Two Bipolar Outflows and Magnetic Fields in a Multiple Protostar System, L1448 IRS 3

We performed spectral line observations of CO J=2-1, 13CO J=1-0, and C18O J=1-0 and polarimetric observations in the 1.3 mm continuum and CO J=2-1 toward a multiple protostar system, L1448 IRS 3, in the Perseus molecular complex at a distance of ~250 pc, using the BIMA array. In the 1.3 mm continuum, two sources (IRS 3A and 3B) were clearly detected with estimated envelope masses of 0.21 and 1.15 solar masses, and one source (IRS 3C) was marginally detected with an upper mass limit of 0.03 solar masses. In CO J=2-1, we revealed two outflows originating from IRS 3A and 3B. The masses, mean number densities, momentums, and kinetic energies of outflow lobes were estimated. Based on those estimates and outflow features, we concluded that the two outflows are interacting and that the IRS 3A outflow is nearly perpendicular to the line of sight. In addition, we estimated the velocity, inclination, and opening of the IRS 3B outflow using Bayesian statistics. When the opening angle is ~20 arcdeg, we constrain the velocity to ~45 km/s and the inclination angle to ~57 arcdeg. Linear polarization was detected in both the 1.3 mm continuum and CO J=2-1. The linear polarization in the continuum shows a magnetic field at the central source (IRS 3B) perpendicular to the outflow direction, and the linear polarization in the CO J=2-1 was detected in the outflow regions, parallel or perpendicular to the outflow direction. Moreover, we comprehensively discuss whether the binary system of IRS 3A and 3B is gravitationally bound, based on the velocity differences detected in 13CO J=1-0 and C18O J=1-0 observations and on the outflow features. The specific angular momentum of the system was estimated as ~3e20 cm^2/s, comparable to the values obtained from previous studies on binaries and molecular clouds in Taurus.Comment: ApJ accepted, 20 pages, 2 tables, 10 figure

Dust emission from young outflows: the case of L1157

We present new high-sensitivity 1.3 mm bolometer observations of the young outflow L1157. These data show that the continuum emission arises from four distinct components: a circumstellar disk, a protostellar envelope, an extended flattened envelope --the dense remnant of the molecular cloud in which the protostar was formed--, and the outflow itself, which represents ~20% of the total flux. The outflow emission exhibits two peaks that are coincident with the two strong shocks in the southern lobe of L1157. We show that the mm continuum is dominated by thermal dust emission arising in the high velocity material. The spectral index derived from the new 1.3 mm data and 850 mu observations from Shirley et al. (2000), is ~5 in the outflow, significantly higher than in the protostellar envelope (~3.5). This can be explained by an important line contamination of the 850 mu map, and/or by different dust characteristics in the two regions, possibly smaller grains in the post-shocks regions of the outflow. Our observations show that bipolar outflows can present compact emission peaks which must not be misinterpreted as protostellar condensations when mapping star forming regions

A Mid-Infrared Study of the Class 0 Cluster in LDN 1448

We present ground-based mid-infrared observations of Class 0 protostars in LDN 1448. Of the five known protostars in this cloud, we detected two, L1448N:A and L1448C, at 12.5, 17.9, 20.8, and 24.5 microns, and a third, L1448 IRS 2, at 24.5 microns. We present high-resolution images of the detected sources, and photometry or upper limits for all five Class 0 sources in this cloud. With these data, we are able to augment existing spectral energy distributions (SEDs) for all five objects and place them on an evolutionary status diagram.Comment: Accepted by the Astronomical Journal; 26 pages, 9 figure

Star formation in the vicinity of the IC 348 cluster

Aims. We present molecular line observations of the southwestern part of the IC 348 young cluster, and we use them together with NIR and mm continuum data to determine the distribution of dense gas, search for molecular outflows, and analyze the ongoing star formation activity in the region. Methods. Our molecular line data consists of C18O(1--0) and N2H+(1--0) maps obtained with the FCRAO telescope at a resolution of about 50'' and CO(2--1) data obtained with the IRAM 30m telescope at a resolution of 11''. Results. The dense gas southwest of IC 348 is concentrated in two groups of dense cores, each of them with a few solar masses of material and indications of CO depletion at high density. One of the core groups is actively forming stars, while the other seems starless. There is evidence for at least three bipolar molecular outflows in the region, two of them powered by previously identified Class 0 sources, while the other one is powered by a still not well characterized low-luminosity object. The ongoing star formation activity is producing a small stellar subgroup in the cluster. Using the observed core characteristics and the star formation rate in the cluster we propose that that similar episodes of stellar birth may have produced the subclustering observed in the halo of IC 348.Comment: 10 pages, 6 figures, A&A accepte

A search for CO+ in planetary nebulae

We have carried out a systematic search for the molecular ion CO+ in a sample of 8 protoplanetary and planetary nebulae in order to determine the origin of the unexpectedly strong HCO+ emission previously detected in these sources. An understanding of the HCO+ chemistry may provide direct clues to the physical and chemical evolution of planetary nebulae. We find that the integrated intensity of the CO+ line may be correlated with that of HCO+, suggesting that the reaction of CO+ with molecular hydrogen may be an important formation route for HCO+ in these planetary nebulae.Comment: 6 pages, 4 figures, accepted for publication in MNRA

