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‘Main survey’ science: Faint end of radio luminosity function for AGN, starbursts

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

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‘Main survey’ science: Faint end of radio luminosity function for AGN, starbursts

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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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