Context. Protostellar jets and outflows are key features of the star-formation process, and primary processes of the feedback of young stars on the interstellar medium. Understanding the underlying ...shocks is necessary to explain how jet and outflow systems are launched, and to quantify their chemical and energetic impacts on the surrounding medium. Aims. We performed a high-spectral resolution study of the OI63μm emission in the outflow of the intermediate-mass Class 0 protostar Cep E-mm. The goal is to determine the structure of the outflow, to constrain the chemical conditions in the various components, and to understand the nature of the underlying shocks, thus probing the origin of the mass-loss phenomenon. Methods. We present observations of the O i 3P1 → 3P2, OH between 2Π1/2J = 3/2 and J = 1/2 at 1837.8 GHz, and CO (16–15) lines with the GREAT receiver onboard SOFIA towards three positions in the Cep E protostellar outflow: Cep E-mm (the driving protostar), Cep E-BI (in the southern lobe), and Cep E-BII (the terminal position in the southern lobe). Results. The CO (16–15) line is detected at all three positions. The OI63μm line is detected in Cep E-BI and BII, whereas the OH line is not detected. In Cep E-BII, we identify three kinematical components in O i and CO. These were already detected in CO transitions and relate to spatial components: the jet, the HH377 terminal bow-shock, and the outflow cavity. We measure line temperature and line integrated intensity ratios for all components. The O i column density is higher in the outflow cavity than in the jet, which itself is higher than in the terminal shock. The terminal shock is the region where the abundance ratio of O i to CO is the lowest (about 0.2), whereas the jet component is atomic (N(O i)/N(CO) ~ 2.7). In the jet, we compare the OI63μm observations with shock models that successfully fit the integrated intensity of 10 CO lines. We find that these models most likely do not fit the OI63μm data. Conclusions. The high intensity of O i emission points towards the propagation of additional dissociative or alternative FUV-irradiated shocks, where the illumination comes from the shock itself. A picture emerges from the sample of low-to-high mass protostellar outflows, where similar observations have been performed, with the effects of illumination increasing with the mass of the protostar. These findings need confirmation with more observational constraints and a larger sample.
Aims. We aim to reveal the morphology, chemical composition, kinematics, and to establish the main processes prevalent in the gas at the footpoints of the giant molecular loops (GMLs) in the Galactic ...center region. Methods. Using the 22-m Mopra telescope, we mapped the M−3.8+0.9 molecular cloud, placed at the footpoints of a GML, in 3-mm range molecular lines. To derive the molecular hydrogen column density, we also observed the 13CO(2 − 1) line at 1 mm using the 12-m APEX telescope. From the 3 mm observations 12 molecular species were detected, namely HCO+, HCN, H13CN, HNC, SiO, CS, CH3OH, N2H+, SO, HNCO, OCS, and HC3N. Results. Maps revealing the morphology and kinematics of the M−3.8+0.9 molecular cloud in different molecules are presented. We identify six main molecular complexes. We derive fractional abundances in 11 selected positions of the different molecules assuming local thermodynamical equilibrium. Conclusions. Most of the fractional abundances derived for the M−3.8+0.9 molecular cloud are very similar over the whole cloud. However, the fractional abundances of some molecules show significant difference with respect to those measured in the central molecular zone (CMZ). The abundances of the shock tracer SiO are very similar between the GMLs and the CMZ. The methanol emission is the most abundant species in the GMLs. This indicates that the gas is likely affected by moderate ~30 km s−1 or even high velocity (50 km s−1) shocks, consistent with the line profile observed toward one of the studied position. The origin of the shocks is likely related to the flow of the gas throughout the GMLs towards the footpoints.
It has long been discussed whether stellar feedback in the form of winds and/or radiation can shred the nascent molecular cloud, thereby controlling the star formation rate. However, directly probing ...and quantifying the impact of stellar feedback on the neutral gas of the nascent clouds is challenging. We present an investigation of this impact toward the RCW 79 H II region using the ionized carbon line at 158 μm (C II) from the FEEDBACK Legacy Survey. We combine this data with information on the dozen ionizing O stars responsible for the evolution of the region, and observe in C II for the first time both blue- and redshifted high-velocity gas that reaches velocities of up to 25 km s
−1
relative to the bulk emission of the molecular cloud. This high-velocity gas mostly contains neutral gas, and partly forms a fragmented shell, similar to recently found shells in a few Galactic H II regions. However, this shell does not account for all of the observed neutral high-velocity gas. We also find high-velocity gas streaming out of the nascent cloud through holes, and obtain a range of dynamical timescales below 1.0 Myr for the high-velocity gas that is well below the 2.3 ± 0.5 Myr age of the OB cluster. This suggests a different scenario for the evolution of RCW 79, where the high-velocity gas does not solely stem from a spherical expanding bubble, but also from gas recently ablated at the edge of the turbulent molecular cloud into the surrounding interstellar medium through low-pressure holes or chimneys. The resulting mass ejection rate estimate for the cloud is 0.9–3.5 × 10
−2
M
⊙
yr
−1
, which leads to short erosion timescales (< 5 Myr) for the nascent molecular cloud. This finding provides direct observational evidence of rapid molecular cloud dispersal.
