SIMBAD references

Near-infrared imaging photometry supplemented by optical spectroscopy and narrowband imaging of the H II region Sh 2-128 and its environment are presented. This region contains a developed H II region and a neighboring compact H II region associated with a pair of water maser sources. Midway between these, the core of a CO cloud is located. The principal ionizing source of Sh 2-128 is an O7 star close to its center. Slit spectroscopy was used to obtain nebular line fluxes, abundances, and the physical parameters of Sh 2-128. This H II region is optically thin from the optical to the radio and appears to be ionization-bounded. The present JHK_simages show the presence of a number of point sources and nebular emission knots with large near-infrared excesses in the northern Sh 2-128N. One of the three red K_sknots coincides with the compact H II region. A few of the infrared-excess objects are close to known mid- and far-infrared emission peaks. Star counts in J and K_sshow the presence of a small cluster of B-type stars, mainly associated with Sh 2-128N. Except for the youngest, reddest objects, the stars in the whole region are moderately obscured. The JHK_sphotometric properties, together with the characteristics of the other objects in the vicinity, suggest that Sh 2-128 and Sh 2-128N constitute a single complex formed from the same molecular cloud but with ages ∼10⁶ and less than 3x10⁵ yr, respectively. A new spectroscopic distance of 9.4 kpc is derived. This implies a galactocentric distance of 13.5 kpc and z=550. No molecular hydrogen emission was detected at 2.12 µm from any part of the surveyed region.