Millimeter- and Submillimeter-Wave Observations of the OMC-2/3 Region; I. Dispersing and Rotating Core around an Intermediate-mass Protostar MMS 7

We report the results of H13CO+(1-0), CO(1-0), and 3.3 mm dust continuum observations toward one of the strongest mm-wave sources in OMC-3, MMS 7, with the Nobeyama Millimeter Array (NMA) and the Nobeyama 45 m telescope. With the NMA, we detected centrally-condensed 3.3 mm dust-continuum emission which coincides with the MIR source and the free-free jet. Our combined H13CO+ observations have revealed a disk-like envelope. The size and the mass of the disk-like envelope are 0.15 times 0.11 pc and 5.1 - 9.1 M_sun, respectively. The combined map also shows that the outer portion of the disk-like envelope has a fan-shaped structure which delineates the rim of the CO(1-0) outflow observed with the NMA. The position-velocity (P-V) diagrams in the H13CO+ (1-0) emission show that the velocity field in the disk-like envelope is composed of a dispersing gas motion and a possible rigid-like rotation. The mass dispersing rate is estimated to be (3.4 - 6.0) times 10^-5 M_sun/yr, which implies that MMS 7 has an ability to disperse ~10 M_sun during the protostellar evolutional time of a few times 10^5 yr. The specific angular momentum of the possible rotation in the disk-like envelope is nearly two orders of magnitude larger than that in low-mass cores. The turn-over point of the power law of the angular momentum distribution in the disk-like envelope (< 0.007 pc), which is likely to be related to the outer radius of the central mass accretion, is similar to the size of the 3.3 mm dust condensation. The intermediate-mass protostar MMS 7 is in the last stage of the main accretion phase and that the substantial portion of the outer gas has already been dispersed, while the mass accretion may still be on-going at the innermost region traced by the dusty condensation.Comment: 19 pages, 9 figures, ApJ accepted pape

Studis on the ecology of feeding of the mackerel, Pneumatophorus japonicus I : On the food habit and the selective feeding,

The ecology of feeding of the mackerel, Pneumatophorus japonicus HOUTTUYN, was studied both through the observations of the stomach contents under the natural conditions and feeding experiments in the aquarium, for the purpose of analysing the angling-technique for the school of the pelagic fishes including the important fish species for the commercial fisheries in Japan. The present paper is concerning with the results on the kinds of prey taken by the mackerel and the selective feeding of these preys in the mackerel. The observations on the stomach contents of I ,310 mackerel, caught by trap-net settled in the surrounding wates of Oshika Peninsula and their adjacent waters, Miyagi, during the period from April to October of I 954, revealed the following facts; (1) While prior to the mid July the number of mackerel feeding on Euphausia pacifica was larger than the number of those feeding on the anchovy, Engraulis japonica, the former was smaller than the latter posterior to the mid July. (2) In the period of feeding on Euphausia, there were more individuals with empty stomach than in the period of feeding on the anchovy. Although the sardine, Sardinops melanosticta, and the horse mackerel, Trachurus japonicus, also were found out in the stomachs of the mackerel, the number of individuals having them in the stomach was very much smaller than the number of those having the anchovy in the stomach. (3) The body length of the anchovy taken most abundantly by the mackerel was 26 to 36% of the body length of the mackerel and the body length of the largest one taken by the mackerel was about 50%. The same relations were observed between the body sizes of the mackerel and of the sardine taken by the mackerel. However, the body length of the horse mackerel taken most abundantly by the mackerel was 18% of the body length of the mackerel and the body length of the largest one was smaller than 30%. (4) The largest amount of the stomach contens observed was 16.3% of the body weight of the mackerel. The results of the feeding experiments performed in August indicated that; (1) The mackerel have taken the anchovy and the Euphausia with almost the same intensity of feeding in spite of the period of feeding on the anchovy. (2) The anchovy was taken with very much higher intensity than the horse mackerel by the mackerel