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Radio sources in the 6dFGS
(Mauch, Sadler, Jackson, Saunders, Cannon, Hunstead)
‘Main survey’ science:
~ 15% of 6dFGS galaxies will be detected as radio sources by
NVSS/SUMSS (vs <2% in 2dFGRS) i.e. 10,000+ spectra!
• Faint end of radio luminosity function for AGN, starbursts
• Accurate z=0 benchmarks for studies of cosmic evolution
• Black hole mass/velocity dispersion relation for radio AGN
‘Extra targets’ science:
• Compact objects and some galaxies with blue colours
(QSOs, X-Ray sources, PNe, starburst galaxies…)
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6dF workshop
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All-sky radio continuum surveys
NVSS
(Condon et al. 1998)
n = 1.4 GHz
dec +90o to -40o
SUMSS (Bock et al. 1999)
n = 843 MHz
dec -30o to -90o
Currently almost 70%
complete, will be finished
by Dec 2003
Both surveys have 45”
beam, 3-5 mJy det. limit,
position accuracy 1-2”
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Typical spectra of faint radio sources
(2dFGRS, Sadler et al. 1999)
Ha
Hb
[OIII]
• Star-forming
galaxy, z=0.14
(40% of 2dFGRS/NVSS)
• Emission-line
AGN, z=0.15
(10%)
• Absorption-line
AGN, z=0.14
(50%)
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Radio emission from star-forming galaxies
UGC 09057
NGC 5257/5258
z=0.0054
z=0.0223
Estimated star formation rate:
1.8 Msun/yr
120 Msun/yr
NGC 7252
z=0.0161
32 Msun/yr
(Radio emission is dominated by synchrotron radiation from electrons accelerated by supernova remnants,
most are detected as IRAS sources)
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6dF workshop
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Local star-formation density from radio
and Ha data
Local star formation
density (zero-point of
Ha
Madau diagram) in
Msun/yr/Mpc3 :
Ha: 0.013 +/-0.006
(Gallego et al. 1995)
Radio: 0.022 +/-0.004
(Sadler et al. 2002)
Radio
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6dF workshop
Radio data show more
galaxies with very high SFR
(> 30 Msun/yr), otherwise
very good agreement. 5
Radio emission from active galaxies
TGN284Z051
z=0.1065
TGN348Z183
z=0.1790
1.4 GHz radio power and projected linear size:
1024.3 W/Hz
1025.0 W/Hz
327 kpc
475 kpc
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6dF workshop
TGS153Z214
z=0.2079
1024.8 W/Hz
471 kpc
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Redshift distribution of 2dFGRS radio
sources (and all galaxies)
(Colless 2001)
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Local radio luminosity function of active
and star-forming galaxies
Below 1025 W/Hz, the
local radio source
population is always
a mixture of AGN and
star-forming galaxies.
i.e. There is probably
no observational
regime where radio
surveys detect only
star-forming galaxies.
Low-lum AGN
are hard to find
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6dF workshop
Spectra vital!
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What do we gain from 6dF?
A LARGE data set of radio-source spectra over
a SMALL redshift range (no evolution).
Total volume (to z=0.04) ~ 2x107 Mpc3
All-sky radio surveys (NVSS/SUMSS) with detection
limits of 2-5 mJy at 1400/843 MHz
typical
radio powers of 1021 - 1025 W/Hz in 6dFGS volume
The deepest current radio surveys (to 10-50 mJy in
HDF N and S)
1022 - 1025 W/Hz at z=2 - 3
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6dF workshop
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6dFGS ‘Additional targets’
6dFGS unallocated fibres placed on NVSS/SUMSS
radio IDs which have bJ<18 mag but which are not
in the main sample:
• Stellar objects (foreground stars, QSOs, compact
galaxies)
• Blue galaxies (starburst, e+A systems?, AGN)
What fraction of the local radio-source population
is missed because hosts appear stellar? Don’t need
all objects observed, just a sub-sample - i.e. flexible
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6dF workshop
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Radio detection of planetary
nebulae
Galactic planetary
nebulae are
detectable as
thermal radio
sources.
NVSS/SUMSS/6dFGS
likely to discover
new high-latitude
PNe among stellar
‘extra targets’.
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6dFGS data, May 2002...
Ks=4.5 mJy, below 6dFGS limit?
Radio galaxy at z=0.0651,
S1.4 = 147 mJy (NVSS)
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