Infrared Source IRS Research Articles

High-velocity Wind from IRS 1 in the NGC 2071IR

AbstractWe present the results of 1.3 and 3.6 cm radio continuum emission toward the NGC 2071IR star-forming region, carried out with the VLA in its A configuration. We detect continuum emission toward the infrared sources IRS 1 and IRS 3 at both wavelengths. In particular, IRS 1 breaks up into three continuum peaks (IRS 1E, 1C, and 1W), aligned in the east-west direction, being IRS 1 the central source. The morphology of the condensation IRS 1W is very interesting, which has an elongated structure and shows a significant curvature towards the north. We suggest that this morphology could be explained as the impact of a high-velocity wind or jetlike outflow from IRS 1 on a close companion or other obstruction, which also explains the strong water maser emission observed toward IRS 1W.

RADIO JETS AND DISKS IN THE INTERMEDIATE-MASS STAR-FORMING REGION NGC2071IR

We report the results of simultaneous radio continuum and water maser observations toward the NGC 2071IR star-forming region, carried out with the VLA in its A configuration. We detect continuum emission toward the infrared sources IRS 1 and IRS 3 at 1.3 and 3.6 cm. In addition, a new continuum source, VLA 1, is also detected at both wavelengths, which is located between IRS 1 and IRS 3. IRS 1 breaks up into three continuum peaks (IRS 1E, 1C, and 1W), aligned in the east-west direction (P.A. = 100°). IRS 1 is the central source, while the sources E and W seem to be condensations ejected by IRS 1. In the same way, IRS 3 is also forming a triple system (IRS 3N, 3C and 3S), which is elongated in the northeast-southwest direction and the condensations, IRS 3N and IRS 3S, are symmetrically located along the major axis. Based on the morphology and the continuum emission, we suggest that both IRS 1 and IRS 3 are radio jets, which have ejected condensations into the interstellar medium. Moreover, IRS 1 and IRS 3 seem to be the driving sources of the large-scale outflows observed in H2 and CO, respectively. In addition, we also detected water emission toward the systems IRS 1, IRS 3, and the new source VLA 1. Based on the spatial-kinematic distribution of the water masers, we find evidence that the water masers are tracing part of circumstellar disks around IRS 1C and IRS 3C. Moreover, we estimate that the sources IRS 1C and IRS 3C have central masses of ~5 and ~1 M ☉, respectively. We conclude that the radio continuum and water maser emission are tracing disk-YSO-outflow systems toward IRS 1 and IRS 3, which are low- and intermediate-mass young stellar objects, respectively.

OH masers, molecular outflows and magnetic fields in NGC 7538

The multi-element radio-linked interferometer network (MERLIN) measurements of 1665-, 1667- and 1720-MHz OH masers associated with NGC 7538 are presented. The masers are located at the centres of three bipolar molecular outflows associated with the infrared sources IRS 1, IRS 9 and IRS 11. The distribution of OH masers in IRS 1 is more extensive than previously reported and is displaced to the south of the methanol 6.7-GHz masers. The OH masers in IRS 9 have not previously been reported. Their distribution seems to be orthogonal to the direction of the outflow and to the distribution of H2O masers. The maser distribution in IRS 11 is parallel to the dust ridge and orthogonal to the outflow. Full polarization measurements of the OH maser emission show systematic differences between the three sources. IRS 1 has moderate polarization, with linear polarization vectors partially aligned with the bipolar outflow; IRS 9 exhibits larger polarization, but little linear component; IRS 11 shows the strongest polarization and has linear polarization vectors aligned parallel to the outflow. There is also evidence for a toroidal component of the magnetic field around the IRS 11 outflow, orthogonal to the outflow direction. It is suggested that the differences in polarization trace a possible evolutionary sequence from oldest (IRS 1) to youngest (IRS 11).

