The detection of a new counter-jet component of AGN 4C39.25

The detection of a new counter-jet component of AGN 4C39.25

20150709 8th EAVN Workshop @Sapporo
The detection of a new counter-jet
component of AGN 4C39.25 using KaVA
Hyemin Yoo(Yonsei Univ./KASI)
Bong Won Sohn(KASI), Sukyoung K. Yi(Yonsei Univ.)
and KaVA team
1/17
Motivation
Target : 4C39.25
Distant radio loud AGN : z~0.695(SDSS), ~0.699(Lynds+66)
High luminous Jet & Low luminous core
Different Jet direction between Kpc-scale and pc-scale
4C39.25
Ordinary Blazar (OJ287)
Relative Dec (mas)
1)
2)
3)
Relative Dec (mas)
•
Core
Resolution : 2.34kpc
VLA
Jet
MOJAVE
Kollgaard et al. 1990
Relative RA(mas)
Core
Jet
Resolution : 5pc
Resolution:
12.78pc
VLBA
MOJAVE
Relative RA(mas)
Kellermann et al.Niinuma
1998 et al. 2014
Relative RA(mas)
2/17
Motivation
• History of 4C39.25
-
-
1970s
a
c
Marcaide+85
: 2.8cm(10GHz),
detection of the superluminal
component “b” ~ 3.6c
Marscher+91, Alberdi+93a
1980s
a
c
b
Bääth+80
▶ “Bent-jet model”
: Partially curved Jet trajectory at positions
of a and c (viewing angle ~ 6°)
1990s~2010
MOJAVE
Caused by “the Helical motion”
of KH instability or Magnetic field
Maracide+89
Motivation
• 4C39.25 : Radio loud AGN
▶ Additional properties :
- Non-variability in the flux density
- Convex spectrum with a high frequency peak(>10GHz) (Orienti+08)
Sν(Jy)
K band
Q band
Orienti+07, VLA
Credit for
Youngjin Jeong, KVN
ν(GHz)
4/17
Motivation
• Motivation
– Studying various cases of the AGN jets is useful to derive the
specific physical parameters of the jet, and, therefore,
understand the interaction between AGNs & ISM.
– Especially, there is lack of knowledge about the parsec-scale jet
physics
– 4C39.25
: the intermediate case between a blazar and a radio galaxy on
parsec-scale
5/17
Observation
• KaVA(KVN&KaVA)
– Frequency : 22GHz(K band)
– Bandwidth : 256MHz
• C5 mode : 16 MHz × 16 IF
• C4 mode : 32MHz × 8 IF
– 2 bit sampling (1Gbps)
– Spatial Resolution : 1.2 mas
– (Currently) 8 epochs
• 6 epochs : C5 mode
• 2 epochs : C4 mode
Credit for KaVA Status Report
Observation
• Observation
ID
Date
(Y.M.D)
# of IF
Stations
Obs.
Polarization
Time(min)
Reduction
Status
r13339b
13.12.05
16
VERA
48
LCP
Complete
r13360a
13.12.26
16
VERA
48
LCP
Complete
r14015a
14.01.15
16
VERA
48
LCP
Complete
r14034b
14.02.03
16
VERA
48
LCP
Complete
k14bs01a
14.04.11
16
KVN+MIZ,IR
K
60
LCP, RCP
Complete
r14308c
14.11.04
16
KVN+VERA
60
LCP
Complete
r14349b
14.12.15
8
KVN+VERA
60
LCP
On going
r15123a
15.05.03
8
KVN+VERA
60
LCP
On going
7/17
Observation
• Data Reduction
1) NRAO Astronomical Image Processing System(AIPS)
: Perform Calibration Steps for Raw VLBI Data
 ACCOR
 Parallatic Angle correction(VLBAPANG)
 dummy FRING
>> decide a reference scan and antenna
 “Manually” Instrumental correction (FRING)
 Global Fringe fitting (FRING)
 Amplitude calibration (APCAL)
 SPLIT
R14308C
Observation
• Data Reduction
2) Difmap
: the interactive software to carry out the Hybrid mapping

Flagging


UV weighting : uniform weighting


uvwei 2,-2
CLEAN & phase self-calibration


vplot, radplot
R13339B
Clean & Selfc
Amplitude self-calibration

gscale, selfc tru,tru,#
9/17
Discussion
• Interpretation of C-jet
– Is it a counter-jet emitted from the core
or another transient source?
• Fact : the Flux density of C-jet is 100mJy/beam, and it’s proper
motion is ~189c
 Check the γ-ray observations to see if there was a flare
 Other wavelengths observations at similar epochs
 Different task try on DIFMAP and Cross-check with other users
10/17
Discussion
• Interpretation of C-jet
– If it is a counter-jet emission, then WHAT are ISSUEs?
• Viewing angle of 4C39.25
• Anti-symmetry of Jet and Counter-jet
– Peculiar 2D movement of Counter-jet
> Encounter of Jet and ISM?
Helical motion?
– More Superluminal speed of Counter-jet(180c) then Jet(3c)
> Large r (Lorentz Factor)?
• Possibility of detecting Counter-jet and its Superluminal motion
– Large viewing angle? If not,
Helical motion(of KH instability or B-field)?
Large opening angle?
11/17
Summary
• Future Work
– Currently, plan to submit a paper(letter) soon.
– Data reduction of following observational results(KaVA)
– Multi-frequency long-term observation(KaVA proposal
submitted)
– Derive physical parameters such as light-curve, polarization etc.
– Simple modeling for the counter-jet component
12/17
Summary
• Summary
– Recent observations made by KaVA suggest a new
component at the counter-jet direction.
– An hyper superluminal motion(~180c) has been detected for
the new component.
– However, the new component needs more confirmation works
to make it certain that it is a real counter-jet component of
4C39.25.
Thank you ;)
13/17