X-ray clues on the nature of sub-mm galaxies. I.Georgantopoulos INAF/OABO A Comastri INAF/OABO E. Rovilos MPE. Outline. What are the sub-mm galaxies SMGs ? What can the X-ray observations tell us about SMGs? (Alexander et al claim that sub-mm galaxies present a phase of co-eval
A Comastri INAF/OABO
E. Rovilos MPE
(Alexander et al claim that sub-mm galaxies present a phase of co-eval
growth of black holes and star-formation).
2. Level of Obscuration
3. What is the major power-mechanism that produces the Bolometric luminosity ?
Large PSF and associated uncertainties in source position 8 arcsec
(see reviews by Maiolino 2008, Blain+02)
Chapman+05 did a breakthrough observing radio positions of SMGs and then observing counterparts with Keck z=2-3
(altough Daddi+09, Capak+08 find counterparts even at z=4-5)
The median luminosity is ~1013 Lsolar
Spitzer IRS spectra show star-forming spectra (Pope+08)
under a veil of dust ?
(a mixture of SMGs with radio positions and
Radio sources with sub-mm detection)
Laird et al find instead a lower fraction of X-ray detections
among ‘true’ SMGs while they claim that many of the X-ray sources are normal galaxies (not AGN)
Here we attempt to address anew these issues in the CDFS
Which is the field with the deepest X-ray observations ever.
(2 MS Chandra + another 2Ms starting in June)
(4 Chandra 200ksec observations around the CDFS)
(3 Ms of XMM observations)
Spitzer IRAC and MIPS observations
Sub-mm observations at 870 μm LABOCA camera APEX telescope.
128 sources detected in the area of the eCDFS
Maximum-Likelihood Method for the association between MIPS and LABOCA
Galaxies are sources
with low luminosity and
Open circles denote
the X-ray classified
very close to the estimates of Laird et al.
IMPLYING THAT THE MAJORITY OF SMGs ARE STARFOMING
Hardness Ratio -0.40 corresponding to Γ~1.4 (or NH~1022 cm-2)
This suggests that most of the undetected SMGs are galaxies
Significant absorption among the AGN
Hash= upper limits
Star-formation is the
dominant power mechanism
A torus is needed in most cases at
24 μm but the IR luminosity is
dominated by the SFR component
in agreement with Laird+09 in the CDFN