Mid‐Infrared Imaging of NGC 6334 I

We present high-resolution (<05) mid-infrared Keck II images of individual sources in the central region of NGC 6334 I. We compare these images to images at a variety of other wavelengths from the near-infrared to centimeter radio continuum and speculate on the nature of the NGC 6334 I sources. We assert that the cometary shape of the ultracompact H II (UCHII) region here, NGC 6334F, is due to a champagne-like flow from a source on the edge of a molecular clump and not due to a bow shock caused by the supersonic motion of the UCHII region through the interstellar medium. The mid-infrared emission is concentrated into an arc of dust that defines the boundary between the UCHII region and the molecular clump. This dust arc contains a majority of the masers in the region. We discuss the nature of the four near-infrared sources associated with IRS I1 and suggest that one of the sources, IRS 1E, is responsible for the heating and ionizing of the UCHII region and the mid-infrared dust arc. Infrared source IRS I2, which has been thought to be a circumstellar disk associated with a linear distribution of methanol masers, is found not to be directly coincident with the masers and elongated at a much different position angle. IRS I3 is found to be a extended source of mid-infrared emission coming from a cluster of young dusty sources seen in the near-infrared.

A Cluster of Radio Sources near GGD 14

We present sensitive Very Large Array (VLA) radio continuum observations at 3.6 cm toward the star-forming region GGD 14 (also known as GGD 12/13/14/15, G213.88-11.84, and AFGL 890). In addition to the previously known cometary H II region, we report the detection of a cluster of six compact radio sources, all with a nearby 2 μm counterpart. These new sources appear to be ultracompact H II regions ionized by B2-B3 zero-age main-sequence (ZAMS) stars. The kinematic age of these six compact radio sources, assuming expansion at 10 km s-1, is less than 25 yr, and we conclude that they must be confined by some mechanism. The sources are so compact that they could be gravitationally bound to the star. One of the new detections, the source VLA 7, is located near the center of the CO molecular outflow. We suggest that VLA 7 is associated with the powering source of the molecular outflow and that the infrared sources IRS 9M and IRS 9E, between which lies VLA 7, could be the lobes of a bipolar reflection nebula tracing the outflow at small scales.

Radio Continuum–H2O Maser Systems in NGC 2071: H2O Masers Tracing a Jet (IRS 1) and a Rotating Proto–Planetary Disk of Radius 20 AU (IRS 3)

We have observed simultaneously the 1.3 cm continuum and H2O maser emission toward the core of the star-forming region NGC 2071 using the Very Large Array in its A configuration. Two 1.3 cm continuum sources have been detected in the region, coinciding with the infrared sources IRS 1 and IRS 3, respectively. The radio emission in IRS 3 is consistent with an ionized thermal bipolar radio jet. Two clusters of H2O maser spots are detected, one associated with IRS 1 (22 spots) and the other one associated with IRS 3 (13 spots). The H2O maser distribution in IRS 1 seems to be tracing at scales of 300 AU the larger scale H2 outflow observed at a few thousands of AU from the exciting source. On the other hand, the H2O masers in IRS 3 are distributed as an apparent disk of 005 (20 AU) radius, oriented almost perpendicular to the major axis of the radio jet. There is a clear velocity gradient (0.35 km s-1 AU-1) along the major axis of the H2O maser distribution, which can be gravitationally bound by a central mass of 1 M☉. These results, together with the low-mass and early evolutionary stage of IRS 3, suggest that masers around this source are tracing a rotating proto-planetary disk within a proto-solar-like system. This represents direct kinematic evidence of the smallest rotating circumstellar disk ever observed around a young stellar object (YSO). We discuss the dichotomy of H2O masers tracing either outflows or disks around YSOs, based on the evolutionary scheme proposed in our earlier work. We suggested that systems in which H2O masers trace disks are less evolved than those in which masers trace outflows. In this scheme, IRS 3 would then represent a relatively less evolved object than IRS 1. This prediction is consistent with independent infrared observations showing that IRS 3 is at an earlier phase of evolution.

Near‐Infrared Polarimetric Study of S140 IRS

We present H- and Ks-band imaging polarimetry for the star-forming region S140 IRS and spectropolarimetry from 1.26 to 4.18 μm for the infrared source IRS 1. The polarimetric images reveal two reflection nebulae illuminated by the deeply embedded infrared sources IRS 1 and IRS 3. The nebula associated with IRS 1 does not simply show a symmetric structure, as expected in the well-known pole-on outflow model, but displays three reflection lobes. Two bipolar reflection lobes are apparently extended in the northeast-southwest direction and lie nearly in the plane of the sky. Another pole-on lobe, corresponding to the blueshifted pole-on molecular outflow, is projected to the southeast of IRS 1. The polarimetric images also resolve an asymmetric density distribution around IRS 1; to the west there is a dense disk structure elongated in the east-west direction; whereas to the east there is a cavity. On the basis of these features, as well as previous radio continuum and CO molecular line observations, we propose that S140 IRS 1 may drive a quadrupolar outflow.

