We present high angular resolution ( \sim 1 ″ ) multi-tracer spectral line observations toward the hot core associated with G34.26+0.15 between 87–109 GHz .
We have mapped emission from ( i ) complex nitrogen- and oxygen-rich molecules like CH _ { 3 } OH , HC _ { 3 } N , CH _ { 3 } CH _ { 2 } CN , NH _ { 2 } CHO , CH _ { 3 } OCH _ { 3 } , HCOOCH _ { 3 } ; ( ii ) sulfur-bearing molecules like OCS , SO and SO _ { 2 } ; and ( iii ) the recombination line H53 \beta .

The high angular resolution enables us to directly probe the hot molecular core associated with G34.26+0.15 at spatial scales of 0.018 pc .
At this resolution we find no evidence for the hot core being internally heated .
The continuum peak detected at \lambda = 2.8 mm is consistent with the free-free emission from component C of the ultracompact H ii region .
Velocity structure and morphology outlined by the different tracers suggest that the hot core is primarily energized by component C. Emission from the N- and O-bearing molecules peak at different positions within the innermost regions of the core ; none are coincident with the continuum peak .
Lack of high resolution complementary datasets makes it difficult to understand whether the different peaks correspond to separate hot cores , which are not resolved by the present data , or manifestations of the temperature and density structure within a single core .

Based on the brightness temperatures of optically thick lines in our sample , we estimate the kinetic temperature of the inner regions of the HMC to be 160 \pm 30 K. Comparison of the observed abundances of the different species in G34.26+0.15 with existing models does not produce a consistent picture .
There are uncertainties due to : ( i ) the unavailability of temperature and density distribution of the mapped region within the hot core , ( ii ) typical assumption of centrally peaked temperature distribution for a hot core with an accreting protostar at the center , by the chemical models , an aspect not applicable to externally heated hot cores like G34.26+0.15 and ( iii ) inadequate knowledge about the formation mechanism of many of the complex molecules .