Identifying young stellar objects in nine Large Magellanic Cloud star-forming regions

Full Iso-Lws spectral scans between about 45 to 190 μm of 17 individual HH objects in 7 star forming regions have revealed essentially only [O I] 63 μm line emission, implying that the Fircooling of these objects is totally dominated by this line alone. In this case, J-shock models can be used to determine the mass loss rates of the HH exciting sources. These mass loss rates are in reasonably good agreement with those estimated for the accompanying CO flows, providing first observational evidence that HH and molecular flows are driven by the same agent. The Lmech – Lbol relation, based on our results with the Lws, implies that young stellar objects of lower mass are loosing mass at relatively higher rates than their more massive counterparts.

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Physical Properties of Molecular Envelopes in Low-Mass Star-Forming Regions

Symposium - International Astronomical Union ◽

10.1017/s007418090016468x ◽

2000 ◽

Vol 197 ◽

pp. 61-70

Author(s):

Nagayoshi Ohashi

Keyword(s):

Physical Properties ◽

Young Stellar Objects ◽

Mass Star ◽

Narrow Line ◽

Stellar Objects ◽

Velocity Pattern ◽

Star Forming ◽

Star Forming Regions ◽

Low Mass ◽

Line Widths

We have carried out interferometric observations of pre-protostellar and protostellar envelopes in Taurus. Protostellar envelopes are dense gaseous condensations with young stellar objects or protostars, while pre-protostellar envelopes are those without any known young stellar objects. Five pre-protostellar envelopes have been observed in CCS JN=32–21, showing flattened and clumpy structures of the envelopes. The observed CCS spectra show moderately narrow line widths, ~0.1 to ~0.35 km s–1. One pre-protostellar envelope, L1544, shows a remarkable velocity pattern, which can be explained in terms of infall and rotation. Our C18O J=1–0 observations of 8 protostellar envelopes show that they have also flattened structures like pre-protostellar envelopes but no clumpy structures. Four out the eight envelopes show velocity patterns that can be explained by motions of infall (and rotation). Physical properties of pre-protostellar and protostellar envelopes are discussed in detail.

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Magnetic Fields and Disks in Star-forming Regions

Publications of the Astronomical Society of Australia ◽

10.1017/s1323358000025777 ◽

1993 ◽

Vol 10 (3) ◽

pp. 247-249 ◽

Cited By ~ 5

Author(s):

C.M. Wright ◽

D.K. Aitken ◽

C.H. Smith ◽

P.F. Roche

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Transverse Component ◽

Young Stellar Objects ◽

Stellar Objects ◽

Star Forming ◽

Star Forming Regions ◽

Molecular Outflow ◽

The Magnetic Field

AbstractThe star-formation process is an outstanding and largely unsolved problem in astrophysics. The role of magnetic fields is unclear but is widely considered to be important at all stages of protostellar evolution, from cloud collapse to ZAMS. For example, in some hydromagnetic models, the field may assist in removing angular momentum, thereby driving accretion and perhaps bipolar outflows.Spectropolarimetry between 8 and 13μm provides information on the direction of the transverse component of a magnetic field through the alignment of dust grains. We present results of 8–13μm spectropolarimetric observations of a number of bipolar molecular outflow sources, and compare the field directions observed with the axes of the outflows and putative disk-like structures observed to be associated with some of the objects. There is a strong correlation, though so far with limited statistics, between the magnetic field and disk orientations. We compare our results with magnetic field configurations predicted by current models for hydromagnetically driven winds from the disks around Young Stellar Objects (YSOs). Our results appear to argue against the Pudritz and Norman model and instead seem to support the Uchida and Shibata model.

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GAMMA-RAY EMISSION FROM MASSIVE STAR FORMING REGIONS

International Journal of Modern Physics D ◽

10.1142/s0218271808013534 ◽

2008 ◽

Vol 17 (10) ◽

pp. 1889-1894 ◽

Cited By ~ 4

Author(s):

A. T. ARAUDO ◽

G. E. ROMERO ◽

V. BOSCH-RAMON ◽

J. M. PAREDES

Keyword(s):

Gamma Ray ◽

Surrounding Medium ◽

Strong Shock ◽

High Energy ◽

Young Stellar Objects ◽

Present Contribution ◽

Stellar Objects ◽

Star Forming ◽

Star Forming Regions ◽

The Impact

Recent radio observations support a picture for star formation where there is accretion of matter onto a central protostar with the ejection of molecular outflows that can affect the surrounding medium. The impact of a supersonic outflow on the ambient gas can produce a strong shock that could accelerate particles up to relativistic energies. Strong evidence for this has been the detection of nonthermal radio emission coming from the jet termination region of some young massive stars. In the present contribution, we study the possible high-energy emission due to the interaction of relativistic particles, electrons and protons, with the magnetic, photon and matter fields inside a giant molecular cloud. Electrons lose energy via relativistic Bremsstrahlung, synchrotron radiation and inverse Compton interactions, and protons cool mainly through inelastic collisions with atoms in the cloud. We conclude that some massive young stellar objects (YSOs) might be detectable at gamma-rays by next generation instruments, both satellite-borne and ground based.

