Zhen-Kai Gao (ASIAA/NCU); Chen-Fatt Lim (ASIAA/NTU); Wei-Hao Wang (ASIAA); Chian-Chou Chen (ASIAA)
We present the deepest 450 μm galaxy number counts in the COSMOS-CANDELS field derived from the first nearly confusion-limited SCUBA-2 450 μm map from the SCUBA-2 Ultra Deep Imaging EAO Survey (STUDIES). This confusion-limited map covers 530 arcmin2 in area and achieves a noise level at the map center of about 0.6 mJy. We detected 515 sources at 3.5σ with flux densities ranging from ~2 to ~60 mJy. We derived the raw number counts from the directly extracted sources and performed Monte Carlo simulations to recover the intrinsic number counts. Compared to the counts in the literature, our counts extend to flux densities of ~50% fainter and ~40% brighter. We find that the trend of the faint-end counts is still consistent with that in the literature and no faint-end drop-off or flatten-out were observed. This suggests that there remain abundant faint 450 μm sources unresolved by current SCUBA-2 imaging. The bright-end counts are now better constrained to show a steeper turn. To understand the possible evolution of this population, we also compare our counts with those derived from models. The results show reasonable consistency, although minor disagreements may be present. We will also compare the integrated surface brightness from our counts with that measured by COBE and discuss the implication.