Blueshifted Outflow Lobe Research Articles

Crescent-shaped Molecular Outflow from the Intermediate-mass Protostar DK Cha Revealed by ALMA

We report on an Atacama Large Millimeter/submillimeter Array study of the Class I or II intermediate-mass protostar DK Cha in the Chamaeleon II region. The 12CO(J = 2–1) images have an angular resolution of ∼1″ (∼250 au) and show high-velocity blueshifted (≳70 km s−1) and redshifted (≳50 km s−1) emissions, which have 3000 au scale crescent-shaped structures around the protostellar disk traced in the 1.3 mm continuum. Because the high-velocity components of the CO emission are associated with the protostar, we concluded that the emission traces the pole-on outflow. The blueshifted outflow lobe has a clear layered velocity gradient with a higher-velocity component located on the inner side of the crescent shape, which can be explained by a model of an outflow with a higher velocity in the inner radii. Based on the directly driven outflow scenario, we estimated the driving radii from the observed outflow velocities and found that the driving region extends over 2 orders of magnitude. The 13CO emission traces a complex envelope structure with arc-like substructures with lengths of ∼1000 au. We identified the arc-like structures as streamers because they appear to be connected to a rotating infalling envelope. DK Cha is useful for understanding characteristics that are visible by looking at nearly face-on configurations of young protostellar systems, providing an alternative perspective for studying the star formation process.

A Detailed Temperature Map of the Archetypal Protostellar Shocks in L1157

We present sensitive NH3 (1,1)–(7,7) line images from the Karl G. Jansky Very Large Array toward successive shocks, which are associated with the blueshifted outflow lobe driven by the compact protobinary system L1157. Within a projection distance of 0.1 pc, our observations not only trace the quiescent and cold gas in the flattened envelope, but also illustrate the complex physical and chemical processes that take place where the high-velocity jet impinges on its surrounding medium. Specifically, the NH3 ortho-to-para ratio is enhanced by a factor of 2–2.5 along the jet path, where the velocity offset between the line peak and the blueshifted wing reaches values as high as 10 km s−1; it also shows a strong spatial correlation with the NH3 column density, which is enhanced to >1016 cm−2 toward the shock cavities. At a linear resolution of 1500 au, our refined temperature map from the seven NH3 lines shows a gradient from the warm B0 eastern cavity wall (>120 K) to the cool cavity B1 and the earlier shock B2 (<80 K), indicating shock heating.

The Molecular Outflow from R Mon*

Abstract We have mapped the young Herbig Be star R Mon in CO(3–2) and 13CO(3–2) with Atacama Pathfinder EXperiment in Chile and analyzed unpublished Herschel images. We find that R Mon is embedded in a small cloud with a gas temperature of ∼20 K and a total mass of ∼70 . We confirm that R Mon drives a bipolar molecular outflow, which is blueshifted north of R Mon. The blueshifted outflow has excavated the molecular cloud north of R Mon, creating the reflection nebula NGC 2261 and filling it with high-velocity gas. At “high” velocities the orientation of the outflow is approximately n–s, which agrees with the optical jet, suggesting that the accretion disk is e–w. The outflow velocities are modest, ±9 km s−1. The outflow is rather massive, ∼0.56 in the blueshifted outflow lobe. The outflow is completely optically thick in CO(3–2) toward R Mon, indicating that its envelope is ≲2000 au. The mass of the accretion disk and surrounding envelope determined from an isothermal graybody fit is ∼0.34 . We estimate a mass-loss rate of ∼(1–3) × 10−5 yr−1, corresponding to an accretion rate of (1–9) × 10−6 yr−1. We find that R Mon has bolometric luminosity of &lt;1000 . R Mon is still in an active accretion phase, contributing to the observed luminosity. Hence, R Mon cannot be a B0 star; it must be a late B star or even an early A star.