Warm gas in protostellar outflows Gómez-Ruiz, A. I.; Gusdorf, A.; Leurini, S. ...
Astronomy and astrophysics (Berlin),
09/2019, Letnik:
629
Journal Article
Recenzirano
Odprti dostop
Context. OMC-2/3 is one of the nearest embedded cluster-forming regions that includes intermediate-mass protostars at early stages of evolution. A previous CO (3–2) mapping survey towards this region ...revealed outflow activity related to sources at different evolutionary phases. Aims. The present work presents a study of the warm gas in the high-velocity emission from several outflows found in CO (3–2) emission by previous observations, determines their physical conditions, and makes a comparison with previous results in low-mass star-forming regions. Methods. We used the CHAMP+ heterodyne array on the APEX telescope to map the CO (6–5) and CO (7–6) emission in the OMC-2 FIR 6 and OMC-3 MMS 1-6 regions, and to observe 13CO (6–5) at selected positions. We analyzed these data together with previous CO (3–2) observations. In addition, we mapped the SiO (5–4) emission in OMC-2 FIR 6. Results. The CO (6–5) emission was detected in most of the outflow lobes in the mapped regions, while the CO (7–6) was found mostly in the OMC-3 outflows. In the OMC-3 MMS 5 outflow, a previously undetected extremely high-velocity gas was found in CO (6–5). This extremely high-velocity emission arises from the regions close to the central object MMS 5. Radiative transfer models revealed that the high-velocity gas from MMS 5 outflow consists of gas with nH2 = 104–105 cm−3 and T > 200 K, similar to what is observed in young Class 0 low-mass protostars. For the other outflows, values of nH2 > 104 cm−3 were found. Conclusions. The physical conditions and kinematic properties of the young intermediate-mass outflows presented here are similar to those found in outflows from Class 0 low-mass objects. Due to their excitation requirements, mid − J CO lines are good tracers of extremely high-velocity gas in young outflows likely related to jets.
ABSTRACT We report a discovery of shocked gas from the supernova remnant (SNR) G357.7+0.3. Our millimeter and submillimeter observations reveal broad molecular lines of CO(2-1), CO(3-2), CO(4-3), ...13CO (2-1), and 13CO (3-2), HCO+, and HCN using the Heinrich Hertz Submillimeter Telescope, the Arizona 12 m Telescope, APEX, and the MOPRA Telescope. The widths of the broad lines are 15-30 km s−1, and the detection of such broad lines is unambiguous, dynamic evidence showing that the SNR G357.7+0.3 is interacting with molecular clouds. The broad lines appear in extended regions (>4 5 × 5′). We also present the detection of shocked H2 emission in the mid-infrared but lacking ionic lines using Spitzer/IRS observations to map a few-arcminute area. The H2 excitation diagram shows a best fit with a two-temperature local thermal equilibrium model with the temperatures of ∼200 and 660 K. We observed C ii at 158 m and high-J CO(11-10) with the German Receiver for Astronomy at Terahertz Frequencies (GREAT) on the Stratospheric Observatory for Infrared Astronomy. The GREAT spectrum of C ii, a 3 detection, shows a broad line profile with a width of 15.7 km−1 that is similar to those of broad CO molecular lines. The line width of C ii implies that ionic lines can come from a low-velocity C-shock. Comparison of H2 emission with shock models shows that a combination of two C-shock models is favored over a combination of C- and J-shocks or a single shock. We estimate the CO density, column density, and temperature using a RADEX model. The best-fit model with n(H2) = 1.7 × 104 cm−3, N(CO) = 5.6 × 1016 cm−2, and T = 75 K can reproduce the observed millimeter CO brightnesses.
Abstract
We quantified the effects of stellar feedback in RCW 49 by determining the physical conditions in different regions using the C
ii
158
μ
m and O
i
63
μ
m observations from SOFIA, the
12
CO ...(3–2) observations from APEX, and the H
2
line observations from Spitzer telescopes. Large maps of RCW 49 were observed with the SOFIA and APEX telescopes, while the Spitzer observations were only available toward three small areas. From our qualitative analysis, we found that the H
2
0–0
S
(2) emission line probes denser gas compared to the H
2
0–0
S
(1) line. In four regions (“northern cloud,” “pillar,” “ridge,” and “shell”), we compared our observations with the updated PDR Toolbox models and derived the integrated far-ultraviolet flux between 6 and 13.6 eV (
G
0
), H nucleus density (
n
), temperatures, and pressures. We found the ridge to have the highest
G
0
(2.4 × 10
3
Habing units), while the northern cloud has the lowest
G
0
(5 × 10
2
Habing units). This is a direct consequence of the location of these regions with respect to the Wd2 cluster. The ridge also has a high density (6.4 × 10
3
cm
−3
), which is consistent with its ongoing star formation. Among the Spitzer positions, we found the one closest to the Wd2 cluster to be the densest, suggesting an early phase of star formation. Furthermore, the Spitzer position that overlaps with the shell was found to have the highest
G
0
, and we expect this to be a result of its proximity to an O9V star.
