1. The VLA Survey of the Chandra Deep Field South X-ray Properties of Radio Sources
Shaji Vattakunnel
- University of Trieste
Paolo Tozzi - Francesca Matteucci
25th May 2010
AGN9 – Ferrara

2. Deep Radio and X-ray Surveys of the Chandra Deep Field South
Outline
Deep Radio and X-ray Surveys of the
Chandra Deep Field South
X-ray properties of Radio Sources
The sub-mJy radio source population

3. Deep Radio and X-ray Surveys
Flattening of the radio counts below one mJy
Possibly due to Star Forming Galaxies
VLA/Chandra Surveys
1Ms X-ray observation
Kellerman et al 2008
Mainieri et al 2008
Tozzi et al 2008
Padovani et al 2009
Flattening below 1 mJy
Kellerman et al. 2008
Radio and X-ray observations are efficient in identifying star formation vs nuclear activity at high redshifts.

4. X-ray luminosity vs Radio power
Padovani et al. 2009

5. Number Counts Padovani et al. 2009
Emerging of the star forming galaxies in the sub-mJy population
Analogous to results found by Gruppioni et al (1999) Prandoni et al (2009)

6. The Extended Chandra Deep Field South (E-CDFS)
6 pointings of the Very Large Array
1.4 GHz (20 cm)
34’.1 x 34’.1 image
sensivity 6-8μJy
1571 sources at 4 σ
(N. Miller)
Radio image (1.4 GHz)

7. The Chandra Deep Field South (CDFS)
0.3 – 1 keV
1 – 2 keV
2 – 7 keV
23 observations (8 years)
for a total of 2 Ms - 16’ x 16’ image
Sensitivity: ~10-17 erg cm-2 s-1
448 sources
(441 with redshifts)
[0.3-7 keV]
X-ray color image of the 2Ms
derived from Luo et al. 2008

8. The Extended Chandra Deep Field South (E-CDFS)
4 pointings
250 ks
9 observations
32’ x 32’ image
sensitivity ~10-16 erg cm-2 s-1
753 sources
(Lehmer et al. 2005)
X-ray color image of the flanking field

9. The 2Ms X-ray Survey Improvements: deeper X-ray image in the CDFS
deeper radio catalog
larger number of found matches
1Ms/VLA (2001) observation
347
266 89
77%
2Ms/EVLA (2007)
observation
448
1571
227
95%
X-ray sources in the CDFS
Radio sources in the ECDFS
Radio sources with an
X-ray counterpart
redshift available

10. Identification of X-Ray Counterparts
Positional match between X-ray and radio sources
Counterparts if the separation is less than 3σd , where:
σ2d = σ2x + σ2r
X-ray rms 0.3” < σx < 1.9”
Radio rms estimated at 0.2”
Optical
X-Ray
Radio

11. AGN / SFG discrimination
Luminosity from:
Sources with few counts
Sources with high counts
(full spectral analysis)
Total sources: 227
# of AGNs: 177
# of SFG candidates: 50
Discriminating AGNs:
X-ray Luminosity
Lx > 1042 erg/s
Radio Power
Pr > W/Hz
column density
NH > 1021 cm-2

12. AGN / SFG discrimination
Low Lum AGNs
Absorbed AGNs
Star Forming Gal
Unabsorbed AGNs

13. Star Formation Rates yr M L SFR / 10 . 4 x = yr M L SFR / 10 6 . 1 =
sources with 0.1 < z < 0.5
sources with 0.5 < z < 1.2 yr M L
SFR
GHz / 10 . 4 28 1 x = yr M L
SFR
keV / 10 6 . 1 2 40 - x =
Condon (1992)
0 < z < 1.2
The normalization is consistent with Ranalli (2003)
There is no evidence of evolution in redshift yr M L
SFR
keV / 10 . 2 40 - x =

14. Conclusions A detailed analysis of the E-CDFS sub-mJy population
X-ray and radio data are a powerfull tool to separate AGNs from SFGs:
~1/4 can be classified as star forming galaxies
~ 3/4 as AGNs
Found a correlation between X-ray and the radio power for star-forming galaxies, in agreement with previous studies
Evaluation of relation between SFR and X-ray luminosities in our sample in the redshift range 0 < z < 1.2
X-ray stacking of the 1307 radio sources without a catalogued X-ray counterpart
Compute the Cosmic Star Formation History
Add data from other wavelenghts (optical, IR)
Another 2Ms set of observations of the CDFS has been approved and will be concluded in the next year. This will allow us the improve our analysis with deeper data.

15. Thanks for your attention