The present study aims at characterizing the massive star forming region G35.20N, which is found associated with at least one massive outflow and contains multiple dense cores, one of them recently found associated with a Keplerian rotating disk. We
used ALMA to observe the G35.20N region in the continuum and line emission at 350 GHz. The observed frequency range covers tracers of dense gas (e.g. H13CO+, C17O), molecular outflows (e.g. SiO), and hot cores (e.g. CH3CN, CH3OH). The ALMA 870 um continuum emission map reveals an elongated dust structure (0.15 pc long and 0.013 pc wide) perpendicular to the large-scale molecular outflow detected in the region, and fragmented into a number of cores with masses 1-10 Msun and sizes 1600 AU. The cores appear regularly spaced with a separation of 0.023 pc. The emission of dense gas tracers such as H13CO+ or C17O is extended and coincident with the dust elongated structure. The three strongest dust cores show emission of complex organic molecules characteristic of hot cores, with temperatures around 200 K, and relative abundances 0.2-2x10^(-8) for CH3CN and 0.6-5x10^(-6) for CH3OH. The two cores with highest mass (cores A and B) show coherent velocity fields, with gradients almost aligned with the dust elongated structure. Those velocity gradients are consistent with Keplerian disks rotating about central masses of 4-18 Msun. Perpendicular to the velocity gradients we have identified a large-scale precessing jet/outflow associated with core B, and hints of an east-west jet/outflow associated with core A. The elongated dust structure in G35.20N is fragmented into a number of dense cores that may form massive stars. Based on the velocity field of the dense gas, the orientation of the magnetic field, and the regularly spaced fragmentation, we interpret this elongated structure as the densest part of a 1D filament fragmenting and forming massive stars.
We report on ALMA observations of continuum and molecular line emission with 0.4 resolution towards the high-mass star forming region G35.20-0.74 N. Two dense cores are detected in typical hot-core tracers, such as CH3CN, which reveal velocity gradie
nts. In one of these cores, the velocity field can be fitted with an almost edge-on Keplerian disk rotating about a central mass of 18 Msun. This finding is consistent with the results of a recent study of the CO first overtone bandhead emission at 2.3mum towards G35.20-0.74 N. The disk radius and mass are >2500 au and 3 Msun. To reconcile the observed bolometric luminosity (3x10^4 Lsun) with the estimated stellar mass of 18 Msun, we propose that the latter is the total mass of a binary system.
Context. G29.96-0.02 is a high-mass star-forming cloud observed at 70, 160, 250, 350, and 500 microns as part of the Herschel survey of the Galactic Plane during the Science Demonstration Phase. Aims. We wish to conduct a far-infrared study of the so
urces associated with this star-forming region by estimating their physical properties and evolutionary stage, and investigating the clump mass function, the star formation efficiency and rate in the cloud. Methods. We have identified the Hi-GAL sources associated with the cloud, searched for possible counterparts at centimeter and infrared wavelengths, fitted their spectral energy distribution and estimated their physical parameters. Results. A total of 198 sources have been detected in all 5 Hi-GAL bands, 117 of which are associated with 24 microns emission and 87 of which are not associated with 24 microns emission. We called the former sources 24 microns-bright and the latter ones 24 microns-dark. The [70-160] color of the 24 microns-dark sources is smaller than that of the 24 microns-bright ones. The 24 microns-dark sources have lower L_bol and L_bol/M_env than the 24 microns-bright ones for similar M_env, which suggests that they are in an earlier evolutionary phase. The G29-SFR cloud is associated with 10 NVSS sources and with extended centimeter continuum emission well correlated with the 70 microns emission. Most of the NVSS sources appear to be early B or late O-type stars. The most massive and luminous Hi-GAL sources in the cloud are located close to the G29-UC region, which suggests that there is a privileged area for massive star formation towards the center of the G29-SFR cloud. Almost all the Hi-GAL sources have masses well above the Jeans mass but only 5% have masses above the virial mass, which indicates that most of the sources are stable against gravitational collapse. The sources with M_env > M_virial and that ...
