The X-Ray Universe The X-Ray Universe Potsdam University Dr. Lidia Oskinova Wintersemester 2013-2014 lida@astro.physik.uni-potsdam.de astro.physik.uni-potsdam.de/~lida/x-ray.html Chandra X-ray, HST optical, Spitzer IR NGC602 in the SMC d=60pc
Clusters of galaxies 01 http://chandra.harvard.edu/
Coma cluster HST: 9 arcmin wide 02 X-rays from Clusters of Galaxies Clusters of galaxies are selfgravitating accumulations of dark matter which have trapped barions: ICM and galaxies. 02 Coma cluster CXO: 17 arcmin wide The baryons in the ICM thermalize to > 10 6 K making clusters strong X-ray sources. Most of the baryons are in the hot ICM plasma - only 10-20% are in the galaxies. NASA/CXC/SAO/A.Vikhlinin et al. Lets rememeber what is bremsstrahlung
03 X-ray measurments 03 From the spectrum we can measure a mean temperature, a redshift, and abundances of the most common elements (heavier than He). With good S/N we can determine whether the spectrum is consistent with a single temperature or is a sum of emission from plasma at different temperatures. Using symmetry assumptions the X-ray surface brightness can be converted to a measure of the ICM density.
04 Cosmology from cluster evolution (Vikhlinin et al. 2003) 04 -- Independent on other methods -- New surveys are underway
05 Sunyaev-Zeldovich effect 05 Interaction between Cosmic Microwave Background Radiation (CMB) and hot gas in the galaxy clusters. CMB photons passing through the hot ICM have a ~1 per cent chance of inverse Compton scattering off the energetic electrons, causing a small (~1 mk) distortion of the CMB spectrum: the Sunyaev-Zeldovich effect. The ICM emits X-rays primarily through thermal bremsstrahlung. The SZE is a function of the integrated pressure, T n e T e dl, the integration is along the line of sight. The X-ray emission: S X n 2 eλdl, Λ is the cooling function. The different dependences on density, along with a model of the cluster gas, enables a direct distance determination to the galaxy cluster.
Clusters of galaxies: Physics 06 http://chandra.harvard.edu/
07 Central regions of galaxy clusters 07 Basic model: Clusters are spherically symmetric balls of plasma that evolved in isolation. Gas density is highest at the center. ε~n 2, cooling time is smaller than the cluster age Gas must lose energy by radiating X-rays Pressure drops, gas gets compressed by garvitational well Density and ε increase leading to a steady cooling inflow of plasma cooling flow. The X-ray spectra are expected to show evidence for a range of temperatures from the ambient for the cluster down to zero. But! They don t! little cooling gas is found cooling flow-problem
Bonamente etal. 2006 08
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10 High-Resolution X-Ray Spectroscopy of CFs Peterson etal. 2003 10 If the blobs of plasma cool in thermal isolation at constant pressure, and the dominant energy loss mechanism is via X- radiation, then the luminosity radiated per unit temperature interval, must be proportional to the mass deposition rate dl X dt = 5 2 Ṁk µm p The only free parmeter is Ṁ - mass deposition. Can be estimated the density distribution inferred from the X-ray image. Then a cluster spectrum has two components: (1) the coolingflow spectrum, as described above, and (2) an isothermal spectrum evaluated at the temperature of the background cluster gas.
From Peterson etal 2003, ApJ 590:207 11 observed, model, best fit Model is inconsistent with observations when temperature is about 1/3 of the ambient value
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13 Hydra A: key to the CF problem? 13 Chandra Image NASA/CXC/SAO
14 AGN feedback - a key to the CF problem? 14 NASA/CXC/SAO/NRAO Chandra + Radio Image
15 Bubbles in Abell 2597 15 Chandra X-ray image Ghost cavities are 100 millionyear-old relics of an ancient eruption that originated around a massive black hole in the core of a centrally located galaxy. Bubbles are hot gas, magnetized, high-energy particles enough to support surrownding pressure. Multiple events deposit into the ICM energy NASA/CXC/SAO/NRAO
16 Sound Waves in Perseus A 16 Sound waves from explosive events In the AGN in the central galaxy Dissipation of sound waves heating of ICM Cavities are radio sources, filled with high-energy particles and magnetic fields. NASA/CXC/SAO/ see annimation
17 Chemical evolution of the Universe 17 What is the origin of the metals in the ICM and when were they injected? What is the origin of the entropy of the ICM?
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19 Summary Hot ICM in the potential well of galaxy cluster 19 Most barions in the cluster are in the hot ICM gas Measuring X-ray flux and temperature profiles across cluster density and temperature distribution barionic mass Clusters are weakly selfsimilar (z-dependence) Can help to contstarin cosmological models NASA/CXC/SAO/NRAO MS 0735.6+7421: Gravitational potnetial traces dark matter AGN feedback keeps central cluster regions hot
Galaxies 20 M31 NASA/CXC
Milky Way Center 21 National Geographic
Artist impression 22
Radio image 23
Radio image 24
Radio image 25
VLT adaptive optics Sgr A* 26
2.2 micron image 27
Mass of the Black Hole 2.2 micron animation of the stellar orbits in the central parsec http://www.astro.ucla.edu/~ghezgroup/gc/pictures/ 28 Use Kepler s III Law to determine the mass of the BH: a 3 =M BH P 2 For this one needs to determine for many stars: a) the period P b) the size of the orbit s semimajor axis a Current best estimate M BH =7.2 millions M
Composite image of Galactic Center in near IR (HST) and X-ray (Chandra) 29 X-ray luminosity of Sgr A* is ~10 32 erg/s
Activity of our Black Hole 30 see flare at http://www.astro.ucla.edu/~ghezgroup/gc/pictures/ SINFONI VLT image
Fermi Bubbles: evidence of previous activity 31 http://www.nasa.gov/mission_pages/glast/news/new-structure.html