Deep Fields

Chair: Valentina Vacca (OAC INAF)

Deep radio observations with LOFAR are a key resource to probe extragalactic sources and cosmic magnetism across a variety of environments and redshifts.

In order to obtain the deepest images ever at LOFAR frequencies, we obtained 240 h (60 h still to be observed in Cycle 15) on the GOODS-North field (Fig. 1). These data will enable to address open questions on cosmic magnetism, to characterize extragalactic source populations and to estimate for the first time the polarization source counts at 144 MHz.

A new technique to combine multi-epoch deep field LOFAR observations has been recently developed and applied to the ELAIS-N1 (Fig. 2), enabling to increase by a factor ~3 the number of polarized sources with respect to a single-epoch observation (Herrera-Ruiz et al. 2020).


Preliminary results from the GOODS-North and ELAIS-N1 fields

Figure 1: GOODS-N field (1.5deg x 1.5deg) over the full HBA bandwidth, 6 arcsec resolution, 70μJy/beam rms noise (Image credit: Tessa Vernstrom).

Figure 2: Faraday spectra of one of the polarized sources detected in the ELAIS-N1 deep field for different numbers of stacked epochs.The dotted horizontal lines represent the corresponding 8σ_QU levels. The vertical gray area represents the range around φ=0 rad/m2 excluded from the analysis due to instrumental polarization (Herrera Ruiz et al. 2020).