Redshift $z=9--10$ object selection is the effective limit of Hubble Space Telescope imaging capability, even when confirmed with Spitzer. If only a few photometry data points are available, it becomes attractive to add criteria based on their morphology in these J- and H-band images. One could do so through visual inspection, a size criterion, or alternate morphometrics. We explore a vetted sample of BoRG $zsim9$ and $zsim10$ candidate galaxies and the object rejected by Morishita+ (2018) to explore the utility of a size criterion in z=9-10 candidate selection. A stringent, PSF-corrected effective radius criterion ($r_e<0farcs3$) would result in the rejection of 65-70% of the interlopers visually rejected by Morishita+. It may also remove up to $sim20$% of bona-fide brightest ($L>>L^*$) z=9 or 10 candidates from a BoRG selected sample based on the Mason+ (2015) luminosity functions, assuming the Holwerda+ (2015) $zsim9$ size-luminosity relation. We argue that including a size constraint in lieu of a visual inspection may serve in wide-field searches for these objects in e.g. EUCLID or HST archival imaging with the understanding that some brightest ($L>>L^*$) candidates may be missed. The sizes of the candidates found by Morishita+ (2018) follow the expected size distribution of $zsim9$ for bright galaxies, consistent with the lognormal in Shibuya+ (2015) and single objects. Two candidates show high star-formation surface density ($Sigma_{SFR} > 25 M_odot/kpc^2$) and all merit further investigation and follow-up observations.
تحميل البحث