BIMA13CO Observations of W3

The W3 molecular cloud core has been observed with the BIMA and NRAO 12 m telescopes in the 13CO (J = 1-0) and C18O (J = 1-0) lines. Two BIMA fields were imaged, centered on the infrared sources IRS 5 and IRS 4 (80'' west of IRS 5). In order to observe large-scale structure, a full-synthesis cube was made with a resolution of 95 × 80. Additionally, a high-resolution cube was made with only the IRS 5 pointing of BIMA to investigate the distribution of gas near IRS 5 at high angular resolution. The total H2 masses of the molecular cores associated with IRS 4 and IRS 5 are 1700 and 1100 M☉, respectively. Six clumps are identified. Derived H2 masses of the clumps are between 120 and 480 M☉, and under simple geometrical assumptions, n(H2) is between 1.8 and 4.5 × 105 cm-3. The virial masses of the clumps are within 30% of the derived H2 masses. For the clumps located at IRS 5 and 20'' south of IRS 4, the 13CO opacities derived were 0.3 and 0.7, respectively. At the positions of IRS 4 and IRS 5, individual clumps are observed; the IRS 4 clump in particular has a n(H2) a factor of 2 larger than the other clumps. At the position of IRS 5, the high-resolution data show a velocity structure suggestive of two clumps, one north and another south of IRS 5. Integrating the emission from these clumps gives an H2 mass of 110 M☉. Using the derived H2 column density toward IRS 5 and a previous H I Zeeman result, we can derive the ratio | B |/NH (which is proportional to the magnetic flux-to-mass ratio ΦB/M). The determined ratio is near the magnetically critical value, which is consistent with the standard theory of high-mass star formation.

The molecular environment of the HH 34 system

view Abstract Citations (30) References (77) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Molecular Environment of the HH 34 System Anglada, G. ; Estalella, R. ; Mauersberger, R. ; Torrelles, J. M. ; Rodriguez, L. F. ; Canto, J. ; Ho, P. T. P. ; D'Alessio, P. Abstract We present single-dish (angular resolution approximately 40 sec) and Very Large Array (VLA; angular resolution approximately 4 sec) ammonia observations toward the HH 34 region. Two main condensations are distinguished in both our single-dish and out VLA maps. The northern ammonia condensation is resolved by the VLA as an arclike structure that surrounds the east side of the star HH 34 IRS (the exciting source of the jet) and coincides in projection with Re 24, the reflection nebula associated with the infrared source IRS 5. We suggest that this ammonia structure is tracing the wall of a cavity around HH 34 IRS. Our results are in good agreement with the hypothesis that this cavity was created by the stellar wind from HH 34 IRS, indicating that along the life of the star two kinds of stellar wind might have been present: a low-collimation wind that created the cavity, and a highly collimated wind that is at the origin of the jet. A second VLA ammonia condensation coincides with Re 23, the brightest part of the arc of optical nebulosity previously proposed to be tracing the western wall of a cavity that contains the jet. The inner edges of these two ammonia condensations coincide with zones of a high level of polarization of the optical emission. With the angular resolution of our VLA observations, no ammonia (1, 1) emission is detected directly associated with the star HH 34 IRS, setting an upper limit of 0.1/(X(NH3)/10-8) solar masses for the mass of a possible circumstellar disk. From our single-dish observations, we find that there is extended emission (approximately 3 min) of high-density gas, not seen with the VLA. For this gas, we estimate a total mass of approximately 15 solar masses and a kinetic temperature of 15 K. Publication: The Astrophysical Journal Pub Date: April 1995 DOI: 10.1086/175560 Bibcode: 1995ApJ...443..682A Keywords: Ammonia; Herbig-Haro Objects; Interstellar Gas; Jet Flow; Molecules; Radio Astronomy; Radio Spectra; Stellar Evolution; Stellar Winds; Astronomical Maps; Cavities; Data Reduction; Optical Polarization; Radio Antennas; Very Large Array (Vla); Astrophysics; ISM: JETS AND OUTFLOWS; ISM: MOLECULES; RADIO LINES: ISM; STARS: INDIVIDUAL ALPHANUMERIC: HH 34; STARS: PRE--MAIN-SEQUENCE full text sources ADS | data products SIMBAD (20)

