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The point-spread function (PSF) of the synthesized beam used in all tests, overlaid with contours of the main lobe of the primary beam at 80%, 60%, 40%, and 20% power. Tests were run with an array of 34 antennas, observing 40 snapshots over the course of 2 hours.
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Many aspects of the Atacama Large Millimeter Array (ALMA) instrument are still unknown due to its young age. One such aspect is the true nature of the primary beam of each baseline, and how changes to the individual primary beams affect astronomical observations when said changes are ignored during imaging. This paper aims to create a more thorough...
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The maximum entropy method (MEM) is a well known deconvolution technique in radio-interferometry. This method solves a non-linear optimization problem with an entropy regularization term. Other heuristics such as CLEAN are faster but highly user dependent. Nevertheless, MEM has the following advantages: it is unsupervised, it has an statistical bas...
Citations
... In addition, a systematic uncertainty due to the uncertainties in the primary beam of around 1% is expected for primary beam levels below 50% (Dirk Petry, private communication), such as where the star and northwest point source are located. However, as this is negligible compared to the flux calibration uncertainty (see also Kundert et al. 2017), this is not taken into account. For the positional accuracy we use Equation 10.7 from Cortes et al. (2022) ...
\epsilon$ Eridani is the closest star to our Sun known to host a debris disc. Prior observations in the (sub-)millimetre regime have potentially detected clumpy structure in the disc and attributed this to interactions with an (as yet) undetected planet. However, the prior observations were unable to distinguish between structure in the disc and background confusion. Here we present the first ALMA image of the entire disc, which has a resolution of 1.6"$\times$1.2". We clearly detect the star, the main belt and two point sources. The resolution and sensitivity of this data allow us to clearly distinguish background galaxies (that show up as point sources) from the disc emission. We show that the two point sources are consistent with background galaxies. After taking account of these, we find that resolved residuals are still present in the main belt, including two clumps with a $>3\sigma$ significance -- one to the east of the star and the other to the northwest. We perform $n$-body simulations to demonstrate that a migrating planet can form structures similar to those observed by trapping planetesimals in resonances. We find that the observed features can be reproduced by a migrating planet trapping planetesimals in the 2:1 mean motion resonance and the symmetry of the most prominent clumps means that the planet should have a position angle of either ${\sim10^\circ}$ or ${\sim190^\circ}$. Observations over multiple epochs are necessary to test whether the observed features rotate around the star.
... This in part can be due to the "purity" of the samples selected for analysis. Even though there is theoretical support for a relation between high magnitude gap and early accretion of a significant fraction of the system's mass (e.g., D'Onghia et al. 2005), Δm 1,2 alone is not a necessary condition for the system to be identified as an FG (e.g., Dariush et al. 2010), since the majority of them will lose the magnitude gap in a few gigayears, i.e., the magnitude gap of an individual system is highly transitory (Kundert et al. 2017;Gozaliasl et al. 2014b;von Benda-Beckmann et al. 2008). Therefore, this selection criterion is prone to be affected by many physical and observational systematics. ...
... The infall of new galaxies by the group may reduce the magnitude gap while the opposite may happen due to bright galaxy mergers with the BCG. The simple orbital motion of member galaxies will produce a variance in the gap that can be as high as 2 mags (Kundert et al. 2017;Raouf et al. 2014). Furthermore, this type of selection is susceptible to galaxy membership misidentification and/or poor completeness (Voevodkin et al. 2010). ...
Fossil groups (FG) of galaxies still present a puzzle to theories of structure formation. Despite the low number of bright galaxies, they have relatively high velocity dispersions and ICM temperatures often corresponding to cluster-like potential wells. Their measured concentrations are typically high, indicating early formation epochs as expected from the originally proposed scenario for their origin as being older undisturbed systems. This is, however, in contradiction with the typical lack of expected well developed cool cores. Here, we apply a cluster dynamical indicator recently discovered in the intracluster light fraction (ICLf) to a classic FG, RX J1000742.53+380046.6, to assess its dynamical state. We also refine that indicator to use as an independent age estimator. We find negative radial temperature and metal abundance gradients, the abundance achieving supersolar values at the hot core. The X-ray flux concentration is consistent with that of cool core systems. The ICLf analysis provides an independent probe of the system’s dynamical state and shows that the system is very relaxed, more than all clusters, where the same analysis has been performed. The specific ICLf is about 6 times higher, than any of the clusters previously analyzed, which is consistent with an older noninteractive galaxy system that had its last merging event within the last ∼5 Gyr. The specific ICLf is predicted to be an important new tool to identify fossil systems and to constrain the relative age of clusters.
... [1], [2], [3], [4]). The present plan is to extend the goals of the QUIJOTE-CMB Experiment ( [5], [6], [7], [8]) by building a new microwave spectrometer in the frequency range [10][11][12][13][14][15][16][17][18][19][20] GHz. The measurement of the CMB spectrum to the accuracy that will reveal interesting science is particularly difficult because there are many uncertainties that lead to effects of the order of this level. ...
