Bipolar Molecular Outflow Research Articles

First Confirmed Detection of a Bipolar Molecular Outflow from a Young Brown Dwarf

Studying the earliest stages in the birth of stars is crucial for understanding how they form. Brown dwarfs with masses between that of stars and planets are not massive enough to maintain stable hydrogen-burning fusion reactions during most of their lifetime. Their origins are subject to much debate in recent literature because their masses are far below the typical mass where core collapse is expected to occur. We present the first confirmed evidence that brown dwarfs undergo a phase of molecular outflow that is typical of young stars. Using the Submillimeter Array, we have obtained a map of a bipolar molecular outflow from a young brown dwarf. We estimate an outflow mass of 1.6 × 10−4 M☉ and a mass-loss rate of 1.4 × 10−9 M☉. These values are over 2 orders of magnitude smaller than the typical ones for T Tauri stars. From our millimeter continuum data and our own analysis of Spitzer infrared photometry, we estimate that the brown dwarf has a disk with a mass of 8 × 10−3 M☉ and an outer disk radius of 80 AU. Our results demonstrate that the bipolar molecular outflow operates down to planetary masses, occurring in brown dwarfs as a scaled-down version of the universal process seen in young stars.

Large-scale mapping of the IRAS 0042 + 5530 region in the 12CO (J = 1−0) and 13CO (J = 1−0) molecular lines

We present new radio observations of molecular lines in the region of high mass star formation, namely G122.0-7.1. A large-scale map of the emission observed in the 12CO (J = 1−0) and 13CO (J = 1−0) lines covers the area of 15′ × 9′, revealing two dense regions. The molecular bipolar outflows have been resolved in ASO1 region. It is associated with the known candidate YSO nearby IRAS 0042 + 5530. Also, a new dense region has been discovered in the North-Western part of the G122.0-7.1 at a distance of 5′ from IRAS 0042 + 5530. Its position is close to the peak of 4850 MHz emission.

SMA CO (2-1) Observations of CG 30: A Protostellar Binary System with a High-Velocity Quadrupolar Molecular Outflow

We present interferometric observations in the12CO (2-1) line and at 1.3 mm dust continuum of the low-mass protostellar binary system in the cometary globule CG 30, using the Submillimeter Array. The dust continuum images resolve two compact sources (CG 30N and CG 30S), with a linear separation of ~8700 AU and total gas masses of ~1.4 and ~0.6 M☉, respectively. With the CO images, we discover two high-velocity bipolar molecular outflows, driven by the two sources. The two outflows are nearly perpendicular to each other, showing a quadrupolar morphology. The northern bipolar outflow extends along the southeast (redshifted, with a velocity up to ~23 km s−1) and northwest (blueshifted, velocity up to ~30 km s−1) directions, while the southern pair has an orientation from southwest (blueshifted, velocity up to ~13 km s−1) to northeast (redshifted, velocity up to ~41 km s−1). The outflow mass of the northern pair, driven by the higher mass source CG 30N, is ~9 times larger than that of the southern pair. The discovery of the quadrupolar molecular outflow in the CG 30 protobinary system, as well as the presence of other quadrupolar outflows associated with binary systems, demonstrate that the disks in (wide) binary systems are not necessarily co-aligned after fragmentation.

The Ionization of Accretion Flows in High-Mass Star Formation: W51e2

Previous observations show that the hypercompact HII region W51e2 is surrounded by a massive molecular accretion flow centered on the HII region. New observations of the H53alpha radio recombination line made with the VLA at 0.45 arc second angular resolution show a velocity gradient in the ionized gas within the HII region of > 500 kms-1 pc-1 comparable to the velocity gradient seen in the molecular accretion flow. New CO line observations made with the SMA at arc second angular resolution detect a molecular bipolar outflow immediately around the W51e2 HII region and extending along the axis of rotation of the molecular flow. These observations are consistent with an evolutionary phase for high mass star formation in which a newly formed massive star first begins to ionize its surroundings including its own accretion flow.

