Transcript No Slide Title

Space VLBI
Sándor Frey
FÖMI Satellite Geodetic Observatory
P.O. Box 546, H-1373 Budapest, Hungary
[email protected]
http://www.sgo.fomi.hu/vlbi/
Space
Very
Long
Baseline
Interferometry
SVLBI in principle: ground-space baseline
VSOP
ISAS (Japan)
(VLBI Space Observatory Programme)
HALCA start: February 12,
1997 (new M-V rocket)
8-m parabolic antenna on board
HALCA
observing frequencies:
1.6 and 5 GHz
recording data rate: 128 Mbps
bandwidth: 32 MHz
orbital period: 6.3 h
21 400km (apogee)
560 km (perigee)
baselines: up to ~30 000 km
http://www.vsop.isas.ac.jp/
Highly
Advanced
Laboratory for
Communications and
Astronomy
Usuda 64 m
a truly global VLBI:
>40 ground radio telescopes
from all over the world
5 ground tracking stations
(USA, Japan, Australia,
Spain)
Usuda 10 m
3 correlators
(USA, Canada, Japan)
VSOP scientific program
General Observing Time (~50% of operational time)
• open for the scientific community via peer-reviewed proposals
(deadlines now coincide with ground VLBI deadlines,
3 times per year)
• a few declared key science programs:
* blazars
* high brightness temperature / intra-day variability
* jet motions (3C 273, 3C 279 and 3C 345)
* key sources (NGC 4258, Centaurus A and Virgo A)
* nearby AGN
* absorption in AGN
* stars
VSOP scientific program (cont.)
VSOP Survey Program (~25%)
• led by the mission at ISAS
• coordinated by the international Survey Working Group
• ~200 brightest, pre-selected AGN to be imaged at 5 GHz
• limited ground resources (typically 3-5 GRTs)
• mainly S2 recording + “extractions” from GOT experiments
• homogeneous information on sub-mas structures,
for statistical studies
• data base will be publicly available
Fomalont et al. (2000), ApJS 131, 95
Selected VSOP scientific results
Selection criteria for inclusion in this talk:
interesting
important
spectacular
certain people in this room are involved...
… including myself
Large collections of various VSOP-related papers:
"VSOP Results and the Future of Space VLBI", Proc. COSPAR
Symposium, Nagoya, Japan, July 1998, eds. Hirabayashi H.,
Preston R.A. & Gurvits L.I., Advances in Space Research 26,
No. 4 (2000)
"Astrophysical Phenomena Revealed by Space VLBI", Proc.
VSOP Symposium, Sagamihara, Japan, January 2000, eds.
Hirabayashi H., Edwards P.G. & Murphy D.W., ISAS (2000)
VSOP Special Issue, Publications of the Astronomical Society
of Japan 52, No. 6 (2000)
Orion-KL water
maser outburst
the only VSOP
image @ 22 GHz
peak:
1.3  105 Jy/beam
elongated structure
+ VLBA monitoring:
overlapping maser
spots?
Kobayashi et al. 2000, VSOP Symp., 109
1519–273 at 1.6 GHz
the first-ever SVLBI image, June 1997
VLBA & VLA
HALCA added
M87 (Virgo A)
VLA
No proper motion is detected in
1.5 years VSOP monitoring @ 5 GHz
(in contrast with superluminal motion
at VLA & HST scales)
Junor et al. 2000, VSOP Symp., 13
VSOP 1.6 GHz
Reid 1998, Science 281, 1815
the impact of
improved angular
resolution:
transverse jet
structure resolved
edge-brightening
regular, oscillating
patterns: instabilities
propagating along the
jet
Lobanov et al. 2000, AdSpR 26, 669
Lobanov et al. 2000, VSOP Symp., 239
1928+734 (z=0.3) monitoring
core
Murphy et al. 2000, VSOP Symp., 47
1997 Aug 22
1997 Dec 16
1998 Apr 29
1998 Jul 9
circumpolar superluminal quasar, ideal for VSOP monitoring
substantial changes near the core on ~months time scale
a variety of different phenomena, inconsistent with a simple
straight jet model
0637–752 quasar
first Chandra target, thought to be unresolved
VSOP
(z=0.65)
 luminous kpc-scale X-ray jet
5 GHz
1999 Aug: coordinated VSOP and Chandra observations
radio (ATCA) vs. X-ray jet structure: striking coincidence
Australia Telescope
and radio jet bending
Compact Array
(8.4 GHz, contours)
polarization E-vectors perpendicular to the jet until X-rays
detected to W, then begin to be parallel with the jet
Chandra X-ray
(color)
simple synchrotron
model is not sufficient to explain all
data (incl. HST optical)
VSOP/VLBI:
mas-scale jet direction, ~11c superluminal motion
Lovell et al. 2000, VSOP Symp., 215
The most distant radio-loud quasars (z>3)
2215+020 (z=3.57)
VLBA+EVN ground-only @ 1.6 GHz
J4
+ baselines to HALCA included
resolved jet cross-section 
~4·109 Mo estimated cental black hole
mass
Lobanov et al. 2001, ApJ 547, 714
1351-018 (z=3.71)
earlier VLBA @ 5 GHz
Frey et al. 1997, A&A 325, 511
SVLBI @ 5 GHz:
dramatic change in jet direction between
sub-mas and ~10 mas scale
VSOP phase-referencing
HALCA cannot switch rapidly between sources ...