Submillimetre and near-infrared observations of L1448: a curving Formula jet with multiple bow shocks

A high-resolution (0.6 arcsec pixel −1 ), narrow-band, H 2 v=1-0 S(1) image of the high-velocity CO outflow in L1448 reveals a remarkable jet-like structure. The coincidence of this H 2 jet with the CO bipolar outflow implies a close association between the two phenomena. The H 2 jet comprises a series of knots, and three bow-shaped features equally spaced along the jet length, which we associate with the sporadic nature of this outflow. K-band imaging of the source also shows a conical reflection nebula extending towards the H 2 jet structure, whilst maps in HCO + J=3-2 and CS J=5-4 show two peaks, one towards the source of the H 2 jet and CO outflow, and the other towards the infrared source IRS 3 situated to the north of this region

Narrow-band imaging and velocity maps of young stellar objects - Initial results

The first trials of a new technique, designed to map low-excitation ionized gas surrounding young stellar objects, are reported. The region surrounding the T Tau stars HL Tau and XZ Tau, that near HH 101, and that near IRS 5 in L1551 have been imaged through a narrow-band (4.7 A FWHM) forbidden S II filter; three-phase CCD chip was used as the detector. By tilting the narrow-band filter, it is possible to vary the wavelength of peak transmission and thus to detect high-velocity radial flows as well as map the morphology of the excited gas near these young stars. Evidence of an apparently helical outflow is found for HH 101. Redshifted gas appears to extend southward from HL Tau toward HH 30; a blueshifted jet extends northeastward of HL Tau. A series of forbidden S II knots is seen to extend along a jet directed southwestward from the infrared source IRS 5; the knot chain appears to delineate a blueshifted outflow that decelerates as it recedes from IRS 5.

Submillimeter observations of W3

A 35 arcsec resolution, 400 micron continuum map of the core of the W3 molecular cloud complex is presented. The map shows prominent peaks centered approximately at the positions of the infrared sources IRS 4 and IRS 5 with stronger-emission at the western (IRS 4) peak. The visual extinction (inferred from the submillimeter measurements) through the center of both peaks is large (A sub v = 200). A total mass for the core of 900 solar masses is estimated, consistent with dynamical estimates if the observed velocity gradient is a result of rotation. The peak H2 density is approximately 2.8 x 10 to the 5th/cu cm. The observations exclude the possibility that the shell H II regions, W3A-C, could be in pressure equilibrium with the surrounding cloud. The observations establish that the core of W3 contains several massive condensations surrounding the youngest stars in the region.

THE GALACTIC NUCLEUS

The ionized gas within 2 parsec from the centre region is distributed in spiral-like features which appear to emanate from a nucleus. This nucleus is close to the ultra-compact radio source and the infrared source IRS 16, but does not exactly coincide with either. The spiral is strongly inclined to the galactic plane. The arms are clumpy. The spiral appears to rotate, but there appear to be also large radial motions.

On the Nature of the Infrared Point Source in the Orion Nebula

view Abstract Citations (75) References (11) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS On the Nature of the Infrared Point Source in the Orion Nebula Becklin, E. E. ; Neugebauer, G. ; Wynn-Williams, C. G. Abstract New photometric observations of the BN infrared source in the Orion Nebula eliminate the possibility that it is simply a highly reddened star, and undermine the conclusion that there are 80 mag of visual extinction to the source. We suggest that there is a generic relationship between it and the infrared source IRS 5 in the H ii region W3. Subject headings: infrared sources - Orion Nebula Publication: The Astrophysical Journal Pub Date: May 1973 DOI: 10.1086/181205 Bibcode: 1973ApJ...182L...7B full text sources ADS | data products SIMBAD (2)