Molecular outflows and hot molecular cores in G24.78+0.08 at sub-arcsecond angular resolution

Abstract

Context. This study is part of a large project to study the physics of accretion and molecular outflows towards a selected sample of high-mass star-forming regions that show evidence of infall and rotation from previous studies. Aims. We wish to make a thorough study at high-angular resolution of the structure and kinematics of the HMCs and corresponding molecular outflows in the high-mass star-forming region G24.78+0.08. Methods. We carried out SMA and IRAM PdBI observations at 1.3 and 1.4 mm, respectively, of dust and of typical high-density and molecular outflow tracers with resolutions of <1 . Complementary IRAM 30-m 12 CO and 13 CO observations were carried out to recover the short spacing information of the molecular outflows. Results. The millimeter continuum emission towards cores G24 A1 and A2 has been resolved into three and two cores, respectively, and named A1, A1b, A1c, A2, and A2b. All these cores are aligned in a southeast-northwest direction coincident with that of the molecular outflows detected in the region, which suggests a preferential direction for star formation in this region. The masses of the cores range from 7 to 22 M , and the rotational temperatures from 128 to 180 K. The high-density tracers have revealed the existence of two velocity components towards A1. One of them peaks close to the position of the millimeter continuum peak and of the HC Hii region and is associated with the velocity gradient seen in CH 3 CN towards this core, while the other one peaks southwest of core A1 and is not associated with any millimeter continuum emission peak. The position-velocity plots along outflow A and the 13 CO (2-1) averaged blueshifted and redshifted emission indicate that this outflow is driven by core A2. Core A1 apparently does not drive any outflow. The knotty appearance of the highly collimated outflow C and the 12 CO position-velocity plot suggest an episodic outflow, where the knots are made of swept-up ambient gas.

Chasing discs around O-type (proto)stars: Evidence from ALMA observations

“…7. In this figure it is clear that the gas velocity in the core is red-shifted to the north and blue-shifted to the south, a result which looks different from the NE-SW velocity gradient found by Beltrán et al (2004Beltrán et al ( , 2005Beltrán et al ( , 2011b. Such a difference is likely due to the different uv coverage of the various data sets.…”

“…Various studies (Beltrán et al 2004(Beltrán et al , 2005(Beltrán et al , 2011b have provided evidence of up to three rotating cores in the region observed with ALMA. Here, we focus on the most prominent core (A1, following the notation by Beltrán et al 2005) containing the hypercompact Hii region studied by Beltrán et al (2007) and indicated by a cross in Fig.…”

Accretion disks in luminous young stellar objects

“…When increasing the resolution to ∼0. 5, the emission of source A1 fragments into three separate sources (Beltrán et al, 2011b). Consequently, the mass of the rotating structure is reduced by a factor ten, while the radius of the rotating structure reduces by almost a factor 3 to 1800 au.…”

“…; g M estimated from the fitting of the velocity field assuming Keplerian rotation; h The mass of this core has been estimated from CS (Bernard et al, 1999); i M estimated from the mass infall rate and the dynamical age of the outflow; j V rot estimated from CH 3 OH maser emission; k ∆V estimated from single-dish observations (Beuther et al, 2002a). l Beltrán et al (2011b) estimated a mass of 22-48 M (for a dust opacity of 1 cm 2 g −1 ) and a radius of 1500 au with PdBI and SMA higher angular resolution (∼ 0. 5) observations.…”

“…5) observations. m Beltrán et al (2011b) estimated a mass of 13 M (for a dust opacity of 1 cm 2 g −1 ) and a radius of 1800 au with PdBI and SMA higher angular resolution (∼ 0. 5) observations.…”