... The instrumental thermal-noise due to finite integration times or shot-noise, intrinsic to the CMB photons distribution can be mitigated by daily stacking of a given sky region data since they are randomn effects. Systematics given by pointing calibration, beam characterization, gain and bandwidth mismatch, component non-ideality, etc., become the largest non negligible contribution to uncertainty as the randomn noise is reduced by integration (e.g., [9], [10], [11], [12]). The systematics generally lie below the noise level through daily observation and can only be seen after various days of stacking data. ...
... where V 1 is considered the reference of the differential phase-shifts and φ ε i j is the relative phase-shift error between two i, j circuits. From (10), and considering that 3DC = V1 + V2 + V3 so 3DC ε = V 1 ε + V 2 ε + V 3 ε it is possible to obtain, after some trigonometry, the analytical expression for the error in the estimation of the DC. This is ...
The QUIJOTE Experiment was developed to study the polarization in the Cosmic Microwave Background (CMB) over the frequency range of 10-50 GHz. Its first instrument, the Multi Frequency Instrument (MFI), measures in the range 10-20 GHz which coincides with one of the naturally transparent windows in the atmosphere. The Tenerife Microwave Spectrometer (TMS) has been designed to investigate the spectrum between 10-20 GHz in more detail. The MFI bands are 2 GHz wide whereas the TMS bands will be 250 MHz wide covering the complete 10-20 GHz range with one receiver chain and Fourier spectral filter bank. It is expected that the relative calibration between frequency bands will be better known than the MFI channels and that the higher resolution will provide essential information on narrow band interference and features such as ozone. The TMS will study the atmospheric spectra as well as provide key information on the viability of ground-based absolute spectral measurements. Here the novel Fourier transform spectrometer design is described showing its suitability to wide band measurement and $\sqrt{N}$ advantage over the usual scanning techniques.
... [1], [2], [3], [4]). The present plan is to extend the goals of the QUIJOTE-CMB Experiment ( [5], [6], [7], [8]) by building a new microwave spectrometer in the frequency range [10][11][12][13][14][15][16][17][18][19][20] GHz. The measurement of the CMB spectrum to the accuracy that will reveal interesting science is particularly difficult because there are many uncertainties that lead to effects of the order of this level. ...
... The instrumental thermal-noise due to finite integration times or shot-noise, intrinsic to the CMB photons distribution can be mitigated by daily stacking of a given sky region data since they are randomn effects. Systematics given by pointing calibration, beam characterization, gain and bandwidth mismatch, component non-ideality, etc., become the largest non negligible contribution to uncertainty as the randomn noise is reduced by integration (e.g., [9], [10], [11], [12]). The systematics generally lie below the noise level through daily observation and can only be seen after various days of stacking data. ...
... where V 1 is considered the reference of the differential phase-shifts and φ ε i j is the relative phase-shift error between two i, j circuits. From (10), and considering that 3DC = V1 + V2 + V3 so 3DC ε = V 1 ε + V 2 ε + V 3 ε it is possible to obtain, after some trigonometry, the analytical expression for the error in the estimation of the DC. This is ...
ε Eridani is the closest star to our Sun known to host a debris disc. Prior observations in the (sub-)millimetre regime have potentially detected clumpy structure in the disc and attributed this to interactions with an (as yet) undetected planet. However, the prior observations were unable to distinguish between structure in the disc and background confusion. Here we present the first ALMA image of the entire disc, which has a resolution of 1.6″×1.2″. We clearly detect the star, the main belt and two point sources. The resolution and sensitivity of this data allow us to clearly distinguish background galaxies (that show up as point sources) from the disc emission. We show that the two point sources are consistent with background galaxies. After taking account of these, we find that resolved residuals are still present in the main belt, including two clumps with a >3σ significance – one to the east of the star and the other to the northwest. We perform n-body simulations to demonstrate that a migrating planet can form structures similar to those observed by trapping planetesimals in resonances. We find that the observed features can be reproduced by a migrating planet trapping planetesimals in the 2:1 mean motion resonance and the symmetry of the most prominent clumps means that the planet should have a position angle of either ∼10○ or ∼190○. Observations over multiple epochs are necessary to test whether the observed features rotate around the star.
The QUIJOTE Experiment was developed to study the polarization in the Cosmic Microwave Background (CMB) over the frequency range of 10-50 GHz. Its first instrument, the Multi-Frequency-Instrument (MFI), measures in the range 10-20 GHz which coincides with one of the naturally transparent windows in the atmosphere. The Tenerife Microwave Spectrometer (TMS) has been designed to investigate the spectrum between 10-20 GHz in more detail. The MFI bands are 2 GHz wide whereas the TMS bands will be 250 MHz wide covering the complete 10-20 GHz range with one receiver chain and Fourier spectral filter bank. It is expected that the relative calibration between frequency bands will be better known than the MFI channels and that the higher resolution will provide essential information on narrow band interference and features such as ozone. The TMS will study the atmospheric spectra as well as provide key information on the viability of ground-based absolute spectral measurements. Here the novel Fourier transform spectrometer design is described showing its suitability to wide band measurement and √N advantage over the usual scanning techniques.