We have mapped in the 2.7 mm continuum and 12CO with the PdBI the IR-dark tail that crosses the IC 1396N globule from south to north, and is the most extincted part of this cloud. These observations have allowed us to distinguish all possible associa
tions of molecular hydrogen emission features by revealing the presence of two well-collimated low-mass protostellar outflows at the northern part of the globule. The outflows are located almost in the plane of the sky and are colliding with each other towards the position of a strong 2.12 microns H2 line emission feature.
Context. This study is part of a large project to study the physics of accretion and molecular outflows towards a selected sample of high-mass star-forming regions that show evidence of infall and rotation from previous studies. Aims. We wish to make
a thorough study at high-angular resolution of the structure and kinematics of the HMCs and corresponding molecular outflows in the high-mass star-forming region G24.78+0.08. Methods. We carried out SMA and IRAM PdBI observations at 1.3 and 1.4 mm, respectively, of dust and of typical high-density and molecular outflow tracers with resolutions of <1. Complementary IRAM 30-m 12CO and 13CO observations were carried out to recover the short spacing information of the molecular outflows. Results. The millimeter continuum emission towards cores G24 A1 and A2 has been resolved into 3 and 2 cores, respectively, and named A1, A1b, A1c, A2, and A2b. All these cores are aligned in a southeast-northwest direction coincident with that of the molecular outflows detected in the region, which suggests a preferential direction for star formation in this region. The masses of the cores range from 7 to 22 Msun, and the rotational temperatures from 128 to 180 K. The high-density tracers have revealed the existence of 2 velocity components towards A1, one of them peaks close to the position of the millimeter continuum peak and of the HC HII region, and is associated with the velocity gradient seen in CH3CN towards this core, while the other one peaks southwest of core A1 and is not associated with any millimeter continuum emission peak. The position-velocity plots along outflow A and the 13CO averaged blueshifted and redshifted emission indicate that this outflow is driven by core A2.
Context. In recent years, we have detected clear evidence of rotation in more than 5 hot molecular cores (HMCs). Their identification is confirmed by the fact that the rotation axes are parallel to the axes of the associated bipolar outflows. We have
now pursued our investigation by extending the sample to 3 known massive cores, G10.62-0.38, G19.61-0.23, and G29.96-0.02. Aims. We wish to make a thorough study of the structure and kinematics of HMCs and corresponding molecular outflows to reveal possible velocity gradients indicative of rotation of the cores. Methods. We carried out PdBI observations at 2.7 and 1.4~mm of gas and dust with angular resolutions of 2-3, and 1-2, respectively. To trace both rotation and expansion, we simultaneously observed CH3CN, a typical HMC tracer, and 13CO, a typical outflow tracer. Results. The CH3CN(12-11) observations have revealed the existence of clear velocity gradients in the three HMCs oriented perpendicular to the direction of the bipolar outflows. For G19 and G29 the molecular outflows have been mapped in 13CO. The gradients have been interpreted as rotating toroids. The rotation temperatures, used to derive the mass of the cores, have been obtained by means of the rotational diagram method, and lie in the range of 87-244 K. The diameters and masses of the toroids lie in the range of 4550-12600 AU, and 28-415 Msun, respectively. Given that the dynamical masses are 2 to 30 times smaller than the masses of the cores (if the inclination of the toroids with respect to the plane of the sky is not much smaller than 45 degrees), we suggest that the toroids could be accreting onto the embedded cluster. For G19 and G29, the collapse is also suggested by the redshifted absorption seen in the 13CO(2-1) line. We infer that infall onto the embedded (proto)stars must proceed with rates of 1E-2 Msun/yr, and on timescales of the order of 4E3-1E4yr...
