Which instrument detected intense star formation within dust-enshrouded galaxies in the HDF sample using infrared capabilities?

Spitzer.

While Hubble gathered the primary optical data for the Deep Fields, follow-up observations using other specialized Great Observatories provided crucial complementary information about the environment within those distant fields. The Spitzer Space Telescope, which observes in the infrared spectrum, was able to penetrate the dense shrouds of cosmic dust that often hide active stellar nurseries. By analyzing the HDF field with Spitzer, astronomers successfully detected galaxies that were intensely forming stars but were obscured from Hubble's visible light view. Similarly, the Chandra X-ray Observatory provided data on active galactic nuclei and elliptical galaxies within the sample.