ALMA 30-mas Data Show Dragon Egg Core C2c1a(a) as Isolated 87-au Compact Peak with No Outflow or Hot-Core Lines

The new data test core-accretion models by pushing resolution an order of magnitude beyond prior NH3 maps. Continuum emission remains unresolved below 175 au while lower-resolution data recover an additional ~110 solar-mass reservoir on 10^4 au scales, implying central densities exceeding 10^9 cm^-3 if temperatures are 10–40 K. No high-velocity CO or SiO outflow is detected and H2CO remains weak and extended, consistent with a still-cold, pre-hot-core phase. Mass estimates swing from 2 to 30 solar masses depending on the adopted temperature gradient, highlighting the dominant uncertainty in optically thick dust emission.

Context from earlier infrared-dark cloud surveys shows that most claimed massive cores fragment at <1000 au, making C2c1a(a) an outlier that either represents an extremely early seed or requires revised fragmentation physics. The 30-mas beam and 1.3 mm sensitivity set a firm upper limit on any undetected companions above ~0.1 solar masses within the primary beam. This places the object in a narrow observational window between massive starless cores and the first detectable protostellar heating.

Next steps include higher-frequency ALMA Band 7/8 imaging to measure the radial temperature profile directly and sensitive JVLA or NOEMA searches for faint free-free or molecular outflow signatures on 100-au scales. A non-detection after 2027 would strengthen the case for a genuine high-mass prestellar core; a detection would reclassify it as the earliest known high-mass protostellar seed.