Context. IC 1396N is a bright-rimmed cloud associated with an intermediate-mass star-forming region, where a number of Herbig-Haro objects, H2 jet-like features, CO molecular outflows, and millimeter compact sources have been observed. Aims. To study
in detail the complex structure of the IC 1396N core and the molecular outflows detected in the region and to reveal the presence of additional YSOs inside this globule. Methods. We carried out a deep survey of the IC 1396N region in the J, H, K broadband filters and deep high-angular resolution observations in the H2 narrowband filter with NICS at the TNG telescope. The completeness limits in the 2MASS standard are Ks~17.5, H~18.5 and J~19.5. Results. A total of 736 sources have been detected in all three bands within the area where the JHK images overlap. There are 128 sources detected only in HK, 67 detected only in K, and 79 detected only in H. We found only few objects exhibiting a Near-Infrared excess and no clear signs of clustering of sources towards the southern rim. In case of triggered star formation in the southern rim of the globule, this could be very recent, because it is not evidenced through Near-Infrared imaging alone. The H2 emission is complex and knotty and shows a large number of molecular hydrogen features spread over the region, testifying a recent star-formation activity throughout the whole globule. This emission is resolved into several chains or groups of knots that sometimes show a jet-like morphology. The shocked cloudlet model scenario previously proposed to explain the V-shaped morphology of the CO molecular outflow powered by the intermediate-mass YSO BIMA 2 seems to be confirmed by the presence of H2 emission at the position of the deflecting western clump. New possible flows have been discovered in the globule,
Glycolaldehyde is the simplest of the monosaccharide sugars and is directly linked to the origin of life. We report on the detection of glycolaldehyde (CH2OHCHO) towards the hot molecular core G31.41+0.31 through IRAM PdBI observations at 1.4, 2.1, a
nd 2.9 mm. The CH2OHCHO emission comes from the hottest (> 300 K) and densest (>2E8 cm^-3) region closest (< 10^4 AU) to the (proto)stars. The comparison of data with gas-grain chemical models of hot cores suggests for G31.41+0.31 an age of a few 10^5 yr. We also show that only small amounts of CO need to be processed on grains in order for existing hot core gas-grain chemical models to reproduce the observed column densities of glycolaldehyde, making surface reactions the most feasible route to its formation.
Context. The youngest protostars that power energetic outflows are surrounded by infalling and rotating envelopes that contain most of the mass of the system. Aims. To study the properties and kinematics of the protostellar envelope surrounding the e
mbedded source IRAS 05173-0555 in L1634. Methods. We carried out VLA ammonia observations at 1.3 cm with the VLA in the D configuration to map the gas towards the core of L1634. Results. The NH3 emission towards IRAS 05173-0555 is resolved and shows two components clearly distinguishable morphologically: a cross-like structure, roughly elongated in the direction of the HH 240/241 outflow and associated with IRAS 05173-0555, plus an arc-like stream elongated towards the north. The properties and kinematics of the gas suggest that the origin of the cross-like morphology could be the interaction between the outflow and the envelope. A more compact and flattened structure, which could be undergoing rotation about the axis of the outflow, has been detected towards the center of the cross-like envelope. The northern stream, which has properties and velocity different from those of the cross-like envelope, is likely part of the original cloud envelope, and could be either a quiescent core that would never form stars, or be in a prestellar phase.
Context. This is the third of a series of papers devoted to study in detail and with high-angular resolution intermediate-mass molecular outflows and their powering sources. Aims. The aim of this paper is to study the intermediate-mass YSO IRAS 20050
+2720 and its molecular outflow, and put the results of this and the previous studied sources in the context of intermediate-mass star formation. Methods. We carried out VLA observations of the 7 mm continuum emission, and OVRO observations of the 2.7 mm continuum emission, CO(1-0), C18O(1-0), and HC3N(12-11) to map the core towards IRAS 20050+2720. The high-angular resolution of the observations allowed us to derive the properties of the dust emission, the molecular outflow, and the dense protostellar envelope. By adding this source to the sample of intermediate-mass protostars with outflows, we compare their properties and evolution with those of lower mass counterparts. Results. The 2.7mm continuum emission has been resolved into three sources, labeled OVRO 1, OVRO 2, and OVRO 3. Two of them, OVRO 1 and OVRO 2, have also been detected at 7 mm. OVRO 3, which is located close to the C18O emission peak, could be associated with IRAS 20050+2720. The mass of the sources, estimated from the dust continuum emission, is 6.5 Msun for OVRO 1, 1.8 Msun for OVRO 2, and 1.3 Msun for OVRO 3. The CO(1-0) emission traces two bipolar outflows within the OVRO field of view, a roughly east-west bipolar outflow, labeled A, driven by the intermediate-mass source OVRO 1, and a northeast-southwest bipolar outflow, labeled B, probably powered by a YSO engulfed in the circumstellar envelope surrounding OVRO 1.
