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2 Million-K Plasma Pervading the Orion Nebula K. Briggs, M. Guedel, Th. Montmerle, M. Audard, L. Rebull, S. Skinner HST/STScI Outline Motivation – Why study X-rays? – Why is Orion Nebula interesting? – What did we aim to do? Results – Hot gas (2 MK) fills nebula (spectrum, low abs, Spitzer) – Produced by shocked winds from Trapezium – Low mass of gas in pressure eqm – escaping Implications: – – – – 1. Hot gas is a feature of all HMSFRs 2. Young solar system immersed in hot gas 3. Shocked winds play role in shaping all HMSFRs 4. Hot gas flows out and enriches ISM Kevin Briggs, PSI/ETH X-rays in star and planet formation Effects of UV and X-ray radiation – Heating and ionizing protoplanetary disks – Driving accretion through disk via magnetorotational instability – Driving dispersal of protoplanetary disks Kevin Briggs, PSI/ETH X-rays in star and planet formation Sources of UV and X-ray radiation – Internal to system X-rays from magnetic activity on star UV and X-rays from accretion onto star X-rays from shocks in out-flowing jets – External to system UV from hot, high-mass O stars X-rays from neighbouring stars X-rays from shocked winds from high-mass stars? Kevin Briggs, PSI/ETH Orion Rich site of recent star formation over last few Myr Orion Nebula Cluster is most recent (0.5 Myr ago) Closest HII region with high-mass O stars (400 pc) Older generations of young stars to immediate N and S of ONC Sun is thought to have been born in a rich cluster like Orion. © Till Credner and Sven Kohle Kevin Briggs, PSI/ETH Features of the Orion Nebula COUP field Kevin Briggs, PSI/ETH Previous X-ray observations of the Orion Nebula Chandra 0.5-8 keV COUP Collaboration Kevin Briggs, PSI/ETH Aims of our investigation Survey of X-ray emission from young stars over range of ages. Investigate evolution of X-ray output, energy, flaring rate in first few Myr. Investigate dependence of X-ray output, temperature of X-ray emitting gas on mass, age, accretion-rate, rotation rate, to understand processes creating X-rays. Kevin Briggs, PSI/ETH XMM-Newton Most sensitive X-ray observatory Large field of view (30 arcmin diameter) 3 telescopes, each with EPIC CCD detector Measures position, arrival time and energy of each detected X-ray photon Energy range 0.15 – 15 keV Survey profits from archive observations of individual interesting objects (O stars, outburst T Tauri stars) and calibration observations Kevin Briggs, PSI/ETH XMM Survey of the Orion Nebula Copyright Anglo-Australian Observatory. Photograph by David Malin. Kevin Briggs, PSI/ETH XMM’s New View of the Orion Nebula Soft diffuse X-ray emission Kevin Briggs, PSI/ETH Physical properties of the X-ray-emitting gas Kevin Briggs, PSI/ETH Spectral extraction Size (d=400 pc) N S Area (pc2) 0.24 1.38 Diameter (pc) 0.6 1.5 0.9-4.0 0.9-4.0 0.22-0.97 1.24-5.5 Depth (pc) Volume (pc3) Kevin Briggs, PSI/ETH Spectral fitting Spectral N S 1.7 2.1 NH (1020 cm-2) 4.10.7 0.40.5 EM = ne2 V (1054 cm-3) 1.50.3 1.90.3 LX (0.1-10 keV, 1031 erg s-1) 2.3 3.2 Te (MK) Kevin Briggs, PSI/ETH Derived observational parameters Derived Quantity ne (cm-3) (EM/V)0.5 (10-23 erg cm3 s-1) tcool (Myr) 3kT/ne Kevin Briggs, PSI/ETH N S 