VLT near- to mid-IR imaging and spectroscopy of the M 17 UC1 – IRS5 region

We investigate the surroundings of the hypercompact HII region M17 UC1 to probe the physical properties of the associated young stellar objects and the environment of massive star formation. Five of the seven point sources in this region show $L$-band excess emission. Geometric match is found between the H_2 emission and near-IR polarized light in the vicinity of IRS5A, and between the diffuse mid-IR emission and near-IR polarization north of UC1. The H_2 emission is typical for dense PDRs, which are FUV pumped initially and repopulated by collisional de-excitation. The spectral types of IRS5A and B273A are B3-B7 V/III and G4-G5 III, respectively. The observed infrared luminosity L_IR in the range 1-20 micron is derived for three objects; we obtain 2.0x10^3 L_\sun for IRS5A, 13 L_\sun for IRS5C, and 10 L_\sun for B273A. IRS5 might be a young quadruple system. Its primary star IRS5A is confirmed to be a high-mass protostellar object (~ 9 M_\sun, ~1x10^5 yrs); it might have terminated accretion due to the feedback from the stellar activities (radiation pressure, outflow) and the expanding HII region of M17. UC1 might also have terminated accretion because of the expanding hypercompact HII region ionized by itself. The disk clearing process of the low-mass YSOs in this region might be accelerated by the expanding HII region. The outflows driven by UC1 are running in south-north with its northeastern side suppressed by the expanding ionization front of M17; the blue-shifted outflow lobe of IRS5A is seen in two types of tracers along the same line of sight in the form of H_2 emission filament and mid-emission. The H_2 line ratios probe the properties of M17 SW PDR, which is confirmed to have a clumpy structure with two temperature distributions: warm, dense molecular clumps with n_H>10^5 cm^-3 and T~575 K and cooler atomic gas with n_H~3.7x10^3-1.5x10^4 cm-3 and T~50-200 K.

Water in star-forming regions withHerschel: highly excited molecular emission from the NGC 1333 IRAS 4B outflow

During the embedded phase of pre-main sequence stellar evolution, a disk forms from the dense envelope while an accretion-driven outflow carves out a cavity within the envelope. Highly excited H2O emission in spatially unresolved Spitzer/IRS spectra of a low-mass Class 0 object, NGC 1333 IRAS 4B, has previously been attributed to the envelope-disk accretion shock but could instead be produced in an outflow. As part of the survey of low-mass sources in the Water in Star Forming Regions with Herschel (WISH-LM) program, we used Herschel/PACS to obtain a far-IR spectrum and several Nyquist-sampled spectral images with to determine the origin of excited H2O emission from NGC 1333 IRAS 4B. The spectrum has high signal-to-noise in a rich forest of H2O, CO, and OH lines, providing a near-complete census of far-IR molecular emission from a Class 0 protostar. The excitation diagrams for the three molecules all require fits with two excitation temperatures, indicating the presence of two physical components. The highly excited component of H2O emission is characterized by subthermal excitation of 1500 K gas with a density of 10^5 - 10^7 cm-3, conditions that also reproduce the mid-IR H2O emission detected by Spitzer. On the other hand, a high density, low temperature gas can reproduce the H2O spectrum observed by Spitzer but underpredicts the H2O lines seen by Herschel. Nyquist-sampled spectral maps of several lines show two spatial components of H2O emission, one centered at 1200 AU south of the central source at the position of the blueshifted outflow lobe and a second centered on-source. Both spatial components of the far-IR H2O emission are consistent with emission from the outflow. The gas cooling from the IRAS 4B envelope cavity walls is dominated by far-IR H2O emission, in contrast to stronger [O I] and CO cooling from more evolved protostars. [one sentence truncated]

