372 research outputs found
Observations of B335 in the Millimeter Continuum and the 226 GHz H2CO Line
The protostar B335 was observed in the 1.3 mm continuum and in the H2CO 312 -
211 line with an angular resolution of about 8 arcsec. The mass of the inner
envelope detected by the dust continuum emission is about 0.02 Msun. The H2CO
spectrum at the protostellar position shows a blue-skewed double peak profile,
suggesting that the kinematics of the inner envelope is dominated by infall
motion. When the blueshifted and the redshifted peaks were imaged separately,
however, there is a small east-west displacement between the maximum positions.
This displacement suggests that some part of the H2CO emission might come from
the outflowing gas. A combined effect of the infalling envelope and the outflow
on the radiative transfer is discussed. This effect can make the line profile
asymmetry severer than what is expected from infall-only models
Radio Imaging of the NGC 1333 IRAS 4B Region
The NGC 1333 IRAS 4B region was observed in the 6.9 mm and 1.3 cm continuum
with an angular resolution of about 0.4 arcseconds. IRAS 4BI was detected in
both bands, and BII was detected in the 6.9 mm continuum only. The 1.3 cm
source of BI seems to be a disk-like flattened structure with a size of about
50 AU. IRAS 4BI does not show any sign of multiplicity. Examinations of
archival infrared images show that the dominating emission feature in this
region is a bright peak in the southern outflow driven by BI, corresponding to
the molecular hydrogen emission source HL 9a. Both BI and BII are undetectable
in the mid-IR bands. The upper limit on the far-IR flux of IRAS 4BII suggests
that it may be a very low luminosity young stellar object.Comment: To appear in the JKA
Ammonia Imaging of the Disks in the NGC 1333 IRAS 4A Protobinary System
The NGC 1333 IRAS 4A protobinary was observed in the ammonia (2, 2) and (3,
3) lines and in the 1.3 cm continuum with a high resolution (about 1.0 arcsec).
The ammonia maps show two compact sources, one for each protostar, and they are
probably protostellar accretion disks. The disk associated with IRAS 4A2 is
seen nearly edge-on and shows an indication of rotation. The A2 disk is
brighter in the ammonia lines but dimmer in the dust continuum than its sibling
disk, with the ammonia-to-dust flux ratios different by about an order of
magnitude. This difference suggests that the twin disks have surprisingly
dissimilar characters, one gas-rich and the other dusty. The A2 disk may be
unusually active or hot, as indicated by its association with water vapor
masers. The existence of two very dissimilar disks in a binary system suggests
that the formation process of multiple systems has a controlling agent lacking
in the isolated star formation process and that stars belonging to a multiple
system do not necessarily evolve in phase with each other
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