11 July 2003 6dF workshop 1

Radio sources in the 6dFGS Tom Mauch & Elaine Sadler

University of Sydney

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

• Accurate z=0 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, starburst galaxies…)

LAST YEAR:

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All-sky radio continuum surveysNVSS (Condon et al. 1998)

= 1.4 GHz dec +90o to -40o SUMSS (Bock et al. 1999;

Mauch et al. 2003)

= 843 MHz dec -30o to -90o

Currently almost 85% complete (though not

catalogued), will be finished by Dec 2003Both surveys have 45” beam, 3-6 mJy det. limit, position accuracy 1-2”

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Since Last Year:

• ~ 6% of 6dFGS galaxies in initial data release are detected as radio sources.

• 909 Radio sources in 14880 galaxies.• 394 Additional Target spectra.• All spectra eyeballed and classified.• Initial database of radio detections

with multiwavelength data.

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The Database

Convenient method for searching large dataset!

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Radio sources in the main survey:• 909 radio sources out of 14880 total objects

6% Detection Rate! Possibly because of our 10” radio optical separation cutoff.

• All spectra hand classified (star,Aa,Ae,Aae,SF):• 399 AGN• 436 Star-Forming• 71 Unclassifiable• 3 Stars• About 50/50 split between AGN and SF in 6dFGS

(60/40 in 2dFGS)

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

• Absorption line AGN:

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

• Emission Line AGN:

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

• Star Forming Galaxies: IRAS Source

0.28 Jy at 60m

Large fraction of SF galaxies interacting.

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Redshift distribution of 6dFGRS radio sources

2dF Sample 6dF Sample

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Radio emission from star-forming galaxies

Many faint (<5mJy) NVSS sources with no IRAS detection.

6dFGS-NVSS2dFGS-NVSS

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Local radio luminosity function of active and star-forming galaxies

Low-luminosity AGN are hard to find

Distribution of AGN radio luminosities.

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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:

394 objects in initial data release.

• Stellar objects (foreground stars, QSOs, compact galaxies)

• Blue galaxies (starburst, AGN)

What fraction of the local radio-source population is missed because hosts appear stellar? Don’t need all objects observed, just a sub-sample - i.e. flexible

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Detection fractions of additional targets

• Many additional targets are in other additional target samples, large fraction have been observed!– 166 stars– 61 AGN– 74 Star Forming– 93 Unknown

About same fraction as in main survey!

Possible BL-Lac population.

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Redshift Distribution of Additional Target Galaxies

• Median z=0.08– Fainter sources

– Emission line AGN

– Starburst galaxies

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Some interesting Additional Targets (1):

• QSO- No previously recorded redshift. – Bright radio source (1.8 Jy in NVSS) also PKS 1955-35

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Some interesting Additional Targets (2):

• Higher-z QSO (4.9 mJy at 1.4 MHz)– Incorrect z from runz; actual z is 0.75

MgII

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Some interesting Additional Targets (3):

• Starburst Galaxy (ULIRG?)

43.5 mJy at 1.4 GHz (1024.5 W Hz-1) 0.189 Jy at 60m

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Some interesting Additional Targets (4):

• Radio emission from white dwarfs?– Willes & Wu 2003 (astro-

ph/0302583) claim white dwarf pairs can be strong radio sources!

– 2.9 mJy radio source.– 3 found in current sample.– Only 0.1 per deg2 and 10%

of these could be radio sources.

– Class 2 in the initial data release, but class 4 spectrum!