OH and H2O masers in star forming regions are important because they are readily detectable indicators of star formation and because they provide unique information on the kinematics and physical conditions in high density regions (106 – 1010 cm−3) surrounding young stars, regions which cannot be studied by other means at present. The Jodrell Bank MERLIN interferometer has been used to map a sample of OH and H2O masers associated with bipolar molecular outflows. The maps of Cepheus A show that the masers are closely associated with the densest compact H II regions at the centre of the flow. The masers appear to be located at the inner edges of the circumstellar disk thought to play a role in collimating the outflow. It is suggested that the H2O masers trace the interaction between the stellar wind and the dense molecular gas, and the OH masers trace shocks propagating into the molecular gas. Rapid and sometimes correlated variations in the maser emission suggest that radiative pumping is likely in this source (Rowland and Cohen, Mon. Not. R. Astr. Soc. in press). Study of the other sources is still in progress.

The observed H2, CO, OI(63 μm), SiII(34.8 μm) and H51α emission line intensities in the BN-KL region of Orion are modeled as arising from two types of shock waves. The molecular emission arises from non-dissociative shocks with low peak postshock temperatures (< 3000 K), traveling at speeds of vs ∼ 40 km/s into ambient gas of density n0∼105-6 cm−3 and transverse magnetic field B0 ∼0.5 milligauss. The OI(63 μm), Sill(34.8 μm) and H51α emission arises in the cooling regions behind faster (∼80 km/s) dissociative shocks with high peak postshock temperatures (∼105 K) and with preshock densities n0 >3x104 cm−3.

Observations of molecular outflows from regions of star formation show that they cannot be radiatively driven ((Ṁv)mol ≥ 102 – 103 (L./c)). The thrust observed to be associated with the smaller scale ionized outflows is also incapable of driving the molecular gas ((Ṁv)ion ≃ (L./c), Persson et al 1984). The results may be explained if bipolar flows are hydromagnetic winds from molecular disks around protostars. These winds carry off disk rotational energy (observed as the mechanical energy of the outflows) and angular momentum (observed when rotation of the outflowing gas is found), which drives an accretion flow through it and onto the protostellar core (Pudritz 1985, Pudritz and Norman 1983, 1986). Therefore star formation and bipolar outflows occur simultaneously when magnetized, rotating disks are the source of activity.

Using the Mepsicron detection system, we obtained images of the region around Herbig-Haro objects 1 and 2. These images were taken with interference filters centred on Hα, on the red continuum (6648 A) and on the [S II] line at 6731 A.

HH39 is the group of Herbig-Haro (HH) objects associated with the young semi-stellar object R Monocerotis (R Mon) and the variable reflection nebula NGC 2261. An R CCD frame and a B prime focus plate of the region show a filament connecting NGC 2261 with HH39, confirming the association between R Mon and the HH objects. This filament is probably composed of emission material. The southern knot in HH39 has brightened over the last 20 years; its proper motion has been determined and is similar to that of the other knots. A total of 8 knots can be distinguished in HH39 surrounded by diffuse nebulosity. High resolution spectroscopy of the Hα and [N II] emission lines shows the spatial variation of the radial velocity structure over the largest knots (HH39 A and C). Distinct differences in excitation and velocity structure between the knots are apparent. The observations are compatible with the knots being high velocity ejecta from R Mon, decelerated by interaction with ambient material and with bow shocks on their front surfaces.

So far discoveries of Herbig-Haro objects were done mainly by either of two different methods. The first relies on their non-stellar appearances on direct photographs, followed by low-dispersion slit spectroscopy; this is the most standard method. But sometimes only the former step is made; then picked-up objects are possible HH objects (e.g. Gyul'budagyan 1982, and Reipurth 1985). The second is based on objective-prism observations in the red with Schmidt telescopes. We have invented a third method to find new HH objects. This utilizes Schmidt telescopes, too, but can reach a fainter limiting-magnitude than that obtained with objective-prism observations.

Most of our understanding of BPF's is based on observations of the neutral and ionized gas in bright, high luminosity sources. Data on low luminosity (L ≲ 30 L⊙) objects has now become more available (e.g. Frerking and Langer, Astrophys. J. 256, 523, 1982) permitting a test of models at this end of the luminosity range. We have performed a series of multi-wavelength observations, emphasizing low luminosity objects.

The class of Low-Excitation Herbig-Haro Objects are characterised by [SII] and [OI] lines which are comparable in strength to H-Alpha, by [NI] lines that are comparable to H-Beta, relatively weak [NII] and [OII] lines, little or no [OIII] emission and a very strong blue-UV “excess”. This blue and UV continuum in low-excitation HH Objects was noted as a problem by Brugel, Böhm and Mannery (1981), Ortalani and D'Odorico (1980) and Böhm, Böhm-Vitense and Brugel (1981). The first suggestion that it results from collisionally enhanced Hydrogen two-photon (2q) continuum was by Dopita (1981). The subsequent observations of Dopita, Binette and Schwartz (1982) proved that this was indeed the case. However, although very close correlations between this enhancement and the emission-line spectrum were found, a fair theoretical description could only be obtained for very youthful shock models with ages of order 30 years. However, there seems to be no reason why low excitation HH shocks should be much younger than the high excitation shocks.

There is excellent evidence that jets originate in protostars of low mass (M ∼ M⊙). Flow speeds are typically of order a few 100 km s−1; the energy for the motion must be generated close to or below the stellar surface, where the escape velocity is of the same order. Here it will be argued that the origin of the jets is connected with the thermodynamics of the accreted gas as it settles towards equilibrium. At some distance below the photosphere, in a spherically symmetrical star, the opacity of the material becomes so high that the outward flow of radiant energy is too slow to balance the inward convection of thermal energy. Consequently there can be no equilibrium, and the symmetry must be broken. The occurrence of jets can be led back to this effect, and the power required to drive them restores the energy balance.

