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Although the existence of dark matter is generally accepted by the mainstream scientific community, there is no generally agreed direct detection of it. Also, observations show that some Bok globules are prolate in some regions without suitable explanation for its cause. In this paper, we investigate the effect of dark matter sub-halo in transformation of the Bok globules from spherical to the prolate shape. We limit the investigation to a particular case that the magnetic field and turbulent effects are negligible through the Bok globule. We consider the gravitational effect of dark matter sub-halo on the isothermal Bok globule that is exposed to suitable distance of it. The results show that the dark matter sub-halo can justify the transformation of Bok globules in some regions. In this paper, we introduce a new method for proving the existence of dark matter sub halo.

We examine the effects of f(R) gravity on Jeans analysis of collapsing dust clouds. We provide a method for testing modified gravity models by their effects on star formation as the presence of f(R) gravity is found to modify the limit for collapse. In this analysis we add perturbations to a de Sitter background. As the standard Einstein-Hilbert Lagrangian is modified, new types of dynamics emerge. Depending on the characteristics of a chosen f(R) model, the appearance of new limits is possible. The physicality of these limits is further examined. We find the asymptotic Jeans masses for f(R) theories compared to standard Jeans mass. Through this ratio, the effects of the f(R) modified Jeans mass for viable theories are examined in molecular clouds. Bok globules have a mass range comparable to Jeans masses in question and are therefore used for comparing different f(R) models. Viable theories are found to assist in star formation.

We trace the peripheral magnetic field structure of Bok globule CB130, by estimating the linear polarization of its field stars in the R band. The magnetic field orientation sampled by these stars, aligned on average among themselves and the polarization produced within the cloud has a different direction from that of Galactic plane with an offset of 53$^\circ$. The offset between minor axis and the mean magnetic field of CB130 is found to be 80$^\circ$. The estimated strength of the magnetic field in the plane-of-the-sky is $\sim$ 116$\pm$19 $\mu$G. We constructed the visual extinction map using Near Infrared Color Excess (NICE) method to see the dust distribution around CB130. Contours of Herschel {Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA} SPIRE 500$\mu$m dust continuum emission maps of this cloud is over-plotted on the visual extinction map which shows the regions having higher optical extinction corresponds to higher densities of dust. Three distinct high dust density cores (named as C1, C2, and C3) are identified in the extinction map. It is observed that the cores C1 and C3 located close to two previously known cores CB130-1 and CB130-2 respectively. Estimate of visual extinction of some moderately obscured stars of CB130 are made utilizing near-infra red photometry. Its observed that there is a feeble dependence of polarization on extinction; and polarization efficiency (defined as $ \textit{p}$/A$ {V}$) of the dust grains decreases with the increase in extinction., Comment: Accepted in Astrophysics and Space Science journal (14 pages, 5 figures, 3 tables)

Highly-collimated outflows are believed to be the earliest stage in outflow evolution, so their study is essential for understanding the processes driving outflows. The BHR71 Bok globule is known to harbour such a highly-collimated outflow, which is powered by a protostar belonging to a protobinary system. Using the APEX telescope on Chajnantor, we mapped the BHR71 highly-collimated outflow in CO(3-2), and observed several bright points of the outflow in the molecular transitions CO(4-3), CO(7-6), 13CO(3-2), C18O(3-2), CH3OH(7-6) and H2CO(4-3). We use an LVG code to characterise the temperature enhancements in these regions. These observations are particularly interesting for investigating the interaction of collimated outflows with the ambient molecular cloud. In our CO(3-2) map, the second outflow driven by IRS2, which is the second source of the binary system, is completely revealed and shown to be bipolar. We also measure temperature enhancements in the lobes. The CO and methanol LVG modelling points to temperatures between 30 and 50 K in the two lobes. The methanol emission in the southern lobe bright knot is barely resolved with the APEX single-dish. ALMA will thus be a central tool to study the shock chemistry in these regions.

We study the influence and structure of the magnetic field in the early phases of low-mass star formation using polarization maps of Bok globules at a wavelength of 850micron, obtained with the Submillimeter Common-User Bolometer Array (SCUBA) at the James Clerk Maxwell Telescope (JCMT). We discuss observations of the following sources: CB26 - a small globule with a nearly dispersed dense core and a young and large circumstellar disk, CB54 - a large globule with a massive dense core and a deeply embedded young stellar cluster, and B335, CB230, and CB244 - three nearby, relatively isolated small globules with low-mass protostellar cores. We find strongly aligned polarization vectors in the case of CB26, B335, and CB230, while the vector orientations in the case of CB54 and CB244 are more or less randomly distributed. The degree of polarization, amounting to several percent, was found to decrease toward the center in each source. Assuming dichroic emission by aligned non-spherical grains as the polarization mechanism, where the magnetic field plays a role in the alignment process, we derive magnetic field strengths and structures from the observed polarization patterns. We compare the magnetic field topology with the morphology and outflow directions of the globules. In the Class 0 sources B335, CB230, and CB244, the magnetic field is oriented almost perpendicular to the ouflow direction. In contrast, the inclination between outflow axis and magnetic field direction is much more moderate (36deg) in the more evolved Class I source CB26., to be published in Conf. Proc. "Magnetic Fields and Star Formation"

SEEN in silhouette against the numerous ionized H II regions in the Milky Way are groups of small dark clouds of neutral gas and dust known as Bok globules. In some cases the stellar wind from a nearby star strips material from the globules, creating a tail pointing away from the source of the wind. Here I report the use of a photographic enhancement technique to reveal a family of four such 'cometary' globules in the southeast quadrant of the Rosette nebula, NGC2237 – 2246. The globules are not visible on R-glass copies of the National Geographic/ Palomar Observatory Sky Survey. The tails of the globules all point away from the IRAS (Infrared Astronomy Satellite) source 06314 + 0427, the position of which coincides with the peak of CO emission1. The far-infrared luminosity of 06314 + 0427 is estimated to be a factor of at least 880 greater than the Sun's luminosity, with a total energy output enough to drive a stellar wind that could produce the observed globules.

We have modelled chemical abundances and line profiles in the Bok globule B335. The chemical characteristics of this star-forming core are largely determined by gas-grain interaction in the inflowing material. By comparing high resolution observational data with our model it should be possible to determine the evolutionary status of B335 and to establish the role that surface chemistry plays in protostellar clouds.

Gravitational settling of dust grains in dark clouds has been considered. It has been shown that such a process gives rise to a modification of the grain size distribution. Starting with a simple model of uniform spherical cloud and normal interstellar grain size distribution for the dust we derive expressions for the modified grain size distribution function, average grain size and extinction as functions of distance from the cloud's center and the age of the cloud. The mean grain size increases towards the center of the cloud as does the extinction. Results of the numerical evaluation of these quantities have been discussed with their implications for the observations of anomalous reddening and polarization within dark clouds and Bok globules.

The author gives examples of radial systems consisting of dark globules and ''elephant trunks''. Besides already known systems, which contain hot stars at their center, data are given on three radial systems of a new kind, at the center of which there are stars of spectral types later than B. Data are given on 32 globules of radial systems of the association Cep OB2. On the basis of the observational data, it is concluded that at least some of the isolated Bok globules derive from elephant trunks and dark globules forming radial systems around hot stars. It is also suggested that the two molecular clouds situated near the Rosette nebula and possessing velocities differing by ca 20 km/sec from the velocity of the nebula could have been ejected in opposite directions from the center of the nebula. One of these clouds consists of dark globules forming the radial system of the Rosette nebula.