A Study of Sgr A* and Non-thermal Radio Filaments F. Yusef-Zadeh X-Ray (XMM) G. Belanger Radio (VLA+ATCA) D. Roberts Near-IR (HST) H. Bushhouse C. Heinke M. Wardle S. Shapiro A, Goldwurm Sub-millimeter (CSO, SMT) D. Dowel B. Vila Vilaro L. Kirby Non-thermal Filaments S. Boldyrev

Sgr A* –Light curves in NIR wavelengths –Sub-mm emission is variable –Cross correlation –Power spectrum of NIR emission Non-thermal Filaments –Recent observations – Global vs local origin –Strong vs weak magnetic field – a new turbulent model Outline X-rayNIRSub-mm

XMM ATCA SMT VLA CSO HST XMM March Campaign September Campaign Two Epochs of Observations of SgrA* in 2004 VLA BIMA NMA INTEGRAL CSO Sub-mm mm Radio X/  ray Sub-mm Radio NIR

Near-IR Line and Continuum (NICMOS /HST) Observations: – 32 orbits of Camera 1 NICMOS in three bands: F160:W Broad band at 1.6  m ( mum) F187:N Narrow band at 1.  m( ) (P  line) F190N: Narrow band at 1.  m (continuum) – Each cycle: Alternating between the three bands for about 7-8 min – Six observing time intervals

1.6  m image Pixel size 0.043” Field of view 11” Sigma=0.002 mJy after 30sec The position of S2 wrt SgrA* estimated from orbit calculations (Ghez et al. 2003) S2 offset from SgrA* is 0.13”N and 0.03”E PSF has a four pixel diameter S2 is a steady source (PSF contamination) Great instrument because of background and PSF stability PSF has a 4-pixel diameter

Near-IR Light Curves of SgrA* (blue, red, green) Amp: 10 % to 25% or 3 to 5 times the quiescent flux (11-14 mJy) Duration: multiple peaks, lasting from 20 minutes to hours Flare activity: overall fraction of activity is about 30-40% of the observed time (background 8.9 mJy) a b c e d Near-IR variability in 1.6, 1.87 (Pa  line), 1.9  m

Submillimeter 0.87mm and 0.45mm Emission (CSO) September Campaign Variability with maximum: 4.6Jy and minimum: 2.7 Jy Likely to be due to hourly than daily variability

IR (  m) vs. X-Ray (September Campaign) NIR X-ray NIR

Simultaneous X-ray and NIR flare NIR due to Synchrotron:  nir = 40min, Beq=10G, Ee=1.1 GeV X-Rays due to Synchrotron:  nir =1min, B=10G, Ee=10 GeV X-Rays due to ICS: diameter=10Rsch, F 850  m =4Jy, Ee=1GeV Ex=2x erg/cm2/s/keV, Eobs=1.2x erg/cm2/s/keV Spectral index between near-IR and X-rays is  = bu in near-IR and X- rays,  =-0.6 If  is flatter by 0.2, the X-ray flux is reduced by a factor of 2, so no X-ray counterpart is detected. ICS with  =-0.6 produces soft  ray emission with L = 7.6x10 34 erg/s (2-20 keV) which is 5 times lower than observed

Lomb-Scargle periodogram searches for periodicity Significant power with a period of ~ 1.3h and ~ 30min a/M=0 (r/M) orbit = 6R sch The same scale size as the region of the seed photons for ICS

Radio (7mm) vs X-ray (March Campaign) Lag time between X- ray/NIR flare and sub- mm peak 4-5 hours Time delay between X- ray/NIR and radio peak is one day The flux variation in sub-mm is about 30% whereas at 7mm is 10% An expanding synchrotron source in an optically thick medium X-ray NIR Sub-mm Radio

Sub-mm and Radio Time Lags D.P. Marrone, 2005

Conclusions I Flare correlation: simultaneous vs delayed Correlation between a near-IR and X-ray flare: consistent with SSC (Eckart et al. 2004) An expanding synchrotron self-absorbed blob: radio and NIR wavelengths Evidence for a NIR flare with quasi-periodic 1-1.3h and 30min behavior The flow always fluctuates even in its quiescent phase

Non-thermal radio continuum emission is significant (40-50%) –Excess SNRs –Stellar clusters (Arches cluster, Sgr B2) –Diffuse background emission –Magnetized Filaments Law et al. (2005 )

