What is the Lyman break technique?
The Lyman-break galaxy selection technique relies on the fact that radiation at higher energies than the Lyman limit at 912 Å is almost completely absorbed by neutral gas around star-forming regions of galaxies.
What are Lyman alpha photons?
Lyman α is light Radiation consists of light particles, or photons, which are small packets of energy. The higher the energy, the higher the frequency, but the shorter the wavelength, and vice versa. The different terms are just different ways of talking about the light.
What causes the Lyman alpha forest?
The Lyman-alpha absorption lines in the quasar spectra result from intergalactic gas through which the galaxy or quasar’s light has traveled. Each individual cloud leaves its fingerprint as an absorption line at a different position in the observed spectrum.
What is the 4000 angstrom break?
A primary feature is the strong break at 4000A (Angstroms), caused by the blanket absorption of high energy radiation from metals in stellar atmospheres and by a deficiency of hot, blue stars. A smoothly varying function can easily be fit to spectra, with a clear drop off in intensity at 4000A.
Why is Lyman-alpha important?
Lyman-alpha emissions convey a major part of the solar-flare photon energy reaching Earth and play a significant role in flare-driven enhancements of ionospheric conductivity.
How is the Lyman-alpha line split due to fine structure?
Fine structure Because of the spin–orbit interaction, the Lyman-alpha line splits into a fine-structure doublet with the wavelengths of 1215.668 and 1215.674 angstroms. Thus, the j = 32 state is associated with the more energetic (having a shorter wavelength) spectral line in the doublet.
What is a Lyman limit system?
From Wikipedia, the free encyclopedia. The Lyman limit is the short-wavelength end of the hydrogen Lyman series, at 91.2 nm (912 Å). It corresponds to the energy required for an electron in the hydrogen ground state to escape from the electric potential barrier that originally confined it, thus creating a hydrogen ion.
How many elliptical galaxies are there?
Observations of 46 elliptical galaxies, 20 classical bulges, and 22 pseudobulges show that each contain a black hole at the center.
What is a Balmer break?
The Balmer jump, Balmer discontinuity, or Balmer break is the difference of intensity of the stellar continuum spectrum on either side of the limit of the Balmer series of hydrogen, at approximately 364.5 nm.
What is the rest wavelength of the Lyman-alpha absorption line?
1216 Å
The Lyman-alpha spectral line has a laboratory, or rest, wavelength of 1216 Å, which is in the ultraviolet portion of the electromagnetic spectrum. The Lyman-alpha absorption lines in the quasar spectra result from intergalactic gas through which the galaxy or quasar’s light has traveled.
What wavelength is the Lyman-alpha?
122 nm
There are clouds of gas between distant quasars and the Earth that absorb ultraviolet light at the wavelength of the Lyman alpha line of hydrogen at a wavelength of 122 nm.
What causes Lyman alpha emission?
The Lyman-alpha line in most LAEs is thought to be caused by recombination of interstellar hydrogen that is ionized by an ongoing burst of star-formation. Such Lyman alpha emission was first suggested as a signature of young galaxies by Bruce Partridge and P. J. E. Peebles in 1967.