Publication Date:
2016-10-09
Description:
Using Atacama Large Millimeter/submillimeter Array observations of the C 18 O(2–1) line emission of the gas envelope of protostar L1527, we have reconstructed its morphology and kinematics under the assumption of axisymmetry about the west–east axis. The main original contribution to our understanding of the formation process of L1527 is the presentation of a simple 3D parametrization based solely on regions that are not dominated by absorption. In the explored range (~0.7 to 5 arcsec from the star), the model reproduces observations better than earlier attempts. The main results include: a measurement of the rotation velocity that confirms its evolution to Keplerian towards short distances; a measurement of the mean in-fall velocity, 0.43 ± 0.10 km s –1 , lower than free-fall velocity, with no evidence for the significant r -dependence suggested by an earlier analysis; a measurement of the central mass, 0.23 ± 0.06 M within a distance of 1.5 arcsec from the star, in agreement with earlier estimates obtained from a different range of distances; evidence for a strong disc plane depression of the in-falling flux resulting in an X -shaped flow possibly caused by the freeze-out of CO molecules on dust grains; a measurement of the accretion rate, 3.5 ± 1.0 10 –7 M yr –1 at a distance of 1 arcsec (140 au) from the star; evidence for a 10° tilt of the symmetry plane of the envelope about the line of sight, cancelling below ~3 arcsec from the star, but matching infrared observations and being also apparent on the sky map of the mean Doppler velocity.
Print ISSN:
0035-8711
Electronic ISSN:
1365-2966
Topics:
Physics
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