J/A+A/450/959 VLBA images of High Frequency Peakers (Orienti+, 2006)
VLBA images of High Frequency Peakers.
Orienti M., Dallacasa D., Tinti S., Stanghellini C.
<Astron. Astrophys. 450, 959 (2006)>
=2006A&A...450..959O 2006A&A...450..959O
ADC_Keywords: Active gal. nuclei ; QSOs ; Radio sources
Keywords: galaxies: active - galaxies: nuclei - radio continuum: galaxies -
galaxies: quasar: general
Abstract:
We propose a morphological classification based on the parsec scale
structure of fifty-one High Frequency Peakers (HFPs) from the
"bright" HFP sample. VLBA images at two adjacent frequencies (chosen
among 8.4, 15.3, 22.2 and 43.2GHz) have been used to investigate the
morphological properties of the HFPs in the optically thin part of
their spectrum. We confirm that there is quite a clear distinction
between the pc-scale radio structure of galaxies and quasars: the 78%
of the galaxies show a "Double/Triple" morphology, typical of
Compact Symmetric Objects (CSOs), while the 87% of the quasars are
characterised by Core-Jet or unresolved structure. This suggests that
most HFP candidates identified with quasars are likely blazar objects
in which a flaring self-absorbed component at the jet base was
outshining the remainder of the source at the time of the selection
based on the spectral shape. Among the sources classified as CSOs or
candidates it is possible to find extremely young radio sources with
ages of about 100 years or even less.
Description:
We present results from new multi-frequency VLBA of a sample of 51
High Frequency Peaker radio sources. Physical parameters like the
total flux density, the spectral index, and the deconvolved angular
sizes of major and minor axis, the position angle and the
equipartition magnetic field of the sources have been estimated on the
VLBA images.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 80 55 The VLBA flux density of candidates
High Frequency Peaker
table3.dat 72 34 The VLBA flux density of each component,
for the sources with a CSO-like morphology
table4.dat 72 12 The VLBA flux density of Core-Jet (CJ) source
components
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See also:
J/A+A/363/887 : High frequency peakers. I. The bright sample (Dallacasa+, 2000)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Source Source name (J2000) (1)
14- 20 F7.5 --- z ? Redshift
23- 24 A2 --- Type [BL EF G Q] Optical type (2)
26- 30 I5 mJy S8A ?=- VLA 8.4GHz flux density
32- 36 I5 mJy S8B ?=- VLBA 8.4GHz flux density
39- 43 I5 mJy S15A ?=- VLA 15.3GHz flux density
46- 49 I4 mJy S15B ?=- VLBA 15.3GHz flux density
52- 55 I4 mJy S22A ?=- VLA 22.2GHz flux density
59- 62 I4 mJy S22B ?=- VLBA 22.2GHz flux density
64- 67 I4 mJy S43B ?=- VLBA 43.2GHz flux density
69- 72 F4.1 --- alpha ?=- Spectral index (G1)
74- 76 I3 mgauss Heq ?=- Equipartition magnetic field (G2)
78- 80 A3 --- Morph Morphological classification from
VLBA images (3)
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Note (1): The two sources J0111+3906 and J1751+0939 were not observed,
since they are already plenty of information. The sources
J0927+3902 and J1407+2827 have been observed only for an
extremely short period of time, to verify the system performance.
Note (2): Optical identification from
Dallacasa et al. (2000, J/A+A/363/887),
Dallacasa et al. (2002A&A...382...53D 2002A&A...382...53D),
Dallacasa et al. (2006, in preparation)
(BL Lac, EmptyField, Galaxy or Quasar)
Note (3): Morphological classification as follows:
CJ = Core-Jet structure
MR = Marginally Resolved
Un = unresolved structure
CSO = Compact Symmetric Objects
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Byte-by-byte Description of file: table3.dat table4.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Source Source name (J2000)
12- 13 A2 --- m_Source Component label
15- 17 I3 mJy S8B ? VLBA flux density at 8.4GHz
19- 21 I3 mJy S15B ? VLBA flux density at 15.3GHz
23- 26 I4 mJy S22B ? VLBA flux density at 22.2GHz
28- 31 I4 mJy S43B ? VLBA flux density at 43.2GHz
33- 36 F4.1 --- alpha ? Spectral index (G1)
38- 41 F4.2 mas thetamaj Deconvolved angular size of major axis (1)
44- 47 F4.2 mas thetamin Deconvolved angular size of minor axis (1)
49- 51 I3 deg PA ? Position angle of the major axis (1)
54- 56 I3 10-7T Heq Equipartition magnetic field (G2)
58- 62 F5.1 --- FreqMax ? Turnover frequency
64- 67 F4.1 mas LAS ? Angular distance between components
69- 71 I3 pc LLS ? Linear distance between components
72 A1 --- Note [*] *: For the sources with redshift unknown,
we adopt z=1.00
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Note (1): Deconvolved angular sizes of major and minor axis of the
best-fitting Gaussian component and the position angle of the
major axis as estimated on the most suitable images at the
different frequencies, using JMFIT
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Global notes:
Note (G1): Spectral index between the two frequencies where VLBA images
are available
Note (G2): Equipartition magnetic field, we assume a spectral index of 0.7,
expressed in mGauss.
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Acknowledgements:
Monica Orienti, orienti(at)ira.cnr.it
(End) Patricia Vannier [CDS] 02-Feb-2006