We report ground-based follow-up observations of the exceptional source, ID 141, one of the brightest sources detected so far in the Herschel Astrophysical Terahertz Large Area Survey cosmological ...survey. ID 141 was observed using the IRAM 30 m telescope and Plateau de Bure interferometer (PdBI), the Submillimeter Array, and the Atacama Pathfinder Experiment submillimeter telescope to measure the dust continuum and emission lines of the main isotope of carbon monoxide and carbon (C I and C II). The detection of strong CO emission lines with the PdBI confirms that ID 141 is at high redshift (z = 4.243 ? 0.001). The strength of the continuum and emission lines suggests that ID 141 is gravitationally lensed. The width ( Delta *DV FWHM ~ 800 km s--1) and asymmetric profiles of the CO and carbon lines indicate orbital motion in a disk or a merger. The properties derived for ID 141 are compatible with an ultraluminous (L FIR ~ (8.5 ? 0.3) X 1013 Delta *m--1 L L , where Delta *mL is the amplification factor), dense (n 104 cm--3), and warm (T kin 40 K) starburst galaxy, with an estimated star formation rate of (0.7-1.7) X 104 Delta *m--1 L M yr--1. The carbon emission lines indicate a dense (n 104 cm--3) photon-dominated region, illuminated by a far-UV radiation field a few thousand times more intense than that in our Galaxy. In conclusion, the physical properties of the high-z galaxy ID 141 are remarkably similar to those of local ultraluminous infrared galaxies.
We report SOFIA/GREAT, Herschel/HIFI, and ground-based velocity-resolved spectroscopy of carbon monoxide (CO) rotational transitions from J = 2–1 to J = 16–15 toward two positions in the ...circum-nuclear disk (CND) in our Galactic center. Radiative transfer models were used to derive information on the physical state of the gas traced by CO. The excitation of the CO gas cannot be explained by a single physical component, but is clearly the superposition of various warm gas phases. In a two-component approach, our large velocity gradient (LVG) analysis suggests high temperatures of ~200 K with moderate gas densities of only ~104.5 cm-3 for the bulk of the material. A higher excited phase, carrying ~20–30% of the column densities, is warmer (~300–500 K) but only slightly denser (~105.3 cm-3). These densities are too low to self-stabilize the clumps against their high internal turbulence and fall below the Roche density (>107 cm-3) at 1.5 pc galactocentric distance. We conclude that the bulk of the material in the CND is not organized by self-gravity nor stable against tidal disruption, and must be transient.
In molecular outflows from forming low-mass protostars, most oxygen is expected to be locked up in water. However, Herschel observations have shown that typically an order of magnitude or more of the ...oxygen is still unaccounted for. To test if the oxygen is instead in atomic form, SOFIA-GREAT observed the R1 position of the bright molecular outflow from NGC 1333-IRAS4A. The O i 63 μm line is detected and spectrally resolved. From an intensity peak at +15 km s-1, the intensity decreases until +50 km s-1. The profile is similar to that of high-velocity (HV) H2O and CO 16–15, the latter observed simultaneously with O i. A radiative transfer analysis suggests that ~15% of the oxygen is in atomic form toward this shock position. The CO abundance is inferred to be ~10-4 by a similar analysis, suggesting that this is the dominant oxygen carrier in the HV component. These results demonstrate that a large portion of the observed O i emission is part of the outflow. Further observations are required to verify whether this is a general trend.
Context. The molecular species hydrogen peroxide, HOOH, is likely to be a key ingredient in the oxygen and water chemistry in the interstellar medium. Aims. Our aim with this investigation is to ...determine how abundant HOOH is in the cloud core ρ Oph A. Methods. By observing several transitions of HOOH in the (sub)millimeter regime we seek to identify the molecule and also to determine the excitation conditions through a multilevel excitation analysis. Results. We have detected three spectral lines toward the SM1 position of ρ Oph A at velocity-corrected frequencies that coincide very closely with those measured from laboratory spectroscopy of HOOH. A fourth line was detected at the 4σ level. We also found through mapping observations that the HOOH emission extends (about 0.05 pc) over the densest part of the ρ Oph A cloud core. We derive an abundance of HOOH relative to that of H2 in the SM1 core of about 1 × 10-10. Conclusions. To our knowledge, this is the first reported detection of HOOH in the interstellar medium.
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