ASIAA Summer Students Program
ASIAA Summer Student Program 2024
July 1 - August 30

2024 Project Description

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Understand the Origin of the Cosmic Infrared Background Radiation

High-Redshift Galaxies


Wei-Hao Wang
Find out more about supervisors on ASIAA website

Task Description and Goals

The cosmic infrared background (CIB) is the reprocessed radiation output of all young massive stars and accreting supermassive black holes combined throughout the history of the Universe. The intense ultraviolet radiation from these objects was first absorbed by the dust particles in dense interstellar medium, and than re-radiated in the far-infrared. Numerous distant galaxies and their central black holes produced such infrared radiation and the radiation appears as a diffuse background light in low-resolution far-infrared satellite images (the CIB). The intensity of CIB is as strong as the cosmic optical/UV background. This implies that half of the star formation and black hole accretion activities in the Universe is hidden by dust. Without understanding the sources that produced such infrared radiation, we cannot obtain a full picture of the evolution of galaxies and their central black holes in the Universe. Unfortunately, because of the technical challenges in high-resolution infrared observations, even with the largest ground-based and space-based telescopes, we still have not detected all individual galaxies that give rise to the CIB. This forms a large missing piece of our knowledge about galaxy formation and evolution.

In this summer project, we will use an extremely deep submillimeter map observed at a wavelength of 450 micron to study faint far-infrared sources. Even though this is the deepest far-infrared map of the Universe that human ever obtained, individual galaxies detected in this map can only account for ~40% of the CIB at 450 micron. The remaining 60% of CIB comes from fainter undetected sources and is hidden by the noise of the map. We will employ different statistical techniques to detect galaxies fainter than the noise level on this map. The goal is to estimate how many faint galaxies (per unit solid angle) are there and how much they contribute to the CIB. Only after measuring the number of faint far-infrared galaxies, we can determine how many galaxies in the Universe had gone through the infrared phase, how long is that phase, and how much mass in stars and supermassive black holes have grown during that phase. This is an important step toward a full picture of galaxy formation and evolution.

Required Background

The student will be required to use Python to conduct the analyses. The analysis will be statistical. So the student is required to have basic skills on using Python to analyze image data, and also to have basic knowledge in statistics (such as error propagation, weighted mean and median, probability distribution function, and the idea of maximum likelihood).

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