Galaxy Structural Parameters: Star Formation Rate and Evolution with Redshift

Details Galaxy Structural Parameters: Star Formation Rate and Evolution with Redshift Galaxy Structural Parameters: Star Formation Rate and Evolution with Redshift

Dec 1998

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998phdt.........1t&link_type=abstract

Thesis (PHD). THE UNIVERSITY OF CHICAGO , Source DAI-B 59/07, p. 3498, Jan 1999, 178 pages.

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Scientific paper

The evolution of the structure of galaxies as a function of redshift is studied in this thesis. Two structural parameters are considered: the metric radius of the galaxy (Rη) and the power at high spatial frequencies (/chi) in the disk of the galaxy. A direct comparison is made between nearby (z~ 0) and distant (0.2~5/pm1 kpc and the median radius of the HDF sample is < Rη>~6/pm2 kpc for qo=0.5/ Ho=65/ km/ s-1/ Mpc-1, however for qo=0.1/ < Rη>~7 kpc and for qo=1/ < Rη>~5 kpc. Among the HDF galaxies, the galaxies with redshifts larger than z>0.6 have flatter Rη distributions than galaxies with redshifts smaller than z<=0.6. However, the median Rη values of high and low redshift galaxies are consistent with each other. This result is consistent with the simulations of galaxy images at redshifts z=0.35,/ z=0.5 and z=0.9 which show that the metric sizes can be recovered within ±2 kpc. The flocculency or power at high spatial frequencies is quantified using a simple method that is based on surface photometry in one band and that depends on the size of the star-forming regions and on the intensity profile of the galaxy. In nearby galaxies, the flocculency is found to trace the star formation rate as χ is correlated with optical colors (B-V) and the strength of the hydrogen recombination lines (Hα). For HDF galaxies at redshifts smaller than z~1 and with fluxes brighter than B = 25,/ /chi reaches values similar to what is measured in nearby galaxies and to what is expected from simulations of distant galaxy images. Among the HDF galaxies, I find that at most 4% can be identified as dwarf galaxies with rates of star formation similar to NGC 4449 or NGC 1569. Most HDF galaxies are giants with star formation rates similar to those in nearby giant galaxies. In summary, in this study I have introduced a method to measure the metric sizes and flocculency of the two-dimensional light distribution of galaxies. As a result, I find that the high spatial frequency power is related to the star formation rate. Further, I find that the sizes and power at high spatial frequencies of HDF galaxies remain largely unchanged at redshifts lower than z~1.

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