Infall, outflow, and rotation in the G19.61-0.23 hot molecular core

TL;DR

This study uses high-resolution submillimeter observations to analyze the structure, kinematics, and accretion processes in the hot molecular core G19.61-0.23, revealing multiple cores, signs of rotation, and ongoing mass accumulation.

Contribution

It provides the first detailed sub-arcsecond analysis of G19.61-0.23, identifying multiple cores and evidence of accretion flows in a high-mass star formation region.

Findings

Resolved the hot molecular core into three cores with 10^1-10^3 Msun masses.

Detected rotation and outflow signatures in the most massive core, SMA1.

Observed high accretion rates suggesting cluster formation rather than single-star formation.

Abstract

Aims: The main goal of this study is to perform a sub-arcsecond resolution analysis of the high-mass star formation region G19.61-0.23, both in the continuum and molecular line emission. While the centimeter continuum images 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. Results: Our observations resolve the HMC into three cores whose masses are on the order of 10^1-10^3 Msun. No submm core presents detectable free-free emission in the centimeter regime, but they 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 reveal 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 $ge 3 ~10^{-3}$ Msun/yr. Due to the linear scales and the large values of the accretion rate, we hypothesize that we are observing an accretion flow towards a cluster in the making, rather than towards a single massive star.