Transcript talk_ias
What do we know about the HISM? Sun For a review, see D. Cox (2005, ARAA) ROSAT X-ray All-sky Survey Red – 1/4 keV band Green – 3/4 keV band ~50% of the ¾-keV background is thermal and local (z < 0.01); rest is mostly from AGNs Blue – 1.5 keV band McCammon et al. 2002 What we do not know: • • • • Overall spatial distribution Filling factor Physical and chemical states Kinematics • Heating, transporting, and cooling • Effects on galaxy formation and evolution New Tool: Chandra CCD •resolution res. ~ 1” •Spectral Res. E/E ~ 20 Grating •Spectral Res. ~ 500 km/s The Global Hot ISM: New Perspectives Absorption spectroscopy: External views: • Add the depth • Measure the column density, thus the mass • Direct line diagnostics • Independent of cool gas absorption • Global properties • Relationship between various components • Dependence on galaxy properties and environment Modeling of the SN-dominated hot ISM • 1-D galactic bulge wind • 3-D simulations Detection of X-ray absorption lines: Mrk 421; Nicastro et al. 2005 Mkn 421 LETG/HRC LETG/ACIS 3C 273 Where is the absorbing gas located? Wang & Yao 2005 LMC X-3 as a distance marker • BH X-ray binary, typically in a high/soft state • Roche lobe accretion • 50 kpc away • +310 km/s • Away from the LMC main body H image Obs. Of LMC X-3 •Chandra LETG: 100 ks. •FUSE: 100 ks •RXTE: 100 ks Wang et al. 2005 LMC X-3: absorption lines OVII Ne IX The EWs are about the same as those seen in AGN spectra! Absorption line diagnostics OVII OVIII Ne IX Ne VIII OVI Ne IX Assuming CIE and solar abundances I()=Ic() exp[-()] ()NHfafi(T)flu(,0,b) b=(2kT/mi+2)1/2 accounting for line saturation and multiple line detections Yao & Wang 2005 Results from extragalactic sources Source Log[T(K)] Log[NH(cm-2)] PKS 2125-304 6.3(6.2-6.4) 19.8(19.5-20.3) 3C 273 6.3(6.1-6.4) 19.9(19.7-20.1) MRK 421 6.2(6.1-6.3) 19.2(19.1-19.3) LMC X-3 6.1(5.9-6.3) 19.6(19.4-19.8) No evidence for significant X-ray absorption beyond the LMC!!! LMXB 4U 1820-303: A Galactic distance marker • In GC NGC 6624 – Distance = 7.6; l, b = 2o.8, -8o tracing the global ISM – 1 kpc away from the Galactic plane NHI • Two radio pulsars in the GC DM Ne • Chandra observations: – 15 ks LETG (Futamoto et al. 2004) – 21 ks HETG Yao & Wang 2005 LETG+HETG spectrum 4U 1820-303: Results • Hot gas accounts for ~ 6% of the total O column density • O abundance: – 2.0 (0.8-3.6) solar in ionized gas – 0.3 (0.2-0.6) solar in neutral atomic gas. • Ne/O =1.4(0.9-2.1) solar • Filling factor (relative to total ionized gas): ~0.95, if ph ~ pw ~0.8, if ph ~ 5pw as in the solar neighborhood • LogT(k) = 6.34 (6.29-6.41) • Velocity dispersion 255 (165–369) km/s Temperature Dist. d NH(T) = T dlogT More Sources Global HISM distribution • LMXBs with |b| > 2o • S/N > 7 per bin at ~0.6 keV • Excluding sources with identified intrinsic emission/absorption features • Ten LMXBs with 17 observations (6 with the LETG) Yao & Wang 2005 Absorption Sight Lines AGN X-ray binary No detection ROSAT all-sky survey in the ¾-keV band Global distribution models Disk model •nH = 5.0(-1.8,+2.6)x10-3 cm-3 exp[-|z|/1.1(-0.5,+0.7) kpc] •Total NH~1.6 x1019 cm-2 Sphere model •nH = 6.1(-3.0,+3.6)x10-2 cm-3 exp[-R/2.7(-0.4,+0.8) kpc] ~3 x 10-3 cm-3 at the Sun •Total NH~6.1 x1019 cm-2 •MH~7.5(2.5-16)x108 Msun X-ray absorption is primarily around the Galactic disk within a few kpc! Summary: Galactic hot ISM • No significant X-ray absorption beyond the LMC (~< 1019 cm-2, assuming the solar abundance) • A thick Galactic disk with a scale height 1-2 kpc, ~ the values of OVI absorbers and free electrons • O abundance ~ solar or higher • Mean T ~ 106.3+-0.2 K, ~ 106.1 K at solar neighborhood • Large nonthermal v dispersion, especially at the GC • High volume filling factor (> 0.8) within |z| < 1 kpc External Perspective: NGC 3556 (Sc) •Active star forming •Hot gas scale height ~ 2 kpc •Lx ~ 1% of SN mech. Energy input Red – optical Green – 0.3-1.5 keV band