Outflow, Infall, and Protostars in the Star-Forming Core W3-SE (original) (raw)
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Star Formation and Feedback: A Molecular Outflow–Prestellar Core Interaction in L1689N
The Astrophysical Journal
We present Herschel 1 , ALMA Compact Array (ACA), and Caltech Submillimeter Observatory (CSO) observations of the prestellar core in L1689N, which has been suggested to be interacting with a molecular outflow driven by the nearby solar type protostar IRAS 16293-2422. This source is characterized by some of the highest deuteration levels seen in the interstellar medium. The change in the NH 2 D line velocity and width across the core provides clear evidence of an interaction with the outflow, traced by the high-velocity water emission. Quiescent, cold gas, characterized by narrow line widths is seen in the NE part of the core, while broader, more disturbed line profiles are seen in the W/SW part. Strong N 2 D + and ND 3 emission is detected with the ACA, extending S/SW from the peak of the single-dish NH 2 D emission. The ACA data also reveal the presence a compact dust continuum source, with a mean size of ∼1100 au, a central density of (1 − 2) × 10 7 cm −3 , and a mass of 0.2-0.4 M. The dust emission peak is displaced ∼5 to the south with respect to the N 2 D + and ND 3 emission, as well as the single-dish dust continuum peak, suggesting that the northern, quiescent part of the core is characterized by spatially extended continuum emission, which is resolved out by the interferometer. We see no clear evidence of fragmentation in this quiescent part of the core, which could lead to a second generation of star formation, although a weak dust continuum source is detected in this region in the ACA data.
Dense Cores, Filaments, and Outflows in the S255IR Region of High-mass Star Formation
The Astrophysical Journal, 2020
We investigate at a high angular resolution the spatial and kinematic structure of the S255IR high-mass starforming region, which demonstrated recently the first disk-mediated accretion burst in the massive young stellar object. The observations were performed with the Atacama Large Millimeter/submillimeter Array (ALMA) in Band 7 at an angular resolution of ∼ 0 1, which corresponds to ∼180au. The 0.9mm continuum, C 34 S(7-6) and CCH N=4−3 data show a presence of very narrow (∼1000 au), very dense (n ∼ 10 7 cm −3), and warm filamentary structures in this area. At least some of them represent apparently dense walls around the high velocity molecular outflow with a wide opening angle from the S255IR-SMA1 core, which is associated with the NIRS3 YSO. This wide-angle outflow surrounds a narrow jet. At the ends of the molecular outflow there are shocks, traced in the SiO(8-7) emission. The SiO abundance there is enhanced by at least 3 orders of magnitude. The CO(3-2) and SiO(8-7) data show a collimated and extended high velocity outflow from another dense core in this area, SMA2. The outflow is bent and consists of a chain of knots, which may indicate periodic ejections possibly arising from a binary system consisting of low-or intermediate-mass protostars. The C 34 S emission shows evidence of rotation of the parent core. Finally, we detected two new low-mass compact cores in this area (designated as SMM1 and SMM2), which may represent prestellar objects.
Dust and HCO+ Gas in the Star-Forming Core W3SE
Astrophysical Journal - ASTROPHYS J, 2010
We report new results from recent Combined Array for Research in Millimeter-wave Astronomy (CARMA) observations of both continuum and HCO+(1-0) line emission at lambda3.4 mm from W3-SE, a molecular core of intermediate mass, together with the observations of continuum emission at lambda1.1 and lambda0.85/lambda0.45 mm with the Submillimeter Array (SMA) and the James Clerk Maxwell Telescope, respectively. A continuum emission core elongated from SE to NW, with a size of ~10'', has been observed at the millimeter and submillimeter wavelengths. The dust core has been resolved into a double source with the SMA at lambda1.1 mm. The angular separation between the two components is ~4''. Together with the measurements from the Spitzer Space Telescope and the Midcourse Space Experiment at mid-IR wavelengths, we determined the spectral energy distribution (SED) of the continuum emission from W3-SE and fit it with a thermal dust emission model. Our best fitting of the SED ...
