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