Kinematics and Chemistry of the Hot Molecular Core in G34.26+0.15 at High Resolution

Abstract

We present high angular resolution ($1 00 ) multitracer spectral line observations toward the hot molecular core (HMC) associated with G34.26+0.15 between 87 and 109 GHz. We have mapped emission from (1) complex nitrogenand oxygen-rich molecules such as CH 3 OH, HC 3 N, CH 3 CH 2 CN, NH 2 CHO, CH 3 OCH 3 , and HCOOCH 3 ; (2) sulfurbearing molecules such as OCS, SO, and SO 2 ; and (3) the recombination line H53 . At this high resolution (0.018 pc) we find no evidence for the HMC being internally heated. The continuum peak detected at k ¼ 2:8 mm is consistent with the free-free emission from component C of the ultracompact H ii region, which primarily energizes the HMC. Emissions from the N-and O-bearing molecules peak at different positions within the core; none is coincident with the continuum peak. Lack of high-resolution complementary data sets makes it difficult to decipher whether the different peaks correspond to separate hot cores not resolved by the present data, or whether they are manifestations of the temperature and density structure within a single core. Using brightness temperatures of the optically thick lines in our sample, we estimate the kinetic temperature of the inner regions of the HMC to be 160 AE 30 K. Observed abundances of the different chemical species are not consistently reproduced by the existing hot-core models. There are uncertainties due to (1) unavailability of temperature and density distribution within the hot core, (2) the assumption of a centrally peaked temperature distribution by the chemical models, which is not applicable to externally heated hot cores such as G34.26+0.15, and (3) inadequate knowledge about the formation mechanism of many of the complex molecules.

Millimetre spectral line mapping observations towards four massive star-forming H ii regions

“…5); this shocked region and the tracer velocity are in agreement with the results of the study of SiO in Hatchell et al (2001). Their emitting region corresponds to a cometary CH II region, which is called C in the literature (Mookerjea et al 2007). Fig.…”

“…The cloud contains 1.1 × 10 4 M of dense gas (Hill et al 2005), and has a luminosity of 3.2 × 10 5 L (van der Tak et al 2013), with an age of a few × 10 4 yr (Paron et al 2009). From radio continuum observations, this source shows two very condensed UCH II regions (called A and B), a more evolved CH II region with a cometary shape (called C) and an extended ringlike H II region (called D) (Reid & Ho 1985;Mookerjea et al 2007). There are several outflows in G34, as evidenced by SiO emission extending to the north-west, south-east and north-east of the CH II region (Hatchell, Fuller & Millar 2001).…”

A high-resolution study of complex organic molecules in hot cores

“…Chemical differentiation in hot cores has been observed before (Mookerjea et al 2007;Garay & Lizano 1999) and attributed to either differences in their host star mass and/or differences in ages. Results of chemical models in the past have suggested that determining abundance ratios of typical hot core tracers (e.g.…”

Water deuterium fractionation in the high-mass star-forming region G34.26+0.15 based on Herschel/HIFI data

“…Several components have been identified in radio continuum observations: two ultra compact HII regions called A and B, a more evolved HII region with a cometary shape (component C), and an extended (1 ) HII region (component D) in the south-east. Chemical surveys were carried out towards the A, B and C components using single-dish telescopes (MacDonald et al 1996;Hatchell et al 1998) and interferometric observations (Mookerjea et al 2007). Many complex species, characteristic of hot cores, have been detected.…”

“…Many complex species, characteristic of hot cores, have been detected. From molecular line observations, the emission peak does not coincide with the HII components (Watt & Mundy 1999;De Buizer et al 2003), but is shifted to the East of the component C by ∼1 (Mookerjea et al 2007: Figure 3). This difference may arise due to the external influence of the nearby HII regions, or may reveal separate regions of chemical enrichment.…”