Polarization properties of Polarization properties of Extragalactic Point Sources (EPS) Extragalactic Point Sources (EPS)

at high frequenciesat high frequencies

M. Massardi, J. Gonzalez-Nuevo & M. Massardi, J. Gonzalez-Nuevo & G. De ZottiG. De Zotti

Orsay, 27 October (2006)Orsay, 27 October (2006)

Existing observations of EPS Existing observations of EPS polarization propertiespolarization properties

Survey/refSurvey/refFreqFreq

[GHz][GHz]

Number Number of of

sourcessourcesNotes & main resultsNotes & main results

NVSS NVSS (Condon et al. 1998)(Condon et al. 1998)

1.41.4 ~ 2 ~ 2 x x 101066

Extrapolated at higher frequencies in Extrapolated at higher frequencies in

Tucci et al. (2004).Tucci et al. (2004). See See references therein for other references therein for other observationsobservations

VLA VLA calibratorscalibrators [5 - 43] [5 - 43] 6262 Mainly flat pol degree 2.5% Mainly flat pol degree 2.5% increasing with frequencyincreasing with frequency

Kuhr sampleKuhr sample (Ricci et al. 2004)(Ricci et al. 2004)

18.5 18.5 250250pol degree 2.7% flatpol degree 2.7% flat

pol degree 4.8% steeppol degree 4.8% steep

Pilot AT20GPilot AT20G(Sadler et al. 2006)(Sadler et al. 2006)

20 20 173173

Pol deg 2.3% Pol deg 2.3% (2.7% for100mJy<S(2.7% for100mJy<S2020<200mJy<200mJy

1.7% for S1.7% for S2020>200mJy)>200mJy)

Extrapolation to Higher FrequenciesExtrapolation to Higher Frequencies

Planck Reference SkyPlanck Reference Sky Realistic all-sky simulations Realistic all-sky simulations

(background+foregrounds) at all the (background+foregrounds) at all the Planck channels: total Planck channels: total intensity+polarizationintensity+polarization

Analytical methodAnalytical method Based on source number counts models Based on source number counts models

and simple assumptions about the PS and simple assumptions about the PS polarization properties.polarization properties.

The Planck Reference-Sky: Point The Planck Reference-Sky: Point Sources (1)Sources (1)

@ Radio Sources:

Positions and 5GHz fluxes of real sources in 96% of cases (PMN, GB6, SUMSS, NVSS).

Extrapolation of the Spectral behaviour using observed distributions (AT20G Pilot survey, WMAP, Fomalont et al. (1991))

@ FIR Sources:

IRAS sources combining Serjeant & Harrison (2005) and Clements compilation for Planck WG2.

Proto-spheroidal galaxies (Granato et al. 2004 model & Gonzalez-Nuevo et al., 2005 software)

Lensed Proto Spheroids (Perrotta et al., 2003)

The Planck Reference-Sky: Point The Planck Reference-Sky: Point Sources (2)Sources (2)

@ Radio Sources:

Polarization Degree: Random association according to Ricci et al. (2004) @ 18 GHz

Polarization Angle: Uniform random distribution

@ FIR Sources:

Polarization Degree: 1%

Polarization Angle: Uniform random distribution

Analytical MethodAnalytical Method

Q 2 2 2 2 I 2υ υ υ

1C =N Q N S p cos 2φ = C p

2

Following Tucci et al (2004)…

Q=S p cos 2φ

Independent variables

Source Number Counts Models

De Zotti et al. (2005)

Granato et al. (2004)

…

Pol. Degree distribution

- Simplest assumption: p= 0.028

-

12 2

υ υ υ υ

0

p = (p )p dpP

PS polarization power spectra for BpolPS polarization power spectra for Bpol

- PS contamination is almost negligible for l<300 (model & frequency dependence)

- RefSky=Analytical method for <p2>=(0.028)2

- The minimum of the PS contamination at l=100 is reached at 143 GHz

- New data at higher frequencies could modify this situation

5 (40mJy) 20’

T/S=0.1l=10

0200 mJy

T/S=0.001

On-going observations: AT20G survey

AT20G is a 20 GHz survey (total intensity AT20G is a 20 GHz survey (total intensity and polarization) of the southern sky and polarization) of the southern sky (galactic & extragalactic sources)(galactic & extragalactic sources)

Survey strategy (2.3’ primary beam Survey strategy (2.3’ primary beam @20GHz):@20GHz): 8 GHz bandwidth analog correlator in 18-24 GHz8 GHz bandwidth analog correlator in 18-24 GHz High scan rate (15 deg/min in declination)High scan rate (15 deg/min in declination) 3 22m dishes ATCA antenna in EW configuration3 22m dishes ATCA antenna in EW configuration Scanning along the meridianScanning along the meridian

In 2004-2005, 10000 sq deg with 4146 In 2004-2005, 10000 sq deg with 4146 sources down to 50 mJy (-90<dec<-30) sources down to 50 mJy (-90<dec<-30)

In 2006 -30<dec<-15 almost 2000 new In 2006 -30<dec<-15 almost 2000 new candidate sourcescandidate sources

On-going observations: AT20G survey

6 sources S>100

mJy

median 2.6%

mean 3.3±0.1%

1421 objects (2004 data)

853 upper limits

On-going observations: AT20G survey

Follow ups:Follow ups: @20 GHz to confirm positions, fluxes and @20 GHz to confirm positions, fluxes and

polarization (mosaic)polarization (mosaic) 4.8, 8.6 & 4.8, 8.6 & 100100 GHz to study spectral behaviour, GHz to study spectral behaviour,

polarization, variability, HII regions, …polarization, variability, HII regions, … Polarization Polarization follow up (Oct 2006) at 18 GHzfollow up (Oct 2006) at 18 GHz

183 sources brighter than 500 mJy observed in 2004-183 sources brighter than 500 mJy observed in 2004-20062006

7 extended7 extended 8 with polarized flux>100mJy8 with polarized flux>100mJy Median polarization degree (on pointlike sources) Median polarization degree (on pointlike sources)

2.9%2.9%

10.9 Jy of total intensity -> 1.4 Jy polarized integrated flux

Core depolarized down to 5mJy

On-going observations: AT20G survey

ConclusionsConclusions Our knowledge about the radio source Our knowledge about the radio source

polarization properties is mainly based on data polarization properties is mainly based on data below 20 GHz. Practically we have no information below 20 GHz. Practically we have no information for the IR sources.for the IR sources.

Different methods to extrapolate the polarization Different methods to extrapolate the polarization properties agree to predict that the PS properties agree to predict that the PS polarization contamination could play an polarization contamination could play an important role in the B-mode observability.important role in the B-mode observability.

New data (VLA, ATCA, APEX, ALMA, SKA, …) may New data (VLA, ATCA, APEX, ALMA, SKA, …) may introduce serious modification in our methods introduce serious modification in our methods and, as a consequence, in our predictions.and, as a consequence, in our predictions.

Polarization Power SpectrumPolarization Power Spectrum

I 2υC =N S

Q 2 2 2 2υ υ

2 2 2 I 2υ υ υ

C =N Q =N S p cos 2φ

1N S p cos 2φ = C p

2

Source Number Counts

Pol. Degree distribution

Independent variables

Tucci et al., 2004