Piggyback redshift surveys of radio galaxies at z0'3

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Piggyback redshift surveys of radio galaxies at
zgt0.3

• Combining 2dFGRS/6dFGS spectra with all-sky
  radio continuum surveys yields highly-accurate
  radio LFs for local AGN and starburst galaxies.
• Almost nothing is known about radio-galaxy
  evolution beyond z0.3 except at extreme
  luminosities. Needs new large-area (50-100 deg2)
  sub-mJy radio survey.
• Low surface density means optical redshifts
  best measured as add-on to other LRG-type
  surveys.

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Previous add-on radio surveys
1) 2dFGRS NVSS (main survey only) 1.5 radio
det. rate, 3200 objects to 2.5 mJy, zlt0.3 2)
6dFGS NVSS/SUMSS (main surveyadd. targets) 16
radio det. rate, DR1 4145 objects to 2.5 mJy 3)
SDSS/2dF LRG FIRST (main survey only) 3 radio
det. rate, 210 objects to 0.8 mJy (0.5ltzlt0.7)
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2dFGRS radio emission from starburst galaxies
UGC 09057 NGC
5257/5258 NGC 7252
z0.0054
z0.0223
z0.0161 Derived SFR 1.8 Msun/yr 120
Msun/yr 32 Msun/yr
(Radio emission is dominated by synchrotron
radiation from electrons accelerated by supernova
remnants)
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2dFGRS Radio emission from AGN
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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Typical 2dFGRS radio-source spectra

• Star-forming galaxy, z 0.14 (40)
  Starburst
• Emission-line AGN, z 0.15 (10) Seyfert
• Absorption-line AGN, z 0.14 (50) Radio galaxy

Ha
Hb
OIII
(Sadler et al. 1999)
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2dFGRS Local radio LFs for active and
star-forming galaxies
Below 1025 W/Hz, the local radio-source
population is always a mixture of AGN and
star-forming galaxies. With 6dFGS data, can
construct accurate bivariate RLFs for AGN (e.g.
split by black-hole mass). 12,000 spectra of
radio AGN to z0.3 by 2006.
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PKS 0019-338, a post-starburst radio galaxy in
the 2dFGRS at z0.128
Balmer abs. implies massive (1010 Msun)
starburst occurred 0.15 Gyr ago. Compact
(young) radio source has P1.4 1025 W/Hz. Study
rare objects (transient phases?) in context of
parent population.
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6dFGS radio sources (NVSS/SUMSS)
Main sample SF AGN. Add. Targets many QSOs
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LRG radio galaxies (0.4ltzlt0.7)
2003/4 100 deg2, 9200 spectra, 204 radio AGN
NRAO FIRST, 1.4 GHz
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Why a fainter radio survey?
3 of SDSS/2dF LRGs detected as radio sources.
Evolution clearly seen (3x number of sources
expected from z0 RLF). BUT 1 mJy flux limit
means only top end of RLF is sampled at zgt0.5, v.
few objects at zgt0.7
Detectable with LRG FIRST
2dFGRS radio LF
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Radio flux densities for LRG/FIRST
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Specs for newwide-deep radio surveys

• VLA
• 1s noise level of 0.1 mJy in 12 min
• 100 deg2 to 0.4 mJy det limit in 140 hr
• ATCAWBC (2007)
• 1s noise level of 0.06 mJy in 10 min
• 100 deg2 to 0.4 mJy det limit in 56 hr, or
  50 deg2 to 0.2 mJy det limit in 120 hr.

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AAOmega requirements...

• Can piggyback onto almost any survey which
  includes luminous early-type galaxies at zgt0.3
  (z0.7 to 1 ideal).
• Area coverage ideally 50-100 deg2 (5000
  galaxies).
• For microJy-level continuum over 50-100 deg2, to
  reach radio power few x 1023 W/Hz, need ATCA
  with MNRF wide-band corrrelator. Therefore need
  to avoid regions near declination 0o
• No special requirements for pre-imaging in
  optical (radio imaging can be done either before
  or after optical spectroscopy).

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