A String of Radio Emission Associated with Iras 16562-3959: A Collimated Jet Emanating from a Luminous Massive Young Stellar Object (original) (raw)
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Detection of a Collimated Jet Towards the High-Mass Protostar IRAS 16547-4247
Open Issues in Local Star Formation, 2003
Here we present the discovery of a triple radio continuum source associated with IRAS 16547-4247. The spectral indices of the three components are consistent with a jet powered by a massive O-type star in the process of formation, with the outer radio components being the shocked gas at the working surfaces of the jet. The detected radio continuum emission from the central object is thought to arise from the jet itself, prior to the formation of a detectable HII region. All three radio continuum components are located within a molecular core of mass 10 3 M ⊙. Our discovery makes IRAS 16547-4247 the most luminous (∼ 6.2 × 10 4 L ⊙) young stellar object from which a thermal jet emanates, suggesting that the mechanism that produces jets in low-mass star formation also operates in high-mass star formation.
Astrophysical Journal, 2005
A triple radio source recently detected in association with the luminous infrared source IRAS 16547-4247 has been studied with high angular resolution and high sensitivity with the Very Large Array at 3.6 and 2 cm. Our observations confirm the interpretation that the central object is a thermal radio jet, while the two outer lobes are most probably heavily obscured HH objects. The thermal radio jet is resolved angularly for the first time and found to align closely with the outer lobes. The opening angle of the thermal jet is estimated to be ∼ 25 • , -2confirming that collimated outflows can also be present in massive protostars. The proper motions of the outer lobes should be measurable over timescales of a few years. Several fainter sources detected in the region are most probably associated with other stars in a young cluster.
2003
IRAS 16547−4247 is the most luminous (6.2×10 4 L⊙) embedded young stellar object known to harbor a thermal radio jet. We report the discovery using VLT-ISAAC of a chain of H2 2.12 µm emission knots that trace a collimated flow extending over 1.5 pc. The alignment of the H2 flow and the central location of the radio jet implies that these phenomena are intimately linked. We have also detected using TIMMI2 an isolated, unresolved 12 µm infrared source towards the radio jet. Our findings affirm that IRAS 16547−4247 is excited by a single O-type star that is driving a collimated jet. We argue that the accretion mechanism which produces jets in low-mass star formation also operates in the higher mass regime. Subject headings: ISM: individual (IRAS 16547−4247) — ISM: jets and outflows — stars: formation – 2 – 1.
Radio and IR study of the massive star-forming region IRAS 16353−4636
Astronomy & Astrophysics, 2010
Context. With the latest infrared surveys, the number of massive protostellar candidates has increased significantly. New studies have posed additional questions on important issues about the formation, evolution, and other phenomena related to them. Complementary to infrared data, radio observations are a good tool to study the nature of these objects, and to diagnose the formation stage. Aims. Here we study the far-infrared source IRAS 16353-4636 with the aim of understanding its nature and origin. In particular, we search for young stellar objects (YSOs), possible outflow structure, and the presence of non-thermal emission. Methods. Using high-resolution, multi-wavelength radio continuum data obtained with the Australia Telescope Compact Array ⋆ , we image IRAS 16353-4636 and its environment from 1.4 to 19.6 GHz, and derive the distribution of the spectral index at maximum angular resolution. We also present new JHK s photometry and spectroscopy data obtained at ESO NTT ⋆⋆ . 13 CO and archival H i line data, and infrared databases (MSX, GLIMPSE, MIPSGal) are also inspected. Results. The radio continuum emission associated with IRAS 16353-4636 was found to be extended (∼10 arcsec), with a bow-shaped morphology above 4.8 GHz, and a strong peak persistent at all frequencies. The NIR photometry led us to identify ten near-IR sources and classify them according to their color. We used the H i line data to derive the source distance, and analyzed the kinematical information from the CO and NIR lines detected. Conclusions. We have identified the source IRAS 16353−4636 as a new protostellar cluster. In this cluster we recognized three distinct sources: a low-mass YSO, a high-mass YSOs, and a mildly confined region of intense and non-thermal radio emission. We propose the latter corresponds to the terminal part of an outflow.
Astronomy & Astrophysics, 2013
Context. The formation of OB-type stars up to (at least) 140 M can be explained via disk-mediated accretion and in fact growing observational evidence of disk-jet systems is found in high-mass star-forming regions. Aims. With the present observations we wish to investigate at sub-arcsecond resolution the jet structure close to the well studied high-mass protostar IRAS 20126+4104, which is known to be surrounded by a Keplerian disk. Methods. Adaptive optics imaging of the 2.2 μm continuum and H 2 and Brγ line emission have been performed with the Large Binocular Telescope, attaining an angular resolution of ∼90 mas and an astrometric precision of ∼100 mas. Results. While our results are consistent with previous K-band images by other authors, the improved (by a factor ∼3) resolution allows us to identify a number of previously unseen features, such as bow shocks spread all over the jet structure. Also, we confirm the existence of a bipolar nebulosity within 1 from the protostar, prove that the emission from the brightest, SE lobe is mostly due to the H 2 line, and resolve its structure. Conclusions. Comparison with other tracers such as masers, thermal molecular line emission, and free-free continuum emission proves that the bipolar nebulosity is indeed tracing the root of the bipolar jet powered by the deeply embedded protostar at the center of the Keplerian disk.