The Detection of a Molecular Bipolar Flow in the Multipolar Planetary Nebula NGC 2440

We report the detection of a molecular bipolar outflow in the CO J = 3–2 line in the optical multipolar planetary nebula NGC 2440. The observed CO J = 3–2 emission shows two major velocity components which are blue- and redshifted by 18 km s−1 relative to the systemic velocity of VLSR = 43 km s−1. Both components are detected only near the central region and have a size of about 24''. In addition to this bulk motion, weak CO emissions in the central region are detected at higher velocities of ±20 to ±40 km s−1. The presence of the fast CO components are in line with the picture that the neutral dense torus is being torn apart by very fast outflowing winds. The spatial distribution of CO emission shows two emission peaks at the systemic velocity that are located 30'' to the northeast and 30'' to the southwest from the center in point symmetry. The positions of the two CO emission peaks coincide well with the emission knots in the optical, suggesting that the CO outflow corresponds to one pair of the multiple optical bipolar lobes of the nebula. This particular pair of bipolar lobes seem distinctly rich in heavy molecules compared with the other optical bipolar lobes. The extent of CO emission in NGC 2440 is well constrained. The total amount of CO molecules in NGC 2440 is 3.5 × 1051 if the distance to NGC 2440 is 2.19 kpc and the excitation temperature is 25 K.

The CO Molecular Outflows of IRAS 16293−2422 Probed by the Submillimeter Array

We have mapped the protobinary source IRAS 16293–2422 in CO 2-1,13CO 2-1, and CO 3-2 with the Submillimeter Array (SMA). The maps with resolution of 1.5''-5'' reveal a single small-scale (~3000 AU) bipolar molecular outflow along the east-west direction. We found that the blueshifted emission of this small-scale outflow mainly extends to the east and the redshifted emission to the west from the position of IRAS 16293A. A comparison with the morphology of the large-scale outflows previously observed by single-dish telescopes at millimeter wavelengths suggests that the small-scale outflow may be the inner part of the large-scale (~15,000 AU) east-west outflow. On the other hand, there is no clear counterpart of the large-scale northeast-southwest outflow in our SMA maps. Comparing analytical models to the data suggests that the morphology and kinematics of the small-scale outflow can be explained by a wide-angle wind with an inclination angle of ~30°-40° with respect to the plane of the sky. The high-resolution CO maps show that there are two compact, bright spots in the blueshifted velocity range. An LVG analysis shows that the one located 1'' to the east of source A is extremely dense, n(H2) ~107 cm−3, and warm, Tkin > 55 K. The other one located 1'' southeast of source B has a higher temperature of Tkin > 65 K but slightly lower density of n(H2) ~106 cm−3. It is likely that these bright spots are associated with the hot core-like emission observed toward IRAS 16293. Since both bright spots are blueshifted from the systemic velocity and are offset from the protostellar positions, they are likely formed by shocks.

Observation and Study of the 13CO, C 18O, HCO + and N 2H + Molecular Lines Towards IRAS 02232+6138

