Dependence of the Integrated Faraday Rotations on Total Flux

Density in Radio SourcesChen Y.J, Shen Z.-Q

Background of Integrated RM in BL Lac

Dependence of EVPA on wavelength squared

For BL Lacs, Our galaxy makes the most contribution to the observed RM between 1.4 to 1.6 GHz

20 RM

Background Analysis

Polarized VLBI observations show that the maximum RM is frequently much more than 100 rad/ m2, up to several thousand is not unusual in some quasars; Galactic contributions is not enough

BL Lac objects show little or no emissions lines. It means the surrounding medium is very tenuous

Synchrotron emission comes from charges moving in magnetic field; The source itself must have contribution to the observed RM

Wide band of EVPA with squared lamda reflects to some degree the true RM estimation

Process in searching for sample

There should be long term monitoring measurements of multi-frequency polarimetric observations available.

Michigan University DATA base: 5, 8, 15GHz, no longer available

VLBA polarization calibrators: 137 sources; 27 of them over 10 epochs

Measurements with VLA

Observational Frequencies: 5 GHz, 8 GHz, 22 GHz and 43 GHz

Uniformly distributed in right ascension Observed monthly for those famous sources Calibrators: 3C48 (0137+331) and 3C286

(1331+305)

Configure: A B C D; The same configure used in one epoch

Measurement: R/L Phase Difference, twice the EVPA

All EVPA values are normalized to the range of -/2 to /2 →n ambiguities

Measurements with VLA

Uncertain factors in RM Estimation and Alleviation

Uncertain Factors:n ambiguitiesAntenna beam smoothing: in a beam size including

components of different spectral index: f=pcos, → Beam size varies with frequency, hence including

different components at different freq. →different Using the configure at different frequencies at one

epoch Observed at 4 frequencies alleviate the n

ambiguity effect to some degree Long-term monitoring will increase credibility of

RM and flux correlation results

RM FITTING SITUATION (example: 0238+166)

Statistic Distribution of RM

25 OF 27 sources have maximum absolute RM values larger than 200

n ambiguities will most probably underestimate these values

Variation of RM with Flux density

Variation of RM with Fractional Polarization

Correlation Results of RM with flux density and Fractional Polarization

SourceAl i as Name Type Redshi f t Data Num Corr. Coef Corr. Coef Confi dencerm vs. fl ux rm vs. FracP 5%

0136+478 DA55 Quasar 0. 859 10 0. 300 0. 090 0. 632 no0137+331 3C48 G 0. 367 170 0. 164 0. 083 <0. 159 fl x0238+166 0235+164 BL Lac 0. 94 57 0. 124 0. 272 <0. 273 f rp0319+415 3C84 G 0. 01756 30 0. 022 0. 150 <0. 361 no0359+509 0355+508 Quasar 1. 51 69 0. 308 0. 062 <0. 250 fl x0423-013 0420-014 Quasar 0. 914 35 0. 389 0. 367 <0. 349 both0521+166 0528+134* Quasar 2. 07 27 0. 657 0. 779 0. 381 both0555+398 DA193 Quasar 2. 365 92 0. 222 0. 048 0. 205 fl x0609-157 0607-157 Quasar 0. 324 14 0. 459 0. 396 0. 532 no0646+448 0642+449 Quasar 3. 396 21 0. 368 0. 210 0. 433 no0713+438 0710+439 G 0. 518 146 0. 046 0. 055 <0. 174 no0854+201 OJ 287 BL Lac 0. 306 142 0. 253 0. 074 <0. 174 fl x0927+390 0923+392 Quasar 0. 695 150 0. 039 0. 068 0. 159 no1146+399 1144+402 Quasar 1. 089 84 0. 521 0. 319 0. 217 both1159+292 1156+295 Quasar 0. 729 133 0. 247 0. 075 <0. 174 fl x1229+020 3C273 Quasar 0. 158 133 0. 106 0. 009 <0. 174 fl x1256-057 3C279 Quasar 0. 5362 123 0. 403 0. 513 <0. 195 both1310+323 1308+326 Quasar 0. 996 133 0. 103 0. 439 <0. 174 f rp1331+305 3C286 Quasar 0. 846 151 0. 394 0. 033 0. 159 fl x1337-129 1334-127 Quasar 0. 539 25 0. 329 0. 514 0. 396 f rp1743-038 1741-038 Quasar 1. 054 101 0. 079 0. 038 0. 195 no1751+096 1749+096 BL Lac 0. 322 113 0. 378 0. 120 <0. 195 fl x1924-292 1921-293 Quasar 0. 352 74 0. 392 0. 449 0. 232 both2015+371 2013+370 U 26 0. 475 0. 584 0. 388 both2136+006 2134+004 Quasar 1. 932 138 0. 051 0. 028 <0. 174 no2202+422 BL Lac BL Lac 0. 0686 153 0. 151 0. 114 0. 159 no2253+161 3C 454. 3 Quasar 0. 859 144 0. 047 0. 125 <0. 174 no

Statistical Results

Quasar: 19; BL Lac: 4(RBL); Galaxy: 3; U: 1 14 of 27 sources show strong correlation of

RM with total flux density 9 of 27 sources show correlation of RM with

fractional polarization 6 of 27 sources show correlation of RM with

both total flux density and fractional polarization

DISCUSSION

The resultant RM at 4 frequencies from 1.45 to 1.65 GHz can be used to correct PA at higher frequencies to some degree (e.g. 4.8 GHz, 15GHz) (Rudnick et al. AJ 88,518)

The intrinsic EVPA is similar over wide separations in wavelength

CP is Faraday converted from LP (Faraday Conversion) within jet.

RM may dominantly occurs within jet, and related to total flux density

Summary RM is variable with time in the selected sample About half of the 27 source show correlation with

flux density, about 9 of them have correlation with fractional polarization, in spite that n ambiguities may weaken the correlation relationship

RM in the selected sample may predominantly arise from targets itself, not from medium outside

RM is correlated with flux density, suggesting that in emission particle number density might be related to flux density assuming magnetic field keeps constant

KVN USAGE IN POLARIZATION AGN RESEARCH

Receiver 22 GHz 43 GHz 86 GHz 129 GHz

Freq[GHz] 21.25~23.25 42.1~44.1 85~87 128~130

Polarization RCP/LCP RCP/LCP RCP/LCP RCP/LCP

Resolution 5.89 mas 3.01mas 1.51 mas 1.00 mas

BLAZARS have higher fractional polarization at higher frequency

Polarization Structure at very high frequency closer to acceleration and collimation region

RM distribution reveal more information around emission region

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