The Importance of Winds and Radiative Feedback in Massive Star Formation

Transcription

1 The Importance of Winds and Radiative Feedback in Massive Star Formation Anna Rosen (UCSC) Mark Krumholz (UCSC), Enrico Ramirez-Ruiz (UCSC), Laura Lopez (CfA), Jeff Oishi (AMNH), Aaron Lee (UCB), Chris McKee (UCB), Richard Klein (UCB) Hubble panoramic image of the Carina Nebula (NASA)

2 Stellar feedback is one of the largest uncertainties in star and galaxy formation. 30 Doradus in the LMC Hot gas (X-rays) Chandra/Spitzer/MCELS Hα (credit: L. Townsley) 30 Doradus in the LMC (NASA) Cooler gas/dust (Hα/Infrared)

3 Massive stars affect their environments in a variety of ways Direct Radiation pressure (P dir ) 30 Doradus (Krumholz & Matzner 2009, Fall+2010, Murray+2010) Dust reprocessed radiation pressure (P IR ) (Thompson+2005, Murray+2010) Photoionization flows (P HII ) (Dale+2013) Stellar Winds (P X ) (Castor+1975, Weaver+1977, Canto+2000, Stevens & Hartwell 2003, Harper-Clark & Murray 2009) Supernovae (McKee & Ostriker 1977, Chevalier & Clegg 1985) Lopez+2011

4 Massive stars affect their environments in a variety of ways Direct Radiation pressure (P dir ) 30 Doradus (Krumholz & Matzner 2009, Fall+2010, Murray+2010) Dust reprocessed radiation pressure (P IR ) (Thompson+2005, Murray+2010) Photoionization flows (P HII ) (Dale+2013) Stellar Winds (P X ) (Castor+1975, Weaver+1977, Canto+2000, Stevens & Hartwell 2003, Harper-Clark & Murray 2009) Supernovae (McKee & Ostriker 1977, Chevalier & Clegg 1985) Lopez+2011

5 Outline Motivation: The damaging effects stellar feedback has on star-forming environments The importance (or lack thereof) of stellar winds in star formation and HII region dynamics (aka The Missing Wind Energy Problem ) The importance of radiation pressure in massive star formation and it s application in star formation simulations (new hybrid radiation scheme in ORION)

6 Outline Motivation: The damaging effects stellar feedback has on star-forming environments The importance (or lack thereof) of stellar winds in star formation and HII region dynamics (aka The Missing Wind Energy Problem ) The importance of radiation pressure in massive star formation and it s application in star formation simulations (new hybrid radiation scheme in ORION)

7 Feedback from massive stars ejects gas from clouds leading to low star formation efficiencies Top: NIR, Bottom:Visible/Hα (red) Bastian+2014 (NASA)

8 Super-bubbles are observed around young massive star clusters (MSC) which are devoid of gas. T2005 in NGC 3256 Cluster 23 in ESO 338-IG04 Age < 5 Myr Age ~ 6 Myr (NASA) Bastian+2014

9 Young ages and super-bubble sizes require efficient feedback R MSC R SB Bastian+2014 Young ages imply most gas ejected before SNe go off. (NASA)

10 Outline Motivation: The damaging effects stellar feedback has on star-forming environments The importance (or lack thereof) of stellar winds in star formation and HII region dynamics (aka The Missing Wind Energy Problem ) The importance of radiation pressure in massive star formation and it s application in star formation simulations (new hybrid radiation scheme in ORION)

11 High luminosities of massive stars produce fast line driven winds from the stellar surface Bestenlehner+2014 Wind-luminosity Relation (Repolust 2004) L Bol 2c = Ṁwv 1

12 Total energy injected by massive stars is equivalent to resulting supernovae. Agertz+2013 E w = L w t erg = E SN (NASA)

13 Injection of energy by stellar winds in a massive star cluster (MSC) Stellar winds collide with each other and the ISM shock heating gas to ~10 7 K Typical values for MSCs: L w = NX i=1 1 2Ṁw,iv 2 w,i L w erg s 1 Canto+2000

14 Post-shock heated gas cools very inefficiently. Cluster wind adiabatically expands. Russell & Dopita 1992, Dere+1997, Grevesse & Sauval 1998, Rosen Lopez+2011 Shock heated gas fills HII region and primarily radiates in X-rays.

15 Chandra kev diffuse emission The importance of winds as a feedback mechanism in star formation and HII region dynamics relies on how the wind energy is transferred to the ISM. (NASA)

16 X-ray observations of HII regions suggest that the shockheated gas is not dynamically important (Dunne+03, Harper-Clark & Murray+09, Lopez+11) 30 Doradus Hot Gas Pressure Radiation Pressure Lopez+2011

17 so where s the missing energy? Our model and HII region requirements Description of how we account for the missing energy Our results and how they affect our understanding for stellar winds as an important feedback mechanism in star formation

18 so where s the missing energy? Our model and HII region requirements Description of how we account for the missing energy Our results and how they affect our understanding for stellar winds as an important feedback mechanism in star formation

19 Our Model Castor+1975, Weaver+1977 (1) Require spectral typing of massive stars in HII region to estimate total L w

20 Our Model Castor+1975, Weaver+1977 (2) Require X-ray observations to characterize the properties of the hot gas

21 Our Model Castor+1975, Weaver+1977 (3) Require radio observations to determine the HII region radius and shell expansion rate

22 Our HII Region Sample 30 Doradus Carina Nebula NGC 3603 M17 M17 (NASA) (2011c) 30 Doradus: Lopez+2011, Doran+2013, Lopez+2013; Carina: Smith 2000,Smith 2006, Smith & Brooks 2007,Townsley+2011c; NGC 3603: Balick+1980, Crowther & Dessart 1998, Townsley+2011c; M17: Clayton+1985, Dunne+2003, Townsley+2003, Hoffmeister+2008, Townsley+2011c