Discovery of a Molecular Outflow in the Haro 6‐10 Star‐forming Region

We present high sensitivity 12CO and 13CO (1-0) molecular line maps covering the full extent of the parsec scale Haro~6-10 Herbig-Haro (HH) flow. We report the discovery of a molecular CO outflow along the axis of parsec-scale HH flow. Previous molecular studies missed the identification of the outflow probably due to their smaller mapping area and the confusing spectral features present towards the object. Our detailed molecular line study of the full 1.6 pc extent of the optical flow shows evidence for both blueshifted and redshifted gas set in motion by Haro~6-10 activity. The molecular outflow is centered at Haro~6-10, with redshifted gas being clumpy and directed towards the northeast, while blueshifted gas is in the southwest direction. The molecular gas terminates well within the cloud, short of the most distant HH objects of the optical flow. Contamination from an unrelated cloud along the same line of sight prevents a thorough study of the blueshifted outflow lobe and the mass distribution at the lowest velocities in both lobes. The cloud core in which Haro~6-10 is embedded is filamentary and flattened in the east-west direction. The total cloud mass is calculated from 13CO(1-0) to be ~200Msun. The lower limit of the mass associated with the outflow is ~0.25Msun.

The Protostar in B335: Near-Infrared Observations of the Class 0 Outflow

This Letter reports the results of very deep near-infrared imaging of the core of the star-forming Bok globule B335 in H, K, and 2.12 μm H2 ν=1-0 S(1) line emission. The outflow cavity associated with the class 0 protostar embedded in B335 and features in the blueshifted outflow lobe are detected in the deep K-band images, mostly by emission from shock-excited molecular hydrogen. Only extremely faint traces of the outflow are seen in the H band. Several knots of S(1) emission are found near the edge of the globule on either side of the outflow. The cloud core is outlined in absorption against diffuse H- and K-band flux in B335, presumably scattered starlight.

The L1551NE molecular outflow

L1551NE is a very young protostar (class I or perhaps class 0), located very close to L1551NE IRS 5. It is the second brightest far-infrared source in the Taurus molecular cloud complex, but its proximity to the brightest source IRS 5 has prevented effective observations of any molecular outflow. We here present evidence that it does indeed process an outflow, that the optical/infrared reflection nebula is associated with the blueshifted outflow lobe, and that the L1551W outflow does not originate from L1551NE, as has been suggested.

The L1448 Molecular Jet

view Abstract Citations (66) References (20) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The L1448 Molecular Jet Bally, John ; Lada, Elizabeth A. ; Lane, Adair P. Abstract We have obtained near-infrared images of the L1448 molecular outflow in the J, H, and K bands and through a 1% passband filter centered on the 2.122 microns V = 1-0 S(1) line of molecular hydrogen. We report the discovery of a highly collimated, clumpy, and bipolar molecular hydrogen jet associated with the L1448 molecular outflow. We estimate that the total H2 luminosity of the L1448 outflow is about 0.2 Lsun. Most of the line emission in the northern outflow lobe arises from a narrow, curving filament consisting of a chain of knots. Some H2 knots and the bow-shaped emission regions protruding several arcseconds to the west of the filament may be shocks associated with CO- and SiO-emitting "bullets" seen in millimeter-wave observations. We interpret the H2 emission in the context of a jet-driven model for molecular outflows. Bright H2 emission near the molecular "bullets" may be produced by shocks propagating into the moving medium, while the extended and curving filament may be driven by expanding bow shocks in the wakes of the "bullets." A conical 2.2 microns continuum nebula extends from the driving source of the L1448 outflow toward the blueshifted outflow lobe. Several knots of H2 emission to the northeast of the main L1448 H2 filament may be associated with a separate outflow emerging from L1448 IRS 3, which we estimate has a total H2 luminosity of about 0.01 Lsun. Publication: The Astrophysical Journal Pub Date: November 1993 DOI: 10.1086/173393 Bibcode: 1993ApJ...418..322B Keywords: INFRARED: INTERSTELLAR: CONTINUUM; ISM: INDIVIDUAL ALPHANUMERIC: L1448; ISM: JETS AND OUTFLOWS; ISM: MOLECULES; STARS: FORMATION full text sources ADS | data products SIMBAD (19)