CO Observations of NGC 2359: The Molecular Clouds Revisited (original) (raw)
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A Submillimeter Dust and Gas Study of the Orion B Molecular Cloud
The Astrophysical Journal, 2001
Using SCUBA on the James Clerk Maxwell Telescope, we obtained a map of 850 km continuum emission from the Orion B molecular cloud. The map is 20@ ] 40@ in extent and covers much of the northern half of the giant molecular cloud. A total of 67 discrete continuum sources, or clumps, have been identiÐed, many of which are grouped in three regions, near NGC 2071IR, NGC 2068, and HH 24/25/26. Masses of the sources range from 0.2 to 12 About half of the area of our 850 km map is M _. covered by the current release of the 2MASS infrared survey. Of 40 clumps covered by the 2MASS, 14 have associated infrared sources detected in J, H, and K. Maps of 13CO J \ 2È1 and C18O J \ 2È1 line emission were obtained for two regions in order to Ðnd the gas column density. Formaldehyde spectra were obtained toward eight of the continuum clumps to determine the gas kinetic temperature. Three of the clumps with measured temperature are hot K) while the other Ðve are cold K). (T kin º 80 (T kin ¹ 20 The gas-to-dust ratios di †er substantially between the two regions mapped in CO. In the NGC 2068 region we Ðnd close to constant ratios of dust-togas emission, except in one compact source. However, in the HH 24/25/26 region the dust-togas emission ratio varies substantially with some of the brightest dust continuum sources almost absent in CO emission. One explanation is that CO molecules have frozen onto grains in the dense cores. Why this freeze-out should happen in the HH 24/25/26 cores but not in the NGC 2068 cores remains unexplained. A 12CO J \ 3È2 map of the NGC 2068 region shows patches of high-velocity gas associated with Ðve of the compact continuum sources. The presence of out-Ñows provides strong evidence that the group of sources south of NGC 2068 is actively forming stars.
H I bubbles surrounding southern optical ring nebulae: Anon (WR 23) and RCW 52
Astronomy and Astrophysics, 2005
We analyze the interstellar medium in the environs of two hot and massive stars, HD 92809 (=WR 23, WC6) and LSS 1887 (O8V), which ionize the optical ring nebulae Anon (WR 23) and RCW 52, respectively. Our analysis is based on neutral hydrogen (H) 21 cm line data, which reveal interstellar bubbles surrounding the massive stars and their optical ring nebulae. The H bubble related to WR 23 is 13.3 pc in radius and is expanding at 10 km s −1. The associated atomic neutral mass is 830 M. The H structure related to LSS 1887 is about 6.3 pc in radius, has an expansion velocity of 7 km s −1 and an associated atomic neutral mass of 100 M. These H features are the neutral counterparts of the optical ring nebulae and were mainly created by the action of the stellar winds of the massive stars on their environs. The dynamical age of the H bubble around WR 23 (7 × 10 5 yr) suggests that it was created during the WR phase of stellar evolution. However, the large tangential motions of WR 23 and LSS 1887 suggest that part of the observed optical and H structures may be due to a bow shock. The analysis of the distribution of emission in the far infrared and in the CO(1−0) molecular line in the environs of WR 23 and LSS 1887 reveals that there are also infrared and molecular counterparts of the detected H bubbles.
Kinematics of the Molecular Hydrogen from the Planetary Nebula NGC 2346
The Astronomical Journal, 2001
We present scanning Fabry-Perot observations of the planetary nebula NGC 2346 at the near-infrared vibrationally excited line S(1) 1È0 at 2.122 km. The kinematics matches a model of two ellipsoids H 2 with an outÑow velocity proportional to the distance of the gas from the central star and moving radially outward. The stronger emission is located in an equatorial torus expanding at 16 km s~1. It is likely that a shock between 6 and 16 km s~1, depending on the assumed velocity of the red giant envelope (0 to 10 km s~1), excites the molecular gas. Depending on those limiting values for the shock velocity, the density of the preshock gas falls in the range (0.3È1.7) ] 104 cm~3, and consequently the mass of the molecular gas in the nebula is estimated to be between 0.34 and 1.85 much larger than the mass of M _ , the ionized gas, and marginally in agreement with the estimate coming from CO observations alone.
