Distributions of Gas and Galaxies From Galaxy Clusters to Larger Scales
CitationPatej, Anna. 2016. Distributions of Gas and Galaxies From Galaxy Clusters to Larger Scales. Doctoral dissertation, Harvard University, Graduate School of Arts & Sciences.
AbstractThis thesis addresses the distributions of baryonic matter on three scales: the outskirts of the gas and galaxy profiles in galaxy clusters, the clustering of galaxies of galaxies on large scales and its relation to the underlying matter distribution, and the extremes of the galaxy distribution: the connections between the most distant galaxies ever discovered and the closest galaxies to our own, the Local Group Dwarfs. We begin with investigations of the outskirts of galaxy clusters, where long-standing analytical models of structure formation as well as recent simulations predict the existence of steep density jumps in the gas (the 'virial shock') and dark matter profiles near the virial radius. We describe a new method for deriving models for the gas distribution in galaxy clusters, which relies on a few basic assumptions --- including the existence of the virial shock and a coincident density jump in the dark matter --- and show a resulting profile for the gas that is in good agreement both with X-ray observations of cluster interiors and simulations of the outskirts, and requires fewer parameters than the traditional three-parameter beta-model.
Recent simulations have strengthened the arguments in favor of the existence of a dark matter density jump, arising from the accumulation of particles at the apocenter of their first orbit. Since cluster member galaxies are expected to follow similar collisionless dynamics as the dark matter, the galaxy density profile should show a steep density jump as well. We present evidence for a feature consistent with a density jump in galaxy density profiles constructed from photometry from the Sloan Digital Sky Survey and Hectospec (MMT) spectroscopy of cluster members and discuss avenues for probing the density jumps with future data sets.
Moving to larger scales where massive galaxies of different types are expected to trace the same large-scale structure, we present a test of this prediction by measuring the clustering of red and blue galaxies at z~0.6 using the CMASS sample of galaxies from the 12th Data Release of SDSS-III. The stochasticity between these two samples is quantified via the correlation coefficient r, which can be constructed from two different statistics. Both statistics indicate that on intermediate scales (20 < R < 100 Mpc/h) there is low stochasticity between the two samples of galaxies, providing a constraint on a key systematic in using large galaxy redshift surveys for cosmology.
In cosmology, dense redshift surveys permit the measurement of the scale of baryon acoustic oscillations (BAO), which appear as a modest amplification at scales of about R = 105 Mpc/h in the two-point auto-correlation function of galaxies, provided that there is a sufficiently high density of galaxies with accurately measured three-dimensional positions. As a result, due to the expense of spectroscopic observations, to date most BAO analyses have been performed at fairly low redshifts where present surveys can attain the requisite densities without sacrificing efficiency. We present a new method of measuring the BAO using the cross-correlation of a sparse spectroscopic sample with a denser, photometric sample of galaxies that will allow us to extend BAO measurements to higher redshifts than are presently accessible with spectroscopy alone. We discuss applications of this new method to current and upcoming datasets.
Finally, we connect galaxies both near --- the Local Group dwarf galaxies --- and far --- the high-redshift galaxies discovered by space-based observatories like Hubble and Spitzer. We evolve the local dwarfs back in time using stellar population synthesis code and juxtapose the properties of their ancient selves against those of the galaxies already discovered at high redshift. We additionally compare the properties of the dwarfs' progenitors with the detection limits of the future James Webb Space Telescope (JWST), finding that JWST should be able to detect the progenitors of galaxies similar to a few of the brightest local galaxies.
Citable link to this pagehttp://nrs.harvard.edu/urn-3:HUL.InstRepos:33493358
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