Blue – 1.5-7 keV band Wang et al. 2004 NGC 4565 (Sb) Wang (2004) Red – optical Green – 0.3-1.5 keV band Blue – 1.5-7 keV band Very low specific SFR William McLaughlin (ARGO Cooperative Observatory) No sign for any outflows from the disk in radio and optical NGC 2841 (Sb) Red: optical Blue: 0.3-1.5 keV diffuse emission NGC 4594 (Sa) H ring Red: optical Green: 0.3-1.5 keV Blue: 1.5-7 keV disk Inner bulge Outer bulge Point source NGC 4594: X-ray spectra •Average T ~ 6 x 106 K •Strong Fe –L complex •Lx ~ 4 x 1039 erg/s NGC 4631 Missing stellar feedback in early-type disk galaxies • For NGC 4594, hot gas radiative cooling rate ~ 2% of the energy input from Type Ia SNe alone • Not much cool gas to hide or convert the SN energy • Mass and metals are also missing! – Mass input rate of evolved stars ~ 1.3 Msun/yr – Each Type Ia SN 0.7 Msun Fe Galaxy formation simulations vs. observations NGC 4594 NGC 4594 NGC 4565 NGC 4565 Toft et al. (2003) Summary: Nearby galaxies • Good News – At least two components of diffuse hot gas: • Disk – driven by massive star formation • Bulge – heated primarily by Type-Ia SNe – Characteristic extent and temperature similar to the Galactic values • Bad news – Missing stellar feedback, at least in early-type spirals. – Little evidence for X-ray emission or absorption from IGM accretion --- maybe good news for solving the over-cooling problem. Are these problems related? Bulge wind model • Spherical, steady, and adiabatic • NFW Dark matter halo + stellar bulge • Energy and mass input follows the stellar light distribution • CIE plasma emission • Implemented in XSPEC for both projected spectral and radial surface brightness analyses Li & Wang 2005 Data vs model Consistent with the expected total mass loss and SN rates as well as the Fe abundance of ~ 4 x solar! The best-fit model density and temperature profiles of the bulge wind 3-D hydro simulations • Goals – To characterize the density, temperature, and metal abundance structures, the heating and cooling processes, and the kinematics of the HISM – To calibrate the 1-D model • Hydro simulations with metal particle tracers – Parallel, adaptive mesh refinement FLASH code – Whole galactic bulge simulation with the finest refinement in one octant down to 6 pc – Stellar mass injection and SNe, following stellar light – Realistic gravitational potential of the bulge and the dark matter halo Galactic bulge simulation: density • 3x3x3 kpc3 box • SN rate ~ 4x10-4 /yr • Mass injection rate ~0.03 Msun/yr • Logarithmic scale • Statistical steady state • ~ adiabatic Tang et al. 2005 Galactic bulge simulation: Fe • Fe-rich ejecta dominate the high-T emission • Not well-mixed with the ambient medium • May cool too fast to be mixed with the global hot ISM Non-uniformity effects High Res. 1-D Low Res. 1-D Log(T(K)) Conclusions and implications • Large inhomogeneity is expected – particularly in the hot Fe distribution – enhanced emission at both low and high temperatures (compared to the 1-D solution) • SNe generate waves in the HISM – Energy not dissipated locally or in swept-up shells – Maybe eventually damped by cool gas or in the galactic hot halo – Galactic wind not necessary – Possible solution to the over-cooling problem of galaxy formation Acknowledgement • Absorption line studies – Y. Yao, T. Tripp, T.-T. Fang, … • X-ray imaging of nearby galaxies – T. Chevas, J. Irwin, Z. Li… • 1-D and 3-D model and simulations – Z. Li, S. Tang, M. Mac Low Comparison with X-ray emission Disk dist. Observed Uniform dist. Consistency check: timescales Radiative cooling O recom. T/(dT/dt) Fe recom. Dependence on the energy/mass input rate Chandra Grating Instrument Properties FWHM ~ 5x102 km/s Sample of normal disk galaxies Galaxy Name Hubble Type D (Mpc) Incl. ang. Exp. Time (ks) (deg) N4244 Sd/LSB 3.6 85 60 N4631 Sd 7.5 85 60 N3556 Sc 14.1 80 60 N4565 Sb 13.4 87 60 N4594 Sa 8.9 84 19 All with low Galactic foreground absorption (NH < 3 x 1020 cm-2)