0.22-0.47 0.11-0.23 8.28 6.44 0.6-1.3 1.8-3.9 Spatial distribution of X-ray emitting gas X-ray emission fills a cavity in IR image “Lid” or “Veil” of absorbing material in front of Trapezium, NH = 4.8 x 1021 cm-2. Reduces toward SW X-ray surface brightness would be 30 times fainter in direction of Trapezium due to absorption Kevin Briggs, PSI/ETH Spatial distribution of X-ray-emitting gas Gas extrapolated to full volume of cavity: LX = 2 x 1032 erg s-1 MX = 0.07 M LX (1 Ori C) = 1.9 x 1033 erg s-1 LX (hot stars) = 2.3 x 1033 erg s-1 LX (cool stars) = 3.5 x 1033 erg s-1 (Feigelson et al. 2005, ApJS, 160, 379) Kevin Briggs, PSI/ETH Origin of the X-ray-emitting gas Kevin Briggs, PSI/ETH Origin of hot gas: The Wind-Blown Bubble Powerful winds of O stars – Mdot ~ 10-6 M yr-1 – Vw > 1500 km s-1 Wind shocked to T > 1 MK: expanding hot bubble: X-rays Expanding thin shell of shocked, swept-up IS gas: T ~ 104 K Weaver et al. 1977, ApJ, 218, 377 Kevin Briggs, PSI/ETH Wind shocks from 1 Ori C (O7 V) Energetics Mass loss rate Mdot 8 x 10-7 M yr-1 * Terminal velocity Vw 1650 km s-1 * Kinetic power Mdot Vw2/2 7 x 1035 erg s-1 * Leitherer 1988, ApJ, 326, 356 Timescales Travel time > 103 x LX 1.5 x 104 yr < 10-2 tcool (1.5 pc @ 100 km s-1) Replenishment time 105 yr Kevin Briggs, PSI/ETH < 0.03 tcool Outflow of the X-ray-emitting gas Evidence: – Low NH toward S diffuse emission – Short replenishment time of X-ray emitting gas – Pressure equilibrium between radio and X-ray emitting material Kevin Briggs, PSI/ETH Implications Kevin Briggs, PSI/ETH Implication 1: Hot gas not only in very massive star-forming regions Previously thought supernovae or colliding winds from multiple O stars needed (Townsley et al. 2003, ApJ, 593, 874) 30 Doradus, LMC, XMM-Newton first-light image Kevin Briggs, PSI/ETH Implication 2: Young solar system immersed in hot, X-ray-emitting gas But photoionization and heating effects from X-rays on disks much smaller than from UV irradiation from O stars (Alexander, Clarke & Pringle 2004, MNRAS, 354, 71) Kevin Briggs, PSI/ETH Implication 3: Structure & evolution of the Orion Nebula Previously thought UV radiation from Trapezium stars drives structural evolution. NASA/STScI Tenorio-Tagle 1979, A&A, 71, 59 Now wind-blown bubble appears to have played significant role. Kevin Briggs, PSI/ETH Implication 4: Outflow and enrichment 2MASS near-IR 2 micron Chandra X-rays 0.5-8 keV M17, The Omega Nebula (Townsley et al. 2003, ApJ, 593, 874) Kevin Briggs, PSI/ETH Implication 4: Outflow and enrichment Gamma rays indicate outflow from Orion Nebula into Eridanus Superbubble X-ray outflow carries – Hot gas – Fresh nucleosynthetic products from O stars (26Al??) Enrichment of ISM – Likely common process throughout Galaxy Kevin Briggs, PSI/ETH Conclusions Orion Nebula filled with X-ray emitting gas at 2 MK. Originates from shocks in winds of O stars, esp. 1 Ori C. Hot wind-blown bubbles can occur in all high-mass SFRs, even with few O stars. The young solar system was likely immersed in such a hot gas. Hot gas flows out of cavity … … enriching Eridanus superbubble? Outflows of hot gas are likely common in HII regions, adding to soft X-ray halo of Galaxy, continuously enriching ISM. Kevin Briggs, PSI/ETH