23 so where s the missing energy? Our model and HII region requirements Description of how we account for the missing energy Our results and how they affect our understanding for stellar winds as an important feedback mechanism in star formation

24 Avenues that the hot gas can transfer energy L cool : Radiative cooling of the hot gas (Castor+1975, Weaver+1977, Dere+1997, Draine 2011)

25 Avenues that the hot gas can transfer energy L mech : Mechanical work on the dense shell (Castor+1975, Weaver+1977)

26 Avenues that the hot gas can transfer energy L cond * : Laminar Thermal Conduction of the Hot Electrons (Spitzer 1962, Cowie & McKee 1977) Unsaturated Saturated (* conservative estimate)

27 Avenues that the hot gas can transfer energy L dust * : Collisional Heating of Dust Grains (Dwek 1987, Smith+1996, Draine 2011, Krumholz 2013) (* conservative estimate)

28 so where s the missing energy? Our model and HII region requirements Description of how we account for the missing energy Our results and how they affect our understanding for stellar winds as an important feedback mechanism in star formation

29 L X,obs constrains hot gas density and temperature Russell & Dopita 1992, Dere+1997, Grevesse & Sauval 1998 Rosen+ 2014

30 Allowed T-n X curves for our HII region sample Rosen+ 2014

31 Accounting for the missing energy Rosen+ 2014

32 Accounting for the missing energy Rosen Hot gas not strongly coupled with the ISM.

33 Accounting for the missing energy Rosen Could winds be important for young, compact HII regions?

34 Ways Out: Where s the Missing Energy? Thermal conduction? Probably not. a=0.1 μm Krumholz+2007 Dust heating via collisions? It might help. Rosen+ 2014

35 Ways Out: Where s the Missing Energy? Physical leakage of the hot gas (Harper-Clark & Murray 2009, Rogers & Pittard 2013, Dale+2014) tex Rogers & Pittard 2013 Harper-Clark & Murray 2009 Rosen (a)l rad + L mech (b)l rad + L mech + L dust + L cond

36 Ways Out: Where s the Missing Energy? Strickland & Stevens 1998 Rapid mixing of cold and hot gas via turbulent conduction (McKee+1984, Strickland & Stevens 1998, Nakamura+2006)

37 Outline Motivation: The damaging effects stellar feedback has on star-forming environments The importance (or lack thereof) of stellar winds in star formation and HII region dynamics (aka The Missing Wind Energy Problem ) The importance of radiation pressure in massive star formation and it s application in star formation simulations (new hybrid radiation scheme in ORION)

38 Radiation pressure extremely important in massive star and massive star cluster formation. Accretion is Eddington limited L? < > 4 Gc M? apple R L? M? = 1300 L M apple R 10 cm 2 g 1 Radiation Pressure 1 Fails for stars with M 20 M Krumholz et al., 2009 Instead material funneled through disk via gravitational torques and envelope via radiative Rayleigh Taylor instabilities.

39 Radiation pressure extremely important in massive star and massive star cluster formation. Hot Gas Pressure Radiation Pressure ζ>1 = Rad dominated Fall, Krumholz & Matzner 2010 Krumholz & Matzner 2009 Observed dense, massive star clusters are radiation pressure dominant.

40 Chandra kev diffuse emission Massive star formation simulations require radiation. However, most treatments to date are approximate. (NASA)

41 Treatment of radiation in the astrophysical AMR code ORION Old: Flux Limited Diffusion (FLD) Hot Gas Pressure Radiation Pressure New: Hybrid Radiation Scheme Adaptive multi-ν ray tracing ~F r / ~ re r = X i L?,i W (~x ~x i ) FLD Lopez+2011 ~F r = ~ F?,RT + ~ F th,fld

42 Treatment of Direct Radiation Pressure with Adaptive Ray Trace Number of rays spread equally on initial healpix level l 0 : N pix (l 0 ) = 12 4 l 0 Parent ray splits into 4 child rays when where ray = ( x) 2 ray R N pix < c Energy and solid angle conserving! Wise & Abel 2011 Gorski, Hivon, & Wandelt 1998; Abel & Wandelt 2002

43 Treatment of Direct Radiation Pressure with Adaptive Ray Trace Photon packet radiative transfer equation 1 c = applen p Photons absorbed across cell dn p = N p 1 e apple dl Energy and momentum added to cell de = dp i = XN j=1 XN j=1 L ray,j e apple j dl dt L ray,j c e apple j dlˆn ray,i dt for i = x, y, z

44 Current Hybrid Radiation Application: Massive Star Formation FLD only simulation t ff =42,710 yrs R c =0.1 pc M c =150 M Σ=1 g cm -2 Δx min = 20 AU E rot /E grav =0.02 z [cm] y [cm] z [cm] y [cm]! Simulations with ray tracing are being run! y [cm] y [cm] x [cm] x [cm]

45 (Very) Preliminary Results: Massive Star Formation FLD+ART FLD only t ff =42,710 yrs R c =0.1 pc M c =150 M Σ=1 g cm -2 E rot /E grav =0.02 Δx min = 20 AU Ray slitting criterion Ω c =4

46 Summary Bulk of the stellar wind energy does not go into mechanical work for young HII regions surrounding MSCs. We have implemented a hybrid radiation scheme in ORION to accurately treat the radiation field in star formation simulations Hybrid scheme splits radiative transport step into: 1. Adaptive raytracing step for stellar radiation (P dir ) 2. Diffusion step for thermal radiation (P ir ).