We present high-angular-resolution ALMA (Atacama Large Millimeter Array) images of N$_{2}$H$^{+}$ (1--0) that has been combined with those from the Nobeyama telescope toward OMC-2 and OMC-3 filamentary regions. The filaments (with typical widths of $\sim$ 0.1 pc) and dense cores are resolved. The measured 2D velocity gradients of cores are between 1.3 and 16.7 km\,s$^{-1}$\,pc$^{-1}$, corresponding to a specific angular momentum ($J/M$) between 0.0012 and 0.016 pc\,km\,s$^{-1}$. With respect to the core size $R$, the specific angular momentum follows a power law $J/M \propto R^{1.52~\pm~0.14}$. The ratio ($β$) between the rotational energy and gravitational energy ranges from 0.00041 to 0.094, indicating insignificant support from rotation against gravitational collapse. We further focus on the alignment between the cores' rotational axes, which is defined to be perpendicular to the direction of the velocity gradient ($θ_{G}$), and the direction of elongation of filaments ($θ_{f}$) in this massive star-forming region. The distribution of the angle between $θ_{f}$ and $θ_{G}$ was f ound to be random, i.e. the cores' rotational axes have no discernible correlation with the elongation of their hosting filament. This implies that, in terms of angular momentum, the cores have evolved to be dynamically independent from their natal filaments.
We report the discovery of the oldest stellar substructure in the Orion star forming region (OSFR), the Orion relic filament. The relic filament is physically associated with the OSFR as demonstrated by Gaia DR2 photometry and astrometry, as well as targeted radial velocity follow-up observations of a bright sub-sample of proper-motion selected candidate members. Gaia DR2 parallaxes place the Orion relic filament in the more distant part of the OSFR, approx. 430pc from the Sun. Given its age, velocity dispersion, spatial extent, and shape, it is not possible for the Orion relic filament to hav…
A unique filament is identified in the {\it Herschel} maps of the Orion A giant molecular cloud. The filament, which, we name the Stick, is ruler-straight and at an early evolutionary stage. Transverse position-velocity diagrams show two velocity components closing in on the Stick. The filament shows consecutive rings/forks in C$^{18}$O(1-0) channel maps, which is reminiscent of structures generated by magnetic reconnection. We propose that the Stick formed via collision-induced magnetic reconnection (CMR). We use the magnetohydrodynamics (MHD) code Athena++ to simulate the collision between t…
We identify 45 protostellar outflows in CO maps of the Orion A giant molecular cloud from the CARMA-NRO Orion survey. Our sample includes 11 newly detected outflows. We measure the mass and energetics of the outflows, including material at low-velocities by correcting for cloud contributions. The total momentum and kinetic energy injection rates of outflows is comparable to the turbulent dissipation rate of the cloud. We also compare the outflow position angles to the orientation of C$^{18}$O filaments. We find that the full sample of outflows is consistent with being randomly oriented with re…
The Orion-Eridanus superbubble, formed by the nearby Orion high mass star-forming region, contains multiple bright H$α$ filaments on the Eridanus side of the superbubble. We examine the implications of the H$α$ brightnesses and sizes of these filaments, the Eridanus filaments. We find that either the filaments must be highly elongated along the line of sight or they cannot be equilibrium structures illuminated solely by the Orion star-forming region. The Eridanus filaments may, instead, have formed when the Orion-Eridanus superbubble encountered and compressed a pre-existing, ionized gas cloud…
Angular momentum is one of the most important physical quantities that govern star formation. The initial angular momentum of a core may be responsible for its fragmentation and can have an influence on the size of the protoplanetary disk. To understand how cores obtain their initial angular momentum, it is important to study the angular momentum of filaments where they form. While theoretical studies on filament rotation have been explored, there exist very few observational measurements of the specific angular momentum in star-forming filaments. We present high-resolution N2D+ ALMA observati…
The Integral Shaped Filament (ISF) is the nearest molecular cloud with rapid star formation, including massive stars, and it is therefore a star-formation laboratory. We use Gaia parallaxes, to show that the distances to young Class II stars ('disks') projected along the spine of this filament are related to the gas radial velocity by $$ v = -{D\overτ} + K;\qquad τ= 4\,{\rm Myr}, $$ where $K$ is a constant. This implies that the ISF is a standing wave, which is consistent with the Stutz & Gould (2016) 'Slingshot' prediction. The $τ=4\,{\rm Myr}$ timescale is consistent with the 'Slingshot' pic…
