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Synergy of Gamma-ray and (mm-) Radio O bservations in Studying M olecular Clouds

Synergy of Gamma-ray and (mm-) Radio O bservations in Studying M olecular Clouds. July 23, 2014@Nobeyama T. Mizuno (Hiroshima Astrophysical Science Center). 分子雲 研究 におけるガンマ線観測と ( ミリ波 ) 電波観測の連携. July 23, 2014@Nobeyama T. Mizuno (Hiroshima Astrophysical Science Center).

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Synergy of Gamma-ray and (mm-) Radio O bservations in Studying M olecular Clouds

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  1. Synergy of Gamma-ray and (mm-) Radio Observations in Studying Molecular Clouds July 23, 2014@Nobeyama T. Mizuno (Hiroshima Astrophysical Science Center)

  2. 分子雲研究におけるガンマ線観測と(ミリ波)電波観測の連携分子雲研究におけるガンマ線観測と(ミリ波)電波観測の連携 July 23, 2014@Nobeyama T. Mizuno (Hiroshima Astrophysical Science Center)

  3. Introduction: Gamma-Ray Astrophysics g-rays = CRs x ISM (or ISRF) Fermi-LAT (GeV, FOV of ~2.4psr) or IACT (TeV, FOV of a few deg.) Cosmic-rays Interstellar Medium • known ISM distribution => CRs • those “measured” CRs => ISM A powerful probe to study CRs and ISM in distant locations => Molecular Clouds

  4. Fermi-LAT Performance • Large FOV (~2.4psr) • Large effective area (>=0.7 m2 in >= 1 GeV • Moderate PSF (~0.8 deg@1 GeV, ~0.2 deg@10 GeV) http://www.slac.stanford.edu/exp/glast/groups/canda/lat_Performance.htm Effective Area(P7rep) PSF Ackermann+12, ApJS 203, 70 (CA: Baldini, Charles, Rando) Bregeon+13, arXiv:1304.5456

  5. All-Sky Map in Microwave • Planck microwave map (30-857 GHz) = dust thermal emission = ISM Cepheus & Polaris Taurus Orion R CrA Chamaeleon MBM53,54,55 nearby molecular clouds in high latitude

  6. All-Sky Map in g-Rays • GeVg-ray sky ~ Diffuse g-rays ~ Cosmic Rays (CRs) x ISM Fermi-LAT 1 year all-sky map Cepheus & Polaris Taurus Orion R CrA Chamaeleon MBM53,54,55 detailed study of individual clouds (+ISM in galactic plane) published

  7. Modeling of g-ray Data • Under the assumption of a uniform CR density, g-rays can be represented by a linear combination of template maps ∝ICR ∝(ICR x XCO) Fermi-LAT data qCOx WCO qHIx N(HI) + = (2.6 mm) (21 cm) Isotropic Inverse Compton + + (e.g., galprop) + Dark Neutral Gas (gas not properly traced by HI and WCO) + point sources (HI is usually assumed to be opt-thin; Ts>=120K) (WCO is not a all-sky map)

  8. Dark Gas Seen in GeVg-rays (1) • ISM has been mapped by radio surveys (HI by 21 cm, H2 by 2.6 mm CO) • Fermi revealed a component of ISM not measurable by those standard tracers Chamaeleon Molecular Cloud Residual g-rays when fitted by N(HI)+WCO g-rays w/ CO contour Ackermann+12, ApJ 755, 22 (CA: Hayashi, TM)

  9. Dark Gas Seen in GeVg-rays (2) • ISM has been mapped by radio surveys (HI by 21 cm, H2 by 2.6 mm CO) • Fermi revealed a component of ISM not measurable by those standard tracers, confirming an earlier claim based on EGRET study (Grenier+05) Residual g-rays when fitted by N(HI)+WCO Residual gas inferred by dust Ackermann+12, ApJ 755, 22 (CA: Hayashi, TM) (“dark-gas“ no longer dark in g-rays)

  10. Amount of Dark Gas Residual g-rays when fitted by N(HI)+WCO • Fermi revealed a component of ISM not measurable by those standard tracers • Amount of “dark gas” is comparable to or greater than gas mass traced by WCO (Both MCO and MDG∝ ICR∝ N(HI)) See also Abdo+10 (ApJ 710, 133), Ackermann+11 (ApJ 726, 81) and Ackermann+12 (ApJ 756, 4)

