Context. The transition between the low density groups of T Tauri stars and the high density clusters around massive stars occurs in the intermediate-mass (IM) range (M * ∼2–8 M ⊙). High spatial resolution studies of IM young stellar objects (YSO) can provide important clues to understand the clustering in massive star forming regions. Aims. Our aim is to search for clustering in IM Class 0 pro...

Identifying the processes that determine strength, duration and variability of protostellar mass growth is a fundamental ingredient of any theory of star formation. I discuss protostellar mass accretion rates Ṁ from numerical models which follow molecular cloud evolution from turbulent fragmentation towards the formation of stellar clusters. In a dense cluster environment, Ṁ is strongly time va...

We present a search for water maser emission at 22 GHz associated with young low-mass protostars in six H ii regions —M16, M20, NGC 2264, NGC 6357, S125, and S140. The survey was conducted with the NRAO Very Large Array from 2000 to 2002. For several of these H ii regions, ours are the first high-resolution observations of water masers. We detected 16 water masers: eight in M16, four in M20, th...

We describe new, deep MIPS photometry and new high signal-to-noise optical spectroscopy of the 2.5 Myr-old IC 348 Nebula. To probe the properties of the IC 348 disk population, we combine these data with previous optical/infrared photometry and spectroscopy to identify stars with gas accretion, to examine their mid-IR colors, and to model their spectral energy distributions. IC 348 contains man...

A number of different formation scenarios have been proposed to explain the formation of stars with masses larger than about 8 M⊙. These include formation through the merger of less massive stars (Coalescence model) or through the accretion of unbound gas from the molecular cloud (Competitive accretion model). In the third scenario, Core accretion model, massive stars form through gravitational...

The evidence of a relation between the mass accretion rate and disk is established for young, Class II pre-main sequence stars. This observational result opened an avenue to test theoretical models constrain initial conditions formation, fundamental in understanding emergence planetary systems. However, it becoming clear that planet formation starts even before stage, disks around 0 I protostar...

This paper describes the first optical spectroscopic survey of class I sources (also known as embedded sources and protostars) in the Taurus-Auriga dark cloud. We detect 10 of the 24 known class I sources in the cloud at 5500–9000 Å. All detected class I sources have strong Hα emission; most also have strong [O I] and [S II] emission. These data – together with high quality optical spectra of T...

We explore the possibility that, in the vicinity of an OB star, a prestellar core which would otherwise have formed an intermediate or low-mass star may form a free-floating brown dwarf or planetary-mass object, because the outer layers of the core are eroded by the ionizing radiation from the OB star before they can accrete onto the protostar at the centre of the core. The masses of objects fo...

We have obtained lowand medium-resolution optical spectra of 20 candidate young low-mass stars and brown dwarfs in the nearby Chamaeleon II dark cloud, using the Magellan Baade telescope. We analyze these data in conjunction with near-infrared photometry from the 2-Micron All Sky Survey. We find that one target, [VCE2001] C41, exhibits broad Hα emission as well as a variety of forbidden emissio...