Diapositiva 1

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Faint blazars potential target for KaVA
observations F. Mantovani 1,2, M. Bondi 2,
K.-H. Mack 2, W. Alef 1, E. Ros 1, J.A. Zensus
1 1 Max-Planck-Institut für Radioastronomie,
Bonn, Germany 2 Istituto di Radioastronomia -
INAF, Bologna, Italy

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Blazars an extreme class of Active Galactic
Nuclei FSRQs (high luminosity radio
galaxies) BLLacs (low luminosity radio
galaxies) Characteristics high
luminosity rapid variability high optical
polarisation Emission a broad continuum of
non-thermal origin, extending from the radio
wavelengths through gamma rays Radio
band flat (a lt 0.5) radio spectra
core-dominated objects apparent superluminal
speeds Gamma band vast majority of sources in
the Fermi 2FGL catalogue Interpretation
based on bright and luminous sources discovered
in radio or X-ray
surveys

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Any connection between radio and ?-ray emission
? Radio emission synchrotron radiation from
relativistic electrons
?-ray emission low energy photons plus
relativistic beaming ? up-scattering of the
photons (Inverse Compton)
Origin of gamma-ray emission ?

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Fermi - Large Area Telescope Single-Dish
Monitoring Programmes programme freq. (GHz)
sampling size OVRO 15 2-3 weeks
gt 1000 Effelsberg 2.6 43 monthly
60 IRAM 86 270 monthly 60
F-GAMMA APEX 345 monthly
60 UMRAO 4.8, 8, 14.5 15 days
35 Metsähovi 37 monthly
100 RATAN-600 1 22 2-4 weeks 600
VLBI monitoring programmes VLBA Monitoring
at 43 GHz of EGRET blazars (Jorstad et al.
2001) MOJAVE VLBA observations at 2 cm of 300
sources (Lister et al. 2009) VISP VLBA
Imaging and Polarimetry Survey at 5 GHz and 15
GHz survey of 1100 AGN TANAMI Tracking AGN
with AU-SA array, 80 sources at 8.4GHz and 22GHz

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Direct relation between the ?-ray and
parsec-scale synchrotron radiation
Average Fermi LAT 100 MeV-1 GeV photon flux (Abdo
et al. 2009) vs. quasi-simultaneous 15 GHz flux
density. Filled circles total VLBI flux
density. Open circles single-dish flux
density. (Kovalev et al. 2009 ApJ 696,L17)

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Integrated 0.1100 GeV Fermi photon flux vs.
15 GHz VLBA core flux density (for data pairs
in which the VLBA flux density measurement was
taken 2.5 0.2 months after the LAT flux
measurements)
MOJAVE flux density cut
(Pushkarev et al. 2010 ApJ 722, L7)

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• Deep X-ray Radio Blazars Survey
• (Perlman et al. 1998 Landt et al.
  2001)
• Cross-correlation ROSAT sources WGCAT
  White, Giommi, Angelini 1995
  
• and radio sources
  with flat radio spectra
• GB6
  Gregory et al. 1996
• 
  NORTH20CM White and Becker 1992
• 
  PNM Griffith and Wright, 1993
• flux density down to 50 mJy at 5 GHz
• power down to 10 24 W Hz - 1
• nearly complete optical identification
• includes both FSRQs and BL Lac sources
• 234 quasars, 181 FSRQs, 53 SSRQs
• 36 BL Lacs
• 28 NLRG

redshift distribution lt z gt 1

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• Weak blazars sample
• 87 sources selected from the Deep X-ray Radio
  Blazars Survey
• Selection criteria Dec gt - 10 deg
• Investigation
• Effelsberg multi-frequency
• observations
• European VLBI Network 5 GHz observations
• Source coordinates
  derived from NVSS and FIRST images

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• Main aims
• verify the spectral index classification
• make the first mas resolution observations
• do the observations while Fermi is making its
  survey
• make a comparison with samples of bright
  blazars
• (MOJAVE, TANAMI, etc )

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• Effelsberg observations (1-6 July 2009)
• 66 sources bona fide blazars (FSRQs)
• 6 objects show an inverted spectra
• 27 sources show a steep spectrum
• 9 sources show a GPS type spectral index
• 43 show variability on a time scale of 20 years
• 36 sources are polarised at 5 GHz
• 7 of them have RMgt 200 rad m-2
• Mantovani et al. 2011 AA 533,
  79

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EVN observations Frequency 5 GHz Stations 12
Recording 512 Mbits, 2 bit sampling ( 2.5
TBytes/station) Strategy 5 scans, 6 minutes long
each per source Observations EM077A
22 Oct 2009 EM077B 30 May 2010 EM077C
31 May 2010 EM077D 23 Nov 2010
(e-VLBI correlation at JIVE) EM077E 15 Dec
2010 (e-VLBI correlation at JIVE) EM077F
31 May 2011 EM097A 24 Feb 2013 EM097B
27 May 2013 Correlation MPIfR DiFX software
correlator 1 sec integration time ? field of
view 11

