The MOJAVE AGN
Program
Chandra
Fermi
Matthew Lister
Dept. of Physics
Purdue University
(currently on sabbatical at
Univ. College Cork, Ireland)
VLBA
UMRAO
OVRO
MOJAVE Collaborators

M. Lister (P.I.), N. Cooper, B. Hogan, S. Kuchibhotla,
T. Hovatta (Purdue)

T. Arshakian, C.S. Chang, L. Fuhrmann, Y. Kovalev, A.
Lobanov, A. Pushkarev, T. Savolainen, J. A. Zensus (Max
Planck Inst. for Radioastronomy, Germany)

M. and H. Aller (Michigan)

M. Cohen, A. Readhead (Caltech)

D. Homan (Denison)

M. Kadler, M. Boeck (U. Erlangen-Bamberg, Germany)

K. Kellermann (NRAO)

Y. Kovalev (ASC Lebedev, Russia)

E. Ros (Valencia, Spain)

N. Gehrels, J. McEnery, J. Tueller (NASAGSFC)
Very Long Baseline Array
Fermi
The MOJAVE Program is supported under
NASA Fermi Grant NNX08AV67G and NSF
grant 0807860-AST.
Monitoring
Of
Jets in
Active Galaxies with
VLBA
Experiments
Outline

The MOJAVE program: present and
future

Kinematics of highly beamed AGN jets
– parsec-scale radio imaging
– connections with gamma-ray emission

Case study: Impact of 8 antenna VLBA
array on jet studies
The MOJAVE Program
Monitoring
Of
Jets in
Active Galaxies with
VLBA
Experiments
Regularly taking VLBA images of the ~300
brightest jets in the northern sky
Jet kinematics on decadal timescales
 full polarization images provide
additional information on jet magnetic
fields
Concurrent multiwavelength studies of the
sample
Currently funded by the National Science
Foundation and NASA
http://www.physics.purdue.edu/MOJAVE
Lister et al., 2009, AJ, 137, 3718
Scientific Highlights: Jet Kinematics

Motions of superluminal bright features are
related to true flow speed
– some near-stationary features are seen (6%), more common in
lower power BL Lac jets

Most AGN jets are only mildly relativistic (Γ ~ few)
– extended tail to speed distribution
– some exceedingly rare jets (blazars) have Γ ~ 50

Fastest jets all have very high synchrotron and
gamma-ray luminosity (not likely a beaming
effect)
Lister et al., 2009, AJ, 138, 1874
Lister et al., 2009, ApJ 696, L22
Scientific Highlights: Accelerations

Accelerations of features are common (at least 50%) in
both speed and direction
– sudden events: collimation of 3C279 jet Homan et al., 2003, ApJ, 589, L9
– continuous: curved motions around stationary bends
– unpredictable: different accelerations/non-accelerations seen
in the same jet

Positive (speeding up)
accelerations more prevalent
close to the base of the jet
 jet flows are still becoming
organized on parsec scales
Homan et al., 2009, ApJ, 706, 1253
1308+326
Jet Activity States
Stacked image: 1995-2009

At any given time, only the
energized portion of a broader
jet is visible

Activity states of jets evolve
over time
– long quiescent periods of no jet
ejections are seen
– new features ejected at new position
angles (precession?)

Image from
Recent
image:
March
June1996
2009
Lister et al., 2009, AJ, 137, 3718
Fermi is preferentially detecting
currently active jets (brighter than their
historical average radio level)
(Kovalev et al. 2009, ApJL 696, L17)
What makes a jet gamma–ray bright?
Complex combination of:
1. Light output peaked at high energy
(more important at fainter gamma-ray levels)
2. Preferred viewing angle (aimed toward us)
3. Fast intrinsic jet speed (highly beamed)
4. High current activity state

Blazar gamma-ray emission is directly related to pcscale radio jet properties
Preliminary
– more Doppler boosting in gamma-rays than radio (Lister et al. in prep)
– Gamma-ray emission may be intrinsically anisotropic (Savolainen et al. 2010)
Other MOJAVE Studies

Intraday variability (Kuchibhotla, Ph.D. Thesis 2010)
 rapid flux variations common in quasars, rare in BL Lacs
 origin is likely galactic ISM scattering, but requires compact,
highly beamed emitting regions

