A near-infrared (JHK) survey of the vicinity of the H II region NGC 7538: Evidence for a young embedded cluster

We describe the results of two near-infrared (K-band) imaging surveys and a three-color (JHK) survey of the vicinity of NGC 7538. The limiting magnitudes are K ≃ 16.5 and 17.5 mag for the K-band surveys and K ≃ 15 mag for the JHK survey. We identify more than 2000 and 9000 near-infrared (NIR) sources on the images of the two K-band surveys and 786 NIR sources in the JHK survey. From color-color diagrams, we derive a reddening law for background stars and identify 238 stars with NIR excesses. Contour maps indicate a high-density peak coincident with a concentration of stars with NIR excesses. We identify this peak as a young embedded cluster and confirm this result with the K-band luminosity function (KLF), color histograms, and color-magnitude diagrams. The center of the cluster is at R.A. = 23 ^h 13 ^m39 ^s.34, decl. = 61°29′18″9. The cluster radius is ∼3′, ∼2.5 pc for an adopted distance d ≃ 2.8 kpc. For d = 2.8 kpc and reddening E _J-K = 0.55 mag, the slope of the logarithmic KLF of the cluster, s ∼ 0.32 ± 0.03, agrees well with previous results for L1630 (s = 0.34) and M17 (s = 0.26) found by C. Lada, E. Lada, and coworkers.