The Formation of High-Mass Stars: from High-Mass Clumps to Accretion Discs and Molecular Outflows
High-mass stars play a significant role in the evolution of the Universe and the process that leads to the formation of such objects is still an open question in Astrophysics. The details of the structures connected to the central sources, such as the circumstellar discs and the morphology of the jets at their launching points, still lack of observational evidence. In this thesis, the high-mass star forming process is investigated in terms of the evolution of high-mass clumps selected from the ATLASGAL survey based on their 12 CO emission in the sub-millimetre. While single-dish sub-millimetre observations provide a large-scale view of the high-mass star formation process, higher angular resolution observations are required to disentangle the details of the protostars within the clumps. For this, threedimensional infrared spectroscopy was obtained for a group of RMS sources to characterise the circumstellar environment of high-mass YSOs in linear scales of ∼100-1000 AU. The ATLASGAL TOP100 sample offers a unique opportunity to analyse a statistically complete sample of high-mass clumps at different evolutionary stages. APEX data of three rotational J transitions of the CO (the CO (4-3), CO (6-5) and CO (7-6)) were used to characterise the properties of their warm gas (155 K) content and to derive the relations between the CO and the clump properties. The CO line luminosities were derived and the analysis indicated that the CO emission increases as a function of the evolutionary stage of the clumps (from infrared-weak to H ii regions) and as a function of the bolometric luminosity (L bol) and mass of the sources (M clump). The comparison of the TOP100 with low-mass objects observed in the CO (6-5) and CO (7-6), together with CO (10-9) data observed for a complementary sample of objects indicated that the dependency of the CO luminosity (L CO) with the bolometric luminosity of the sources gets steeper towards higher-J transitions. Although the CO luminosity of more luminous clumps are systematically larger than the values obtained for the less luminous sources, the individual analysis of each subsample suggests a similar dependency of L CO versus L bol for each luminosity regime. Finally, the presence of high-velocity CO emission observed for the TOP100 suggests that ∼85% of the sources are driving molecular outflows. The selection of isolated high-mass objects undergoing mass accretion is fundamental to investigate if these objects are formed through an accretion disc or if they are formed by merging of low-mass YSOs. The near-infrared window provides one of the best opportunities to investigate the interior of the sub-mm clumps and study in details their individual members. Thanks to the relatively high-resolution obtained in the K-band and the moderate reddening effectsin the K-band, a sample of eight (8) HMYSOs exhibiting large-scale H 2 outflows were selected to follow-up K-band spectroscopic observations using the NIFS spectrometer (Gemini North). All sources exhibit extended continuum emission and exhibit atomic and molecular transitions typical of embedded objects, such as Brγ, H 2 and the CO lines. The H 2 lines are tracing the launching point of the large-scale jets in scales of ∼ 100 AU in five of eight sources (63%). The identification of jets at such small scales indicates that these objects are still undergoing mass accretion. The Brγ emission probes the ionised gas around the HMYSOs. The analysis of the Brγ spectro-astrometry at sub-pixel scales suggests that the line arises from the cavity of the outflows or from rotating structures perpendicular to the H 2 jets (i.e., disc). Five sources also exhibit CO emission features (63%), and three HMYSOs display CO absorption features (38%), indicating that they are likely associated with circumstellar discs. By further investigating the kinematics of the spatially resolved CO absorption features, the Keplerian mass of three sources was estimated in 5±3, 8±5 and 30±10 M ⊙. These results support that high-mass stars are formed through discs, similarly as observed towards low-mass stars. The comparison between the collimation degree of the molecular jets or outflows detected in the NIFS data with their large-scale counterparts indicate that these structures present a relatively wide range of collimation degrees.
Molecular outflows in low-and high-mass star forming regions
Arxiv preprint astro-ph/ …, 2006
We review the known properties of molecular outflows from low-and high-mass young stars. General trends among outflows are identified, and the most recent studies on the morphology, kinematics, energetics, and evolution of molecular outflows are discussed, focusing on results from high-resolution millimeter observations. We review the existing four broad classes of outflow models and compare numerical simulations with the observational data. A single class of models cannot explain the range of morphological and kinematic properties that are observed, and we propose a possible solution. The impact of outflows on their cloud is examined, and we review how outflows can disrupt their surrounding environment, through the clearing of gas and the injection of momentum and energy onto the gas at distances from their powering sources from about 0.01 to a few pc. We also discuss the effects of shock-induced chemical processes on the ambient medium, and how these processes may act as a chemical clock to date outflows. Lastly, future outflow research with existing and planned millimeter and submillimeter instruments is presented.
