2011A&A...525A..72F

We carried out sub-arcsecond resolution observations towards the high-mass star formation region G19.61-0.23, in both continuum and molecular line emission. While the centimeter continuum images, representing ultra compact HII regions, will be discussed in detail in a forthcoming paper, here we focus on the (sub)mm emission, devoting special attention to the hot molecular core (HMC). A set of multi wavelength continuum and molecular line emission data between 6cm and 890µm were obtained with the Very Large Array, Nobeyama Millimeter Array, Owens Valley Radio Observatory millimeter array, and Submillimeter Array (SMA). These data were analyzed in conjunction with previously published data. Our SMA observations resolve the HMC into three cores whose masses are on the order of 10¹-10³M_☉. No submm core exhibits detectable free-free emission in the centimeter regime, but appear to be associated with masers and thermal line emission from complex organic molecules. Towards the most massive core, SMA1, the CH₃CN (18_K-17_K) lines provide hints of rotation about the axis of a jet/outflow traced by H₂O maser and H¹³CO⁺(1-0) line emission. Inverse P-Cygni profiles of the ¹³CO (3-2) and C¹⁸O (3-2) lines seen towards SMA1 indicate that the central high-mass (proto)star(s) is (are) still gaining mass with an accretion rate ≥3x10^–3M_☉/yr. Owing to the linear scales and high accretion rate, we hypothesize that we are observing an accretion flow towards a star cluster in the making, rather than towards a single massive star.