TY - JOUR

T1 - The kinematics of NGC 1333-IRAS2A - A true Class O protostar

AU - Brinch, C.

AU - Jørgensen, J. K.

AU - Hogerheijde, M. R.

PY - 2009/7

Y1 - 2009/7

N2 - Context. Low-mass star formation is described by gravitational collapse of dense cores of gas and dust. At some point during the collapse, a disk is formed around the protostar and the disk will spin up and grow in size as the core contracts because of angular momentum conservation. The question is how early the disk formation process occurs Aims. In this paper we aim to characterize the kinematical state of a deeply embedded, Class O young stellar object, NGC 1333-IRAS2A, based on high angular resolution (<1" ≈ 200 AU) interferometric observations of HCN and H13CN J = 4-3 from, the Submillimeter Array, and test whether a circumstellar disk can be detected based on gas kinematic features Methods. We adopt a physical model which has been shown to describe the object well and obtain a fit of a parameterized model of the velocity field, using a two-dimensional axis-symmetric radiation transfer code. The parameterization and fit to the high angular resolution data characterize the central dynamical mass and the ratio of infall velocity to rotation velocity Results. We find a large amount of infall and very little rotation on all scales. The central object has a relatively low mass of 0.25 M⊙. Our best fit is consistent with both the interferometer data and single-dish observations of the same molecule Conclusions. As an object with a low stellar mass compared to the envelope mass, we conclude that NGC 1333-IRAS2A is consistent with the suggestion that, as a Class O object, it represents the earliest stages of star formation. The large amount of infall relative to rotation also suggests that this is a young object. We do however find the need of a central compact component on scales of a few hundred AU based on the continuum data, which suggests that disk formation happens shortly after the initial gravitational collapse The data do not reveal a distinct velocity field for this 0.1 M⊙ component.

AB - Context. Low-mass star formation is described by gravitational collapse of dense cores of gas and dust. At some point during the collapse, a disk is formed around the protostar and the disk will spin up and grow in size as the core contracts because of angular momentum conservation. The question is how early the disk formation process occurs Aims. In this paper we aim to characterize the kinematical state of a deeply embedded, Class O young stellar object, NGC 1333-IRAS2A, based on high angular resolution (<1" ≈ 200 AU) interferometric observations of HCN and H13CN J = 4-3 from, the Submillimeter Array, and test whether a circumstellar disk can be detected based on gas kinematic features Methods. We adopt a physical model which has been shown to describe the object well and obtain a fit of a parameterized model of the velocity field, using a two-dimensional axis-symmetric radiation transfer code. The parameterization and fit to the high angular resolution data characterize the central dynamical mass and the ratio of infall velocity to rotation velocity Results. We find a large amount of infall and very little rotation on all scales. The central object has a relatively low mass of 0.25 M⊙. Our best fit is consistent with both the interferometer data and single-dish observations of the same molecule Conclusions. As an object with a low stellar mass compared to the envelope mass, we conclude that NGC 1333-IRAS2A is consistent with the suggestion that, as a Class O object, it represents the earliest stages of star formation. The large amount of infall relative to rotation also suggests that this is a young object. We do however find the need of a central compact component on scales of a few hundred AU based on the continuum data, which suggests that disk formation happens shortly after the initial gravitational collapse The data do not reveal a distinct velocity field for this 0.1 M⊙ component.

KW - Circumstellar matter

KW - IRAS2A

KW - Ism: Individual objects: Ngc 1333

KW - Ism: Kinematics and dynamics

KW - Line: Profiles

KW - Radiative transfer

UR - http://www.scopus.com/inward/record.url?scp=68349107951&partnerID=8YFLogxK

U2 - 10.1051/0004-6361/200810831

DO - 10.1051/0004-6361/200810831

M3 - Journal article

AN - SCOPUS:68349107951

VL - 502

SP - 199

EP - 205

JO - Astronomy & Astrophysics

JF - Astronomy & Astrophysics

SN - 0004-6361

IS - 1

ER -