Degree-Scale Galactic Radio Emission at 122 MHz around the North Celestial Pole with LOFAR-AARTFAAC. (arXiv:2112.00721v1 [astro-ph.IM])

Degree-Scale Galactic Radio Emission at 122 MHz around the North Celestial Pole with LOFAR-AARTFAAC. (arXiv:2112.00721v1 [astro-ph.IM])
<a href="http://arxiv.org/find/astro-ph/1/au:+Gehlot_B/0/1/0/all/0/1">B. K. Gehlot</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Koopmans_L/0/1/0/all/0/1">L. V. E. Koopmans</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Offringa_A/0/1/0/all/0/1">A. R. Offringa</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gan_H/0/1/0/all/0/1">H. Gan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ghara_R/0/1/0/all/0/1">R. Ghara</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Giri_S/0/1/0/all/0/1">S. K. Giri</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kuiack_M/0/1/0/all/0/1">M. Kuiack</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mertens_F/0/1/0/all/0/1">F. G. Mertens</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mevius_M/0/1/0/all/0/1">M. Mevius</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mondal_R/0/1/0/all/0/1">R. Mondal</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pandey_V/0/1/0/all/0/1">V. N. Pandey</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Shulevski_A/0/1/0/all/0/1">A. Shulevski</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wijers_R/0/1/0/all/0/1">R. A. M. J. Wijers</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Yatawatta_S/0/1/0/all/0/1">S. Yatawatta</a>

Aims: Contamination from bright diffuse Galactic thermal and non-thermal
radio emission poses crucial challenges in experiments aiming to measure the
21-cm signal of neutral hydrogen from the Cosmic Dawn (CD) and Epoch of
Reionization (EoR). If not included in calibration, this diffuse emission can
severely impact the analysis and signal extraction in 21-cm experiments. We
examine large-scale diffuse Galactic emission at 122~MHz, around the North
Celestial Pole, using the Amsterdam-ASTRON Radio Transient Facility and
Analysis Centre (AARTFAAC)- High Band Antenna (HBA) system.

Methods: In this pilot project, we present the first-ever wide-field image
produced with a single sub-band of the data recorded with the AARTFAAC-HBA
system. We demonstrate two methods: multiscale CLEAN and shapelet
decomposition, to model the diffuse emission revealed in the image. We use
angular power spectrum metric to quantify different components of the emission
and compare the performance of the two diffuse structure modelling approaches.

Results: We find that multiscale CLEAN is suitable to model the compact and
diffuse structures on a wide range of angular scales, whereas the shapelet
decomposition method better models the large scales, which are of the order of
a few degrees and wider.The point sources dominate the angular power spectrum
of the emission in the field on scales $ellgtrsim100$ ($lesssim 2$~degree),
and the diffuse emission dominates on scales with $elllesssim200$. The
diffuse emission has a brightness temperature variance of $Delta^2_{ell=180}
= (145.64 pm 13.45)~{rm K}^2$ at 122~MHz on angular scales of 1~degree, and
is consistent with a power-law following $C_{ell}propto ell^{-2.0}$.

Aims: Contamination from bright diffuse Galactic thermal and non-thermal
radio emission poses crucial challenges in experiments aiming to measure the
21-cm signal of neutral hydrogen from the Cosmic Dawn (CD) and Epoch of
Reionization (EoR). If not included in calibration, this diffuse emission can
severely impact the analysis and signal extraction in 21-cm experiments. We
examine large-scale diffuse Galactic emission at 122~MHz, around the North
Celestial Pole, using the Amsterdam-ASTRON Radio Transient Facility and
Analysis Centre (AARTFAAC)- High Band Antenna (HBA) system.

Methods: In this pilot project, we present the first-ever wide-field image
produced with a single sub-band of the data recorded with the AARTFAAC-HBA
system. We demonstrate two methods: multiscale CLEAN and shapelet
decomposition, to model the diffuse emission revealed in the image. We use
angular power spectrum metric to quantify different components of the emission
and compare the performance of the two diffuse structure modelling approaches.

Results: We find that multiscale CLEAN is suitable to model the compact and
diffuse structures on a wide range of angular scales, whereas the shapelet
decomposition method better models the large scales, which are of the order of
a few degrees and wider.The point sources dominate the angular power spectrum
of the emission in the field on scales $ellgtrsim100$ ($lesssim 2$~degree),
and the diffuse emission dominates on scales with $elllesssim200$. The
diffuse emission has a brightness temperature variance of $Delta^2_{ell=180}
= (145.64 pm 13.45)~{rm K}^2$ at 122~MHz on angular scales of 1~degree, and
is consistent with a power-law following $C_{ell}propto ell^{-2.0}$.

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