Identifying Engines of Reionization For the Intergalactic Medium - PowerPoint PPT Presentation

Identifying Engines of Reionization For the Intergalactic Medium Jacob Martin Mentor: Alaina Henry Faculty Advisor: Crystal Martin Physics Department Thursday, August 23 rd

Ionization of hydrogen is poorly understood ● Hydrogen clouds were ionized during the epoch of reionization ● Hydrogen is ionized by ultraviolet light ● We want to try and observe the source of this light </imagine.gsfc. nasa. gov/docs/sats_n_d ata/satellites/jwst_d arkages.htm>l

Finding faint galaxies is easier said than done ● Galaxies from reionization are extremely faint, making them difficult to identify ● Surveys which look for emission lines are extremely sensitive, but have the drawbacks of not covering a very large amount of sky, and being sensitive to emissions from the atmosphere

Has to be verified that an emission line is a galaxy ● Look more carefully at line profile ● Look for characteristic cutoff in imaging

Beta is related to ultraviolet light output ● All light with wavelength shorter than around 900 angstroms (1 log(Luminosity [erg s -1 Å -1 ]) angstrom=10 -10 m) from the galaxies we view is absorbed in ionizing neutral hydrogen ● Slope of light emitted just before cutoff, called beta, relates to ionizing light emitted log(Wavelength [Å])

One approach I have tried is looking at survey images ● We wanted to see if our galaxies are resolved in previous images taken of the area ● If they were we would then measure their fluxes in multiple bands of wavelengths to derive a value of beta

Now I am analyzing spectra for trends ● We are utilizing the continua of emission lines taken previously while analyzing the profile ● A procedure known as stacking can be used to try and resolve an average continua for our galaxies, even though the individual continua is not visible ● Stacking averages data to see trends in the overall 'noise'

Spectra must first be fit to determine the line's redshift Flux Wavelength [Å]

Beta values will be significant to Cosmologists ● Beta is affected by metallicity, population age, and dust from nebula ● If we find a very blue value of beta this means that there is some mechanism which is neutralizing nebular continuum ● Cosmologists can then use our data as a constraint for models of this mechanism <Bouwens R. J. et al., 2010a, ApJ, 708, L69>

Acknowledgements Crystal Martin Alaina Henry Arica Lubin