Studying high-redshift galaxies with ALMA: biases due to complex source structure and companion sources

Since the arrival of millimeter wave interferometers and their subsequent advancement, the resolution of observations has improved significantly. However, the effects of these improvements have not yet been investigated. This research examines the effect of improving resolutions to SubMillimeter Galaxies (SMGs) like simulated Gaussian sources. To achieve this, simulated 350 GHz ALMA observations with 20 different antenna configurations with resolutions ranging from 0.05 to 1.1 arcsec of simulated Gaussian sources performed with CASA are used. For resolutions better than 0.2 arcsec, depending on the SNR, the flux and size from observations obtained with an image plane analysis, where the size is found using CASA, can be significantly lower than the true flux and size, due to the largest angular scale of the observations. Fitting a circular Gaussian to the uv-plane data demonstrates that the $uv$-plane analysis more accurately recovers the true FWHM than the image plane analysis using...Show moreSince the arrival of millimeter wave interferometers and their subsequent advancement, the resolution of observations has improved significantly. However, the effects of these improvements have not yet been investigated. This research examines the effect of improving resolutions to SubMillimeter Galaxies (SMGs) like simulated Gaussian sources. To achieve this, simulated 350 GHz ALMA observations with 20 different antenna configurations with resolutions ranging from 0.05 to 1.1 arcsec of simulated Gaussian sources performed with CASA are used. For resolutions better than 0.2 arcsec, depending on the SNR, the flux and size from observations obtained with an image plane analysis, where the size is found using CASA, can be significantly lower than the true flux and size, due to the largest angular scale of the observations. Fitting a circular Gaussian to the uv-plane data demonstrates that the $uv$-plane analysis more accurately recovers the true FWHM than the image plane analysis using CASA. However, the major and minor axes of an elliptical source are not recovered and the size of an elliptical source is overestimated with the uv-plane analysis. Different SMG companion fields from the ALESS and UDS survey originally observed by Hodge et al. (2013), Simpson et al. (2015) and Wardlow et al. (2018) and quasar fields with a companion detected by Decarli et al. (2017) were simulated with circular Gaussian sources to examine the influence of companion sources to the FWHM of the main source acquired with the $uv$-plane analysis. Generally, the companions in the companion fields examined do not show an influence on the FWHM of the main source.Show less

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Studying high-redshift galaxies with ALMA: biases due to complex source structure and companion sources