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

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 are Unidentified! 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. Phoebe de Wilt NANTEN2 meeting, UWS, 5-6 Feb 2015

The H.E.S.S. Sky and 12 mm Mopra mapping coverage Image from Gast et al 2011 (For the HESS Collaboration) , H 2 O southern Galactic Plane Survey (HOPS, Walsh et al 2011 ) data used HOPS overlap Dedicated 12mm observations Molecular clumps initially identified by NH 3 (1,1) emission within 5 σ of TeV centroid Additional transitions searched for NH 3 (2,2), NH 3 (3,3), H 2 O maser, HC 3 N (3-2), H69 α Phoebe de Wilt NANTEN2 meeting, UWS, 5-6 Feb 2015

The H.E.S.S. Sky and 12 mm Mopra mapping coverage Image from Gast et al 2011 (For the HESS Collaboration) , H 2 O southern Galactic Plane Survey (HOPS, Walsh et al 2011 ) data used HOPS overlap • NH 3 (1,1), NH 3 (2,2), NH 3 (3,3) Dedicated 12mm observations – 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. enh anced ortho-to-para NH 3 abundance) Molecular clumps initially identified by NH 3 (1,1) emission within 5 σ of TeV centroid Additional transitions searched for NH 3 (2,2), NH 3 (3,3), H 2 O maser, HC 3 N (3-2), H69 α Phoebe de Wilt NANTEN2 meeting, UWS, 5-6 Feb 2015

Preliminary results from this study Of 43 Galactic TeV sources covered, NH 3 (1,1) emission is detected within • the region of 34 of them. H 2 O maser emission within ~1/3 of these molecular clumps H69 α emission is detected towards < 1/5 of them Mass and density has been estimated for all MCs displaying NH 3 (2,2) • emission Phoebe de Wilt NANTEN2 meeting, UWS, 5-6 Feb 2015 NANTEN2 meeting, UWS, 5-6 Feb 2015

HESS J1729-345 • Several HII regions towards HESS J1729-345 22 GHz H 2 O masers detected • nearby (Walsh et al 2011) • TeV emission offset from nearby TeV SNR (HESS J1731-347) image from de Wilt et al in prep Angular resolution ~ 1 arcmin • Cool, dense cloud cores detected in NH 3 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 ~ 10 4 years old. The SNR age is not known. Phoebe de Wilt NANTEN2 meeting, UWS, 5-6 Feb 2015

HESS J1640-465 Dense gas adjacent to TeV emission Leptonic source? • High energy data makes it difficult to discriminate between leptonic and hadronic emission • Recent PSR detected (Gotthelf at al 2014) π 2 F / ˙ Apparent Efficiency ≡ 4 D E γ • Known TeV PWNe have Apparent efficiency, ε de Wilt et al. (in prep) 0.01% < ε < 7% Aharonian et al. (2006) de Wilt et al. (in prep) (Gallant et al. 2007 – for the HESS H.E.S.S. TeV excess ε = 0.01% Collaboration) contours • More diffuse gas ε = 7% e.g. CO (1-0) is ATNF PSR catalogue sources being investigated HESS J1640-465 TeV emission (Manchester et al. 2005) (see James' talk) PSRs associated with TeV PWNe (de On ̃ a-Wilhelmi et al. for the CTA Collaboration 2012) Phoebe de Wilt ASA ASM Monash, 8-12 July 2013

HESS J1848-018 / W43 • 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 NH 3 emission • coincident with TeV centroid • More TeV data available. TeV morphology studies currently being undertaken – may give clues to source of TeV emission Angular resolution ~ 1 arcmin Image from de Wilt et al (in prep) Phoebe de Wilt NANTEN2 meeting, UWS, 5-6 Feb 2015

Ortho-Para NH 3 abundance ratio – Looking for shocks NH 3 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) (1,1) (2,2) (3,3) (4,4) (5,5) (6,6) (J,K) (J,K) K=3n / K=3n Para NH 3 Ortho NH 3 In gas phase formation of NH 3 , the ortho-para NH 3 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 NH 3 from dust grains into the gas phase (e.g. Faure et al. 2013, Umemoto et al 1999) With NH 3 (J,K) J=K=1,2,3,4,5,6 observations we can estimate the OPR • Phoebe de Wilt NANTEN2 meeting, UWS, 5-6 Feb 2015

HESS J1745-303 NH 3 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 origin – Previous shock...? Wind blown bubble? NH (3,3)-to-(1,1) Tmb ratio 3 NANTEN2 meeting, UWS, 5-6 Feb 2015 Aharonian et al. (2008) : H.E.S.S. TeV excess contours

HESS J1745-303 NH 3 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 origin – Previous shock...? Wind blown bubble? NH (3,3)-to-(1,1) Tmb ratio 3 NANTEN2 meeting, UWS, 5-6 Feb 2015 Aharonian et al. (2008) : H.E.S.S. TeV excess contours

HESS J1801-233 (W28) W28 NH 3 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) Phoebe de Wilt

Summary / Future Work • The first large scale systematic study of dense (>10 4 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 NH 3 inversion transitions, used to • estimate ortho-para NH 3 ratios, could be used to search for regions of dense gas with previous shock activity – futher observations of NH 3 (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 Phoebe de Wilt NANTEN2 meeting, UWS, 5-6 Feb 2015

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