A disrupted molecular ring in planetary nebula G119.3+00.3 (BV 5-1)
Astronomy and Astrophysics, 2001
New, high-sensitivity interferometric CO observations of BV 5-1 show that the molecular gas in this bipolar planetary nebula is distributed along a very inhomogeneous ring made of clumps. The individual masses of such molecular clumps are ∼10 −4 M. The BV 5-1 molecular ring is seen edge-on, it is nearly perpendicular to the axis of bipolarity of the nebula, and it is expanding with an expansion velocity of ∼9 km s −1. BV 5-1 is confirmed to be a relatively evolved nebula, as indicated by both its kinematic age (∼2.4 × 10 4 yrs) and its molecular to ionized mass ratio (∼0.3). The structure of the BV 5-1 molecular ring, as well as that of other rings previously observed in a few additional nebulae, underscore the importance of strongly asymmetrical mass loss processes starting early at the asymptotic giant branch phase.
The radio and infrared counterparts of the ring nebula around HD 211564
Monthly Notices of the Royal Astronomical Society, 2010
We report the detection of the radio and infrared counterparts of the ring nebula around the WN3(h) star HD 211564 (WR 152), located to the southwest of the Hii region Sh2 132. Using radio continuum data from the Canadian Galactic Plane Survey, we identified the radio counterparts of the two concentric rings, of about 9 ′ and 16 ′ in radius, related to the star. After applying a filling factor f = 0.05-0.12, electron densities and ionized masses are in the range 10-16 cm −3 and 450-700 M ⊙ , respectively. The analysis of the Hi gas emission distribution allowed the identification of 5900 M ⊙ of neutral atomic gas with velocities between -52 and -43 km s −1 probably linked to the nebula. The region of the nebula is almost free of molecular gas. Only four small clumps were detected, with a total molecular mass of 790 M ⊙ . About 310 M ⊙ are related to a small infrared shell-like source linked to the inner ring, which is also detected in the MSX band A. An IRAS YSO candidate is detected in coincidence with the shell-like IR source.
Molecules, dust, and protostars in NGC 3503
Astronomy & Astrophysics, 2014
Aims. We are presenting here a follow-up study of the molecular gas and dust in the environs of the star forming region NGC 3503. This study aims at dealing with the interaction of the Hii region NGC 3503 with its parental molecular cloud, and also with the star formation in the region, that was possibly triggered by the expansion of the ionization front against the parental cloud. Methods. To analyze the molecular gas we use CO(J=2→1), 13 CO(J=2→1), C 18 O(J=2→1), and HCN(J=3→2) line data obtained with the on-the-fly technique from the APEX telescope. To study the distribution of the dust, we make use of unpublished images at 870 µm from the ATLASGAL survey and IRAC-GLIMPSE archival images. We use public 2MASS and WISE data to search for infrared candidate YSOs in the region. Results. The new APEX observations allowed the substructure of the molecular gas in the velocity range from ∼ −28 to −23 km s −1 to be imaged in detail. The morphology of the molecular gas close to the nebula, the location of the PDR, and the shape of radio continuum emission suggest that the ionized gas is expanding against its parental cloud, and confirm the "champagne flow" scenario. We have identified several molecular clumps and determined some of their physical and dynamical properties such as density, excitation temperature, mass, and line width. Clumps adjacent to the ionization front are expected to be affected by the Hii region, unlike those that are distant to it. We have compared the physical properties of the two kind of clumps to investigate how the molecular gas has been affected by the Hii region. Clumps adjacent to the ionization fronts of NGC 3503 and/or the bright rimmed cloud SFO 62 have been heated and compressed by the ionized gas, but their line width is not different to those that are too distant to the ionization fronts. We identified several candidate YSOs in the region. Their spatial distribution suggests that stellar formation might have been boosted by the expansion of the nebula. We discard the "collect and collapse" scenario and propose alternative mechanisms such as radiatively driven implosion on pre-existing molecular clumps or small-scale Jeans gravitational instabilities.
