Radio sources in the 6dFGS Mauch, Sadler, Jackson, Saunders, Cannon, Hunstead

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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 lt2
  in 2dFGRS) i.e. 10,000 spectra!
• Faint end of radio luminosity function for AGN,
  starbursts
• Accurate z0 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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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)

• Star-forming galaxy, z0.14 (40 of 2dFGRS/NVSS)
• Emission-line AGN, z0.15 (10)
• Absorption-line AGN, z0.14 (50)

Ha
Hb
OIII
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Radio emission from star-forming galaxies
UGC 09057 NGC 5257/5258
NGC 7252
z0.0054 z0.0223
z0.0161 Estimated star
formation rate
1.8
Msun/yr 120 Msun/yr
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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Local star-formation density from radio and Ha
data
Local star formation density (zero-point of 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 data show more
galaxies with very high SFR (gt 30 Msun/yr),
otherwise very good agreement.
Ha
Radio
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Radio emission from active galaxies
TGN284Z051 TGN348Z183
TGS153Z214 z0.1065
z0.1790
z0.2079 1.4 GHz radio power and projected linear
size 1024.3 W/Hz
1025.0 W/Hz 1024.8 W/Hz
327 kpc 475 kpc
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
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 z0.04) 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 z2 -
3
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6dFGS Additional targets

• 6dFGS unallocated fibres placed on NVSS/SUMSS
  radio IDs which have bJlt18 mag but which are not
  in the main sample
• Stellar objects (foreground stars, QSOs, compact
  galaxies)
• Blue galaxies (starburst, eA systems?, AGN)
• What fraction of the local radio-source
  population is missed because hosts appear
  stellar? Dont need all objects observed, just a
  sub-sample - i.e. flexible

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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...
Ks4.5 mJy, below 6dFGS limit?
Radio galaxy at z0.0651, S1.4 147 mJy (NVSS)