Using the 13.7 m millimeter-wave telescope at the Qinghai Station of Purple Mountain Observatory, we have made observations of 13CO, C 18O, HCO + and N 2H + molecular lines towards IRAS 02232+6138. As the excitation density of the probe molecule increases from 13CO to HCO +, the size of the cloud core associated with IRAS 02232+6138 decreases from 2.40 pc to 0.54 pc, and the virial mass of the cloud core decreases from 2.2 × 10 3 M ⊙ to 5.1 × 10 2 M ⊙. A bipolar molecular outflow is found towards IRAS 02232+6138. Using the power function n( r) ∝ r −α to fit the spatial density structure of the cloud core, we obtain the power-law index α = 2.3 − 1.2; and we find that, as the probed density increases, the power function becomes more flat. The abundance ratio of 13CO to C 18O is 12.4 ± 6.9, comparable with the values 11.8 ± 5.9 for dark clouds and the values 9.0–15.6 for massive cores. The abundance of N 2H + molecules is 3.5 ± 2.5 × 10 −10, consistent with the value 1.0 − 5.0 × 10 −10 for dark cloud cores and the value 1.2 − 12.8 × 10 −10 for massive cores. The abundance of HCO + molecules is 0.9 ± 0.5 × 10 −9, close to the value 1.6 − 2.4 × 10 −9 for massive cores. An increase of HCO + abundance in the outflow region was not found. Combining with the IRAS data, the luminosity-mass ratio of the cloud core is obtained in the range 37–163( L/ M) ⊙. Based on the IRAS luminosity, it is estimated that a main-sequence O7.5 star is probably embedded in the IRAS 02232+6138 cloud core.

Multiple Sources toward the High-Mass Young Star S140 IRS 1

S140 IRS 1 is a remarkable source where the radio source at the center of the main bipolar molecular outflow in the region is elongated perpendicular to the axis of the outflow, an orientation opposite to that expected if the radio source is a thermal jet exciting the outflow. We present results of 1.3 cm continuum and H2O maser emission observations made with the Very Large Array in its A configuration toward this region. In addition, we also present results of continuum observations at 7 mm and reanalyze observations at 2, 3.5, and 6 cm (previously published). IRS 1A is detected at all wavelengths, showing an elongated structure. Three water maser spots are detected along the major axis of the radio source IRS 1A. We have also detected a new continuum source at 3.5 cm (IRS 1C) located ≃0.6'' northeast of IRS 1A. The presence of these two young stellar objects (IRS 1A and 1C) could explain the existence of the two bipolar molecular outflows observed in the region. In addition, we have also detected three continuum clumps (IRS 1B, 1D, and 1E) located along the major axis of IRS 1A. We discuss two possible models to explain the nature of IRS 1A: a thermal jet and an equatorial wind.

Gemini observations of disks and jets in young stellar objects and in active galaxies

We present first results from the Near-infrared Integral Field Spectrograph (NIFS) located at Gemini North. For the active galaxies Cygnus A and Perseus A we observe rotationally-supported accretion disks and adduce the existence of massive central black holes and estimate their masses. In Cygnus A we also see remarkable high-excitation ionization cones dominated by photoionization from the central engine. In the T-Tauri stars HV Tau C and DG Tau we see highly-collimated bipolar outflows in the [Fe II] 1.644 micron line, surrounded by a slower molecular bipolar outflow seen in the H_2 lines, in accordance with the model advocated by Pyo et al. (2002).

Arcsecond‐Resolution Submillimeter HCN Imaging of the Binary Protostar IRAS 16293−2422

(Abridged) With the SMA we have made high angular-resolution (~1" = 160 AU) observations of the protobinary system IRAS 16293-2422 in the J = 4-3 lines of HCN and HC^15N, and in the continuum at 354.5 GHz. The HCN (4-3) line was also observed using the JCMT to supply missing short spacing information. Submillimeter continuum emission is detected from the individual binary components with a separation of ~5". The HC^15N (4-3) emission has revealed a compact (~500 AU) flattened structure (P.A. = -16 degree) associated with Source A, and shows a velocity gradient along the projected minor axis, which can be interpreted as an infalling gas motion. Our HCN image including the short-spacing information shows an extended (~3000 AU) circumbinary envelope as well as the compact structure associated with Source A. A toy model consisting of a flattened structure with radial infall towards a 1 Msun central star reproduces the HCN/HC^15N position-velocity diagram along the minor axis of the HC^15N emission. In the extended envelope there is also a North-East (Blue) to South-West (Red) velocity gradient across the binary alignment, which is likely to reflect gas motion in the swept-up dense gas associated with the molecular outflow from Source A. At Source B, there is only a weak compact structure with much narrower line widths (~2 km/s) seen in the optically-thin HC^15N emission than that at Source A (>10 km/s), and there is no clearly defined bipolar molecular outflow associated with Source B. These results imply the different evolutionary stages between Source A and B in the common circumbinary envelope.

