Low polarization selection of a complete sample of CSO/MSO

P. Cassaro C. Stanghellini D. Dallacasa

4th CSS/GPS Workshop, Riccione, 26-29 May 2008

Selection method and criteria

Search on NVSS p < 0.3 % (Fanti et al. 2004) at low polarization sources with ℓsize < few kpc

68 candidates

Search on FIRST 07h00m < RA < 17h30m

S1.4GHz > 500 mJy

θ < 7” (observed)

40o < δ < 60o

We used the 1.4 GHz surveys because of resolution and sensitivity in polarized flux

Morphological classification

We searched images of resolution suitable to classify the sources

Bibliography

NRAO image archive

VLA and VLBA data archive

32 objects need new observations

Observation strategy

VLA A-array observations at X and K-bandto obtain images ~arcsec resolution

Follow up of VLBI observations for the sources unresolved in the VLA images

…only “blindly” EVN observations

VLBI maps

4 confirmed CSO

EVN observations at 18 cm single polarization

11 objects observed

VLBI maps

1 core-halo

VLBI maps 4 resolved to much

10 - 25 mJy ⇓

95-99 % of flux lost

VLBI maps

VLA C-band

VLA X-band

EVN L-band

VLBI maps CSO? May be too much resolved

Morphological classification

1 candidates

40 morphological identifications33 confirmed CSO/MSO7 core-jet (archive and literature images)

59 % of the candidates identified82 % of CSO on the total identified sources

28 more objects to be observed

Known sources

5 sources in the COINS sample (Peck & Taylor '00)

12 sources in the B3-VLA CSS sample (Dallacasa et al '02)

several sources in other papers

Redshift

16 sources with spectroscopic redshift 32 sources with photometric redshift (SDSS)

Spectral properties

Flux density from 8C,WENSS, FIRST, GB6…cover from 151 MHz to8.4 GHz (74 MHz data for a few sources)

Steep spectrum,peaked spectrum,GPS

Selection bias

Peak frequency and linear size distributions

Flux limit at 1.4 GHz ⇓cut in peak frequencyat about 3 GHz

Low polarization ⇓linear size < 10 kpc (Fanti et al. 2004)

Light histogram: all the candidates with

151 MHz < νpeak < 8.4 GHz

Dark histogram: all the confirmed CSO/MSO

Linear size of the symmetric objects

Selection of a CSO/MSO sample

Method highly efficient

νpeak< 3 Ghz

ℓsize < 10 kpc

Follow up

Radio maps of the unidentified objects:VLA then EVN (+MERLIN?)

Selection at lower flux limit or with a higher frequency survey