Review critically the Science Traceability Matrix and derive the final values of the Scientific

The main objectives are:

• Selection function: demonstrate validity of statistically representative sample hypothesis
• Estimate number of satellites/streams to be discovered compared to state-of-the-art ground-based observations
• Full simulation of the observation sequence to ensure adequate depth in all images for the complete galaxy sample.
• Optimize procedure to observe the maximum number of galaxies in 2 years.
• Identify the preferred “window” for the broader community access to ARRAKIHS while minimizing the impact on the main science program.
• Define the sequence for calibrations and data transmission to the ground stations.
• Apply procedure to possible extension of mission to 5 years: 
  • (i) increase MW-galaxy sample over larger distances;
  • (ii) include galaxies over a range of galaxy masses; and/or 
  • (iii) include galaxy clusters at z=0.2 for splash-back radius studies in coordination with CATARSIS.

The main objectives are:

• Demonstrate the optimumstatistical galaxy background subtraction, including confusion-limit
• Identify the halo satellite population and evaluate statistical uncertainty.
• Doordinate with SAGA survey access to their brighter sample of confirmed satellites to investigate biases and uncertainties in our procedures.
• Define the statistical significance of planar distributions vs randomdistributions and orientations

 Investigate uncertainties in modelling ages/metallicities of the stellar populations of satellites using the four bands adopted in ARRAKIHS.

The main objectives are:

• To define an objective criterion for estimating stellar streams frequency in our observed sample and in the mock catalogue images obtained from cosmological simulations for different baryonic physics/dark matter parameters.
• To develop an automatic algorithm for the detection and morphological classification (based on the method of spray-particles) of stream parameters, which should supplement the current ones by visual inspection.
• To establish a criterion to estimate the contamination by ‘galactic feathers’ in the observed stream samples.
• To derive an accurate photometry of characterize streams with Gnuastro for the ARRAKIHS imaging and to develop a robust method for measuring their stellar mass and stellar population properties.
• To fit with spray-particle models those complex (full) streams (eg several loops) which can allow the measurement of density and flattening of the dark matter halo of their host galaxy.
• To determine the possibility of detecting gaps in low streams around nearby galaxies with ARRAKIHS and select the best galaxy targets for doing it (distance, orientation, etc).
• Using the tools described above, to quantify how the stream frequency vs. surface brightness limit for Milky Way galaxies would allow establish a diagnostic of the hierarchical galaxy formation scenario predicted by the CDM/WDM, which is sensitive to the baryonic physics and dark matter nature used in these models. 

The main objectives are:

• Demonstrate how the magnitude and color of the IHL can be computed and used to estimate the low-redshift stellar contribution from that of early sources.
• Derive the constraints that stellar tidal streams in the local Universe offer on ab initio cosmological simulations and how those constraints can provide detailed predictions for the integrated diffuse emission arising from galaxy formation.

The main objectives are:

• Under different assumptions for dark matters (LCDM, WDM, SIDM, etc), keeping everything else (treatment of baryons) the same, assess for each case, 
  • (i) the expected number of satellites and their mass distribution, (ii) the number of streams and shapes.
• Predict luminosities and colours in the ARRAKIHS filters.
• Identify the best observable discriminants between different scenarios of DM.

The main objectives are:

• Wpdated CCD and H2RG detectors systematic noise for the final operating temperature and readout effects.
• Full straylight characterization and subtraction, especially the ghost image effect due to the galaxy bulge.
• Final simulations of ARRAKIHS observation including data reduction for: 
  • (i) single galaxy halo in different orientations; 
  • (ii) different galaxies; and
  • (iii) different cosmologies.
• Derive the statistical descriptor from our observations that can best discriminate between the different cosmological model predictions.
• Validate with current deep observations (HST/HSC) the reference stellar catalogue at faint magnitudes VIS < 31, as a function of colour and galactic latitude.

The main objectives are:

• Coordinate with Euclid/Planck the assessment of this effect at the scale of our FOV.
• Expand the analysis of Roman,Trujillo & Montes to the four bands adopted in ARRAKIHS.

The main objectives are:

• Design and optimize the data reduction pipeline, including correction for darks, flats, background subtraction and removal of stray-light and ghost images.
• Place limits on the location and brightness of sources within and outside the FOV to minimize stray-light contamination.
• Characterize the PSF across the FOV and wavelength range and characterize its stability.
• Implement and optimize algorithms for super-resolution.

• Develop an automatic algorithm using AI/ML techniques for the detection and morphological classification of stream parameters, which should supplement the current ones by visual inspection.
• Determine the method to differentiate narrow vs broad streams.
• Derive luminosity functions of satellite galaxies function of color, etc.
• Define the method to estimate the statistical significance planar distributions.

• Establish formal agreement of collaboration with Euclid and Roman.
• Identify areas of interest for both observatories where ARRAKIHS will provide competitive advantage.
• Develop joint science cases for those areas with joint science teams.
• Include such areas as part of the broader access to ARRAKIHS by the community and schedule these observations in CONOPS.