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 23rd

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
• bserve 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

• Look more carefully at line profile
• Look for characteristic cutoff in imaging

Has to be verified that an emission line is a galaxy

Beta is related to ultraviolet light output

• All light with wavelength

shorter than around 900 angstroms (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]) log(Luminosity [erg s-1 Å-1])

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

Wavelength [Å] Flux

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

• f this mechanism

<Bouwens R. J. et al., 2010a, ApJ, 708, L69>

Acknowledgements

Crystal Martin Alaina Henry Arica Lubin