The formation of hypercompact ( HC ) H II regions is an important stage in massive star formation .
Spectral line and continuum observations can explore its dynamic conditions .
We present high angular resolution observations carried out with the Submillimeter Array ( SMA ) and the Very Large Array ( VLA ) toward the HC H II region G35.58-0.03 .
With the 1.3 mm SMA and 1.3 cm VLA , we detected a total of about 25 transitions of 8 different species and their isotopologues ( CO , CH _ { 3 } CN , SO _ { 2 } , CH _ { 3 } CCH , OCS , CS , H , and NH _ { 3 } ) .
G35.58-0.03 consists of an HC H II core with electron temperature T _ { e } ^ { * } \geqq 5500 K , emission measure EM \approx 1.9 \times 10 ^ { 9 } pc cm ^ { -6 } , local volume electron density n _ { e } = 3.3 \times 10 ^ { 5 } cm ^ { -3 } , and a same width of radio recombination line FWHM \approx 43.2 { km~ { } s } ^ { -1 } for both H30 \alpha and H38 \beta at its intrinsic core size \sim 3714 AU .
The H30 \alpha line shows evidence of an ionized outflow driving a molecular outflow .
Based on the derived Lyman continuum flux , there should be an early-type star equivalent to O6.5 located inside the H II region .
From the continuum spectral energy distribution from 3.6 cm , 2.0 cm , 1.3 cm , 1.3 mm and 0.85 mm to 0.45 mm , we distinguished the free-free emission ( 25 % \sim 55 % ) from the warm dust component ( 75 % \sim 45 % ) at 1.3 mm .
The molecular envelope shows evidence of infall and outflow with an infall rate 0.05 M _ { \sun } yr ^ { -1 } and a mass loss rate 5.2 \times 10 ^ { -3 } { M _ { \sun } ~ { } yr ^ { -1 } } .
The derived momentum ( \sim 0.05 M _ { \sun } { km~ { } s } ^ { -1 } ) is consistent between the infalling and outflowing gas per year .
It is suggested that the infall is predominant and the envelope mass of dense core is increasing rapidly , but the accretion in the inner part might already be halted .