Ammonia Emission in Various Star-forming Environments: A Pilot Study of Planck Galactic Cold Clumps

O Fehér,Yuefang Wu,Di Li,Naomi Hirano,Ken’Ichi Tatematsu,Alex Kraus,Sheng-Yuan Liu,L Viktor Tóth,Victor Tóth,Gwanjeong Kim,Kee-Tae Kim,David J Eden,Tie Liu,Rebeka Bőgner,Mika Juvela

doi:10.3847/1538-4365/ac3337

Abstract

Abstract The Planck Catalogue of Galactic Cold Clumps provides an all-sky sample of potential star-forming regions based on the submillimeter emission of their dust content. Around 1000 of these Planck objects were mapped with the James Clerk Maxwell telescope in the submillimeter range during the SCOPE survey, identifying prestellar and protostellar dense clumps inside them. We used the Effelsberg 100 m telescope to observe the emission lines of the NH3 inversion transitions toward a sample of 97 dense objects in varying environments in order to assess the physical parameters of their gas content. We derive their temperature, density, and velocity dispersion, correlating the resulting parameters with the environmental and evolutionary characteristics of the targets and with regard to their distance and physical size. We examine the dependence of physical parameters on distance and Galactic position and compare the gas-based and dust-continuum-based temperatures and densities. Together with the presence of maser emission and higher inversion transitions of ammonia, we may differentiate between certain groups of targets, e.g., filamentary, protostellar clumps, and high-latitude, core-sized, starless sources.

Highlights

The initial conditions inside star-forming clouds determine the number and parameters of the stars forming in it (Bergin 2007)
We find more multiple velocity components (MVCs) at the Galactic plane, which is expected owing to the higher chance of overlapping molecular clouds in the line of sight in this region
As a pilot study of Planck Galactic Cold Clumps (PGCCs), we have observed three ammonia inversion transitions with the Effelsberg 100 m radio antenna toward 97 cold, dense objects selected from the TOP-SCUBA-2 Continuum Observations of Pre-protostellar Evolution (SCOPE) sample of PGCCs

Summary

Introduction

The initial conditions inside star-forming clouds determine the number and parameters of the stars forming in it (Bergin 2007). According to the Planck data, the objects show temperatures of T = 6–20 K and hydrogen column densities of N(H2) = 1020–1023 cm−2, with sizes ranging from 0.1 pc to over 10 pc and masses from below 0.1 Me to over 104 Me. Several studies have been made to investigate the morphology, dust properties, and the characteristics and kinematics of the gas content in subsets of the Planck catalog (Juvela et al 2012b; Wu et al 2012; Meng et al 2013; Montillaud et al 2015; Juvela et al 2015a, 2015b) or of well-known complex molecular regions in the framework of these new data, like the Heiles Cloud 2 (Tóth et al 2004; Fehér et al 2016)

Objectives

Results

Conclusion