Synergy of Gamma-ray and (mm-) Radio Observations in Studying - PowerPoint PPT Presentation

2014-07_NobeyamaWS.ppt Synergy of Gamma-ray and (mm-) Radio Observations in Studying Molecular Clouds July 23, 2014@Nobeyama T. Mizuno (Hiroshima Astrophysical Science Center) /13 1 T. Mizuno et al.

2014-07_NobeyamaWS.ppt 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) /13 2 T. Mizuno et al.

2014-07_NobeyamaWS.ppt Introduction: Gamma-Ray Astrophysics  -rays = CRs x ISM (or ISRF) Fermi-LAT (GeV, FOV of ~2.4  sr) Cosmic-rays or IACT (TeV, FOV of a few deg.) Interstellar Medium • known ISM distribution => CRs • those “measured” CRs => ISM A powerful probe to study CRs and ISM in distant locations => Molecular Clouds /13 3 T. Mizuno et al.

2014-07_NobeyamaWS.ppt Fermi-LAT Performance • Large FOV (~2.4  sr) • Large effective area (>=0.7 m 2 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 /13 4 T. Mizuno et al.

2014-07_NobeyamaWS.ppt 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 /13 5 T. Mizuno et al.

2014-07_NobeyamaWS.ppt All-Sky Map in  -Rays • GeV  -ray sky ~ Diffuse  -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 /13 6 T. Mizuno et al.

2014-07_NobeyamaWS.ppt Modeling of  -ray Data Under the assumption of a uniform CR density,  -rays can be • represented by a linear combination of template maps ∝ I CR ∝ ( I CR x X CO ) q CO x W CO Fermi-LAT data q HI x N (H I ) + = (2.6 mm) (21 cm) Isotropic Inverse Compton + + (e.g., galprop) + Dark Neutral Gas (gas not properly traced by H I and W CO ) + point sources (H I is usually assumed to be opt-thin; T s >=120K) (W CO is not a all-sky map) /13 7 T. Mizuno et al.

2014-07_NobeyamaWS.ppt Dark Gas Seen in GeV  -rays (1) • ISM has been mapped by radio surveys (H I by 21 cm, H 2 by 2.6 mm CO) • Fermi revealed a component of ISM not measurable by those standard tracers Chamaeleon Molecular Cloud Residual  -rays when fitted by N (H I )+ W CO  -rays w/ CO contour Ackermann+12, ApJ 755, 22 (CA: Hayashi, TM) /13 8 T. Mizuno et al.

2014-07_NobeyamaWS.ppt Dark Gas Seen in GeV  -rays (2) • ISM has been mapped by radio surveys (H I by 21 cm, H 2 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  -rays when fitted by N (H I )+ W CO Residual gas inferred by dust Ackermann+12, ApJ 755, 22 (“dark-gas“ no longer dark in  -rays) (CA: Hayashi, TM) /13 9 T. Mizuno et al.

2014-07_NobeyamaWS.ppt Amount of Dark Gas Residual  -rays when fitted by N (H I )+ W CO • 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 W CO (Both M CO and M DG ∝ I CR ∝ N(H I )) Molecular cloud Gas mass traced by CO “dark gas” ( M solar ) ( M solar ) Chamaeleon ~5x10 3 ~2.0x10 4 R CrA ~10 3 ~10 3 Cepheus & Polaris ~3.3x10 4 ~1.3x10 4 See also Abdo+10 (ApJ 710, 133), Ackermann+11 (ApJ 726, 81) and Ackermann+12 (ApJ 756, 4) /13 10 T. Mizuno et al.

2014-07_NobeyamaWS.ppt Compilation of Xco  -ray is a useful probe to study X co • – 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) /13 11 T. Mizuno et al.

2014-07_NobeyamaWS.ppt Compilation of local I CR • “local” CR densities among regions agree by a factor of 1.5, within systematic uncertainty (mostly due to the assumption of T s ) E 2 x Emissivity ( ∝ I CR ) All-sky average individual regions /13 12 T. Mizuno et al.

2014-07_NobeyamaWS.ppt Summary  -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 I CR , X co ( M CO ), M DG – 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 /13 13 T. Mizuno et al.

2014-07_NobeyamaWS.ppt Reference • Dame et al. 2001, ApJ 547, 792 • Kalberla et al. 2005, A&A 440, 775 • Grenier et 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 /13 14 T. Mizuno et al.

2014-07_NobeyamaWS.ppt Backup Slides /13 15 T. Mizuno et al.

2014-07_NobeyamaWS.ppt 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.) 2008.06 launch 2008.08 Sci. Operation 3c454.3 Cape Canaveral, 1873 sources Florida Nolan+ 2012, ApJS 199, 31 /13 16 T. Mizuno et al.

2014-07_NobeyamaWS.ppt  -ray Telescopes Imaging Atmospheric Cherenkov Telescopes Fermi-LAT (Satellite) (HESS, MAGIC, VERITAS) 20 MeV-300 GeV, FOV of ~2.4  sr 30 GeV-10 TeV, FOV of a few degree GeV  -rays (<100 GeV) by Fermi-LAT TeV  -rays (>100 GeV) by IACTs /13 17 T. Mizuno et al.

2014-07_NobeyamaWS.ppt Processes to Produce  -rays (2)  -rays = CRs x ISM (or ISRF)  -ray data and model (mid-lat. region)  0 decay,  ~2.7 (isotropic) Bremsstrahlung, Abdo+09, PRL 103, 251101  ~3.2 Inverse Compton, (CA: Porter, Strong, Johanneson)  ~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 /13 18 T. Mizuno et al.

2014-07_NobeyamaWS.ppt Dark Neutral Gas • Grenier+05 claimed there exist considerable amount of gas not properly traced by radio surveys (H I by 21 cm, H 2 by 2.6 mm CO) surrounding nearby CO clouds Grenier+05, – cold H I ? CO-dark H 2 ? Science 307, 1292 center@ l =70deg E (B-V) excess (residual gas inferred by dust) “Dark-gas” inferred by  -rays and W co (CGRO EGRET) Confirmation and detailed study by current telescopes are important /13 19 T. Mizuno et al.

2014-07_NobeyamaWS.ppt Dark Gas Seen in TeV  -rays • Fukui+12 claimed there exist considerable amount of “dark H I ” in RX J1713.7-3946 by comparing H I , CO and  -rays N p (H 2 ) Corrected N p (H I ) N p (H tot ) TeV  -ray (H.E.S.S.) /13 20 T. Mizuno et al.

2014-07_NobeyamaWS.ppt X CO and X DG by  -rays • No apparent spectral change in q CO / q HI and q DG / q HI , indicating CR penetration to dense H 2 (CO) and dark gas low E High E Ackermann+12, ApJ 755, 22 (CA: Hayashi, TM) /13 21 T. Mizuno et al.