We have made 15″ resolution observations of CO J = 1-0 emission toward L723 and S140 using the Nobeyama 45-m radio telescope. The maps resolved the molecular flow structures clearly. The outflow in the S140 molecular cloud was resolved to be a bipolar structure with its axis being nearly perpendicular to the elongation of the dense core observed in CS emission and to the direction of the infrared polarization. The blueshifted and redshifted components in L723 were resolved into two pairs of bipolar outflows with a point-symmetric structure.

We have made HCO+ (J = 1-0), HCN (J = 1-0) and CS (J = 2-1) observations of a bipolar flow source GL490 (Lada and Harvey 1981; Snell et al. 1984) using the Nobeyama 45-m telescope with 20″ resolution. A HCO+ spectrum obtained toward a central infrared source (Harvey et al. 1979) has prominent line wings extending up to 15-25 km s−1 from the line center (Figure 1). Figure 2 shows a map of HCO+ high velocity emission more than 8 km s−1 off the line center. The emission has “head-tail”-structures in both the blue- and the red-shifted sides; a “head” with stronger emission and a “tail” with weaker narrow ridge emission extending to the opposite side of the “head” through the center. The “head” emission has the same bipolar structure as the CO flow. Intermediate velocity emission at 38 km s−1 from the line center shows (1) a narrow ridge elongated in the NE-SW direction, at the blue-shifted side, and (2) a pair of shell-like structures symmetrically placed SW and NE of the center of the high velocity emission, at the red-shifted side (Figure 3).

Observation of the high-velocity flows in the core region of the NGC7538 molecular cloud are carried out with CO (J=1-0) molecular line using NRO 45-m radio telescope. The beam size is 14″ and the mapping area covers about 4'x3′. Four high-velocity flows are found in the core region. The high-velocity flows are prominent at and around IRS1, 9, and 11.

The region of NGC 2071 and NGC 2068 is one of the active sites of star formation in Orion. An extended CO cloud in this region has been studied previously (e.g., White et al. 1981). Here, we report new J = 1-0 CO, 13 CO, and C18 O observations of this region with a 2.7′ beam. Up to the present, we have obtained 400, 800, and 100 spectra for CO, 13 CO, and C18 O lines, respectively. The data cover an area of ∼ 1°x2°.

GL490 is a solitary infrared source toward a heavily obscured region. The source exhibits indications of energetic mass outflows of the ionized and molecular gas (e.g. Simon et al. 1981, Lada and Harvey 1981). Generally, GL490 is considered as a young stellar object as suggested by the association with dense molecular gas (Morris et al. 1974, Kawabe et al 1984). In order to understand the distribution of the molecular gas around GL490, we have undertaken an extensive mapping in the J = 1-0 CO and 13CO lines with a 3′ beam (the Nagoya 4-m telescope) and a 15″ beam (the 45-m telescope).

S106-IRS4 is the brightest near IR source associated with the S106 bipolar nebula. It is located exactly at the centre of the bipolar structure, inside the narrow gap of emission between the two radio lobes. It is also a weak radio source. An analysis of the near IR photometric measurements and of the radio fluxes suggests the presence of an ionized envelope produced by mass loss of the early type star which is responsible for the ionization of the nebula (Felli et al. 1984).

The Cep A molecular cloud has been mapped in the 87 GHz continuum and in the J = 1-0 transition of HCN with a combination of single antenna and interferometer observations. The resolution is 19″x14″ (about 0.06 pc at the distance of Cep A) and 0.8 km/sec in velocity.

Many bipolar flow sources have been found around infrared sources with a wide luminosity range. The bipolar sources are thought to be a common stage of early stellar evolution. Recently, compact dense molecular clouds have been detected, just around the exciting infrared sources of several bipolar flow sources (e.g. Torrelles et al. 1983). An investigation of the nature of these surrounding dense molecular clouds should be important to study the acceleration and collimation mechanisms of the bipolar outflow.

The NASA 64-m antenna at Tidbinbilla and the CSIRO 64-m antenna at Parkes have been used to observe the Bok Globule 210-6a (“Valentine's Night”) in the (1,1), (2,2), and (3,3) transitions of ammonia. The beam sizes of the two telescopes were 55 arcsec and 81 arcsec, respectively.

CS(J = 2-1) observations of B335 are carried out using the NRO 45-m telescope with a 16″ beam. We get many self-reversed profiles with good S/N ratio. Assuming that this region consists of a core and a halo, we get the molecular hydrogen density and the CS relative abundance in the halo. The CS wings are located within the cavity of the CO wing (Goldsmith et al. 1984).

We present high resolution (HPBW = 5 arcsec) continuum and molecular-line observations of the circumstellar environment of the emission-line star LkHα 234 made with the Owens Valley Millimeter-Wave Interferometer. These 98 GHz observations have revealed an unresolved continuum source coincident with the star and a 10 000 by 17000 A.U. ridge of enhanced CS(2-1) emission which peaks ∼ 4″ east of the star. The resulting spectral dependence for the radio continuum emission of ν1.5 is most easily interpreted as arising from a partially ionized stellar wind. Attempts are made to describe the properties of the CS emission in terms of a rotating molecular disk which would link LkHα 234 with large scale mass loss activity in the cloud. However, it appears most likely that the CS emission is arising from a dense (n(H2) ∼ 106 cm −3) condensation of gas adjacent to, but not dynamically associated with, the star.