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We perform a census of the reddest, and potentially youngest, protostars in the Orion molecular clouds using data obtained with the PACS instrument on board the Herschel Space Observatory and the LABOCA and SABOCA instruments on APEX as part of the Herschel Orion Protostar Survey (HOPS). A total of 55 new protostar candidates are detected at 70 μm and 160 μm that are either too faint (m24> 7 mag) to be reliably classified as protostars or undetected in the Spitzer/MIPS 24 μm band.We find that the 11 reddest protostar candidates with log λFλ70/λFλ24 > 1.65 are free of contamination and can thus be reliably explained as protostars. The remaining 44 sources have less extreme 70/24 colors, fainter 70 μm fluxes, and higher levels of contamination. Taking the previously known sample of Spitzer protostars and the new sample together, we find 18 sources that have log λFλ70/λFλ24 > 1.65; we name these sources "PACS Bright Red sources," or PBRs. Our analysis reveals that the PBR sample is composed of Class 0 like sources characterized by very red spectral energy distributions (SEDs; Tbol < 45 K) and large values of sub-millimeter fluxes (Lsmm /Lbol > 0.6%). Modified blackbody fits to the SEDs provide lower limits to the envelope masses of 0.2-2M☉ and luminosities of 0.7-10 L☉. Based on these properties, and a comparison of the SEDs with radiative transfer models of protostars, we conclude that the PBRs are most likely extreme Class 0 objects distinguished by higher than typical envelope densities and hence, high mass infall rates. [ABSTRACT FROM AUTHOR]

We present centimeter (cm) and millimeter (mm) observations of the NGC 2071 star-forming region performed with the Very Large Array (VLA) and Combined Array for Research in Millimeter-wave Astronomy (CARMA). We detected counterparts at 3.6 cm and 3 mm for the previously known sources IRS 1, IRS 2, IRS 3, and VLA 1. All these sources show spectral energy distributions (SEDs) dominated by free-free thermal emission at cm wavelengths and thermal dust emission at mm wavelengths, suggesting that all of them are associated with young stellar objects (YSOs). IRS 1 shows a complex morphology at 3.6 cm, with changes in the direction of its elongation. We discuss two possible explanations to this morphology: the result of changes in the direction of a jet due to interactions with a dense ambient medium, or that we are actually observing the superposition of two jets arising from two components of a binary system. Higher angular resolution observations at 1.3 cm support the second possibility, since a double source is inferred at this wavelength. IRS 3 shows a clear jet-like morphology at 3.6 cm. Over a timespan of four years, we observed changes in the morphology of this source that we interpret as due to ejection of ionized material in a jet. The emission at 3 mm of IRS 3 is angularly resolved, with a deconvolved size (FWHM) of ~120 AU, and seems to be tracing a dusty circumstellar disk perpendicular to the radio jet. An irradiated accretion disk model around an intermediate-mass YSO can account for the observed SED and spatial intensity profile at 3 mm, supporting this interpretation. [ABSTRACT FROM AUTHOR]

We present observations of continuum emission in the mid-infrared to millimeter wavelength range, complemented with ammonia observations, of the dense core ahead of the radio Herbig-Haro (HH) object HH 80N. found in the GGD 27 region. The continuum emission in all the observed bands peaks at the same position, consistent with the presence of an embedded object, HH 80N-IRS1, within the core. The distribution of the Very Large Array ammonia emission is well correlated with that of the dust, suggesting that photochemical effects caused by the nearby HH object do not play an important role in shaping this particular molecular emission. In order to unveil the nature of HH 80N-IRS1, we analyzed the continuum data of this source, using self-consistent models of protostellar collapse. We find that a young protostar surrounded by a slowly rotating collapsing envelope of radius ~0.08 pc and 20 M⊙ plus a circumstellar disk of radius ~300 AU and 0.6 A/Q provide a good fit to the observed spectral energy distribution and to the maps at 350 µm, 1.2 mm, and 3.5 mm of HH 80N-IRS1. Besides, the Atacama Pathfinder Experiment and Plateau de Bure Interferometer continuum maps at 350 µm and 3.5 mm. respectively, reveal additional clumps in the continuum emission. Given the modeling results and the observed morphology of the emission, we propose a scenario consisting of a central embedded Class 0 object, HH 80N-IRS1, with the rest of the material of the HH SON core possibly undergoing fragmentation that may lead to the formation of several protostars. [ABSTRACT FROM AUTHOR]