PROGRESS TOWARD A VLBA MOVIE OF THE JET
COLLIMATION REGION IN M87
R. Craig Walker NRAO
Collaborators:
Chun Ly (UCLA - was NRAO summer student)
William Junor (LANL), Philip Hardee (U. Alabama)
Why Study the Jet Base in M87• Best case for a study of a jet near a black hole
– “Near” in terms of characteristic lengths of system– The galaxy is relatively nearby at 16 Mpc– Large black hole mass ~3X109 Msun – VLBA resolution is about 60 Schwarzschild radii
• Core has about 1 Jy at 43 GHz• Jet bright enough to see significant structure
– Well resolved across jet very near core
• Wide range of speeds seen in the jet on larger scales– Includes 6c superluminal speeds which suggest a jet
orientation near line-of-sight– VLBI measured speeds mostly subluminal
• Wish to compare observations with theory and numerical simulations
M87 Inner Jet
43 GHz Global VLBIJunor, Biretta, & Livio 1999, Nature, 401, 891
Shows hints of jet collimation region
Black Hole / Jet Model
Global VLBI Image
VLA Images
Resolution 0.000330.00012
JET FORMATION:BASE OF M87 JET
STScI
M87 43 Hz Images at ~1 yr Intervals
• Rates 2001.78 - 2002.42 are 0.25 - 0.40c– 1.0 to 1.7 mas/yr
• Other epochs too widely spaced• Feature seen east of core - counterjet or inner jet?
– If counterjet, speeds and brightness give orientation• 30-45 deg to line-of-sight, 0.3-0.5c• Result inconsistent with constraints from superluminal motion
observed on larger scales
Our old observationsand archivedata. Mostly from use of M87 as phase reference source.(Ly, Walker, & Junor, 2007, Ap. J. 660, 200.)
• Basic edge brightened structure maintained
• Dominant edge shifts from south to north
PILOT PROJECT
• Wish to make a VLBA movie to study dynamics• Previous data showed 1 year intervals are too long.
– Rate ≥ 0.25 - 0.4 c (up to 1.7 mas/yr)
• Did not know the appropriate frame rate• Superluminal speeds would require sampling every few
days– Up to 6 c (24 mas/yr) seen on larger scales
• Pilot project: – Observations at 0, 3, 10, 13, 35 and 97 days – Observed April - July 2006– 43 GHz, 10hr observations, 128 Mbps
Pilot Project Images
• Good consistency between close epochs
• Motions near 2.2 mas/yr (0.6c) at 1.5 mas from core
• About 1.5 mas/yr near core
• Superluminal motions not seen
• Feature east of core still seen
Beam: 0.42x0.18 mas 0.2mas = 0.016pc = 60Rs
1mas/yr = 0.25c
Day 0
Day 3
Day 10 Day 97
Day 35
Day 13No PT
M87 43 GHz Pilot Movie 97 Days
• Actual observations at the tick marks• Note the movie frame rate varies
• 0.8% on peak• Polarized peak
offset from total intensity
• Position angle rotates
• Polarization not detected off peak
Polarization Structure
The VLBA 43 GHz M87 Movie
• Scheduled for 18 frames at 3 week intervals– Interval based on Pilot Project results– Dynamic scheduling within windows– Observations began Jan. 27, 2007
• Five frames observed and correlated so far. Two imaged• Frame 1 Missing Kitt Peak - weak on sort baselines• Frame 2 bad weather at Mauna Kea - reduced resolution
• Observational parameters– 10 hr/frame– 256 Mbps (Twice the bandwidth of pilot)– Full stokes– Primary calibrators 3C279 and OJ287
The VLBA 43 GHz M87 MovieFirst Frame Jan 27, 2007
Beam: 0.40x0.20 mas 0.2mas = 0.016pc = 60Rs
1mas/yr = 0.25c
No KP
The VLBA 43 GHz M87 MovieSecond Frame - Low resolution version
Feb 17, 2007
Beam: 0.56x0.41 mas 0.2mas = 0.016pc = 60Rs 1mas/yr = 0.25c
MK bad weather
The VLBA 43 GHz M87 MovieNot much yet, but here’s the start
Beam: 0.40x0.20 mas 0.2mas = 0.016pc = 60Rs
1mas/yr = 0.25c