We present filamentary structure analysis based on the CARMA Orion Project through which we obtained high resolution (0.01pc) and high dynamic range (2~deg in DEC) images of the Orion A molecular cloud. We show a preliminary emission map of the $^{13}$CO emission with the addition of identified filaments. The data product resulted from 1500~hr of observing time at CARMA interferometer, and the Nobeyama 45~m telescope. We address basic filament properties along with calculated typical kinematical properties. Furthermore, we present a pilot study where we compare the observed [C{\sc II}] and [C{…
By comparing 3 constituents of Orion A (gas, protostars, and pre-main-sequence stars), both morhologically and kinematically, we derive the following. The gas surface density near the integral-shaped filament (ISF) is well represented by a power law, Sigma(b)=72 Msun/pc^2(b/pc)^{-5/8} for our entire range, 0.05<b/pc<8.5, of distance from the filament ridge. Essentially all protostars lie on the ISF or other filament ridges, while almost all pre-main-sequence stars do not. Combined with the fact that protostars move <1 kms relative to the filaments while stars move several times faster, this im…
We present combined observations of the NH3 (J,K) = (1,1) and (2,2) inversion transitions towards OMC1 in Orion A obtained by the Karl G. Jansky Very Large Array (VLA) and the 100 m Robert C. Byrd Green Bank Telescope (GBT). With an angular resolution of 6" (0.01 pc), these observations reveal with unprecedented detail the complex filamentary structure extending north of the active Orion BN/KL region in a field covering 6' x 7'. We find a 0.012 pc wide filament within OMC1, with an aspect ratio of ~37:1, that was missed in previous studies. Its orientation is directly compared to the relative …
We present a multi-wavelength observational study of the NGC 2024 filament using infrared to sub-millimeter continuum and the NH$_3$ $(1,1)$ and $(2,2)$ inversion transitions centered on FIR-3, the most massive core therein. FIR-3 is found to have no significant infrared point sources in the Spitzer/IRAC bands. But the NH$_3$ kinetic temperature map shows a peak value at the core center with $T_{\rm k}=25$ K which is significantly higher than the surrounding level ($T_{\rm k}=15-19$ K). Such internal heating signature without an infrared source suggests an ongoing core collapse possibly at a t…
Filaments are a key step on the path that leads from molecular clouds to star formation. However, their characteristics are heavily debated, and the exact processes that lead to their formation and fragmentation into dense cores still remain to be fully understood. We aim at characterising the mass, kinematics, and stability against gravitational collapse of a statistically significant sample of filaments in the Orion B molecular cloud, which is renown for its very low star formation efficiency. We characterise the gas column densities and kinematics over a field of 1.9 deg$^2$, using C$^{18}$…
[Abridged] We have recently reported on the collapse and fragmentation properties of the northernmost part of this structure, located ~2.4pc north of Orion KL -- the Orion Molecular Cloud 3 (OMC 3, Takahashi et al. 2013). As part of our project to study the integral-shaped filament, we analyze the fragmentation properties of the northern OMC 1 filament. This filament is a dense structure previously identified by JCMT/SCUBA submillimeter continuum and VLA ammonia observations and shown to have fragmented into clumps. We observed OMC1 n with the Submillimeter Array (SMA) at 1.3mm and report on o…
We study the fragmentation of the nearest high line-mass filament, the integral shaped filament (ISF, line-mass $\sim$ 400 M$_\odot$ pc$^{-1}$) in the Orion A molecular cloud. We have observed a 1.6 pc long section of the ISF with the Atacama Large Millimetre/submillimeter Array (ALMA) at 3 mm continuum emission, at a resolution of $\sim$3" (1 200 AU). We identify from the region 43 dense cores with masses about a solar mass. 60% of the ALMA cores are protostellar and 40\% are starless. The nearest neighbour separations of the cores do not show a preferred fragmentation scale; the frequency of…
We studied the filament structures and dense cores in OMC-2,3 region in Orion A North molecular cloud using the high-resolution N2H+ (1-0) spectral cube observed with the Atacama Large Millimeter/Submillimeter Array (ALMA). The filament network over a total length of 2 pc is found to contain 170 intersections and 128 candidate dense cores. The dense cores are all displaced from the infrared point sources (possible young stars), and the major fraction of cores (103) are located around the intersections. Towards the intersections, there is also an increasing trend for the total column density Nt…
