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28-06-2018
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Colloquium - X-ray, mm and radio wavelength observations of the nuclear activity in lensed dusty star forming galaxies

Submitter: Marcella Massardi
Description: According to co-evolutionary scenarios, nuclear activity and star formation play relevant roles in the early stages of galaxy formation. I will show how it is possible to exploit high-resolution and high-sensitivity X-ray, millimeter and radio-wavelength data to confirm the presence or absence of star formation and nuclear activity in high redshift galaxies and describe their relative roles in shaping the spectral energy distributions and in contributing to the energy budgets of the galaxies.

I will present the data, model, and analysis in the X-ray and millimeter (mm) bands for two strongly lensed galaxies, SDP.9 (HATLAS J090740.0-004200) and SDP.11 (HATLAS J091043.1-000322), selected in the Herschel-ATLAS catalogs for their excess emission in the mid-IR regime at redshift ≳1.5. This emission suggests nuclear activity in the early stages of galaxy formation. We observed both of them with Chandra ACIS-S in the X-ray regime and analyzed the high-resolution mm data that are available in the ALMA Science Archive for SDP.9 (see the figure). By combining the information available in mm, optical, and X-ray bands, we reconstructed the source morphology.

By taking advantage of the lensing magnification, we identify weak nuclear activity associated with high-z galaxies with high star formation rates. This is useful to extend the investigation of the relationship between star formation and nuclear activity to two intrinsically less luminous high-z star-forming galaxies than was possible so far. Given our results for only two objects, they alone cannot constrain the evolutionary models, but provide us with interesting hints and set an observational path toward addressing the role of star formation and nuclear activity in forming galaxies. We plan to complement the multi-band investigation for a larger sample of objects with the radio band information on the AGN activity. I will present preliminary results obtained with ATCA and archival data for the FIR-radio correlation in lensed galaxies and discuss the possibilities that will be offered by SKA to constrain the galactic evolutionary scenario.
Copyright: Colloquium
 
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