[en] A set of 1.4-mm continuum measurements for a sample of 15 Galactic and extragalactic sources obtained with a millimeter-wave interferometer are presented. Maps at 3 arcsec resolution reveal compact dust emission regions in L1551 IRS 5, HH 7-11, NGC 7538 IRS 1, DR 21(OH) and Arp 220. In Arp 220 about 50 percent of the total 1.4-mm flux originates from a compact source less than 650 pc in radius centered on the NIR nucleus. The mass of interstellar matter in the central source of Arp 220 is approximately 3 X 10 to the 9th solar masses. Comparison of the 1.4 and 2.7-mm dust emission in 10 Galactic sources indicates a spectra index of 3.0 + or - 0.2 for the frequency dependence of the observed small-scale flux. 15 refs

[en] High-resolution (3 arcsec) aperture synthesis maps in the J = 2 to 1 transition of CO-18 have been obtained for the star formation regions DR 21(OH) and L1551 IRS 5. Two compact sources, separated by 7 arcsec, have been discovered at the centers of H2O maser activity associated with DR 21(OH). Mass estimates from the 1.4 mm continuum and CO-18 line emission are similar to the 110 solar masses required for a bound system with the observed 4 km/s radial velocity difference, suggesting that a massive multiple star system is forming. The CO-18 emission from L1551 IRS 5 is extended in an elongated structure of radius 700 AU and mass of 0.1 solar masses. 17 refs

[en] Infrared photometry and spectroscopy (1-25 μm) of background stars reddened by the Lupus molecular cloud complex are used to determine the properties of grains and the composition of ices before they are incorporated into circumstellar envelopes and disks. H₂O ices form at extinctions of A_K = 0.25 ± 0.07 mag (A_V = 2.1 ± 0.6). Such a low ice formation threshold is consistent with the absence of nearby hot stars. Overall, the Lupus clouds are in an early chemical phase. The abundance of H₂O ice (2.3 ± 0.1 × 10^–5 relative to N_H) is typical for quiescent regions, but lower by a factor of three to four compared to dense envelopes of young stellar objects. The low solid CH₃OH abundance (<3%-8% relative to H₂O) indicates a low gas phase H/CO ratio, which is consistent with the observed incomplete CO freeze out. Furthermore it is found that the grains in Lupus experienced growth by coagulation. The mid-infrared (>5 μm) continuum extinction relative to A_K increases as a function of A_K. Most Lupus lines of sight are well fitted with empirically derived extinction curves corresponding to R_V ∼ 3.5 (A_K = 0.71) and R_V ∼ 5.0 (A_K = 1.47). For lines of sight with A_K > 1.0 mag, the τ_9.7/A_K ratio is a factor of two lower compared to the diffuse medium. Below 1.0 mag, values scatter between the dense and diffuse medium ratios. The absence of a gradual transition between diffuse and dense medium-type dust indicates that local conditions matter in the process that sets the τ_9.7/A_K ratio. This process is likely related to grain growth by coagulation, as traced by the A_7.4/A_K continuum extinction ratio, but not to ice mantle formation. Conversely, grains acquire ice mantles before the process of coagulation starts

[en] We present the N₂H⁺ (J = 1 → 0) map of the Serpens South molecular cloud obtained as part of the CARMA Large Area Star Formation Survey. The observations cover 250 arcmin² and fully sample structures from 3000 AU to 3 pc with a velocity resolution of 0.16 km s^–1, and they can be used to constrain the origin and evolution of molecular cloud filaments. The spatial distribution of the N₂H⁺ emission is characterized by long filaments that resemble those observed in the dust continuum emission by Herschel. However, the gas filaments are typically narrower such that, in some cases, two or three quasi-parallel N₂H⁺ filaments comprise a single observed dust continuum filament. The difference between the dust and gas filament widths casts doubt on Herschel ability to resolve the Serpens South filaments. Some molecular filaments show velocity gradients along their major axis, and two are characterized by a steep velocity gradient in the direction perpendicular to the filament axis. The observed velocity gradient along one of these filaments was previously postulated as evidence for mass infall toward the central cluster, but these kind of gradients can be interpreted as projection of large-scale turbulence

[en] We present subarcsecond resolution observations of continuum emission associated with the GG Tau quadruple star system at wavelengths of 1.3, 2.8, 7.3, and 50 mm. These data confirm that the GG Tau A binary is encircled by a circumbinary ring at a radius of 235 AU with a FWHM width of ∼60 AU. We find no clear evidence for a radial gradient in the spectral shape of the ring, suggesting that the particle size distribution is spatially homogeneous on angular scales ≳0.''1. A central point source, likely associated with the primary component (GG Tau Aa), exhibits a composite spectrum from dust and free-free emission. Faint emission at 7.3 mm is observed toward the low-mass star GG Tau Ba, although its origin remains uncertain. Using these measurements of the resolved, multifrequency emission structure of the GG Tau A system, models of the far-infrared to radio spectrum are developed to place constraints on the grain size distribution and dust mass in the circumbinary ring. The non-negligible curvature present in the ring spectrum implies a maximum particle size of 1-10 mm, although we are unable to place strong constraints on the distribution shape. The corresponding dust mass is 30-300 M _⊕, at a temperature of 20-30 K. We discuss how this significant concentration of relatively large particles in a narrow ring at a large radius might be produced in a local region of higher gas pressures (i.e., a particle 'trap') located near the inner edge of the circumbinary disk.