VLBA Observations of G5.89−0.39: OH Masers and Magnetic Field Structure

We present VLBA observations of 1667 MHz OH maser emission from the massive star formation region G5.89-0.39. The observations were phase-referenced, allowing the absolute positions of the masers to be obtained. The 1667 MHz masers have radial velocities that span ~50 km s-1 but show little evidence of tracing the bipolar molecular outflow, as has been claimed in previous studies. We identify 23 Zeeman pairs through comparison of masers in left and right circular polarization. Magnetic field strengths range from -2 to +2 mG, and an ordered reversal in magnetic field direction is observed toward the southern region of the UC H II region. We suggest that the velocity and magnetic field structure of the 1667 MHz masers can be explained in the context of a model in which the masers arise in a neutral shell just outside a rapidly expanding ionized shell.

Hard X‐Rays and Fluorescent Iron Emission from the Embedded Infrared Cluster in NGC 2071

We present first results of XMM-Newton X-ray observations of the infrared cluster lying near the NGC 2071 reflection nebula in the Orion B region. This cluster is of interest because it is one of the closest regions known to harbor embedded high-mass stars. We report the discovery of hard X-ray emission from the dense central NGC 2071-IR subgroup, which contains at least three high-mass young stellar objects (NGC 2071 IRS 1, IRS 2, and IRS 3). A prominent X-ray source is detected within 1'' of the infrared source IRS 1, which is thought to drive a powerful bipolar molecular outflow. The X-ray spectrum of this source is quite unusual compared to the optically thin plasma spectra normally observed in young stellar objects (YSOs). The spectrum is characterized by a hard broadband continuum plus an exceptionally broad emission line at ≈6.4 keV from neutral or near-neutral iron. The fluorescent Fe line likely originates in cold material near the embedded star (i.e., a disk or envelope) that is irradiated by the hard, heavily absorbed X-ray source.

Discovery of an energetic bipolar molecular outflow towards IRAS 16547-4247

Aims. We present molecular line observations of the molecular core associated with IRAS 16547-4247, which have allowed us to determine its physical and kinematical properties at angular resolutions of ~18´´. Methods. The observations were made using the Atacama Pathfinder Experiment Telescope in the $J = 3 \rightarrow 2$ transitions of 12 CO and 13 CO, $J = 4 \rightarrow 3$ transitions of HCO + and H 13 CO + , and $J = 7 \rightarrow 6$ transition of CS. Results. Our observations reveal the presence of a collimated bipolar outflow with lobes ~0.7 pc in extent and aligned with the thermal jet located at the center of the core. The morphology and velocity structure of the flow are well described by a biconical outflow that is inclined from the line of sight by an angle of 84°, has a semi-opening angle of 14°, and in which the gas moves outwards with a constant total velocity, with respect to the cone apex, of ~120 km s -1 . The outflow is massive and energetic (flow mass ~110 $M_{\odot}$; mass outflow rate ~$2\times10^{-2}$ $M_{\odot}$ yr -1 ; momentum ~$2\times10^3$ $M_{\odot}$ km s -1 and kinetic energy ~$9\times 10^{47}$ erg), and has a dynamical time scale of $6\times10^3$ yr. These parameters are consistent with the flow being driven by a young massive stellar object with $L_{\rm bol} \sim 6\times10^4$ $L_{\odot}$.

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 C 18 O(1–0) and N 2 H + (1–0) maps obtained with the FCRAO telescope at a resolution of about $50''$ and CO(2–1) data obtained with the IRAM 30 m 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 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 similar episodes of stellar birth may have produced the subclustering seen in the halo of IC 348.

