Feedback in Elliptical Galaxies

1. Feedback in Elliptical Galaxies A Thesis Prospectus Presentation David A. Riethmiller March 16, 2009

2. 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

3. What is an Elliptical Galaxy? X-Ray properties very different from optical M87: X-Ray, 11’ chandra.harvard.edu/photo/m87/m87_xray.jpg

4. What is an Elliptical Galaxy? Composite image yellow = optical red = radio blue = x-ray chandra.harvard.edu/photo/m87/m87_scale.jpg

5. 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

6. Goals of the Project “Feedback is important. We don’t know what it is.” • Simulate cooling and feedback in elliptical galaxies. • Discard models that fail to match observational constraints.

7. 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

8. History of X-Ray Observations and Models: “Cooling Flow” • Sinks and Sources • Flow Dynamic More prevalent on cluster scale Fabian 1994

9. History of X-Ray Observations and Models: ROSAT • ROSAT (Röntgen Satellite) launched in 1990 • same spatial resolution, improved spectral resolution heasarc.gsfc.nasa.gov

10. History of X-Ray Observations and Models: Chandra Chandra X-Ray Observatory launched in 1999. • High spectral resolution • High spatial resolution (narrow PSF) • High sensitivity FOV 16.5’ chandra.harvard.edu http://chandra.harvard.edu/graphics/resources/illustrations/chandra_earth.jpg

11. Physics of Galactic X-Ray Emitting Gas: Radiative Cooling Bremsstrahlung vs Line Emission http://proteus.pha.jhu.edu/dks/Code/Coolcurve_create/index.html

12. Physics of Galactic X-Ray Emitting Gas: Runaway Cooling? We don’t observe this.  Must be method of returning energy to gas to balance cooling. • Signature: • very bright center • steep drop in luminosity with increasing radius

13. Physics of Galactic X-Ray Emitting Gas: Feedback “Feedback is important. We don’t know what it is.” Three main forms of feedback: • Stellar Wind • Supernova Feedback • AGN activity

14. 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.

15. Isophotes Diehl & Statler, 2008a

16. Observational Constraints: Hydrostatic? If hydrostatic, expect hot gas isophotes to follow shape of stellar potential (at small radii). From Diehl & Statler, 2007

17. Observational Constraints: Asymmetry (I) Quantify morphological asymmetry in x-ray isophotes Diehl & Statler, 2008a

18. Observational Constraints: Asymmetry (II) Diehl & Statler, 2008a

19. Observational Constraints: Asymmetry (III) Diehl & Statler, 2008a

20. Observational Constraints: Gradients 4 types: Diehl & Statler (2008b)

21. Observational Constraints: Gradients (I) Diehl & Statler (2008b)

22. Observational Constraints: Gradients (II) Central velocity dispersion: Dispersion in stellar radial velocity Diehl & Statler (2008b)

23. Observational Constraints: Gradients (III) Diehl & Statler (2008b)

24. Observational Constraints: XGFP Face-on Edge-on X-Ray Gas Fundamental Plane Diehl & Statler 2005

25. Observational Constraints: AGN Scenarios I Scenario 1

26. 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

27. 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

28. Basics of SPH Code: Kernel But the numerical code requires a discrete function, so we approximate: 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)

29. 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.

30. Snapshot y (kpc) x (kpc)

31. Hydrostatic Check -dP / dr g * rho

32. Pressure (r) Pressure r (kpc)

33. Radial Accelertion a(r) (kpc / myr2) r (kpc)

34. Proposed Project: Work to Date (I) • Ran test of a simplistic T1/2 cooling function • “Can of gas” simulation • self gravity and hydrostatic pressure disabled • Bremsstrahlung-only cooling enabled (no line emission)

35. Proposed Project: Objectives Cooling • Implement more complex cooling functions into SPH • Sutherland & Dopita 1993 • Cloudy (Ferland et al., 1998) • Mappings III (Groves et al., 2008) • Gnat & Sternberg 2007 From Wiersma et al., 2009

36. Proposed Project: Objectives (I) “Feedback is important. We don’t know what it is.” Stellar wind models (Thacker and Couchman, 2000): Energy Smoothing Single Particle Feedback Temperature Smoothing

37. Proposed Project: Objectives (II) • 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)  After matching simpler feedback models, we graduate to newer prescriptions.

38. 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

39. 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 LaboratoryAlso secured time on several Teragrid supercomputing facilities.

40. Extra Slide 1: Alternate Initial Conditions Diehl et al. 2009

41. Extra Slide 2: SPH Initial Conditions Weighted Voronoi Tesselations (WVT) Initial Conditions • Begin with configuration according to particle probability distribution P(r)  h(r)-3 dV for smoothing length h and volume dV Taken from Diehl et al. 2009. (Colors are simply for a better 3-D understanding.)

42. Extra Slide 3: Theoretical Cooling Function

43. History of X-Ray Observations and Models: “Cooling Flow” Abel 1795 (Chandra ACIS) http://www.nasa.gov/centers/marshall/images/content/98568main_a1795_xray_m.jpg

44. Physics of Galactic X-Ray Emitting Gas: Inflow • Sinks and Sources • Flow Dynamic http://www.gemini.edu/index.php?q=node/276