The clumpy structure of the chemically active L1157 outflow

We present high spatial resolution maps, obtained with the Plateau de Bure Interferometer, of the blue lobe of the L1157 outflow. We observed four lines at 3 mm, namely CH3OH (2_K-1_K), HC3N (11-10), HCN (1-0) and OCS (7-6). Moreover, the bright B1 clump has also been observed at better spatial resolution in CS (2-1), CH3OH (2_1-1_1)A-, and 34SO (3_2-2_1). These high spatial resolution observations show a very rich structure in all the tracers, revealing a clumpy structure of the gas superimposed to an extended emission. In fact, the three clumps detected by previous IRAM-30m single dish observations have been resolved into several sub-clumps and new clumps have been detected in the outflow. The clumps are associated with the two cavities created by two shock episodes driven by the precessing jet. In particular, the clumps nearest the protostar are located at the walls of the younger cavity with a clear arch-shape form while the farthest clumps have slightly different observational characteristics indicating that they are associated to the older shock episode. The emission of the observed species peaks in different part of the lobe: the east clumps are brighter in HC3N (11-10), HCN (1-0) and CS (2-1) while the west clumps are brighter in CH3OH(2_K-1_K), OCS (7-6) and 34SO (3_2-2_1). This peak displacement in the line emission suggests a variation of the physical conditions and/or the chemical composition along the lobe of the outflow at small scale, likely related to the shock activity and the precession of the outflow. In particular, we observe the decoupling of the silicon monoxide and methanol emission, common shock tracers, in the B1 clump located at the apex of the bow shock produced by the second shock episode.Comment: 11 pages, 8 figures, accepted for publication in the MNRA

Shells, jets, and internal working surfaces in the molecular outflow from IRAS 04166+2706

Context: IRAS 04166+2706 in Taurus is one of the most nearby young stellar objects whose molecular outflow contains a highly collimated fast component. Methods: We have observed the IRAS 04166+2706 outflow with the IRAM Plateau de Bure interferometer in CO(J=2-1) and SiO(J=2-1) achieving angular resolutions between 2'' and 4''. To improve the quality of the CO(2-1) images, we have added single dish data to the interferometer visibilities. Results: The outflow consists of two distinct components. At velocities <10 km/s, the gas forms two opposed, approximately conical shells that have the YSO at their vertex. These shells coincide with the walls of evacuated cavities and seem to result from the acceleration of the ambient gas by a wide-angle wind. At velocities >30 km/s, the gas forms two opposed jets that travel along the center of the cavities and whose emission is dominated by a symmetric collection of at least 7 pairs of peaks. The velocity field of this component presents a sawtooth pattern with the gas in the tail of each peak moving faster than the gas in the head. This pattern, together with a systematic widening of the peaks with distance to the central source, is consistent with the emission arising from internal working surfaces traveling along the jet and resulting from variations in the velocity field of ejection. We interpret this component as the true protostellar wind, and we find its composition consistent with a chemical model of such type of wind. Conclusions: Our results support outflow wind models that have simultaneously wide-angle and narrow components, and suggest that the EHV peaks seen in a number of outflows consist of internally-shocked wind material.Comment: 13 pages, 10 figures. To appear in A&

W40 region in the Gould Belt : An embedded cluster and H II region at the junction of filaments

We present a multiwavelength study of W40 star-forming region using IR observations in UKIRT JHK bands, Spitzer IRAC bands & Herschel PACS bands; 2.12 micron H2 narrow-band imaging; & radio observations from GMRT (610 & 1280 MHz), in a FoV of ~34'x40'. Spitzer observations along with NIR observations are used to identify 1162 Class II/III & 40 Class I sources in the FoV. The NN stellar surface density analysis shows that majority of these YSOs constitute the embedded cluster centered on the source IRS1A South. Some YSOs, predominantly younger population, are distributed along & trace the filamentary structures at lower stellar surface density. The cluster radius is obtained as 0.44pc - matching well with the extent of radio emission - with a peak density of 650pc^-2. The JHK data is used to map the extinction which is subsequently used to compute the cloud mass. It has resulted in 126 Msun & 71 Msun for the central cluster & the northern IRS5 region, respectively. H2 narrow-band imaging displays significant emission, which prominently resembles fluorescent emission arising at the borders of dense regions. Radio analysis shows this region as having blister morphology, with the radio peak coinciding with a protostellar source. Free-free emission SED analysis is used to obtain physical parameters of the overall region & the IRS5 sub-region. This multiwavelength scenario is suggestive of star formation having resulted from merging of multiple filaments to form a hub. Star formation seems to have taken place in two successive epochs, with the first epoch traced by the central cluster & the high-mass star(s) - followed by a second epoch which is spreading into the filaments as uncovered by the Class I sources & even younger protostellar sources along the filaments. The IRS5 HII region displays indications of swept-up material which has possibly led to the formation of protostars.Comment: 17 pages, 12 figures, 2 tables. Accepted for publication in The Astrophysical Journa