Radio sources in the 6dFGS Tom Mauch Sydney, Elaine Sadler Sydney

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Radio sources in the 6dFGS Tom Mauch
(Sydney), Elaine Sadler (Sydney) Steve
Rawlings (Oxford)
A Radio Source Redshift Survey

• Main survey science
• Faint end of radio luminosity function for AGN,
  starbursts
• Clustering study via the 2-point Correlation
  function
• Accurate z0 benchmarks for studies of cosmic
  evolution
• Extra targets science
• Compact objects and some galaxies with blue
  colours (QSOs, 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 Mauch et al. 2003) n
843 MHz dec -30o to
-90o Currently almost 95 complete (though not
catalogued), will be finished by early 2006 Both
surveys have 45 beam, 3-6 mJy det. limit,
position accuracy 1-2
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Radio Source Detection

• Primary Sample (Klt12.75)
• Preliminary list of all NVSS radio sources within
  30 of 2MASS-XSC (18).
• Confirmed identifications by eye
• 4537 out of 29000 observed objects in first
  data release accepted as genuine (16 detection
  rate)
• Additional Targets
• NVSS/SUMSS Radio sources within 10 of
  extended objects and 5 of stellar objects
  with Blt18 in the SuperCOSMOS database
• 6997 NVSS (dec.gt-40deg) and 2614 SUMSS
  (dec.lt-50deg) additional targets
• 1191 NVSS (17) and 6 SUMSS (0.2) observed
  serendipitously in first data release

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Spectral Classification

• mJy radio surveys probe a mixture of sources
  which are hard to distinguish
• Starforming galaxies (Slt10 mJy)
• AGN (Sgt50 mJy)
• Spectra useful for classification!
• All spectra hand classified into 5 types
• star (Galactic stars)
• Aa (Early types)
• Aae (LINER type spectrum)
• Ae (Emission line AGN)
• SF (HII region type spectrum)

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Typical Spectra of Faint radio Sources in 6dFGS
(1)

• Absorption line AGN (Aa)

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Typical Spectra of Faint radio Sources in 6dFGS
(2)

• Emission Line AGN (Ae)

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Typical Spectra of Faint radio Sources in 6dFGS
(3)

• Star Forming Galaxies

IRAS source 1.8Jy at 60?m
Many SF galaxies interacting
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Radio Sources in the Primary Sample

• 4537 NVSS radio sources in 6dF-FDR
• 16 Detection rate
• 109 SUMSS
• 7.6 Detection rate
• Spectral classification for NVSS
• 1301 Aa
• 153 Ae
• 167 Aae
• 2673 SF
• 8 Star
• 235 Unclassifiable (Low S/N spectra)
• 40 AGN , 60 SF (2dFGRS 60 AGN , 40 SF)
• Largest local (zlt0.1) sample of radio source
  redshifts ever obtained!

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Redshifting Problems
3 objects with incorrect redshifts!
46 Q1,2 objects re-redshifted. (And 51 QSOs)
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Redshift distribution of 6dFGRS radio sources
All
SF
AGN
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Radio emission from star-forming galaxies
1718 SF 151 AGN NVSS and IRAS-FSC flux density
limits comparable. IRAS-FSC has incomplete
coverage.
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Luminosity Distribution
Radio AGN are found in brightest elliptical
galaxies (Kgt2K). Starforming galaxies span wide
range of absolute K magnitude. Both AGN and SF
galaxies span a range of radio power
(20ltlog(P)lt25).
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2 point correlation function
All
SF
AGN
?1.80.1 ro12.60.9 Mpc 0 Mpcltslt40 Mpc
?1.70.1 ro7.90.6 Mpc 0 Mpcltslt40 Mpc
?1.70.1 ro7.90.7 Mpc 0 Mpcltslt40 Mpc
Magliocchetti et al.(2004) ro10.91.0 Mpc
(AGN), ro6.71.0 Mpc (ALL)
Norberg et al. (2002) (2dFGRS Galaxies) bright
early types ro13.851.7 Mpc faint late-type
ro5.21.1 Mpc bright late-type ro9.01.4 Mpc
Radio sources cluster in a similar fashion to the
optical host galaxy population.
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Local radio luminosity function of active and
star-forming galaxies
Work in progress
Sadler et al. (2002) Radio luminosity function
Population of low luminosity AGN in this sample!
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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
• What fraction of the local radio-source
  population is missed? Dont need all objects
  observed, just a sub-sample - i.e. flexible
• 1065 objects in first data release (17).
• Stellar objects (394 foreground stars, 51
  QSOs,23 compact galaxies)
• Extended objects (262 SF,183 AGN)
• 146 Unknown objects (BL-Lacs?? Low S/N spectra.)

Same fraction as primary sample
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Redshift Distribution of Additional Target
Galaxies

• Median z0.08
• Fainter sources
• Emission line AGN
• Tail (zlt0.05) of blue starforming galaxies.

AGN
SF
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Whats missing?
Extended additional targets are a combination
of fainter objects Bgt17 with B-K4.5 and blue
objects Blt16 with B-Klt3
About 1 of (Blt16) radio sources are missing from
the primary (K-selected) sample because they are
too blue.
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A Blue Galaxy
B15.7 (SCos) K13.0 (2MASS) S3mJy (NVSS)
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Quasars
51 Quasars found, 26 have no NED id. Only 10 of
stellar input list. For bgt50deg. 50 of
objects are quasars. Does radio selection differ
from optical selection?
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QSO Colours
Compare with 6QZ (optical-uv colour
selection) Construct 6QZ subsample with Blt18. K
magnitudes from 2MASS-PSC.
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Summary

• This sample comprises the largest and most
  homogeneous set of radio source spectra obtained
  in the local universe.
• Benchmark for studies of higher redshift radio
  sources.
• Compare with higher z samples

More than 10,000 radio source redshifts in
complete 6dF sample! Can break into smaller
subsamples. Study effects of source environment,
test AGN unified models etc.
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2 point correlation function in redshift space
All
SF
AGN
?1.870.08 so13.070.40 (Mpc) 3 Mpcltslt60 Mpc
?1.590.03 so9.650.12 (Mpc) 4 Mpcltslt40 Mpc
?1.570.03 so10.070.11 (Mpc) 4 Mpcltslt40 Mpc
776 AGN and 1314 SF in region bounded
by 8hltR.A.lt24h ,-40oltdec.lt-20o,bgt10o
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The two-point correlation function

• Radio sources are good probes of large-scale
  structure (median redshift z0.8)
• ?(r) measures probability over random dP that a
  pair of objects are found at comoving separation
  r

dP?21 ?(r) dV1dV2
?(r) usually modeled as a power-law of the form