arXiv subjects

Z. X. Chang

Publications and source records attributed to Z. X. Chang.

2 recordsLinked to original sources

arXiv2025

A distance measurement of galaxies from JWST using star formation rate-stellar mass relation

We use the star formation rate-stellar mass relation ($SFR - {M_ * }$) of galaxies to measure their luminosity distances as well as estimate cosmological parameters. We compile a sample of 341 high-redshift galaxies at $5 < z < 14$ and an additional 51 galaxies at $1.8 < z < 3.5$ from the JWST observations, which can be used to investigate the correlation between the star formation rate and stellar mass, and determine their cosmological distance. The relation $SFR \propto {\kern 1pt} {({M_ * }/{M_ \odot })^γ}$ can be applied to check the nonlinear correlation between the star formation rate and stellar mass ${M_ * }$ of galaxies and give their distance. Additionally, it also can be used to test if the $SFR - {M_ * }$ relation depends on redshift, and the data suggest that the $SFR $ is positively correlated with stellar mass, the $SFR - {M_ * }$ relation of the high-redshift galaxies has a redshift dependence. Finally, we combine the galaxy sample with Type Ia supernova (SNIa) data from the Pantheon compilation to test the property of dark energy, specifically addressing whether its density deviates from the constant, and give the statistical analysis results.

astro-ph.CO↗

arXiv2023

A cosmological distance measure using radio-loud quasars

We use the X-ray luminosity relation of radio-loud quasars (RLQs) to measure these luminosity distances as well as estimate cosmological parameters. We adopt four parametric models of X-ray luminosity to test luminosity correlation for RLQs and radio-intermediate quasars (RIQs) and give these cosmological distances. By Bayesian information criterion (BIC), the data suggest that the luminosity relation ${L_X} \propto L_{UV}^{γ_{uv}}L_{Radio}^{γ_{radio}'}$ for RLQs has better goodness of fit, relative to other models, which can be interpreted as this relation being preferred for RLQs. Meanwhile, we compare the results from flat-spectrum radio-loud quasars (FSRLQs) and steep-spectrum radio-loud quasars (SSRLQs), which indicate that their luminosity correlations are not exactly the same. We also consider dividing the RLQs sample into various redshift bins, which can be used to check if the X-ray luminosity relation depends on the redshift. Finally, we apply a combination of RLQs and SNla Pantheon to verify the nature of dark energy concerning whether or not its density deviates from the constant, and give the statistical results.

astro-ph.CO↗