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6dF Radio Source Redshift Survey: Main and Extra Targets Science

Explore radio source redshifts in 6dFGS for AGN, starbursts, and clustering studies. Identify galaxy types and benchmark cosmic evolution research. Discover spectral classifications and luminosity distributions in this comprehensive survey.

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6dF Radio Source Redshift Survey: Main and Extra Targets Science

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  1. 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 z=0 benchmarks for studies of cosmic evolution • ‘Extratargets’ science: • Compact objects and some galaxies with blue colours (QSOs, starburst galaxies…) 6dF workshop

  2. 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” 6dF workshop

  3. Radio Source Detection • Primary Sample (K<12.75): • 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 B<18 in the SuperCOSMOS database • 6997 NVSS (dec.>-40deg) and 2614 SUMSS (dec.<-50deg) additional targets • 1191 NVSS (17%) and 6 SUMSS (0.2%) observed serendipitously in first data release 6dF workshop

  4. Spectral Classification • mJy radio surveys probe a mixture of sources which are hard to distinguish: • Starforming galaxies (S<10 mJy) • AGN (S>50 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) 6dF workshop

  5. Typical Spectra of Faint radio Sources in 6dFGS (1) • Absorption line AGN (Aa): 6dF workshop

  6. Typical Spectra of Faint radio Sources in 6dFGS (2) • Emission Line AGN (Ae): 6dF workshop

  7. Typical Spectra of Faint radio Sources in 6dFGS (3) • Star Forming Galaxies: IRAS source: 1.8Jy at 60m Many SF galaxies interacting 6dF workshop

  8. 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 (z<0.1) sample of radio source redshifts ever obtained! 6dF workshop

  9. Redshifting Problems 3 objects with incorrect redshifts! 46 Q=1,2 objects re-redshifted. (And 51 QSO’s) 6dF workshop

  10. Redshift distribution of 6dFGRS radio sources All SF AGN 6dF workshop

  11. Radio emission from star-forming galaxies 1718 SF 151 AGN NVSS and IRAS-FSC flux density limits comparable. IRAS-FSC has incomplete coverage. 6dF workshop

  12. Luminosity Distribution Radio AGN are found in brightest elliptical galaxies (K>2K*). Starforming galaxies span wide range of absolute K magnitude. Both AGN and SF galaxies span a range of radio power (20<log(P)<25). 6dF workshop

  13. 2 point correlation function All SF AGN γ=1.8±0.1 ro=12.6±0.9 Mpc 0 Mpc<s<40 Mpc γ=1.7±0.1 ro=7.9±0.6 Mpc 0 Mpc<s<40 Mpc γ=1.7±0.1 ro=7.9±0.7 Mpc 0 Mpc<s<40 Mpc Magliocchetti et al.(2004): ro=10.9±1.0 Mpc (AGN), ro=6.7±1.0 Mpc (ALL) Norberg et al. (2002) (2dFGRS Galaxies): bright early types: ro=13.85±1.7 Mpc faint late-type: ro=5.2±1.1 Mpc bright late-type: ro=9.0±1.4 Mpc Radio sources cluster in a similar fashion to the optical host galaxy population. 6dF workshop

  14. 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! 6dF workshop

  15. 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: • What fraction of the local radio-source population is missed? Don’t 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 6dF workshop

  16. Redshift Distribution of Additional Target Galaxies • Median z=0.08 • Fainter sources • Emission line AGN Tail (z<0.05) of “blue” starforming galaxies. AGN SF 6dF workshop

  17. What’s missing? “Extended” additional targets are a combination of fainter objects: B>17 with B-K~4.5 and blue objects: B<16 with B-K<3 About 1% of (B<16) radio sources are missing from the primary (K-selected) sample because they are too “blue”. 6dF workshop

  18. A Blue Galaxy B=15.7 (SCos) K=13.0 (2MASS) S=3mJy (NVSS) 6dF workshop

  19. Quasars 51 Quasars found, 26 have no NED id. Only 10% of “stellar” input list. For |b|>50deg. 50% of objects are quasars. Does radio selection differ from optical selection? 6dF workshop

  20. QSO Colours Compare with 6QZ (optical-uv colour selection) Construct 6QZ subsample with B<18. K magnitudes from 2MASS-PSC. 6dF workshop

  21. 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. 6dF workshop

  22. 2 point correlation function in redshift space All SF AGN γ=1.87±0.08 so=13.07±0.40 (Mpc) 3 Mpc<s<60 Mpc γ=1.59±0.03 so=9.65±0.12 (Mpc) 4 Mpc<s<40 Mpc γ=1.57±0.03 so=10.07±0.11 (Mpc) 4 Mpc<s<40 Mpc 776 AGN and 1314 SF in region bounded by: 8h<R.A.<24h ,-40o<dec.<-20o,|b|>10o 6dF workshop

  23. The two-point correlation function • Radio sources are good probes of large-scale structure (median redshift z~0.8) • ξ(r) measures probability over random dP that a pair of objects are found at comoving separation r: dP=ρ2[1+ ξ(r) ]dV1dV2 ξ(r) usually modeled as a power-law of the form: 6dF workshop

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