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First detection of [13C II] in the Large Magellanic Cloud

Astronomy and Astrophysics ◽

10.1051/0004-6361/201936685 ◽

2019 ◽

Vol 631 ◽

pp. L12 ◽

Cited By ~ 3

Author(s):

Yoko Okada ◽

Ronan Higgins ◽

Volker Ossenkopf-Okada ◽

Cristian Guevara ◽

Jürgen Stutzki ◽

...

Keyword(s):

Optical Depth ◽

Line Profile ◽

Large Magellanic Cloud ◽

Abundance Ratio ◽

Magellanic Cloud ◽

Star Forming ◽

Star Forming Regions ◽

Distant Galaxies ◽

Nearby Galaxies ◽

Galactic Sources

Context. [13C II] observations in several Galactic sources show that the fine-structure [12C II] emission is often optically thick (the optical depths around 1 to a few). Aims. Our goal was to test whether this also affects the [12C II] emission from nearby galaxies like the Large Magellanic Cloud (LMC). Methods. We observed three star-forming regions in the LMC with upGREAT on board SOFIA at the frequency of the [C II] line. The 4 GHz bandwidth covers all three hyperfine lines of [13C II] simultaneously. For the analysis, we combined the [13C II] F = 1−0 and F = 1−1 hyperfine components as they do not overlap with the [12C II] line in velocity. Results. Three positions in N159 and N160 show an enhancement of [13C II] compared to the abundance-ratio-scaled [12C II] profile. This is likely due to the [12C II] line being optically thick, supported by the fact that the [13C II] line profile is narrower than [12C II], the enhancement varies with velocity, and the peak velocity of [13C II] matches the [O I] 63 μm self-absorption. The [12C II] line profile is broader than expected from a simple optical depth broadening of the [13C II] line, supporting the scenario of several PDR components in one beam having varying [12C II] optical depths. The derived [12C II] optical depth at three positions (beam size of 14″, corresponding to 3.4 pc) is 1−3, which is similar to values observed in several Galactic sources shown in previous studies. If this also applies to distant galaxies, the [C II] intensity will be underestimated by a factor of approximately 2.

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Velocity profiles of [CII], [CI], CO, and [OI] and physical conditions in four star-forming regions in the Large Magellanic Cloud

Astronomy and Astrophysics ◽

10.1051/0004-6361/201833398 ◽

2019 ◽

Vol 621 ◽

pp. A62 ◽

Cited By ~ 9

Author(s):

Yoko Okada ◽

Rolf Güsten ◽

Miguel Angel Requena-Torres ◽

Markus Röllig ◽

Jürgen Stutzki ◽

...

Keyword(s):

Physical Properties ◽

High Redshift ◽

Line Emission ◽

Chemical Species ◽

Large Magellanic Cloud ◽

Magellanic Cloud ◽

Continuum Emission ◽

Line Profiles ◽

Star Forming ◽

Star Forming Regions

Aims. The aim of our study is to investigate the physical properties of the star-forming interstellar medium (ISM) in the Large Magellanic Cloud (LMC) by separating the origin of the emission lines spatially and spectrally. The LMC provides a unique local template to bridge studies in the Galaxy and high redshift galaxies because of its low metallicity and proximity, enabling us to study the detailed physics of the ISM in spatially resolved individual star-forming regions. Following Okada et al. (Okada, Y., Requena-Torres, M. A., Güsten, R., et al. 2015, A&A, 580, A54), we investigate different phases of the ISM traced by carbon-bearing species in four star-forming regions in the LMC, and model the physical properties using the KOSMA-τ PDR model. Methods. We mapped 3–13 arcmin2 areas in 30 Dor, N158, N160, and N159 along the molecular ridge of the LMC in [C II] 158 μm with GREAT on board SOFIA. We also observed the same area with CO(2-1) to (6-5), 13CO(2-1) and (3-2), [C I] 3P1–3P0 and 3P2–3P1 with APEX. For selected positions in N159 and 30 Dor, we observed [O I] 145 μm and [O I] 63 μm with upGREAT. All spectra are velocity resolved. Results. In all four star-forming regions, the line profiles of CO, 13CO, and [C I] emission are similar, being reproduced by a combination of Gaussian profiles defined by CO(3-2), whereas [C II] typically shows wider line profiles or an additional velocity component. At several positions in N159 and 30 Dor, we observed the velocity-resolved [O I] 145 and 63 μm lines for the first time. At some positions, the [O I] line profiles match those of CO, at other positions they are more similar to the [C II] profiles. We interpret the different line profiles of CO, [C II] and [O I] as contributions from spatially separated clouds and/or clouds in different physical phases, which give different line ratios depending on their physical properties. We modeled the emission from the CO, [C I], [C II], and [O I] lines and the far-infrared continuum emission using the latest KOSMA-τ PDR model, which treats the dust-related physics consistently and computes the dust continuum SED together with the line emission of the chemical species. We find that the line and continuum emissions are not well-reproduced by a single clump ensemble. Toward the CO peak at N159 W, we propose a scenario that the CO, [C II], and [O I] 63 μm emission are weaker than expected because of mutual shielding among clumps.

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