ABSTRACT We model Pop III star formation in different FUV and X-ray backgrounds, including radiation feedback from protostars. confirm previous results that a moderate background increases the number of systems per unit cosmological volume, but masses multiplicities system are reduced. The stellar mass function also agrees with results, we outward migration stars within protostellar discs. find...

We use mid-infrared to submillimeter data from the Spitzer, Herschel, and APEX telescopes to study the bright sub-mm source OMC-2 FIR 4. We find a point source at 8, 24, and 70 μm, and a compact, but extended source at 160, 350, and 870 μm. The peak of the emission from 8 to 70 μm, attributed to the protostar associated with FIR 4, is displaced relative to the peak of the extended emission; the...

The current status of both the observational evidence and the theory of the stellar initial mass function (IMF) is reviewed, with particular attention to the two basic, apparently universal features shown by all observations of nearby stellar systems: (1) a characteristic stellar mass of the order of one solar mass, and (2) a power-law decline of the IMF at large masses similar to the original ...

Observations indicate that mass accretion rates onto low-mass protostars are generally lower than the rates of infall to their disks; this suggests that much of the protostellar mass must be accreted during rare, short outbursts of rapid accretion. We explore when protostellar disk accretion is likely to be highly variable. While constant α disks can in principle adjust their accretion rates to...

ABSTRACT Radiative feedback from massive Population III (Pop III) stars in the form of ionizing and photodissociating photons is widely believed to play a central role shutting off accretion on these stars. Understanding whether how this occurs vital for predicting final masses reached by Pop stellar initial mass function. To help us better understand impact UV radiation gas surrounding them, w...

One of the most exciting challenges facing theories of post-main sequence evolution today is to understand how Asymptotic Giant Branch (AGB) stars and their round circumstellar envelopes (CSEs) transform themselves into planetary nebulae (PNe) with their dazzling variety of aspherical morphologies. The most succesful model for shaping PNe—the “generalised interacting-stellar-winds” model, in wh...

The Paschen beta (1.2822 μm) emission line found in the near-infrared spectra of T-Tauri stars (TTSs) is believed to trace the accretion of material onto the central star. We present spectroscopic data which suggests that this may not always be the case. The technique of spectro-astrometry is used by us to measure positional displacements in the Paβ emission from four T-Tauri stars, namely DG T...

Stars generally form faster than the ambipolar diffusion time, suggesting that several processes short circuit the delay and promote a rapid collapse. These processes are considered here, including turbulence compression in the outer parts of giant molecular cloud (GMC) cores and GMC envelopes, GMC core formation in an initially supercritical state, and compression-induced triggering in dispers...

Ground based imaging, imaging polarimetry, and recentHubble Space Telescope WFPC2 and NICMOS images of protostars have revealed very complex scattered light patterns that cannot be entirely explained by 2-D radiation transfer models. We present here for the first time radiation transfer models of T Tau and IRAS 04016+2610 that are fully 3-D, with the aim of investigating the effects on image mo...

The current status of both the observational evidence and the theory of the stellar initial mass function (IMF) is reviewed, with particular attention to the two basic, apparently universal features shown by all observations of nearby stellar systems: (1) a characteristic stellar mass of the order of one solar mass, and (2) a power-law decline of the IMF at large masses similar to the original ...