We present the observational results from the 43-GHz Very Long Baseline Array ( VLBA ) observations of 124 compact radio-loud active galactic nuclei ( AGNs ) that were conducted between 2014 November and 2016 May .
The typical dimensions of the restoring beam in each image are about 0.5 mas \times 0.2 mas .
The highest resolution of 0.2 mas corresponds to a physical size of 0.02 pc for the lowest redshift source in the sample .
The 43-GHz very long baseline interferometry ( VLBI ) images of 97 AGNs are presented for the first time .
We study the source compactness on mas and sub-mas scales , and suggest that 95 sources in our sample are suitable for future space VLBI observations .
By analyzing our data supplemented with other VLBA AGN surveys from literature , we find that the core brightness temperature increases with increasing frequency below a break frequency \sim 7 GHz , and decreases between \sim 7–240 GHz but increases again above 240 GHz in the rest frame of the sources .
This indicates that the synchrotron opacity changes from optically thick to thin .
We also find a strong statistical correlation between radio and \gamma -ray flux densities .
Our correlation is tighter than those in literature derived from lower-frequency VLBI data , suggesting that the \gamma -ray emission is produced more co-spatially with the 43-GHz VLBA core emission .
This correlation can also be extrapolated to the un-beamed AGN population , implying that a universal \gamma -ray production mechanism might be at work for all types of AGNs .