Naomi Hirano (ASIAA); Sheng-Yuan Liu (ASIAA); Tie Liu (SHAO); Chin-Fei Lee (ASIAA); Sienny Shang (ASIAA); Dipen Sahu (ASIAA); Somnath Dutta (ASIAA); Anthony Moraghan (ASIAA); Kai-Syun Jhan (NTU/ASIAA); Shi-Ying Hsu (NTU/ASIAA); Kee-Tae Kim (KASI); Ken'ichi Tatematsu (NRO); Gwanjeong Kim (NRO)
The ALMA Survey of Orion PGCCs (ALMASOP) project observed 72 dense cores including 23 starless cores and 49 protostellar cores in the Orion molecular cloud complex at 1.3 mm. In this presentation, we report the discovery of the dense and compact "nucleus" in the starless core G208.68-19.02-N2 (G208-N2) in the Orion Molecular Cloud 3 (OMC-3). The 1.3 mm continuum emission from G208-N2 shows a narrow filamentary structure with a size of 12" (4,700 au) x 1.5" (590 au) and a mean density of ~8 x 10^7 cm-3. In the middle of this filamentary structure , there is a compact "nucleus" having a size of 1.48" (570 au) x 0.89" (350 au). The nucleus has a mass of ~0.6 M_sun and a mean density of 6 x 10^9 cm if T_dust is assumed to be 6.5 K. There is no signature of outflow in the CO and H2CO images. The C18O emission is completely absent in the entire region of G208-N2. There is no C18O emission localized to the nucleus. The N2D+, the spatial distribution of which is similar to that of the 1.3 mm continuum, also shows the local minimum at the nucleus. These results imply that the dense gas in this nucleus is still cold, where both CO and N2 deplete onto dust grain. It is likely that the nucleus of G208-N2 is still prestellar, probably in the evolutionary stage on the verge of star formation.