Whereas the understanding of most phases of stellar evolution made considerable progress throughout the whole of the twentieth century, stellar formation remained rather enigmatic and poorly constrained by observations until about three decades ago, when major discoveries (e.g., that protostars are often associated with highly collimated jets) revolutionized the field. At this time, it became i...

Massive stars are born in very obscured regions, far away from us and within dense (proto)stellar clusters. For these reasons, the study of the earliest phases of massive star formation requires the use of high angular resolution tools and cold gas probes. Methanol masers and (sub)millimetre continuum emission satisfy these requirements. Methanol masers are exclusively associated with the earli...

Low-mass protostars form from condensations inside molecular clouds when gravity overwhelms thermal and magnetic supporting forces. The first phases of the formation of a solartype star are characterized by dramatic changes not only in the physical structure but also in the chemical composition. Since Protostars and Planets IV (e.g., Langer et al., 2000), exciting new developments have occurred...

We present 2 ′′ to 7 ′′ resolution 3 mm continuum and CO(J=1−0) line emission and near infrared K s , H 2 , and [FeII] images toward the massive star forming region W75 N. The CO emission uncovers a complex morphology of multiple, overlapping outflows. A total flow mass of > 255 M ⊙ extends 3 pc from end-to-end and is being driven by at least four late to early-B protostars. More than 10% of th...

Abstract Stars collect most of their mass during the protostellar stage, yet accretion luminosity and stellar parameters, which are needed to compute rate, poorly constrained for youngest sources. The aim this work is fill gap, computing properties rates a large sample Class I protostars located in nearby (<500 pc) star-forming regions analyzing interplay. We used self-consistent method prov...

The final mass of a newborn star is set at the epoch when the mass accretion onto the star is terminated. We study the evolution of accreting protostars and the limits of accretion in low metallicity environments. Accretion rates onto protostars are estimated via the temperature evolution of prestellar cores with different metallicities. The derived rates increase with decreasing metallicity, f...

New AAT near-infrared and SEST CO J = 2 → 1 observations are combined with existing ISO mid-infrared and ATCA cm radio continuum observations to examine the protostellar content of the Bok globule BHR 71. Together with observations of Herbig-Haro objects, these data show: (1) Two protostellar sources, IRS1 and IRS2, with a separation of ∼17 (3400 AU) are located within BHR 71. (2) Each protosta...

We present a model for the formation of massive (M > ∼ 10M⊙) stars through accretioninduced collisions in the cores of embedded dense stellar clusters. This model circumvents the problem of accreting onto a star whose luminosity is sufficient to reverse the infall of gas. Instead, the central core of the cluster accretes from the surrounding gas, thereby decreasing its radius until collisions b...