From the Convergence of Filaments to Disk-Outflow Accretion: Massive Star Formation in W33A
2010
Interferometric observations of the W33A massive star-formation region, performed with the Submillimeter Array (SMA) and the Very Large Array (VLA) at resolutions from 5 ′′ (0.1 pc) to 0.5 ′′ (0.01 pc) are presented. Our three main findings are: (1) parsec-scale, filamentary structures of cold molecular gas are detected. Two filaments at different velocities intersect in the zone where the star formation is occurring. This is consistent with triggering of the star-formation activity by the convergence of such filaments, as predicted by numerical simulations of star formation initiated by converging flows. (2) The two dusty cores (MM1 and MM2) at the intersection of the filaments are found to be at different evolutionary stages, and each of them is resolved into multiple condensations. MM1 and MM2 have markedly different temperatures, continuum spectral indices, molecular-line spectra, and masses of both stars and gas. (3) The dynamics of the "hot-core" MM1 indicates the presence of a rotating disk in its center (MM1-Main) around a faint free-free source. The stellar mass is estimated to be ∼ 10 M ⊙. A massive molecular outflow is observed along the rotation axis of the disk.
Infall and Outflow Motions in the High-Mass Star-Forming Complex G9.62+0.19
The Astrophysical Journal, 2011
We present the results of a high resolution study with the Submillimeter Array towards the massive star forming complex G9.62+0.19. Three sub-mm cores are detected in this region. The masses are 13, 30 and 165 M ⊙ for the northern, middle and southern dust cores, respectively. Infall motions are found with HCN (4-3) and CS (7-6) lines at the middle core (G9.62+0.19 E). The infall rate is 4.3 × 10 −3 M ⊙ ·yr −1 .
The Astrophysical Journal, 2013
We present VLA NH 3 and PdBI NH 2 D and HN 13 C observations of the star forming core ahead of HH 80N, the optically obscured northern counterpart of the Herbig-Haro objects HH 80/81. The main goal is to determine the kinematical information of the high density regions of the core (n > ∼ 10 5 cm −3 ), missed in previous works due to the depletion of the species observed (e.g. CS). The obtained maps show different kinematical signatures between the eastern and western parts of the core, suggesting a possible dynamical interaction of the core with the HH 80/81/80N outflow. The analysis of the Position-Velocity (PV) plots of these species rules out a previous interpretation of having a molecular ring-like structure of 6 × 10 4 AU of radius traced by CS infalling onto a central protostar found in the core (IRS1). High degree of NH 3 deuteration, with respect to the central part of the core harboring IRS1, is derived in the eastern part, where a dust condensation (SE) is located. This deuteration trend of NH 3 suggests that SE is in a prestellar evolutionary stage, earlier than that of the IRS1. Since SE is the closest condensation to the HH 80N/81/80N outflow, in case of having outflow-core dynamical interaction, it should be perturbed first and be the most evolved condensation in the core. Therefore, the derived evolutionary sequence for SE and IRS1 makes the outflow triggered star formation on IRS1 unlikely. found evidence of a bipolar CO outflow centered near the peak
Episodic molecular outflow in the very young protostellar cluster Serpens South
Nature, 2015
ACCEPTED FOR PUBLICATION IN NATURE. The loss of mass from protostars, in the form of a jet or outflow, is a necessary counterpart to protostellar mass accretion. 1,2 Outflow ejection events probably vary in their velocity and/or in the rate of mass loss. Such 'episodic' ejection events 3 have been observed during the Class 0 protostellar phase (the early accretion stage), 4-10 and continue during the subsequent class I phase that marks the first one million years of star formation. 11-14 Previously observed episodic-ejection sources were relatively isolated; however, the most common sites of star formation are clusters. 15 Outflows link protostars with their environment and provide a viable source of turbulence that is necessary for regulating star formation in clusters, 3 but it is not known how an accretion-driven jet or outflow in a clustered environment manifests itself in its earliest stage. This early stage is important in establishing the initial conditions for momentum and energy transfer to the environment as the protostar and cluster evolve. Here we report that an outflow from a very young class 0 protostar, at the hub of the very active and filamentary Serpens South protostellar cluster, 16-18 shows unambiguous episodic events. The 12 C 16 O (J = 2 − 1) emission from the protostar reveals 22 distinct features of outflow ejecta, the most recent having the highest velocity. The outflow forms bipolar lobes-one of the first detectable signs of star formation-which originate from the peak of 1-mm continuum emission. Emission from the surrounding C 18 O envelope shows kinematics consistent with rotation and an infall of material onto the protostar. The data suggest that episodic accretion-driven outflow begins in the earliest phase of protostellar evolution, and that the outflow remains intact in a very clustered environment, probably providing efficient momentum transfer for driving turbulence.