1The compact radio structure of radio-loud narrow line Seyfert 1 galaxies Minfeng Gu & Yongjun ChenSHAO2009 East-Asia VLBI workshopSeoul, March 18 – 20
2Outline Radio-loud narrow line Seyfert 1 galaxies (RL NLS1s)/blazars VLBA images of 4 RL NLS1sDiscussion/summary
3Active Galactic Nuclei Super-massive black holeAccretion disk + jetBroad line regionTorusNarrow line region……
4Narrow 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 multipletsRelatively small black hole mass (e.g. Collin & Kawaguchi 2004), however still controversial: viewing angle, radiation pressure …Accretion close to the Eddington rate Lbol/Ledd ~ 1Accretion possible via slim disk (e.g. Abramowicz et al. 1988; Mineshige et al )
5Blazars: 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 processJet pointing towards us – small viewing angle - beaming effectBlazar sequence: FSRQs – LBL – IBL – HBL.
6Radio-loud NLS1s Radio properties of NLS1s is poorly explored NLS1s were long thought to be radio-quietRadio 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).
7Existing 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.
8Doi et al. (2006): VLBA for SDSS J094857.3+002225 High brightness temperatures; apparent flux variationDoppler factor > 2.7–5.5 – from the high brightness T.Highly relativistic non-thermal jets in an NLS1.
9VLBA Data archived: unpublished; RL NLS1s; see Doi et al VLBA Data archived: unpublished; RL NLS1s; see Doi et al.(2007) for JVN imagesdd
10Data reductionPhase referencing mode: angular distance < 2.3 d (B : 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.
11ResultsCore – component: flux density, position angle, angular size, flux variabilityBrightness temperatureVariability 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)
13(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)
14(2). RXS JInverted 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 DecLog Tb ~11 K K; log Tb,var = 12.2 at 8.4 GHz
15RXS JBlazar-like NLS1s: jet moving towards us with small v.a.HFSRQ: synchrotron peak 2e16 Hz; BeppoSAX X-ray photon index (Grandi et al. 2006) – synchrotron originHigh Frequency Peakers (HFPs) (Dallacasa et al. 2000): 2.3/5/8.4 GHz
16(3). RXS JCore-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)
17RXS JLog Tb = 11.3, 10.5 KOne of two nuclei, separated by 4 arcsec, in an interacting/merger systemFlat X-ray photon index inverse Compton scenario; Broadband SED similar to that of HFSRQs (Yuan et al. 2008).
18(4). BCore-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 J : hot spots retreating toward the core ~ 0.3c (Tremblay et al. 2008); companion galaxy in clusters – relative motion – jet/ISM interaction
19B3 1702+457 Retreatment – different componets ? projection effects ?. Log Tb= 10.6, 11 KIt 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.
20Discussions 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), polarizationMulti-band SED for RL NLS1sVariability – X-ray & optical bandJet formation & accretion modeFermi gamma-ray space telescope detection ? Complete SEDNLS1s/BALQs/CSS,GPS/high-z quasars – young AGNs ?
21KVN – 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 shapeFermi-detected AGNs: high-frequency observationsFIRST-based (faint) CSS/GPS/HFP surveyOptical – radio simultaneous monitoring of e.g. blazars……
22SummaryThree 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.