EDA2 159 MHz Map

Description

We present two 159 MHz all-sky maps as products from the all-sky spherical harmonic transit interferometric survey performed with the Engineering Development Array 2 (EDA2). The maps are created with a maximum angular resolution of 3.1 degrees and are systematic bias and noise corrected. These maps have < 0.5 K measured thermal noise and are super sampled on a 0.91-degree pixel grid. One map consists of purely EDA2 data, covering the sky < 60 degrees in declination, with a global sky component of 247 K added to account for the missing largest scale. The other map covers the whole sky and is prior fit with a rescaled version of the 408 MHz reprocessed desourced and destriped Haslam map (Remazeilles et al. 2015) smoothed to the EDA2 angular resolution. The maps have been created using the m-mode formalism. Along with the sky maps, we also provide a spectral index map calculated relative to the reprocessed Haslam map at 408 MHz and a total intensity noise map.

There are four sets of two files each notated by HPXbin or HPX2D. HPXbin denotes the native HEALPix binary fits file representation. HPX2D denotes the data reorganized into a 2D fits image with the HPX coordinate system (through HPXcvt). The four data products are as follows:

• EDA2_159MHz_I_wPrior - Stokes I 159 MHz EDA2 sky map including the prior sky model in the imaging process.
• EDA2_159MHz_I_noPrior - Stokes I 159 MHz EDA2 sky map imaged without the use of a prior; however, a 247 K offset is added to account for the largest scale the EDA2 is not sensitive to at this frequency.
• noise_map - a noise map obtained through differencing the visibilities, with terrestrial and other common-mode noise removed (as described in Section 4.1 in the paper).
• EDA2prior159_Haslam408_SI - a spectral index map obtained through rescaling our map to the reprocessed 408 MHz Haslam map by Remazeilles et al. (as described in Section 5.6 in the paper).

More details can be found in:

Imaging the Southern Sky at 159 MHz using Spherical Harmonics with the Engineering Development Array 2", Kriele et al. 2022, PASA, 39, 17. PASA