  11. Compilation of Xco • g-ray is a useful probe to study Xco • Penetrate the clouds • CR density can be estimated from nearby HI regions • Does not depend on assumptions about the dynamical state Nearby clouds show smaller Xco Study of other clouds is important individual clouds (NB green shaded region was determined using an a priori assumption on CR flux)

  12. Compilation of local ICR • “local” CR densities among regions agree by a factor of 1.5, within systematic uncertainty (mostly due to the assumption of Ts) E2 x Emissivity (∝ ICR) All-sky average individual regions

  13. Summary • g-ray is a powerful probe to CRs and ISM • optically thin, directly traces all gas phases • Fermi-LAT performed detailed studies of molecular clouds • confirmation of dark neutral gas • measurement of ICR, Xco(MCO), MDG • but limitation exists … • Desirable data to resolve limitations • accurate determination of N(HI) • (more) complete survey of Wco (sorry not a specific suggestion to 45m Telescope. fine resolution maps are certainly important. would be useful if combined with accurate N(HI) and large-scale Wco) Thank you for your Attention

  14. Reference • Dame et al. 2001, ApJ 547, 792 • Kalberla et al. 2005, A&A 440, 775 • Grenieret al. 2005, Science 307, 1292 • Atwood et al. 2009, ApJ 687, 1071 • Abdo et al. 2009, ApJ 703, 1249 • Abdo et al. 2009, PRL 103, 251101 • Abdo et al. 2010, ApJ 710, 133 • Ackermann et al. 2011, ApJ 726, 81 • Fukui et al. 2012, ApJ 746, 82 • Ackermann et al. 2012, ApJ 755, 22 • Ackermann et al. 2012, ApJ 756, 4

  15. Backup Slides

  16. Fermi Gamma-ray Space Telescope • Fermi = LAT + GBM • LAT = GeV Gamma-ray Space Telescope (20 MeV ~ >300 GeV; All-Sky Survey ) (GC-emphasized observation started in 2013 Dec.) 2008.06launch 2008.08 Sci. Operation 3c454.3 Cape Canaveral, Florida 1873 sources Nolan+ 2012, ApJS 199, 31

  17. g-ray Telescopes Imaging Atmospheric Cherenkov Telescopes (HESS, MAGIC, VERITAS) 30 GeV-10 TeV, FOV of a few degree Fermi-LAT (Satellite) 20 MeV-300 GeV, FOV of ~2.4psr GeVg-rays (<100 GeV) by Fermi-LAT TeVg-rays (>100 GeV) by IACTs

  18. Processes to Produce g-rays (2) g-rays = CRs x ISM (or ISRF) g-ray data and model (mid-lat. region) p0 decay, G~2.7 (isotropic) Bremsstrahlung, G~3.2 Abdo+09, PRL 103, 251101 (CA: Porter, Strong, Johanneson) Inverse Compton, G~2.1 A powerful probe to study CRs and ISM Pro: optically-thin, “direct” tracer of all gas phases Con: low-statistics, contamination (isotropic, IC), depend on CR density

  19. Dark Neutral Gas • Grenier+05 claimed there exist considerable amount of gas not properly traced by radio surveys (HI by 21 cm, H2 by 2.6 mm CO) surrounding nearby CO clouds • cold HI? CO-dark H2? Grenier+05, Science 307, 1292 center@l=70deg E(B-V)excess(residual gas inferred by dust) and Wco “Dark-gas” inferred by g-rays (CGRO EGRET) Confirmationand detailed study by current telescopes are important

  20. Dark Gas Seen in TeVg-rays • Fukui+12 claimed there exist considerable amount of “dark HI” in RX J1713.7-3946 by comparing HI, CO and g-rays Np(H2) Corrected Np(HI) Np(Htot) TeVg-ray (H.E.S.S.)

  21. XCO and XDG by g-rays • No apparent spectral change in qCO/qHI and qDG/qHI, indicating CR penetration to dense H2 (CO) and dark gas low E High E Ackermann+12, ApJ 755, 22 (CA: Hayashi, TM)

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