Spokes cluster: The search for the quiescent gas

Autor(en)

J. E. Pineda, P. S. Teixeira

Abstrakt

Context. Understanding the role of turbulent and thermal fragmentation

is one of the most important current questions of star formation. To

better understand the process of star and cluster formation, we need to

study in detail the physical structure and properties of the parental

molecular cloud. In particular, it is important to understand the

fragmentation process itself; this may be regulated by thermal pressure,

magnetic fields, and/or turbulence. The targeted region, the Spokes

cluster, or NGC 2264-D, is a rich protostellar cluster where previous

N2H+ (1-0) observations of its dense cores

presented linewidths consistent with supersonic turbulence. However, the

fragmentation of the most massive of these cores appears to have a scale

length consistent with that of the thermal Jeans length, suggesting that

turbulence was not dominant. Aims: These two results (derived

from N2H+ (1-0) observations and measurements of

the spatial separations of the protostars) probe different density

regimes. Our aim is to determine if there is subsonic or less-turbulent

gas (than previously reported) in the Spokes cluster when probing higher

densities, which would reconcile both previous observational results. To

study denser gas it is necessary to carry out observations using

transitions with a higher critical density to directly measure its

kinematics. Methods: We present APEX N2H+

(3-2) and N2D+ (3-2) observations of the NGC

2264-D region to measure the linewidths and the deuteration fraction of

the higher density gas. The critical densities of the selected

transitions are more than an order of magnitude higher than that of

N2H+ (1-0). Results: We find that the

N2H+ (3-2) and N2D+ (3-2)

emission present significantly narrower linewidths than the emission

from N2H+ (1-0) for most cores. In two of the

spectra, the nonthermal component is close (within 1-σ) to the

sound speed. In addition, we find that the three spatially segregated

cores for which no protostar had been confirmed show the highest levels

of deuteration. Conclusions: These results show that the higher

density gas, probed with N2H+ and

N2D+ (3-2), reveals more quiescent gas in the

Spokes cluster than previously reported. More high-angular resolution

interferometric observations using high-density tracers are needed to

truly assess the kinematics and substructure within NGC 2264-D.

 

This publication is based on data acquired with the Atacama Pathfinder

Experiment (APEX) under programme 088.F-9322A. APEX is a collaboration

between the Max-Planck-Institut für Radioastronomie, the European

Southern Observatory, and the Onsala Space Observatory.

Organisation(en)

Institut für Astrophysik

Externe Organisation(en)

European Southern Observatory (Germany), University of Manchester

Journal

Astronomy & Astrophysics

Band

555

Anzahl der Seiten

7

ISSN

0004-6361

DOI

https://doi.org/10.1051/0004-6361/201220861

Publikationsdatum

07-2013

Peer-reviewed

Ja

ÖFOS 2012

103004 Astrophysik, 103003 Astronomie

Schlagwörter

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/c764d7fa-645e-4e4d-a1fc-0d6f082cccad