An Extremely Young Massive Stellar Object near IRAS 07029-1215
Astrophysical Journal - ASTROPHYS J, 2004
In the course of a comprehensive millimeter/submillimeter survey of massive-star-forming regions, the vicinities of a sample of 47 luminous IRAS sources were closely investigated with the Submillimeter Common-User Bolometric Array and the MPIfR bolometers in order to search for massive protostellar candidates. A particularly interesting object has been found in the surroundings of the bright far-infrared source IRAS 07029-1215. Follow-up line observations show that the object is cold, has a massive envelope, and is associated with an energetic molecular outflow. No infrared point source has been detected at its position. Therefore, it is a very good candidate as a member of the long-sought group of massive protostars.
An Infrared Jet from a High-Mass Young Star
The Astrophysical Journal, 2001
Jets are a direct consequence of accretion in the inner regions of circumstellar disks. They trace the structure of the accretion disk and, indirectly, the star formation mechanism. Here we report on the discovery of a nearinfrared jet from a young B1 star, one of the most luminous young stars known to exhibit such a structure. The jet is seen in LЈ images of IRAS 18556ϩ0136 in the G35.2Ϫ0.74N region; a significant fraction of the emission is due to Bra line emission. At shorter wavelengths, the jet is obscured: the colors of the bipolar nebula are consistent with 25 mag visual extinctions to the near lobe and 40 mag to the far lobe. A previously detected radio continuum source and an elongated clump of OH maser spots coincide with a break in the jet. This is interpreted as the location of the circumstellar disk surrounding the embedded young star. A lower limit of ∼170 mag is derived for the extinction to the exciting source. This provides an estimate of 0.15 M for the mass , of the circumstellar disk within ∼1500 AU of the central source. Emission knots on either side of a second, weaker radio continuum source offset ∼3Љ from the jet source suggests the presence of a second outflow source in the region. The lack of known jets in high-mass protostars, in contrast to their prevalence among low-mass systems, points to a difference in the star formation process, e.g., mergers. The jet from this B1 star suggests that the mechanisms that form low-mass stars can operate up to at least 10 M stars. , Subject headings: accretion, accretion disks -H ii regions -ISM: individual (G35.2Ϫ0.74N) -ISM: jets and outflows -stars: formation
Radio Observations of Infrared-Luminous High-Redshift Quasi-Stellar Objects
The Astronomical Journal, 2001
We present Very Large Array (VLA) observations at 1.4 GHz and 5 GHz of a sample of 12 Quasi-stellar Objects (QSOs) at z = 3.99 to 4.46. The sources were selected as the brightest sources at 250 GHz from the recent survey of Omont et al. (2001). We detect seven sources at 1.4 GHz with flux densities, S 1.4 ≥ 50 µJy. These centimeter (cm) wavelength observations imply that the millimeter (mm) emission is most likely thermal dust emission. The radio-through-optical spectral energy distributions for these sources are within the broad range defined by lower redshift, lower optical luminosity QSOs. For two sources the radio continuum luminosities and morphologies indicate steep spectrum, radio loud emission from a jet-driven radio source. For the remaining 10 sources the 1.4 GHz flux densities, or limits, are consistent with those expected for active star forming galaxies. If the radio emission is powered by star formation in these systems, then the implied star formation rates are of order 10 3 M ⊙ year −1. We discuss the angular sizes and spatial distributions of the radio emitting regions, and we consider briefly these results in the context of co-eval black hole and stellar bulge formation in galaxies.
Detection of a Collimated Jet towards a High-mass Protostar
2002
Here we present the discovery of a triple radio continuum source associated with IRAS 16547-4247. The spectral indices of the three components are consistent with a jet powered by a massive O-type star in the process of formation, with the outer radio components being the shocked gas at the working surfaces of the jet. The detected radio continuum emission from the central object is thought to arise from the jet itself, prior to the formation of a detectable HII region. All three radio continuum components are located within a molecular core of mass 10^3 M_sun. Our discovery makes IRAS 16547-4247 the most luminous (6.2 x 10^4 L_sun) young stellar object from which a thermal jet emanates, suggesting that the mechanism that produces jets in low-mass star formation also operates in high-mass star formation.
Collimated molecular jets from high-mass young stars: IRAS?18151-1208
Astronomy and Astrophysics, 2004
Recent near-IR images of massive star forming regions have revealed two collimated jets in the IRAS 18151-1208 region, one of which is almost a parsec in length (Varricatt et al.). Follow-up high-spectral-resolution echelle spectroscopy and 2-dimensional "integral field" spectroscopy of the associated molecular shock features are presented here. From these data kinematic information and excitation maps are extracted, which show that the two jets are morphologically, kinematically and energetically similar to their counterparts from low mass protostars. The close association between the H 2 emission features and the high-velocity CO emission presented by Beuther et al. also suggests that the CO represents gas entrained by these two very collimated jets. From the mass and momentum of the molecular gas, and the luminosity of the H 2 features, it is clear that the flows must be powered by massive sources. To all intents and purposes, the molecular jets appear to be scaled-up versions of low-mass YSO jets. Collectively, the observations add further support to the idea that massive stars are formed through vigorous disk accretion, and that, while in their earliest stages of evolution, massive protostars drive collimated jets.