… but:
1308+326 / 1308+328 quasar pair (14.3 arcmin separation)
HALCA primary beam: 26 arcmin @ 5 GHz
VLBA + Effelsberg switched between the sources
phase reference mapping, relative astrometry with VSOP
Porcas et al. 2000, VSOP Symp., 245
1342+662 / 1342+663 quasar pair (4.8 arcsec separation)
sources lie within the primary beam of HALCA & VLBA antennas
it works! satellite orbit reconstruction error ~3 m
Guirado et al. 2001, A&A 371, 766
VSOP polarization
HALCA receives only left-circularly polarized radiation ...
… but:
despite the other complications (lower sensitivity, difficult
polarization calibration), it is technically feasible to obtain highresolution polarization images
test observations with the VLBA and VLA @ 1.6 and 5 GHz
of sources with sufficiently high correlated polarized flux density
good perspectives for next-generation SVLBI
Kemball et al. 2000, PASJ 52, 1055
0235+164
a highly variable BL Lac
VSOP @ 5 GHz:
the highest brightness
temperature measured
with VSOP
TB > 5.8  1013 K
Frey et al. 2000, PASJ 52, 975
The Pearson-Readhead Survey from Space
HALCA + VLBA + EVN imaging of 27 sources from the
P-R survey (Pearson & Readhead 1988, ApJ 328, 114)
original sample: 65 sources (>35, S5>1.3 Jy, b>10)
sub-sample for SVLBI: Scorr>0.4 Jy on ground baseliness
2200+420 (BL Lac) @ 5 GHz
ground-only
Lister et al. 2001, ApJ 554, 948
SVLBI
The Pearson-Readhead Survey from Space: results
imaging: true dynamic range typically 30:1 … 100:1
Lister et al. 2001, ApJ 554, 948
source properties: correlation analysis (morphology, IDV,
core dominance, optical polarization, emission line
equivalent width, etc.)
 support to the beaming model
Lister et al. 2001, ApJ 554, 964
brightness temperature distribution:
a significant proportion has TB>1012 K
relation between high TB and IDV activity
Tingay et al. 2001, ApJ 549, L55
The VSOP Survey Program: preliminary results
sample: among 402 sources
(S5>0.95 Jy, >–0.45, b>10),
289 sources sufficiently
compact for VSOP @ 5 GHz
~half of the data sets
reduced, even more observed
rest-frame brightness
temperature (TB) distribution
shows apparent violation of
inverse Compton limit
(~1012 K)
 relativistic beaming is
common
Hirabayashi et al. 2000, PASJ 52, 997
VSOP proposals, observations and data reduction
• open proposals; deadlines: 1 February, 1 June & 1 October
• all info at: www.vsop.isas.ac.jp/obs/AO.html
• Proposers’ Guide, cumulative observation list, etc.
• severe observing constraints (on-board equipment, tracking,
ground network availability, etc.)
• assistance: user software, sample (u,v)-coverages
• schedule is done by the VSOP mission
• data reduction: AIPS and Difmap are available
• calibration information on the VSOP web
• general info: e-mail newsletter (also on the web, with some
delay)
Next generation Space VLBI
SVLBI: technically feasible, scientifically interesting
 next generation satellites with improved performance
(sensitivity, frequency coverage, etc.)
VSOP-2
is being
proposed
at ISAS
in Japan
• 10 increase over VSOP sensitivity
• 20-40 000 km apogee
• 10-m antenna
• frequencies: (1.6?), 5(8), 22, 43, (86?) GHz
• data rate: 1 (2?) Gbit/s
• launch vehicle: modified M-V
• launch: 2008 ?
ARISE (Advanced Radio Interferometry between Space and Earth)
• 5 ground-based resolution
(max. 10-20 as)
• 50 VSOP sensitivity
• 40-50 000 km apogee
• 25-m inflatable antenna
• frequencies: 5(8), 22, 43, 86 GHz
• single-dish: 60 GHz
• data rate: 8 Gbit/s
• lifetime  3 years
• launch: 2008 ?
http://arise.jpl.nasa.gov/
.