Chandra survey (Hogan et al. 2010, ApJ in press)
 X-ray jets are ubiquitous in blazars with extended radio emission
 IC-CMB model requires relativisic jet speeds on kpc-scales

Deep VLA imaging survey (Cooper, Ph.D. Thesis 2010,
Kharb et al. 2010, ApJ)
 low-energy peaked BL Lacs can have FR I or II jet morphologies
MOJAVE: What’s in store

Kinematics of complete set of gamma-ray blazars

Circular and linear polarization jet evolution

SED and optical spectroscopy analysis

Extension of sample down to 1.5 Jy and dec > -30º

Extended Chandra and EVLA surveys
Case Study:
Science Impact of Dropping Two Inner VLBA Antennas
•
Image quality
o
•
total intensity and linear polarization
Model fitting
o
positions and flux densities of Gaussian fits
Observational Dataset
•
BL149CP: MOJAVE Program
o
24 hour run on Sept 17, 2010
o
15 GHz, 512 Mbps, continuum, dual pol.
o
30 compact AGN jets, 0.2 to 16 Jy
o
scans interleaved to optimize u,v coverage
o
~35 min total integration time per source
o
excellent weather at all 10 sites, minimal
downtime
•
Data were reduced twice:
1. with all antennas
2. with two inner antennas (KP and LA) completely flagged
Image comparison: compact jets
8 antennas
8 antennas
8 antennas
10 antennas
10 antennas
10 antennas
Image comparison: extended jets
8 antennas
10 antennas
8 antennas
10 antennas
8 antennas
10 antennas
•
•
Image rms noise slightly higher than theoretical 2 antenna loss
Extended jets suffer higher image rms loss than compact jets
Most of extended jet emission lost
Gaussian model fitting
•
Evolutionary changes in jets are most simply tracked by modeling
emission as discrete Gaussians
•
Positional accuracy: typically ~1/5 beamwidth (0.2 mas)
Comparison: Gaussian component flux densities
•
•
Negligible difference for strongest components (> 300 mJy)
Strong difference between 8 and 10 ants. for weaker components
Comparison: Astrometry (con’t)
•
•
Typical offset from 10 antenna-fitted position is 0.1 mas
Positional error strongly dependent on flux density of feature
Nominal positional
accuracy
Recording sensitivity versus u,v coverage
•
•
What would 2X improved VLBA sensitivity look like for AGN jets?
Image using all 10 antennas, flagging 3/4 of all the IFs
(10 antennas
¼ of IFs)
Full array, low
recording
bandwidth
Colorscale =
fractional
linear
polarization
Recording sensitivity versus u,v coverage
•
•
What would 2X improved VLBA sensitivity look like for AGN jets?
Image using all 10 antennas, flagging no IFs
10 antennas
all IFs
Full array, high
recording
bandwidth
Colorscale =
fractional
linear
polarization
Recording sensitivity versus u,v coverage
•
•
What would 2X improved VLBA sensitivity look like for AGN jets?
Image using all 8 antennas, flagging no IFs
(8 antennas
all IFs)
Reduced array,
high recording
bandwidth
Colorscale =
fractional
linear
polarization
Summary:
•
•
•
Loss of 2 inner VLBA antennas = 38% loss in available baselines
o
but higher rise in image noise
o
10 antenna VLBA is already a ‘minimum array’ for imaging
Improving recording bandwidth cannot make up for loss of short interferometric baselines
o
emission on scales > 3 mas becomes invisible to the VLBA (at 15 GHz)
o
flux and positional measurements significantly degraded for 45% of jet features in MOJAVE survey
o
strongly affects imaging science capabilities, and will affect astrometry of weaker, less compact features
MOJAVE is a comprehensive program aiming to understand the physics of
highly relativistic jets from black holes
o
- Lorentz factors up to at least 50
o
•
- sudden/smooth, parallel and perpendicular accelerations
MOJAVE+Fermi combination is a providing a huge leap forward in our
understanding of AGN outflows, emission and particle acceleration
MOJAVE project webpage and data archive:
www.physics.purdue.edu/MOJAVE