Characterizing The Most Extreme Emission Line Galaxies
Characterizing the Most Extreme Emission Line Galaxies
Spring 2014 UROP Proposal
Ian Jaeger
Background
During the first 379,000 years (redshift z = 1089) after the Big Bang, the matter of the universe consisted primarily of free protons, electrons and photons. After the matter had cooled and spread out, these particles combined to form hydrogen and allowed the photons to freely travel without interacting with free electrons, forming what we know of today as the Cosmic Microwave Background (CMB). Between 150 million and 1 billion years after the Big Bang (6 < z < 20), structures such as stars, galaxies and quasars began to form and release energy sufficient enough to reionize Hydrogen in the intergalactic medium (IGM). However, currently no evidence exists to provide a consensus on what specific sources provided the ionizing radiation. Quasars were long thought to be the best candidates, however the density of quasars near z = 6 has been shown to be too small to provide enough energy to alone ionize the IGM (Shapiro, Giroux 1987). Star-forming galaxies must therefore provide most of the energy.
Lyman-alpha emitters (LAEs) have been proposed as a possible source of the energy required for the reionization of the IGM. LAEs are objects that emit Lyman-α (Lyα) radiation, which specifically results from the Hydrogen electron changing from the n = 2 to the n = 1 state. As a result of this transition, a photon of wavelength 1216Å (UV radiation) is emitted. LAEs have been found to also emit Lyman-continuum (Lyc) radiation, which corresponds to wavelengths shorter than 912Å. This wavelength corresponds to the Lyman limit: the energy required to ionize a single Hydrogen atom (Figure 1). In star-forming galaxies, the most common sources of this UV radiation are young, massive stars of the spectral type O and B. These stars are able to ionize the interstellar medium around them, and to produce the so-called HII regions: regions of ionized hydrogen, where recombination
Spring 2014 UROP Proposal
Ian Jaeger
Background
During the first 379,000 years (redshift z = 1089) after the Big Bang, the matter of the universe consisted primarily of free protons, electrons and photons. After the matter had cooled and spread out, these particles combined to form hydrogen and allowed the photons to freely travel without interacting with free electrons, forming what we know of today as the Cosmic Microwave Background (CMB). Between 150 million and 1 billion years after the Big Bang (6 < z < 20), structures such as stars, galaxies and quasars began to form and release energy sufficient enough to reionize Hydrogen in the intergalactic medium (IGM). However, currently no evidence exists to provide a consensus on what specific sources provided the ionizing radiation. Quasars were long thought to be the best candidates, however the density of quasars near z = 6 has been shown to be too small to provide enough energy to alone ionize the IGM (Shapiro, Giroux 1987). Star-forming galaxies must therefore provide most of the energy.
Lyman-alpha emitters (LAEs) have been proposed as a possible source of the energy required for the reionization of the IGM. LAEs are objects that emit Lyman-α (Lyα) radiation, which specifically results from the Hydrogen electron changing from the n = 2 to the n = 1 state. As a result of this transition, a photon of wavelength 1216Å (UV radiation) is emitted. LAEs have been found to also emit Lyman-continuum (Lyc) radiation, which corresponds to wavelengths shorter than 912Å. This wavelength corresponds to the Lyman limit: the energy required to ionize a single Hydrogen atom (Figure 1). In star-forming galaxies, the most common sources of this UV radiation are young, massive stars of the spectral type O and B. These stars are able to ionize the interstellar medium around them, and to produce the so-called HII regions: regions of ionized hydrogen, where recombination