The high latitude low mass star forming region Cometary Globule 12: two compact cores and a C18O hot spot

AbstractCometary globule CG 12 lies at the distance of 630 pc more than 200 pc above the Galactic plane. The cloud's structure could be due to the passage of a supernova blast wave. Curiously, the cometary tail points at the galactic plane which would put the putative supernova even farther above the Galactic plane than the globule. The globule contains a low/intermediate mass stellar cluster with at least 9 members (Williams et al. 1977). The head of CG 12 has been observed using NIR imaging (NTT SOFI), mm continuum (SEST SIMBA) and sub mm (APEX) and mm (SEST) spectroscopy (Haikala & Olberg 2006, Haikala et al.). The molecular material is distributed in a North-South 10' long elongated lane with two compact maxima separated by 3'. Strong C18O (3-2), (2-1) and (1-0) emission is detected in both maxima and both have an associated compact 1.2 mm continuum source. The Northern core, CG 12 N, is cold and is possibly still pre-stellar. A dense and compact core is observed in DCO+ and CS emission in the direction of the Southern core, CG 12 S. A remarkable C18O hot spot was detected in CG 12 S. This is the first detection of such a compact, warm object in a low mass star forming region. The hot spot can be modelled with a 60″ to 80″ diameter (~0.2 pc) hot (80 K ≲ Tex≲ 100 K) 1.6 solar mass clump (Haikala et al. 2006). The hot spot lies at the edge of a dense cloud core and on the axis of a highly collimated bipolar molecular outflow (White 1993). The driving source of the outflow is most probably embedded in the dense core. NIR imaging reveals a bright cone like feature with a faint counter cone in the centre of CG 12 S. The size of the CG 12 compact head, 1.1 pc by 1.8 pc, and the C18O mass larger than 100 solar masses are comparable to those of other nearby low/intermediate mass star formation regions.

C$^\mathsf{18}$O (3–2) observations of the Cometary Globule CG 12: a cold core and a C$^\mathsf{18}$O hot spot

The feasibility of observing the C 18 O (3-2) spectral line in cold clouds with the APEX telescope has been tested. As the line at 329.330 GHz lies in the wing of a strong atmospheric H 2 O absorption it can be observed only at high altitude observatories. Using the three lowest rotational levels instead of only two helps to narrow down the physical properties of dark clouds and globules. The centres of two C 18 O maxima in the high latitude low mass star forming region CG 12 were mapped in C 18 O (3-2) and the data were analyzed together with spectral line data from the SEST. The T MB (3-2)/T MB (2-1) ratio in the northern C 18 O maximum, CG 12-N, is 0.8, and in the southern maximum, CG 12-S, ∼2. CG 12-N is modelled as a 120 diameter (0.4 pc) cold core with a mass of 27 M ⊙ . A small size maximum with a narrow, 0.8 km s -1 , C 18 O (3-2) spectral line with a peak temperature of T MB ∼ 11 K was detected in CG 12-S. This maximum is modelled as a 60-80 diameter (∼0.2 pc) hot (80 K? T ex ? 200 K) ∼1.6 M ⊙ clump. The source lies on the axis of a highly collimated bipolar molecular outflow near its driving source. This is the first detection of such a compact, warm object in a low mass star forming region.

The Massive Bipolar Outflow in IRAS 20110+3321

Mapping observations were made towards IRAS 20110+3321 using theNobeyama 45 m and the Delingha 13.7 m radio telescopes. The highangular resolution (~21′′) image with the 45 m telescope showsthat there is a high-velocity bipolar molecular outflow in this region,which is in the NW–SE direction with a collimation factor of ~ 2.2.The outflow has significantly higher mass loss rate and mechanicalluminosity than those from low mass YSOs, indicating that the outflow isdriven by the IRAS source. A dense massive core was detected by mappingC18O (J = 1−0) line in the area with the 13.7 m telescope. TheIRAS source lies within the core but slightly offsets from its emissionpeak.

