The Q band VLBI survey wiht KVN/VERA
Introduction
The popultion of compact sources at high frequncies is not
stidied in full details. We will condact in 2012 an inteferometric
survey at 43 GHz (Q-band) using the Korean VLBI Network (KVN)
and the VLBI Exploration of Radio Astrometry (VERA) arrays, in
total seven antennas.
Scientific goal
We propose to perform a Q-band imaging survey with the goal to get
images of all compact continuum sources with
δ > -20° with anticipated correlated flux densities greater
than 350 mJy. The major scientific goal is to study the population of
high frequency compact radio sources as a whole. In particular, we will
- investigate compactness determined as a ratio of the correlated
flux density at short and long baselines to the single-dish
flux density and compare it with compactness at 2.2, 8.4 GHz,
and 22 GHz.
- measure the brightness temperature for the core and jet components
in order to populate a model of the distribution of the observed core
brightness temperature in terms of the intrinsic properties of
relativistic jets such as the brightness temperature, bulk motion,
viewing angle. The data will also provide the unbiased sample needed
to investigate the unified scheme between quasars, BL Lacs and galaxies.
- test the dependence between the angular size of the core-jet region
and the redshift. This dependence can be interpreted as a measure of
the cosmological term q0.
- analyze the relationship between the core optical depth
as measured by the spectral index and other properties of the
jet emission and optical properties.
- investigate the variation of the spectral index along
the presumably optically thin jets and comparison with the
conditions in small-scale and larger-scale jets.
- test the spectrum of energy distribution of emitting
relativistic particles by analyzing statistics of spectral indexes
along presumably optically thin jets and compare it with conditions
in kiloparsec jets.
For all observed sources we will analyze not only new Q-band images,
but also existing images at S, X, and K-bands. It is essential that the
proposed survey will be complete at a a given correlated flux denisity, and
therefore, the conclusions drawn from analysus of results can be generalized
on the entire population. The results of this survey are supposed to remain
the legacy VERA projects in the area of AGN study.
People
Team members (in alphabetic order):
| Mareki Honma | NAOJ, Japan |
| Yury Kovalev | Astrospace Center, Russia |
| Sang-Sung Lee | KASI, South Korea |
| Junghwan Oh | KASI, South Korea |
| Leonid Petrov | Astrogeo Center, USA |
Source list
Observations
The survey will be made in two campaigns. In the first fringe-search
campaign we will use three-station KVN network and observe at Q-band
a pool of ~600 candidate sources in two scans each. This
fringe-search campaign is scheduled to be observed in November/December
2011, and analysis if these observations will be completed in December 2011.
Those sources that will have correlated flux density greater than 350 mJy
will be scheduled for an imaging campaign at a 7-station network of VERA
and KVN. Each source will be observed in 6 scans of 2 minutes each.
The list of candidates for the fringe-search campaign is formed from
the list of sources with the K-band correlated flux density greater than
350 mJy. These sources were observed in the KQ survey,
VERA FSS, VERA KCAL,
VGaPS, and EGaPS.
This cumulative list of K-band sources at
δ > -30°r; has completeness better than 95% at 350 mJy level.
Therefore, this list will be automatically complete at Q-band provided
the spectra of sources are falling. According to Massaradi (2011)
the fraction of sources with rising spectra in range 10–20 GHz is 8%.
The list will exclude sources for which Q-band images are publicly
available from the KQ survey and from the Boston University monitoring
program.
At present, we do not know exactly how many sources will be detected
in the fringe search campaign. In the case if all the sources will be
detected, the requested time for observing 600 targets in 6 scans of
90 seconds each, including time for slewing and observations of
calibrators, will be 192 hours. We should stress that this is the maximal
estimate. Realistically, we expect 300–400 sources will be detected at
the KVN, and the amount of needed time for completion of this survey
will be more likely in the range of 100–120 hours.
In addition to VLBI observations, we will perform single-dish Q-band
flux measurements of the final target list during winter 2011/2012 at
one of KVN stations.
Current status
- 2012.03.12 Preliminary results from scans 132-877 of the
first fringe-search KVN Q-band experiment k11353a was analyzed.
Of 672 sources correlated, 370 have been detected, including
12 new sources never before observed with VLBI.
- 2012.10.11 The Time Allocation Committee allotted 120 hours
of observing time in 2012 for this project.
- 2011.12.19 The fringe-search KVN Q-band prelimiary survey was observed.
- 2011.10.30 Proposal has been submitted
Preliminary results
Data
References
-
Lanyi, et al., The Celestial Reference Frame at 24 and 43 GHz.
I. Astrometry 2010, AJ, 139, 1695
- Massardi M., et al.,
The Australia Telescope 20 GHz (AT20G) Survey: analysis of the extragalactic source sample
2011, MNRAS, 412, 318
- Petrov L., et al.
VERA 22 GHz fringe search survey,
2007, AJ, 133, 2487
-
Petrov, L., Kovalev, Y.Y., Fomalont, E., Gordon, D.,
The sixth VLBA Calibrator Survey — VCS6, 2008, AJ, 136, 580
- Petrov L., et al.,
he Very Long Baseline Array Galactic Plane Survey\u2014VGaPS
2011, AJ, 142, 5
- Petrov L.,
The EVN Galactic Plane Survey — EGaPS,
2012, MNRAS, 419, 1097
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This web page was prepared by Leonid Petrov
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Last update: 2012.08.13_09:07:42