Probing the TeV Emission and Jet Collimation Regions in M87

Probing the TeV Emission and Jet Collimation Regions in M87

R. C. WalkerM. Beilicke, F. Davies, P.E. Hardee, H. Krawczynski, D.

Mazin, R. Wagner, M. Raue, S. Wagner, C. Ly, W. Junor, and the VERITAS, MAGIC, and H.E.S.S. Collaborations

NM Symposium Jan. 15, 2010 Walker: TeV and VLBA Results from M87 3

M87 - THE BEST SOURCE FOR IMAGING A JET BASE

• Large angular size black hole– Large black hole mass: ~6 X 109 Msun (Gebhardt and Thomas 2009)

– Nearby: 16.7 Mpc (A central galaxy of the Virgo Cluster)– Scale: Rs = 120 au = 7.1 as; 1 c = 3.8 mas/yr– VLBA 43 GHz resolution; 210 X 430 as (~30 X 60 Rs) – Innermost stable orbit (spin dependent): 4 days to 1 month

• Jet is bright enough to see significant structure– Core has about 0.7 Jy at 43 GHz - can self-calibrate VLBI data– Jet well resolved transversely very near core– Can be seen by northern hemisphere instruments – Sgr A* black hole 40% higher angular size but has no jet

• Well studied at all wavelengths from radio to TeV– FERMI detection reported Monday (McConville 411.36)– 1.3mm VLBI observations reported Monday, 4.3Rs beam (Schenck 404.18)

McKinney & Narayan 2007

Max scale40 c2/(GM) 1000

PROSPECTS FOR COMPARISON OF THEORY AND OBSERVATION

• Simulations of disk/jet systems are reaching observable scales– Models indicate the launch and collimation region extends over 10-1000 Rs

– The observational goal of our VLBA project is to provide a data set that constrains the theory

– Need the best possible resolution in gravitational units

– VLBI just able to reach into that regime in M87


20 mas

15 GHz VLBA

1 mas

Krichbaum global array

86 GHz

M87 VLBI IMAGES

Double sided, edge brightened jetWide opening angle base“Counterjet” > 3mas long (420 Rs)Super- and sub-luminal speeds seen

1 mas = 0.001 arcsec = 0.081pc = 141Rs

1mas/yr = 0.26c

5 mas

VLBA 43 GHz23 image average


THE VLBA AND TEV PROJECTS

• VLBA at 43 GHz:– Every 3 weeks for 1 year in 2007 followed by– Every 5 days for 70 days in 2008– Each epoch included 20 phase referencing scans between M87

and M84 (1.5º separation)– Resolution 30 X 60 Rs (0.21 X 0.43 mas)

• TeV joint campaign– Imaging atmospheric Cerenkov telescopes

VERITAS, MAGIC, and H.E.S.S. (E > 100 GeV)– >120 hours in early 2008– Resolution ~5X107 Rs (~0.1 degree)

• Chandra – 4 observations during the TeV campaign + others earlier– Resolution ~1.1X105 Rs (~0.8 arcsecond)


THE VLBA MOVIE PROJECT:DYNAMICS OF THE INNER M87 JET

• Preliminary movie is from the first 11 images Jan-Aug 2007 • Apparent motions ~2 c• Analysis not finished - especially polarization processing


TeV/RADIO FLARE

• A series of large TeV flares seen during the late January to early February observing window – Windows set by Moon– Extra observations made after

trigger

• X-rays from core high in mid February– HST1 X-ray flux steady

• Radio flare – Began at time of the TeV flares– Peaked near scheduled end of

observations in early April– Larger flare than any seen before

in M87 by the VLBA– Flux density increase mostly on

the radio core

TeV

X-ray

Radio<1.2 mas

Peak

Jet >1.2 mas

HST-1

Nucleus

Acciari et al 2009 Science 325, 444

2Apr2007 1Apr2008


THE RADIO FLARE

• A: Pre-flare average• B: Last flare image• C-F: Flare images with

average subtracted• Core already above average

at start• Inner jet was below average• Most of new flux remains on

the core• New weak components

moving at about ~1.1c– Slower than movie saw

farther out - accelerating?


SIMPLE BLAST MODEL

• Radio from self-absorbed synchrotron emission from electrons injected into a slower outer sheath– Hollow cone geometry– Ring of radio emitting plasma -ray flare at time of injection

• Injection function proportional to TeV emission can match data

• Modeled emission region remains unresolved to the VLBA– The new fast, weak components would

be something else• Only a fraction of flare flux density

Radio from 1 injection (plot 80 days full width)

Injection based on TeV data


Implications of the TeV/Radio Flare

• Coincidence in time of TeV and radio flares indicates they are related– Both events abnormally large for this source

• Implies the TeV Emission region is near the black hole– Small size had been known because of rapid TeV variability– Position of TeV emission was unknown previously – Allowing for projection etc, TeV is within < 200 Rs of black hole– Assumes the black hole is near the radio core

• HST1 is not the location of these TeV flares– 2005 HST-1 X-ray flare had made it a candidate

• Emission mechanism must work near the black hole.– Several candidates still viable

• Radio emitting material injected near time of TeV flare– Optically thick


STABILITY OF CORE POSITION

• VLBA project included relative astrometry between M87 and M84– Separation 1.49º = 434 kpc

– RMS scatter during flare 11 X 34 as = 1.6 X 4.8 Rs (Beam: 210 X 430 mas)

– Elongated along beam

• Implies the core position stable to a few Rs.– Reasonable if radio core is near the black hole

– Might expect less stability if core is a shock far down the jet as in some models.

• 2001 data point suggests relative proper motion– ~800km/s

– Reasonable for Virgo Cluster

M84M87


SUMMARY

• M87 allows VLBI observations in the jet collimation region– Edge brightened jet

– Wide opening angle base

– Jet shows ~2c motions

– Rapid structure variations

– “Counterjet” feature seen

– Radio core nearly stationary

• Radio/TeV flare implies the TeV emission region is close to the black hole– TeV emission mechanism must work close to the black hole

• Several viable mechanisms have been proposed– Radio emitting plasma injected at time of TeV flare – Radio is likely synchrotron self-absorbed for around a month

Probing the TeV Emission and Jet Collimation Regions in M87

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