Presentation on theme: "Feedback in Elliptical Galaxies A Thesis Prospectus Presentation David A. Riethmiller March 16, 2009."— Presentation transcript:
Feedback in Elliptical Galaxies A Thesis Prospectus Presentation David A. Riethmiller March 16, 2009
What is an Elliptical Galaxy? Smooth, round, no spiral arms Really big ones at centers of clusters (not the ones I study) Stars show little organized motion Size ~ 10s of kpc Temperature ~ below 1-2 keV M87: Optical, 11 chandra.harvard.edu/photo/m87/m87_optic.jpg
What is an Elliptical Galaxy? X-Ray properties very different from optical M87: X-Ray, 11 chandra.harvard.edu/photo/m87/m87_xray.jpg
What is an Elliptical Galaxy? Composite image yellow = optical red = radio blue = x-ray chandra.harvard.edu/photo/m87/m87_scale.jpg
Outline Goals of the Project History of X-Ray Observations and Models Physics of Galactic X-Ray Emitting Gas Observational Constraints Basics of SPH Code Proposed Project
Goals of the Project Simulate cooling and feedback in elliptical galaxies. Discard models that fail to match observational constraints. Feedback is important. We dont know what it is.
History of X-Ray Observations and Models: Einstein Observatory X-Ray universe poorly understood until Einstein launch in 1978 IPC FOV: 75 1 arcmin resolution heasarc.gsfc.nasa.gov
History of X-Ray Observations and Models: Cooling Flow Fabian 1994 More prevalent on cluster scale Sinks and Sources Flow Dynamic
History of X-Ray Observations and Models: ROSAT ROSAT (Röntgen Satellite) launched in 1990 same spatial resolution, improved spectral resolution heasarc.gsfc.nasa.gov
History of X-Ray Observations and Models: Chandra Chandra X-Ray Observatory launched in High spectral resolution High spatial resolution (narrow PSF) High sensitivity FOV 16.5 chandra.harvard.edu
Physics of Galactic X-Ray Emitting Gas: Radiative Cooling s/Code/Coolcurve_create/ind ex.html Bremsstrahlung vs Line Emission
Physics of Galactic X-Ray Emitting Gas: Runaway Cooling? We dont observe this. Must be method of returning energy to gas to balance cooling. Signature: very bright center steep drop in luminosity with increasing radius
Physics of Galactic X-Ray Emitting Gas: Feedback Three main forms of feedback: Stellar Wind Supernova Feedback AGN activity Feedback is important. We dont know what it is.
Physics of Galactic X-Ray Emitting Gas: Compressive Heating If AGN not dominant, compressive heating may be important dW = -PdV Efficiency depends on mass and temperature.
Isophotes Diehl & Statler, 2008a
Observational Constraints: Hydrostatic? If hydrostatic, expect hot gas isophotes to follow shape of stellar potential (at small radii). From Diehl & Statler, 2007
Observational Constraints: XGFP X-Ray Gas Fundamental Plane Face-on Edge-on Diehl & Statler 2005
Observational Constraints: AGN Scenarios I Scenario 1
Observational Constraints: AGN Scenarios II Scenario 2: AGN heating only dominant in very bright x-ray galaxies Negative gradients in dimmer galaxies indicate prevalence of feedback from compressive heating or supernovae Scenario 3: AGN activity may be cyclic, and observed temperature gradients are simply various snapshots in time
Basics of SPH Code Lagrangian hydrodynamics method (Monoghan 1992) Fluid elements represented as individual particles carrying fluid attributes Spatial derivatives computed by analytical differentiation of interpolation formulae Momentum and energy equations become ODEs, interpreted easily in themodynamical and mechanical terms
Basics of SPH Code: Kernel A(r) expressed in terms of its values at a set of disordered points, so integral interpolant is W(r,h): integration kernel volume element dr h: smoothing length (defines resolution of simulation) But the numerical code requires a discrete function, so we approximate:
Proposed Project: Work to Date Implemented routines into SPH code for: application of external gravitational field application of external pressure application of cooling function based on tabulated list of cooling rates Also wrote several IDL scripts designed to analyze output data of SPH code.
Snapshot x (kpc) y (kpc)
Hydrostatic Check g * rho -dP / dr
Pressure (r) r (kpc) Pressure
Radial Accelertion r (kpc) a(r) (kpc / myr 2 )
Proposed Project: Work to Date (I) Ran test of a simplistic T 1/2 cooling function Can of gas simulation self gravity and hydrostatic pressure disabled Bremsstrahlung- only cooling enabled (no line emission)
Proposed Project: Objectives From Wiersma et al., 2009 Implement more complex cooling functions into SPH Sutherland & Dopita 1993 Cloudy (Ferland et al., 1998) Mappings III (Groves et al., 2008) Gnat & Sternberg 2007 Cooling
Proposed Project: Objectives (I) Feedback is important. We dont know what it is. Stellar wind models (Thacker and Couchman, 2000): 1)Energy Smoothing 2)Single Particle Feedback 3)Temperature Smoothing
Proposed Project: Objectives (II) After matching simpler feedback models, we graduate to newer prescriptions. Feedback properties to investigate: Can be injected sporadically Can model both thermal and mechanical energy AGN / SMBH (Ciotti & Ostriker 2007) Grow SMBH? (Lagos et. al 2008)
Proposed Project: Constraints on Simulation Simulation must preserve observational constraints: Gas disturbed from hydrostatic at small radii Asymmetry correlations Temperature gradient correlations X-Ray Gas Fundamental Plane
Summary Project will simulate a range of feedback and cooling combinations with Smoothed Particle Hydrodynamics Rule out combinations which fail to match observational constraints SPH code compiled in parallel on the Coyote supercomputer at Los Alamos National Laboratory Also secured time on several Teragrid supercomputing facilities.
Extra Slide 1: Alternate Initial Conditions Diehl et al. 2009
Extra Slide 2: SPH Initial Conditions Initial Conditions Taken from Diehl et al (Colors are simply for a better 3-D understanding.) Weighted Voronoi Tesselations (WVT) Begin with configuration according to particle probability distribution P(r) h(r) -3 dV for smoothing length h and volume dV
Extra Slide 3: Theoretical Cooling Function
History of X-Ray Observations and Models: Cooling Flow images/content/98568main_a1795_xra y_m.jpg Abel 1795 (Chandra ACIS)
Physics of Galactic X-Ray Emitting Gas: Sinks and Sources Flow Dynamic hp?q=node/276 Inflow