J/MNRAS/467/L71 Significance of VLBI/Gaia position offsets (Petrov+, 2017)
On significance of VLBI/Gaia position offsets.
Petrov L., Kovalev Y.Y.
<Mon. Not. R. Astron. Soc., 467, L71-75 (2017)>
=2017MNRAS.467L..71P 2017MNRAS.467L..71P (SIMBAD/NED BibCode)
ADC_Keywords: Active gal. nuclei ; Interferometry ; Positional data
Keywords: galaxies: active - radio continuum: galaxies
Abstract:
We have cross matched the Gaia Data Release 1 secondary data set that
contains positions of 1.14 billion objects against the most complete
to date catalogue of very long baseline interferometry (VLBI)
positions of 11.4 thousand sources, almost exclusively active galactic
nuclei. We found 6064 matches, i.e. 53 per cent radio objects. The
median uncertainty of VLBI positions is a factor of 4 smaller than the
median uncertainties of their optical counterparts. Our analysis shows
that the distribution of normalized arc lengths significantly deviates
from Rayleigh shape with an excess of objects with small normalized
arc lengths and with a number of outliers. We found that 6 per cent
matches have radio-optical offsets significant at 99 per cent
confidence level. Therefore, we conclude there exists a population of
objects with genuine offsets between centroids of radio and optical
emission.
Description:
Our study is based on the analysis of the catalogue called Gaia DR1
secondary data set.
Table 2 contains 384 VLBI/Gaia matches with statistically significant
offsets: probability of false association (PFA) less than 0.0002 and
the random noise probability (RNP) less than 0.01.
Table 3 contains 5671 VLBI/Gaia matches with statistically
insignificant offsets: probability of false association (PFA) less
than 0.0002 and the random noise probability (RNP) is equal or greater
than 0.01.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 85 384 384 VLBI/Gaia matches with statistically
significant offsets
table3.dat 85 5671 5671 VLBI/Gaia matches with statistically
insignificant offsets
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See also:
I/337 : Gaia DR1 (Gaia Collaboration, 2016)
Byte-by-byte Description of file: table2.dat table3.dat
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Bytes Format Units Label Explanations
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1- 14 A14 --- VLBI VLBI source name (RFC JHHMM+DDMM)
17- 20 A4 --- --- [Gaia]
22- 40 I19 --- Gaia Gaia source number (Cat. I/337)
43- 50 E8.3 --- PFA Probability of false association
53- 60 E8.3 --- RNP Probability that the offset is caused
by random noise
63- 68 F6.2 --- NAL Normalized arc length
71- 77 F7.2 mas DRA Offset VLBI position with respect to Gaia along
right ascension with cos delta factor applied
79- 85 F7.2 mas DDE Offset VLBI position with respect to Gaia along
declination
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 15-Nov-2019