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KIAA Workshop on Cosmic Reionization July 9-11, 2008

KIAA Workshop on Cosmic Reionization July 9-11, 2008. Brightness temperature for a sample of blazars J.H. Fan, Y. Liu, H.G. Wang, J.Y. Zhang et al. Center for Astrophysics Guangzhou University China. Outline. Introduction Properties of Blazars

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KIAA Workshop on Cosmic Reionization July 9-11, 2008

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  1. KIAA Workshop on Cosmic ReionizationJuly 9-11, 2008 Brightness temperature for a sample of blazars J.H. Fan, Y. Liu, H.G. Wang, J.Y. Zhang et al. Center for Astrophysics Guangzhou University China

  2. Outline • Introduction • Properties of Blazars • Brightness Temperature of Blazars • Discussion • Summary

  3. INTRODUCTION BLazars consist of two subclasses of extragalactic objects, BL Lac and FSRQs RBLs LBLs 1) BL Lacertae objects--BLs, XBLs HBLs 2) Flat Spectrum Radio Quasars—FSRQs

  4. What is a BL Lac Object? Schmitt (1968) identified the “variable star” BL Lacertae with the unusual radio source VRO 44.22.01. Observations showed variation in radio band (Biraud & Veron 1968) and linear polarization (Oslen 1969), and optical radiation was shown to exhibit a continuous spectrum with neither emission nor absorption lines (Oke et al. 1969) and a relatively high degree of linear polarization (Visvanthan 1969).

  5. What is a BL Lac Object? Strittmatter et al. (1972) suggested that objects similar to BL Lac comprise a class—BL Lacertae objects. • Absence of emission lines in the core sources; weak emission lines were found in BLs (Miller et al. 1978) • Rapid variability at radio, infrared, and visual wavelength bands • Nonthermal continuum with most of the luminosity radiated at infrared wavelength • Strong and rapidly varying polarization. Stein et al. 1976, ARA&A, 14

  6. What is an FSRQ? Optically violently variable quasars--OVVs, (m>1.0m) ( Penston & Cannon,1970) Kinman (1975) OVVs tend to have steep optical spectra and be associated with compact variable radio sources which have flat radio spectra at GHz frequencies. Highly polarized quasars--HPQs ( p>3.0%), (Moore and Stockman 1981, ApJ, 243 ) , 45% Core-dominated quasars--CDQs ( R = Lc/Le > 1.0) ….etc

  7. INTRODUCTION Objects with one of the above properties BLAZARS BLAZARS (BL Lacs and FSRQs) Extragalactic objects 1 Rapid variability, 2 High luminosity 3 High and variable polarization, 4 superluminal motions 5 Core-dominated emissions etc The term “blazar” was coined, half in jest, by Ed Speigel at the first conference on BL lac objects in Pittsburg.

  8. Fob=pFin =(,) 窄线区 AGN Model 宽线区 喷流 黑洞 吸积盘 活动星系核的标准模型

  9. Properties of BlazarsI. Variability

  10. Variability Blazars show variation over different time scales. Observations show that there are three types of timescales. Intra-day variability (IDV) with variability time scale within one day; Short term variability with time scale of days to months, and long-term variability with time scale of years.

  11. Individual Source-0605-085 Radio Variability Fan, Liu, Yuan et al, 2007, A&A

  12. Individual Sources-0736 Clements, Jenks, and Torres, 2003, AJ, 126 1.3 mag. over 2.0 hrs

  13. 1985 OJ 287 To observe its expected outbursts, Finalnd organized observing programme of OJ 94 Pietill, et al. 1999, A&A, 345, 760 1994

  14. Individual Sources-OJ287 Fan et al. 2008

  15. Individual Sources-BL Lac-prototype Villata, et al. 2002, A&A, 390, 407

  16. Individual Sources-BL Lacertae Villata, et al. 2002, A&A, 390, 407

  17. Individual Sources-BL Lacertae Villata, et al. 2002, A&A, 390, 407

  18. X-ray Variability-2155-304 Brinkmann et al. 2000, A&A, 362, 105

  19. Individual Sources-0420-014 Wanger, et al. 1995, A&A, 298

  20. During 1993 January the source was unusually bright in optical and gamma-ray regions. During this period Wagner observed a rapid, symmetrical flare in the optical wavelength range which lasted for about 4 days. EGRET detected a similar rapid flare peaking about 22 hr after the optical outburst.Because such rapid flares are rare events, it is likely that the outbursts in the two frequency regimes are correlated. This delay can not be well explained by the existing model. Individual Sources-1406-076 Wanger, et al. 1995, ApJ, 454 L97