New signposts of massive star formation in the S235A-B region

We report on new aspects of the star-forming region S235AB revealed through high-resolution observations at radio and mid-infrared wavelengths. Using the Very Large Array, we carried out sensitive observations of S235AB in the cm continuum (6, 3.6, 1.3, and 0.7) and in the 22 GHz water maser line. These were complemented with Spitzer Space Telescope Infrared Array Camera archive data to clarify the correspondence between radio and IR sources. We made also use of newly presented data from the Medicina water maser patrol, started in 1987, to study the variability of the water masers found in the region. S235A is a classical HII region whose structure is now well resolved. To the south, no radio continuum emission is detected either from the compact molecular core or from the jet-like structure observed at 3.3 mm, suggesting emission from dust in both cases. We find two new compact radio continuum sources (VLA-1 and VLA-2) and three separate maser spots. VLA-1 coincides with one of the maser spots and with a previously identified IR source (M1). VLA-2 lies towards S235B and represents the first radio detection from this peculiar nebula that may represent an ionized wind from a more evolved star. The two other maser spots coincide with an elongated structure previously observed within the molecular core in the C34S line. This structure is perpendicular to a bipolar molecular outflow observed in HCO+(1-0) and may trace the associated equatorial disk. The Spitzer images reveal a red object towards the molecular core. This is the most viable candidate for the embedded source originating the outflow and maser phenomenology. The picture emerging from these and previous data shows the extreme complexity of a small (< 0.5 pc) star-forming region where widely different stages of stellar evolution are present.

An Equatorial Wind from the Massive Young Stellar Object S140 IRS 1

The discovery of the second equatorial ionized stellar wind from a massive young stellar object is reported. High-resolution radio continuum maps of S140 IRS 1 reveal a highly elongated source that is perpendicular to the larger scale bipolar molecular outflow. This picture is confirmed by location of a small-scale monopolar near-IR reflection nebula at the base of the blueshifted lobe. A second epoch of observations over a 5 yr baseline show little ordered outward proper motion of clumps as would have been expected for a jet. A third epoch, taken only 50 days after the second, did show significant changes in the radio morphology. These radio properties can all be understood in the context of an equatorial wind driven by radiation pressure from the central star and inner disk acting on the gas in the surface layers of the disk as proposed by Drew et al. This equatorial wind system is briefly compared with the one in S106 IR, and contrasted with other massive young stellar objects that drive ionized jets.

High?Resolution Observations of Water Masers in Bok Globules

We present Very Large Array observations at 1.3 cm of several water maser detections obtained by previous single-dish studies of Bok globules in the 1988 Clemens and Barvainis (CB) catalog. We report water maser emission in CB 3 (CB 3-mm), CB 54 (IRAS 07020-1618), CB 101 (IRAS 17503-0833), and CB 232 (IRAS 21352+4307) and nondetection toward CB 65 (IRAS 16277-2332) and CB 205 (IRAS 19433+2743). These are the first reported interferometric observations of water masers in Bok globules of the CB catalog. We also present single-dish observations of millimeter and centimeter spectral lines toward CB 101 (IRAS 17503-0833) and CB 65 (IRAS 16277-2332). All the maser emission seems to be associated with star-forming regions hosting bipolar molecular outflows, except IRAS 17503-0833 in CB 101, which we suggest to be a possible Mira evolved star, and IRAS 16277-2332 in CB 65, which is of unknown nature. We have used the precise position of the maser emission to derive information about the powering source of the masers. By analyzing the spatio-kinematical distribution of the water masers, we confirm the millimeter source CB 3-mm as the most likely powering source of the CB 3 masers. We propose the near-IR source CB 232 YC1-I as the best candidate for pumping the maser emission observed in CB 232, while in CB 54 we suggest that the pumping source of the masers could be located at the position of an elongated feature observed in near-IR maps.