We have studied the structure and kinematics of the dense molecular gas in the Orion Molecular Cloud 1 (OMC1) region with the N2H+ 3-2 line. The 6'x9' (~0.7x1.1 pc) region surrounding the Orion KL core has been mapped with the Submillimeter Array (SMA) and the Submillimeter Telescope (SMT). The combined SMA and SMT image having a resolution of ~5.4" (~2300 au) reveals multiple filaments with a typical width of 0.02-0.03 pc. On the basis of the non-LTE analysis using the N2H+ 3-2 and 1-0 data, the density and temperature of the filaments are estimated to be ~10^7 cm-3 and ~15-20 K, respectively…
We present an initial overview of the filamentary structure in the Orion A molecular cloud utilizing a high angular and velocity resolution C$^{18}$O(1-0) emission map that was recently produced as part of the CARMA-NRO Orion Survey. The main goal of this study is to build a credible method to study varying widths of filaments which has previously been linked to star formation in molecular clouds. Due to the diverse star forming activities taking place throughout its $\sim$20 pc length, together with its proximity of 388 pc, the Orion A molecular cloud provides an excellent laboratory for such…
We identify 225 filaments from an H$_2$ column density map constructed using simultaneous $^{12}$CO, $^{13}$CO, and C$^{18}$O (J=1-0) observations carried out as a part of the MWISP project. We select 46 long filaments with lengths above 1.2 pc to analyze the filament column density profiles. We divide the selected filaments into 397 segments and calculate the column density profiles for each segment. The symmetries of the profiles are investigated. The proportion of intrinsically asymmetrical segments is 65.3$\%$, and that of intrinsically symmetrical ones is 21.4$\%$. The typical full width …
Understanding the initial properties of star-forming material and how they affect the star formation process is key. From an observational point of view, the feedback from young high-mass stars on future star formation properties is still poorly constrained. In the framework of the IRAM 30m ORION-B large program, we obtained observations of the translucent and moderately dense gas, which we used to analyze the kinematics over a field of 5 deg^2 around the filamentary structures. We used the ROHSA algorithm to decompose and de-noise the C18O(1-0) and 13CO(1-0) signals by taking the spatial cohe…
The Orion nebula is a prime example of a massive star-forming region in our galaxy. Observations have shown that gravitational and magnetic energy are comparable in its integral shaped filament (ISF) on a scale of ~1 pc, and that the population of pre-main sequence stars appears dynamically heated compared to the protostars. These results have been attributed to a slingshot mechanism resulting from the oscillation of the filament (Stutz & Gould 2016). In this paper, we show that radially contracting filaments naturally evolve toward a state where gravitational, magnetic, and rotational energy …
We present the Herschel Gould Belt survey maps of the L1641 molecular clouds in Orion A. We extracted both the filaments and dense cores in the region. We identified which of dense sources are proto- or pre-stellar, and studied their association with the identified filaments. We find that although most (71%) of the pre-stellar sources are located on filaments there is still a significant fraction of sources not associated with such structures. We find that these two populations (on and off the identified filaments) have distinctly different mass distributions. The mass distribution of the sour…
TRAO Survey of Nearby Filamentary Molecular clouds, the Universal Nursery of Stars (TRAO-FUNS). III. Filaments and dense cores in the NGC 2068 and NGC 2071 regions of Orion B
We present analysis of the gas kinematics of the Integral Shaped Filament (ISF) in Orion~A using four different molecular lines, $^{12}$CO (1-0), $^{13}$CO (1-0), NH$_3$ (1,1), and N$_2$H$^+$ (1-0). We describe our method to visualize the position-velocity (PV) structure using the intensity-weighted line velocity centroid, which enables us to identify structures that were previously muddled or invisible. We observe a north to south velocity gradient in all tracers that terminates in a velocity peak near the center of the Orion Nebula Cluster (ONC), consistent with the previously reported "wave…
We present ALMA images of the dust and molecular line emission in the Orion Hot Core at 349 GHz. At 0.2" angular resolution the images reveal multiple clumps in an arc ~ 1" east of Orion Source I, the protostar at the center of the Kleinmann-Low Nebula, and another chain of peaks from IRc7 towards the southwest. The molecular line images show narrow filamentary structures at velocities > 10 km/s away from the heavily resolved ambient cloud velocity ~5 km/s. Many of these filaments trace the SiO outflow from Source I, and lie along the edges of the dust emission. Molecular line emission at exci…
Observations of DNC and DCO$^+$ toward the $\int$-shaped Filament and Starless Cores in the Orion Molecular Clouds
