We present CCD images of the central part of the star forming region NGC 7129 as well as spectra of moderate spectral and high spatial resolution of some nebular objects and stars. The images show many reflection filaments which seem to trace the edges of the molecular cavity associated with the pre-main-sequence star LkHalpha234. Three new T Tauri-like stars and five new Herbig-Haro (HH) objects have been identified in the region. One of the new young stars probably illuminates an elongated reflection filament. One of the HH objects presents a highly collimated structure and an abrupt and unusually large bending of almost-equal-to 90-degrees. The object emanates from the Halpha-emission line star HL 14. Our spectra indicate that this star is likely to be a T Tauri-like star. Large and systematic variations of the radial velocity, electron density, excitation degree and velocity dispersion exist in the object. The data favor the idea that the object is a jet-like outflow which encounters an obstacle - density enhancement or pressure gradient - in the cloud and deflects. The obstacle could be related to the walls of the molecular cavity associated with LkH alpha234 or to the energetic wind from this star.
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Ice-band spectra and a high-resolution K band image of CEP A IRS 6 are presented. The spectra show indications for qualitative changes in the shape of the ice feature across the reflection nebula. The K band image shows complicated structure consisting of individual knots and filaments. H band polarization measurements of background stars behind the Cep A molecular cloud indicate a bent magnetic field in the vicinity of the Cep A star-forming region that is probably caused by interaction with the nearby Cep OB 3 association.
Optical CCD images and polarimetry as well as near-IR observations of the molecular core S 140N are presented. The images reveal a reflection nebulosity associated with the young IRAS source 22178 + 6317. Two pointlike sources are embedded in the reflection nebulosity. The near-IR colors indicate an IR excess characteristic of PMS objects. The CO outflow detected in the region is likely to be driven by these young objects. Four Herbig-Haro objects are detected in our images. This is the first detection of these kinds of objects in the S 140 molecular cloud. The HH objects are aligned in a scale of about 2.3 arcmin (about 0.7 pc) and point to a faint star, located at the northern end of the brighter HH object. This star is therefore a suitable candidate to excite the HH objects and is likely to be a T Tauri-like star. In addition, the star is centered on a previously detected ammonia core and likely heats the high density gas. Finally, these data show that not only high-mass stars, but also low-mass stars have recently formed in the S 140 molecular cloud.
Debris discs have often been described as gas-poor discs as the gas-to-dust ratio is expected to be considerably lower than in primordial,protoplanetary discs. However, recent observations have confirmed the presence of a non-negligible amount of cold gas in the circumstellar (CS) debris discs around young main-sequence stars.This cold gas has been suggested to be related to the outgassing of planetesimals and cometary-like objects. The aim of the paper is to investigate the presence of hot gas in the surroundings of stars bearing cold-gas debris discs. High-resolution optical spectra of all currently known cold-gas-bearing debris-disc systems, with the exception of $\beta$ Pic and Fomalhaut, have been obtained from different observatories.We have analysed the Ca II H & K and the Na I D lines searching for non-photospheric absorptions of CS origin, usually attributed to cometary-like activity. Narrow, stable Ca II and/or Na I absorption features have been detected superimposed to the photospheric lines in 10 out of the 15 observed cold-gas-bearing debris disc.Features are found at the radial velocity of the stars, or slightly blue- or red-shifted, and/or at the velocity of the local interstellar medium (ISM). Some stars also present transient variable events or absorptions extended towards red wavelengths. These are the first detections of such Ca II features in 7 out of the 15 observed stars. In some of these stars, results suggest that the stable and variable absorptions arise from relatively hot gas located in the CS close-in environment. This hot gas is detected in at least ~80%, of edge-on cold-gas-bearing debris discs, while in only ~10% of the discs seen close to face-on. We interpret this as a geometrical effect, and suggest that the non-detection of hot gas absorptions is due to the disc inclination rather than to the absence of the hot-gas component.
In an attempt to study whether the formation of brown dwarfs (BDs) takes place as a scaled-down version of low-mass stars, we conducted IRAM30m/MAMBO-II observations at 1.2 mm in a sample of 12 proto-BD candidates selected from Spitzer/IRAC data in the B213-L1495 clouds in Taurus. Subsequent observations with the CSO at 350 micron, VLA at 3.6 and 6 cm, and IRAM30m/EMIR in the 12CO(1-0), 13CO(1-0), and N2H+(1-0) transitions were carried out toward the two most promising Spitzer/IRAC source(s), J042118 and J041757. J042118 is associated with a compact (<10 arcsec or <1400 AU) and faint source at 350 micron, while J041757 is associated with a partially resolved (~16 arcsec or ~2000 AU) and stronger source emitting at centimetre wavelengths with a flat spectral index. The corresponding masses of the dust condensations are ~1 and ~5 Mjup for J042118 and J041757, respectively. In addition, about 40 arcsec to the northeast of J041757 we detect a strong and extended submillimetre source, J041757-NE, which is not associated with NIR/FIR emission down to our detection limits, but is clearly detected in 13CO and N2H+ at ~7 km/s, and for which we estimated a total mass of ~100 Mjup, close to the mass required to be gravitationally bound. In summary, our observational strategy has allowed us to find in B213-L1495 two proto-BD candidates and one pre-substellar core candidate, whose properties seem to be consistent with a scaled-down version of low-mass stars.
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