Poster Presentation

Unearthing the Hidden: Number Counts of Dusty Galaxies below Noise

Author(s): Chia-Ching Lin (National Central University; ASIAA) Wei-Hao Wang (ASIAA)

Presenter: Chia-Ching Lin (National Central University; ASIAA)

We use the deepest 450 μm imaging to date from the JCMT STUDIES program in COSMOS, together with JWST F444W galaxy catalogs, to quantify the contribution of faint galaxies to the cosmic infrared background (CIB). We stack the 450 μm map at the positions of more than 130,000 faint 4.44 μm–selected galaxies and estimate the background using simulations with randomly distributed sources. Simple stacking yields an average flux of 0.093±0.002 mJy, consistent with extrapolations from brighter-source number counts but likely biased high by confusion and source clustering. We therefore apply a simultaneous stacking and deblending analysis to account for overlapping emission on beam scales. This reduces the mean flux by around 50% to 0.043±0.001 mJy. Combined with the contribution from individually detected brighter sources, the deblended result corresponds to a total surface brightness of 139.9 Jy deg^-2, recovering 103% of the CIB measured by COBE and Planck (compared to 173% from simple stacking). These results showed that deblended stacking can effectively correct flux overestimation and provide more reliable constraints on the faint source contribution to the CIB.