The shaping of planetary nebula Sh 2-188 through interactionwith the interstellar medium
Monthly Notices of the Royal Astronomical Society, 2006
Sh 2-188 is an example of strong interaction between a planetary nebula (PN) and the interstellar medium (ISM). It shows a single arc-like structure, consisting of several filaments, which is postulated to be the result of motion through the ISM. We present new Hα images from the Isaac Newton Telescope Photometric Hα Survey of the Northern Galactic Plane (IPHAS) which reveal structure behind the filamentary limb. A faint, thin arc is seen opposite the bright limb, in combination forming a closed ring. Behind the faint arc a long wide tail is detected, doubling the size of the nebula. The nebula extends 15 arcmin on the sky in total. We have developed a 'triplewind' hydrodynamical model, comprising of the initial 'slow' asymptotic giant branch (AGB) wind and the later 'fast' stellar wind (the interacting stellar wind model), plus a third wind reflecting the motion through the ISM. Simulations at various velocities of the central star relative to the ISM indicate that a high velocity of 125 km s −1 is required to reproduce the observed structure. We find that the bright limb and the tail already formed during the AGB phase, prior to the formation of the PN. The closure of the ring arises from the slow-fast wind interaction. Most of the mass lost on the AGB has been swept downstream, providing a potential explanation of the missing mass problem in PNe. We report a proper motion for the central star of 30 ± 10 mas yr −1 in the direction of the bright limb. Assuming the central star is moving at 125 ± 25 km s −1 , the distance to the nebula is estimated to be 850 +500 −420 pc, consistent with a spectroscopic distance to the star. Expansion velocities measured from spectroscopic data of the bright filaments are consistent with velocities measured from the simulation. Sh 2-188 is one of the largest PNe known, with an extent of 2.8 pc. The model shows that this size was already set during the AGB phase.
The molecular gas content of the Pipe Nebula
Astronomy & Astrophysics, 2012
Context. Star forming regions may share many characteristics, but the specific interplay between gravity, magnetic fields, large-scale dynamics, and protostellar feedback will have an impact on the star formation history of each region. The importance of feedback from outflows is a particular subject to debate, as we are yet to understand the details of their impact on clouds and star formation. Aims. The Pipe Nebula is a nearby molecular cloud hosting the B59 region as its only active star-forming clump. This paper focuses on the global dynamics of B59, its temperature structure, and its outflowing gas, with the goal of revealing the local and global impact of the protostellar outflows. Methods. Using HARP at the JCMT, we have mapped the B59 region in the J = 3 → 2 transition of 12 CO to study the kinematics and energetics of the outflows, and the same transitions of 13 CO and C 18 O to study the overall dynamics of the ambient cloud, the physical properties of the gas, and the hierarchical structure of the region. Results. The B59 region has a total of ∼ 30 M of cold and quiescent material, mostly gravitationally bound, with narrow line widths throughout. Such low levels of turbulence in the non-star-forming regions within B59 are indicative of the intrinsic initial conditions of the cloud. On the other hand, close to the protostars the impact of the outflows is observed as a localised increase of both C 18 O line widths from ∼ 0.3 km s −1 to ∼ 1 km s −1 , and 13 CO excitation temperatures by ∼ 2 − 3K. The impact of the outflows is also evident in the low column density material which shows signs of being shaped by the outflow bow shocks as they pierce their way out of the cloud. Much of this structure is readily apparent in a dendrogram analysis of the cloud and demonstrates that when decomposing clouds using such techniques a careful interpretation of the results is needed. Conclusions. The low mass of B59 together with its intrinsically quiescent gas and small number of protostars, allows the identification of specific regions where the outflows from the embedded sources interact the dense gas. Our study suggests that outflows are an important mechanism for injecting and sustaining supersonic turbulence at sub-parsec size scales. We find that less than half of the outflow energy is deposited as turbulent energy of the gas, however this turbulent energy is sufficient to slow down the collapse of the region.
The Astrophysical Journal, 2019
We carried out new 12 CO(J = 1-0, 3-2) observations of a N63A supernova remnant (SNR) from the LMC using ALMA and ASTE. We find three giant molecular clouds toward the northeast, east, and near the center of the SNR. Using the ALMA data, we spatially resolved clumpy molecular clouds embedded within the optical nebulae in both the shock-ionized and photoionized lobes discovered by previous Hα and [S ii] observations. The total mass of the molecular clouds is ∼800 M ⊙ for the shockionized region and ∼1700 M ⊙ for the photoionized region. Spatially resolved X-ray spectroscopy reveals that the absorbing column densities toward the molecular clouds are ∼1.5-6.0 × 10 21 cm −2 , which are ∼1.5-15 times less than the averaged interstellar proton column densities for each region. This means that the X-rays are produced not only behind the molecular clouds, but also in front of them. We conclude that the dense molecular clouds have been completely engulfed by the shock waves, but have still survived erosion owing to their high-density and short interacting time. The X-ray spectrum toward the gas clumps is well explained by an absorbed power-law or high-temperature plasma models in addition to the thermal plasma components, implying that the shock-cloud interaction is efficiently working for both the cases through the shock ionization and magnetic field amplification. If the hadronic gamma-ray is dominant in the GeV band, the total energy of cosmic-ray protons is calculated to be ∼0.3-1.4 × 10 49 erg with the estimated ISM proton density of ∼190 ± 90 cm −3 , containing both the shock-ionized gas and neutral atomic hydrogen.