  21. TeV Variability-Mkn 421 Catanese & Weekes 1999, PASP, 111, 1193

  22. Individual Source-Mkn501 Lightcurve above 1.5 TeV energy; . 2-10KeV from RXTE-ASM Kranich et al., 1999, astro- ph/ 9907205

  23. Individual Sources-3C279-1st SM Fan, 1999, MNRAS, 308

  24. Individual Source-3C 273 Fan, Romero & Lin, 2001, ChA&A, 25

  25. Variability on time scales from a few hours up to months and even years have frequently been observed and the light curves seem to be the superposition of many flares with different amplitudes and time scales.

  26. Properties of BlazarsII. Polarization

  27. 1. High PolarizationMead, et al. 1990-A&AS-83 3C279, P=(45.5+/-0.9)%, largest polarization 44 sources: optical and Infrared polarization from 1986 to 1988.

  28. 2. Polarization and the core emissions Impey et al. 1991-ApJ-375

  29. 3. Pol. and dominance parameter Wills et al. 1992-ApJ-398 Core-Dominance parameter

  30. 4. Polarization and variations Fan & Lin 2000-ApJ-537

  31. Polarization & Beaming Fan, et al. 1997, A&A

  32. 偏振是Beaming存在的观测证据.后来1999年的一个GRB990123的余辉中观测到偏振的时候,Hjorth et al. 1999, Science, 指出GRB中有Beaming,还引用了我们的文章 Fan et al. 1997, A&A, 327

  33. Fan 2002, PASJ

  34. Polarization & R Fan, Liu, et al. 2006, PASJ, 58

  35. Fan, Liu, et al. 2006, PASJ, 58 Relation between P and R

  36. Polarization & Δm

  37. Relation between P and m Fan, et al. 2001, PASJ, 53

  38. Polarization and Beaming Effect • The dependence of polarization on the core-dominance parameter can be explained using the beaming model • The correlation between the polarization and the variation can be explained using the model. • Polarization is associated with beaming effect

  39. Properties of BlazarsIII. Superluminal motion

  40. 1.Superluminal Sources Very recently, we compiled a sample of 123 superluminal sources (Zhang & Fan 2008, ChJAA). 84 quasars, 27 BL Lac objects and 12 galaxies.

  41. β= 0.11-46.6, < β max>=10.93±6.54 β= 0.18-36.5, < β max>=10.8±6.87

  42. Log S—log z

  43. Log S—log z From the beaming model: Ghisellini et al. 1993, ApJ, 407 δ～β

  44. Most Properties are associated with the beaming effect in Blazars The high luminosity is associated with the beaming model, The rapid variability is associated with the beaming model Superluminal motion, Polarization, and core-dominance are also associated withthe beaming model. Therefore, the beaming factor (boosting factor) is important for blazars. We tried to estimate this parameter in this talk using the variable time scale.

  45. Brightness Temperature & Estimation of Boosting Factor

  46. Wagner & Witzel Using time scales as a measure of the size of the source, the observed flux may be converted into photon densities or a brightness temperature

  47. F: The flux density in Jy λ: Wavelength in cm d: Distance in Mpc t_obs: Time scale in days Wagner & Witzel, 1995, ARA&A, 33, 163

  48. Definition of the Variability Time Scale

  49. Sample 1. We got a sample from the University of Michigan Radio Astronomy Observatory (UMRAO)

  50. Short-Term Time Scale To determine the short term time scale, we used the following process. For a certain source, there are three light curves at ν=4.8GHz, 8GHz, and 14.5GHz respectively. For each frequency, there are n sets of data, (t_i, S_i, i = 1, 2, ..., n), then we calculate the time difference (△t_(jk)), the variability (△ S_(jk)), and the error transfer (σ_(jk)) between the jth set and the kth set data.

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