (1-0) emission (which traces shocked gas) Nicholas et al 2010 – 1720 MHz OH masers (trace SNR/MC interaction, Frail & Mitchell 1998)

HESS J1801-233 (W28)

Phoebe de Wilt

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Summary / Future Work

  • The first large scale systematic study of dense (>104 cm-3) gas towards

Galactic TeV sources has been completed

  • HOPS equivalent coverage provides a good first look at distribution and

dynamics of dense gas towards Galactic TeV sources

  • Knowledge about gas density profiles towards TeV sources allows for

more robust studies of cosmic ray diffusion (Maxted et al. 2012, Voisin et al. in

prep)

  • Preliminary results suggest 12mm NH3 inversion transitions, used to

estimate ortho-para NH3 ratios, could be used to search for regions

  • f dense gas with previous shock activity – futher observations of

NH3 (4,4) and (5,5) (which are not included in the HOPS band) are needed

  • NANTEN2 CO observations and the Mopra CO Survey provide a large

scale study for more diffuse gas towards Galactic TeV sources

  • New TeV sources are being discovered all of the time – dense gas

towards these sources should be looked at too

NANTEN2 meeting, UWS, 5-6 Feb 2015 Phoebe de Wilt

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SLIDE 14

Phoebe de Wilt NANTEN2 meeting, UWS, 5-6 Feb 2015