Presentation on theme: "Minfeng Gu & Yongjun Chen SHAO 2009 East-Asia VLBI workshop Seoul, March 18 – 20 The compact radio structure of radio- loud narrow line Seyfert 1 galaxies."— Presentation transcript:
Minfeng Gu & Yongjun Chen SHAO 2009 East-Asia VLBI workshop Seoul, March 18 – 20 The compact radio structure of radio- loud narrow line Seyfert 1 galaxies
Outline Radio-loud narrow line Seyfert 1 galaxies (RL NLS1s)/blazars VLBA images of 4 RL NLS1s Discussion/summary
Active Galactic Nuclei Super-massive black hole Accretion disk + jet Broad line region Torus Narrow line region ……
Narrow Line Seyfert 1 galaxies (NLS1s) Balmer lines broader than forbidden lines but narrower than normal type 1 AGNs (FWHM<2000km/s) Some peculiar properties: softer X-ray spectra, fast X-ray variability, strong optical Fe II multiplets Relatively small black hole mass (e.g. Collin & Kawaguchi 2004), however still controversial: viewing angle, radiation pressure … Accretion close to the Eddington rate Lbol/Ledd ~ 1 Accretion possible via slim disk (e.g. Abramowicz et al. 1988; Mineshige et al. 2000)
Blazars: flat-spectrum radio quasars (FSRQ) + BL Lac objects Observed properties: flat radio spectrum, compact radio core, high brightness temperature, superluminal motion, rapid variability, high polarization, broad-band SED with two humps: synchrotron & inverse Compton process Jet pointing towards us – small viewing angle - beaming effect Blazar sequence: FSRQs – LBL – IBL – HBL.
Radio-loud NLS1s Radio properties of NLS1s is poorly explored NLS1s were long thought to be radio-quiet Radio emission detected in some NLS1s in early studies (e.g. Ulvestad et al. 1995, Moran et al. 2000, Stepanian et al. 2003) Two small samples of RL NLS1s studied recently (Komossa et al. 2006, Whalen et al. 2006): mostly steep-spectrum radio sources. RL NLS1s sample from SDSS: >100 out of ~2000 NLS1s (Zhou et al. 2006) – RL (R>10) fraction = 7%; very radio- loud (R>100) NLS1s: very rare – 23 from SDSS DR5 (Yuan et al. 2008).
Existing VLBI imaging of RL NLS1s Doi et al. (2007): JVN 8 GHz phase-referencing: all 5 targets detected – strong jets; 2/5 sources showing inverted spectra suggesting Doppler boosting in pole-on view.
Doi et al. (2006): VLBA for SDSS J094857.3+002225 High brightness temperatures; apparent flux variation Doppler factor > 2.7–5.5 – from the high brightness T. Highly relativistic non-thermal jets in an NLS1.
VLBA Data archived: unpublished; RL NLS1s; see Doi et al.(2007) for JVN images dd
Data reduction Phase referencing mode: angular distance < 2.3 d (B3 1702+457: 3.98 d at 5 GHz). The average on-source observational time ~ 70 mins. AIPS: atmosphere and parallactic angle effects are calibrated before fringe fitting of phase referencing calibrator are made, and its solutions are applied to the corresponding target. Bandpass corrections and self-calibrations are made before data are averaged in 30 seconds – high S/N ratio. The imaging and model fitting process is performed in DIFMAP with all the base contour levels given below being 3 sigma in the final residual images.
Results Core – component: flux density, position angle, angular size, flux variability Brightness temperature Variability brightness temperature: (Yuan et al. 2008) Equipartition brightness temperature Teq=5×10^10 K (Readhead 1994); Inverse Compton limit Tb,int ~ 10^12 K (Kellermann & Pauliny-Toth 1969)
(1). RXS J08066+7248 Unresolved in 1.6 GHz in beam size ~ 4×10 mas Steep spectrum between 1.4, 1.6, 5 and 8.4 GHz – resemble to compact steep spectrum though to be young radio source. Log Tb= 11.4, 11.0 K; X-ray photon index 2.3 (Xu et al. 2003)
(2). RXS J16290+4007 Inverted spectrum from the simultaneous observations at 2.3 and 8.4 GHz (see also Zhou & Wang 2002). Slightly resolved: an eastern component at 5 GHz of Dec. 2005. Log Tb ~11 K - 12.4 K; log Tb,var = 12.2 at 8.4 GHz
RXS J16290+4007 Blazar-like NLS1s: jet moving towards us with small v.a. HFSRQ: synchrotron peak 2e16 Hz; BeppoSAX X-ray photon index 2.58 (Grandi et al. 2006) – synchrotron origin High Frequency Peakers (HFPs) (Dallacasa et al. 2000): 2.3/5/8.4 GHz
(3). RXS J16333+4718 Core-jet at 5GHz, flat 1.6 – 5 GHz (see also Zhou & Wang 2002), steep 5 – 8.4 GHz, inverted spectra above 5 GHz from simultaneous observations (Neumann et al. 1994)
RXS J16333+4718 Log Tb = 11.3, 10.5 K One of two nuclei, separated by 4 arcsec, in an interacting/merger system Flat X-ray photon index 1.37 - inverse Compton scenario; Broadband SED similar to that of HFSRQs (Yuan et al. 2008).
(4). B3 1702+457 Core-jet: flat at 1.6 & 5 GHz for core, however steep at 1.6 & 8.4 GHz/previous: steep 1.4 & 5 GHz, flat 5 & 8.4 GHz. At 5 GHz, component moves toward the core with 3.7 mas in about two month ~ 80 c ? CSO J11584+2450: hot spots retreating toward the core ~ 0.3c (Tremblay et al. 2008); companion galaxy in clusters – relative motion – jet/ISM interaction
B3 1702+457 Retreatment – different componets ? projection effects ?. Log Tb= 10.6, 11 K It is classified as Compact Steep Spectrum (CSS) sources with turnover frequency < 150 MHz in the sample of Compact Radio sources at Low Redshift (CORALZ) (Snellen et al. 2004). The X-ray spectral was investigated by Vaughan et al. (1999), and the photon index from the power-law fit is 2.2.
Discussions NLS1s/CSS (HFPs) – young radio sources ? NLS1s/blazar (HFSRQs) – blazar sequence ? Compact radio structure of large sample of RL NLS1s (e.g. Yuan et al. 2008), polarization Multi-band SED for RL NLS1s Variability – X-ray & optical band Jet formation & accretion mode Fermi gamma-ray space telescope detection ? Complete SED NLS1s/BALQs/CSS,GPS/high-z quasars – young AGNs ?
KVN – multi-band simultaneous high-frequency observations Observe violent variable sources simultaneously, e.g. blazars, to determine the spectral shape, temporal variability. Inverted-spectrum sources, e.g. GPS/HFP – high-frequency spectral shape Fermi-detected AGNs: high-frequency observations FIRST-based (faint) CSS/GPS/HFP survey Optical – radio simultaneous monitoring of e.g. blazars ……
Summary Three out of four sources are unresolved or slightly resolved in mas resolutions, and the remaining one is resolved into core – jet structures at 1.6 and 5 GHz. Two sources have flat spectrum between 1.6 and 5 GHz, and one source have steep spectrum (non-simultaneously)/One source has inverted spectrum between 2.3 and 8.4 GHz (simultaneously). All sources have brightness temperature Tb>10^11 K and one source even exceed 10^12 K, which is confirmed by the estimated variability brightness temperature. The high brightness temperature and/or flat radio spectrum implies a at least mildly relativistic jets may exist in all our sources.