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• Results from the EVN observations
• All sources (87) detected
• SEVN / SEF median 0.36 /- 0.8
• Structure 45 core-jet
• 39 point-like
• 3 triples
• Tb in the range 107 - 1012 K
• 13 sources Tb gt 1011 K

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Peak flux 0.4 mJy rms noise 0.03 mJ/beam

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Classification according to spectral index Flat
Spectra 56 FSRQs (blazars) 2 NLRG Steep
Spectra 10 SSRQs 10 Compact Steep-spectrum
Sources 3 BLLacs Convex Spectra 6
Giga-Peaked Sources

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List of SSRQs, CSSs and GPSs

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CSSs and GPSs X-ray ROSAT observations lt LX gt
5 x 1044 ergs/sec LX similar for CSSs and GPSs
quasars Column density (1 15) x 1020 nH cm2
Galactic nH CSSs and GPSs quasars are
not obscured by large column of cold gas
surrounding their nuclei

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DXRBS sources associated to Fermi objects
50 are BL Lacs BL Lacs are the 13 of DXRBS
sources

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J0448.2-2110
J1231.72848
Fermi detection limit

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External Compton Model (Dermer 1995 ApJ 446, L63)
Lister M.L. 2010

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• Target sources for high frequency observations
• with the
• Korean VLBI Network
• or
• KaVA (KVN plus VLBI Exploration of Radio
  Astrometry)
• A comparison sample of faint blazars

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• Flat Spectrum Radio Quasars
• EVN at 5 GHz
• 11 sources with Score gt 100 mJy
• 22 sources with Score gt 50 mJy
• Flux density and polarisation measurements
• at 22 GHz and 43 GHz
• Source-Frequency Phase Referencing method
• (M. Rioja R. Dodson 2011 AJ 141, 114)
• Map the innermost structure
• Comparison with bright blazars

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KaVA Sensitivity
Sensitivities (1s) in mJy Integration time 120
seconds for baseline sensitivities Integration
time 4 hours for images sensitivities Total
bandwidth of 256 MHz for continuum emission

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Sources with inverted spectral index Name
SEF SEVN Struct. mJy
mJy J0535.1-0239 86.4
49.4 p J0937.15008 110.5
257.6 p J1028.5-0236 132.4
318.6 p J1105.3-1813 34.7 J1359.64010 266.5
267.0 cj J1648.44104 499.9
392.6 p J2329.00834 293.6 43.8 p

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High Frequency Peakers candidates ?
Sources with inverted spectral index

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Giga-Peaked Sources Name SEF
SEVN Struct. mJy mJy
J0227.5-0847 109.5 40.5 p J0434.3-1443
387.9 J0435.1-0811 91.8
37.9 cj J0931.95533 55.7
1.8 cj J1116.10828 397.8
742.5 p J1406.93433 278.1
216.9 cj J1427.93247 60.5
17.4 cj J2159.3-1500 68.2

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Are they true GPS ? Giga-Peaked Sources

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• J0204.81514 (0202149 4C 15.05)
• Included in the MOJAVE programme
• (classified as FSRQ)
• SSRQ associated to a ?-ray object
• Classified as CSS LS 4.7 kpc
• (1.58 arcsec x 1.42 arcsec at PA
  -40.5 deg)
• Faint extended emission detected
• (Cooper et al. 2007).
• Radio variability (Mantovani et al. 2011)
• ?-ray variability (Nolan et al. 2012 )
• Rather peculiar in a CSS

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Sources with very high ? to radio
ratio J0448.2-2110 (PKS 0446-212) FSRQ, z
1.971 S5GHz 227 mJy log FX/FR
-12.25 J1231.72848 (B2 122929) BL Lac, z
? Core-jet structure Score 20 mJy log
FX/FR -11.14

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• Summary
• All 87 target sources detected by the EVN at 5GHz
• Brightness temperature ranges from 107 to 1011 K
• 56 Blazars
• 2 NLRGs
• 29 CSSs plus GPSs
• CSSs and GPSs quasars are not obscured by large
• column of cold gas surrounding the nuclei
• 15 DXRBS sources are associated to ?-ray LAT
  objects
• 50 of the associated objects are BL Lacs
• Correlation between Score and ?-ray photon flux
  confirmed
• External Compton model ruled out
• Many objects are good candidates for KaVA
  observations

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Many thanks for your attention This
work was supported by the - European Community
Framework Programme 7 (2007-2013)
under grant agreements no. 227290 and no.
283393 - COST Action MP0905 Black Holes in a
Violent Universe

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Fermi and the Faint blazars sample 13
of the DXRBS objects has been possibly detected
by Fermi Are they too few or are they too many
? EGRET ? 130 blazars detected Number
counts are Euclidean N(gtS) a S - 1.5
Fermi 30 times more sensitive than EGRET
? 20,000 expected detection 0.5
objects / deg 2 surface density in the Deep
X-ray Radio Band Survey

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External Compton model (Dermer 1995) ?-ray
emission boosted by a higher power of the
Doppler factor than their radio emission
? Synchrotron radiation beaming pattern a
d 3a External Compton-scattered photon
a d 4a (accretion disk photon field) It
implies lower radio / gamma for higher Doppler
factor

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