We derive fundamental parameters of the embedded cluster DBSB 48 in the southern nebula Hoffleit 18 and the very young open cluster Trumpler 14 , by means of deep JH K _ { s } infrared photometry .
We build colour-magnitude and colour-colour diagrams to derive reddening and age , based on main sequence and pre-main sequence distributions .
Radial stellar density profiles are used to study cluster structure and guide photometric diagram extractions .
Field-star decontamination is applied to uncover the intrinsic cluster sequences in the diagrams .
Ages are inferred from K-excess fractions .
A prominent pre-main-sequence population is present in DBSB 48 , and the K-excess fraction f _ { K } = 55 \pm 6 \% gives an age of 1.1 \pm 0.5 Myr .
A mean reddening of A _ { K _ { s } } = 0.9 \pm 0.03 was found , corresponding to A _ { V } = 8.2 \pm 0.3 .
The cluster CMD is consistent with the far kinematic distance of 5 kpc for Hoffleit 18 .
For Trumpler 14 we derived similar parameters as in previous studies in the optical , in particular an age of 1.7 \pm 0.7 Myr .
The fraction of stars with infrared excess in Trumpler 14 is f _ { K } = 28 \pm 4 \% .
Despite the young ages , both clusters are described by a King profile with core radii \mbox { $R _ { core } $ } = 0.46 \pm 0.05 pc and \mbox { $R _ { core } $ } = 0.35 \pm 0.04 pc , respectively for DBSB 48 and Trumpler 14 .
Such cores are smaller than those of typical open clusters .
Small cores are probably related to the cluster formation and/or parent molecular cloud fragmentation .
In DBSB 48 , the magnitude extent of the upper main sequence is \Delta \mbox { $K _ { s } $ } \approx 2 mag , while in Trumpler 14 it is \Delta \mbox { $K _ { s } $ } \approx 5 mag , consistent with the estimated ages .