Deep Radio Survey of the Spitzer FLSv Region with 1.4 GHz VLA, 610 MHz GMRT & 1.4 GHz WSRT The South African SKA Youth into Science and Engineering Programme.

Deep Radio Survey of the Spitzer FLSv Region with 1.4 GHz VLA, 610 MHz GMRT & 1.4 GHz WSRT

The South African SKA Youth into Science and Engineering Programme

3rd Annual Postgraduate Bursary Conference1 to 5 December 2008

Author: Claudio Moises Paulo

Supervisor: DR. C. Cress

Co-supervisor: DR. R. Morganti & DR. I. Prandoni

Introduction

The Spitzer First Look Survey (FLS) was the first scientific program carried out by the Spitzer Space Telescope.

Observing for ~ 110 hours over centred on:

Its 0.85-meter telescope & capable of performing imaging & spectroscopic between 3 and 180 .

Launched in August 2003 & is expected to collect data until April 2009.

24deg

μm

http://www.spitzer.caltech.edu/about/index.shtml

(J2000)

003059dec

001817R.A.'''0

smh

Introduction (Cont.)

A small region of FLS has been imaged very deeply, permitting the detection of cosmologically distant sources.

• 70 main and verification fields are shown by the solid lines.

• 160 main & verification fields are shown by the dashed lines.

• Dotted lines represents the second observation made in 2005 to characterize the performance of the 70 .

μm

μm

μm

μm

Layout of the 70 & 160 fields for xFLS observations (Frayer et al., 2006)

Introduction (Cont.)

• The aim of the extragalactic component of FLS was to study a region with low Galactic background to a significantly deeper level than any previous large-area IR survey, in order to accurately characterise the dominant IR source population.

• The Spitzer FLS field has the advantage of being well studied in different wavebands therefore providing enough information to derive the radio spectral index but also to construct the spectral energy distribution for all the sources where optical, IR etc. data are available.

• A further redshift survey targeting selected 24 sources was made with the MMT/Hectospec fiber spectrograh (Papovich et al., 2002), & a total of 1587 redshift are publicly available.

μm

Introduction (Cont.)

• 1.4 GHz radio survey of the xFLS region have been made by Condon et al. (2003) using the VLA & by Morganti et al. (2004) using the WSRT.

• There is also one existing 0.61 GHz radio survey of this field made with GMRT by Garn et al. (2004).

beamμJy1

( )

Area

(de. sq)

Resolution

(arcsec)

Number of radio components

VLA 23 ~ 4 5 3565

GMRT 30 ~ 4 5.8 x 4.7 3944

WSRT 8.5 ~ 1 14 x 11 1048

σ

Introduction (Cont.)

• The aim of this study is:

• To understand the sub-mJy radio population (a mixture of star-forming galaxies and AGNs) & in particular the multi-component AGN sources.

• Its is relevant for probing super massive black hole growth and accretion (different accreting regimes display different spectral signatures).

• We can potentially use the method of Daly (2008) to measure the spin of the black hole in FRII sources.

Method

• We have done a cross-correlation between radio sources from VLA & GMRT catalogues, with the aim of studying the radio spectral properties of the sample.

• Using the radio components from the cross-correlation, we have extracted images of multi-component sources from the VLA, GMRT & WSRT Mosaic Image.

WSRT (green), VLA (red) & GMRT (yellow) overlaid mosaic image of the

FLS region.

Method (Cont.)

• Visually inspected the source morphology to decide which GMRT components to sum up in order to get the same source structure as for VLA.

• Performed a preliminary classification of the radio source morphology in:

• Fanaroff & Riley Class I and II• Peculiar • Compact • etc.

• Using VLA & GMRT fluxes at different frequency and same resolution, we measured the spectral index.

)ννlog(

)sslog(α

GMRTVLA

GMRTVLA1.4

0.61

Preliminary results

• After the cross-correlation between VLA & GMRT catalogue

• We got 1573 radio component sources with position offsets d<3”.

• From which, we extracted a sample of 165 multi-component source candidates, for which we produced sub-images.

• By visual inspection, we did a preliminary classification of all sub-images & we put all components of the same source together to decide if/how we can sum up fluxes for GMRT components in order to get the same source struture as VLA.

Preliminary results (Cont.)

• Lower power objects showing a variety of forms in which the highest brightness occurs near their centres, excluding their cores: Edge-darkened (Snellen & Best, 2001).

• Gray Scale: VLA

• Red contour: GMRT• 3, 4.5, 6, 10, 20, 50

• Cyan contour: WSRT • 6, 10, 20, 50

FR Class I

beamμJy

beamμJy

Preliminary results (Cont.)

• They are more powerful sources having their regions of highest surface brightness at the ends of a double-lobed structure: Edge-brightened (Snellen & Best, 2001).

• The Gray Scale & Contours are same like FRI image.

FR Class II

Preliminary results (Cont.)

• Extended radio source located in cluster of galaxies (Owen & Rudnik           1976).

• The Gray Scale & Contours are same like FRI image.

• WSRT contours are very confusing because this source is locate on the edge of WSRT Mosaic Image.

Wide angle tail source

Preliminary results (Cont.)

Ultra steep-spectrum sources

4%

Steep-spectrum sources

65%

Flat-spectrum sources

14%

Inverted sources 13%

1.3α

0.5α1.3

0α0.5

0α

Preliminary results (Cont.)

• Similar situation for GMRT.

Preliminary results (Cont.)

• Particulary interesting is the possibility of combining the spectral index information with other observational properties to infer the nature of the faint radio population, with particular respect to flat/inverted-spectrum sources (Mignano et al., 2008).

• This kind of analysis needs information about redshifts and types of galaxies hosting the radio sources.

• It has been known for many years that radio sources with very steep spectra are mostly associated with faint, distant galaxies (Breugel et al., 1997).

• The Ultra-steep spectral source present in the sample, if real, could potentially be associated to very high-redshift galaxies.

Conclusions and future work

• We present here a preliminary result of an analysis of a sample of radio source coming from FLS region. These objects have been cross- correlated with VLA & GMRT FLS catalogue.

• A preliminary classification enabled us to identify sources like FR I/II & some peculiar sources located in cluster of galaxies.

• The evaluation of the radio spectral index as a function of flux density permitted us to get a feeling of which kind of source we are dealing with. As an example, the presence of Ultra-steep spectral indices could potentially be associated to very high-redshift galaxies in the FLS region.

Conclusions and future work (Cont.)

• We are going to search for identifications at other wavelength (FIR, OPT/NIR, Spectroscopy) & for sources with redshift we are going to compute Radio and Optical Luminosity.

• Potentially measure the black hole spins of the FRII radio sources using Daly (2008) method.

Acknowledgement

• SA SKA.

• My supervisors.

• Thanks to:

UWC astrophysics group

References

• Breugel et al., 1997.

• Condon J. J., Cotton W. D., Yin Q. F., Shup D. L., Storrie-Lombardi L. J., Helou G., Soifer B. T., Werner M. W. 2003, AJ 125, 2411.

• Daly A., 2008.

• Garn T., Alexander, 2008, MNRAS, 000,1-9.

• Mignano et al., 2008.

• Morganti R., Garrett M., Chapman S., Baan W., Helou G., Soifer T., 2004, A&A 424, 371.

• Owen & Rudnik, 1976.

• Pavoich et al., 2002.

• Prandoni et al., 2006.

• Snellen & Best, 2001.