The ripple filament: total intensity (top), polarized intensity at 6cm (bottom)

X-ray (2-8 keV) and Radio (15GHz) Images of SgrA-E X-rayRadio Sakano et al Lu et al Yusef-Zadeh et al. 2005

 The spectrum is similar in both radio and X-ray  Using the 1200, 862 and 442 micron flux and RJ tail of Planck function  T dust = K   (dust) =  Using 25 mJy flux at 15 GHz with  =0.75, ICS flux can match the observed X-ray flux 3.2x ergs/ cm 2 /s/keV if:  Tdust =50 K, B=100  G  Beq =140  G for a cutoff of 10MeV

Distribution of Radio Filaments

Origin of the Filaments Models: Loop ejection from a central differentially rotating engine at the Galactic center (Heyvaerts, Norman and Pudritz 1988) Induced electric field by the motion of molecular clouds with respect to organized poloidal magnetic field (Benford 1988) Contraction of a rotating nuclear disk in a medium threaded by poloidal magnetic field Cosmic Strings oscillating in a magnetized medium Interaction of a magnetized galactic wind with molecular clouds (Shore and LaRosa 1999) Reconnection of the magnetic field at the interaction site of molecular clouds and large-scale magnetic field (Serabyn and Morris 1994)

Magnetic Field in the Galactic Center Standard Picture for the last 20 years:  The field has a global, poloidal geometry due to the filaments orientation  The field has a milli-Gauss strength due to dynamical interaction and morphology Some Recent Problems:  A number of filaments don’t run perpendicular to the Galactic plane  Zeeman and Faraday measurements plus synchrotron lifetime  Anisotropy of scatter broadened OH/IR stars  Diffuse non-thermal emission places a limit of pervasive field < 10  mG  Diffuse X-ray emission due to ICS with Tdust=30K requires B~10  G  Filaments not representative of the large-scale Field

A Turbulent Model of the Nonthermal Radio Filaments The mean field is weak but strong turbulent activity amplifies the field locally  Turbulent energy is ~ two orders of magnitude higher than the disk  High velocity dispersion  Hyper-scattering medium  Analogous to hydro turbulence with vorticity and MHD simulations  B increases, produces filamentary structure until it reaches equipartition  Generation:  Amplification rate ~ eddy turnover time scale ~ yrs  The length of the filament ~ outer scale of turbulence ~10s pcs  Expulsion:  Turbulent region is confined in GC, the field is expelled by turbulece  Diffusion time scale ~  (diffusion) ~ L 2 /  ~ 10 times the eddy turnover time scale  In the disk:  The region not confined,  (diffusion) >> eddy turnover time scale in the disk  Turbulent energy is much smaller than in the GC

 ordlund et al. (1992) B field vectors of flux tubes (yellow and red); Vortes tube (grey)

Conclusions II ICS of the seed photons from dust cloud can explain some of the diffuse X-ray features in the GC Although non-thermal radio filaments may have strong magnetic field, they can not be representative of the large-scale filed in the GC A turbulent dynamo model in a highly turbulent region of the GC may explain the origin of nonthermal radio filaments

6 and 1.2cm VLA images of the Galactic Center

The dispersion plot is minimum at ~20min An expanding self- absorbed synchrotron source with a delay of 20min implies plasma ejection took place 54min before the 7mm peak (van der Laan 1966). No near-IR or sub- millimeter data) Continuous ejection?

SMT Observations (870micorn) March Campaign

Submillimeter 7mm and 0.45mm Emission (CSO) March Campaign

IR (  m) vs. Radio (7mm) (September Campaign)

Radio (7mm) vs X-ray (September Campaign)

IR (  m) vs. X-Ray (September Campaign)

Radio (7mm) vs X-ray (March Campaign) 40, 56 or 65min delay

Spectrum of Sgr A * Sgr A*

Radio (7mm) vs X-ray (September Campaign)

Assuming the P= 1.3h variability is due to circular motion: a/M=0 no spin –(r/M) orbit = (P/2  M) 2/3 = 6R sch –(for comparison r ISCO =2R sch The same scale size as the region where sub-mm emission is expected to peak Power Spectrum

Light Curve of SgrA* at 1.6, 1.87 and 1.90 microns The variation is similar in all three filters Great instrument because of background and PSF stability