Nobeyama Radio Observatory, National Astronomical Observatory of Japan, National Institutes of Natural Sciences（日本国立天文台野边山无线电观测站，国立自然科学研究所）；SOKENDAI (The Graduate University for Advanced Studies)（综合研究大学院大学）；Department of Physics, Graduate School of Science, Osaka Metropolitan University（大阪公立大学理学研究科物理学系）；Star and Planet Formation Laboratory, RIKEN（理化学研究所星与行星形成实验室）；Graduate School of Informatics and Engineering, The University of Electro-Communications（电波大学信息工学与研究科）；Faculty of Education, Kagawa University（香川大学教育学部）；Department of Earth and Planetary Sciences, Faculty of Science, Kyushu University（九州大学理学部地球惑星科学系）
New visible and K-band polarization measurements on stars surrounding molecular clouds in Orion A and stars in the BN vicinity are presented. Our results confirm that magnetic fields located inside the Orion A molecular clouds and in their close neighborhood are spatially connected. On and around the BN object, we measured the angular offsets between the K-band polarization data and available submm data. We find high values of the polarization degree, P_{K}, and of the optical depth, τ_{K}, close to an angular offset position of 90^{\circ} whereas lower values of P_{K} and τ_{K} are observed f…
We present a high angular resolution map of 850 um continuum emission of the Orion Molecular Cloud-3 (OMC 3) obtained with the Submillimeter Array (SMA); the map is a mosaic of 85 pointings covering an approximate area of 6'.5 x 2'.0 (0.88 x 0.27 pc). We detect 12 spatially resolved continuum sources, each with an H_2 mass between 0.3-5.7 Mo and a projected source size between 1400-8200 AU. All the detected sources are on the filamentary main ridge n_H2>10^6 cm^-3), and analysis based on the Jeans theorem suggests that they are most likely gravitationally unstable. Comparison of multi-waveleng…
The spectral energy distribution (SED) in the millimetre (mm) to centimetre (cm) range is a useful tool for characterising the dust in protostellar envelopes as well as free-free emission from the protostar and outflow. While many studies have been carried out towards low- and high-mass protostars, little exists so far about solar-type protostars in high-mass star-forming regions, which are likely to be representatives of the conditions where the Solar System was born. We focus here on the OMC-2/3 solar-type protostars, which are bounded by nearby HII regions and which are, therefore, potentia…
We used the APEX telescope to observe the 372 GHz o-H$_2$D$^+(J_{K_a,\,K_c}=1_{1,\,0}-1_{1,\,1})$ line towards three prestellar cores and three protostellar cores in Orion B9. We also employed our previous APEX observations of C$^{17}$O, C$^{18}$O, N$_2$H$^+$, and N$_2$D$^+$ line emission, and 870 $μ$m dust continuum emission towards the target sources. The o-H$_2$D$^+$ line was detected in all three prestellar cores, but in only one of the protostellar cores. The corresponding o-H$_2$D$^+$ abundances were derived to be $\sim(12-30)\times10^{-11}$ and $6\times10^{-11}$. Two additional spectral…
(abridged) Within the Orion A molecular cloud, the integral-shaped filament (ISF) is a prominent, degree-long structure of dense gas and dust, with clear signs of recent and on-going high-mass star formation. We used the ArTeMiS bolometer camera at APEX to map a 0.6x0.2 deg^2 region covering OMC-1, OMC-2, OMC-3 at 350 and 450 micron. We combined these data with Herschel-SPIRE maps to recover extended emission. The combined Herschel-ArTeMiS maps provide details on the distribution of dense, cold material, with a high spatial dynamic range, from our 8'' resolution (0.016 pc) up to the size of th…
We present a detailed study of the Orion B clouds (d~400 pc), imaged with the PACS/SPIRE cameras at 70-500 $μ$m by the Herschel Gould Belt survey (HGBS). We release new high-res. maps of column density and dust temperature. In the filamentary sub-regions NGC2023/2024, NGC2068/2071, and L1622, 1768 starless dense cores were identified, ~28-45% of which are self-gravitating prestellar cores. A total of 76 protostellar dense cores were also found. The typical lifetime of the prestellar cores was found to be $t_{\rm pre}=1.7_{-0.6}^{+0.8}$ Myr. The prestellar core mass function (CMF) peaks at ~0.5…
Recently Stanchev et al. (2015) proposed a technique to derive density scaling relations in a star-forming region from analysis of the probability distribution function of column density. We address the possible dependence of the outcome on the selection of probe zones, applying the method to Planck dust-opacity data on Orion A. The derived steep scaling relation of mean density with index -1.6 in the molecular cloud (so called `Central filament') points to its self-gravitating nature. The result is reproduced also for large parts of the clouds' vicinity which indicates major role of gravity i…
The present study aims to characterise the physical and chemical properties of the protostellar core Orion B9-SMM3. The APEX telescope was used to perform a follow-up molecular line survey of SMM3. The following species were identified from the frequency range 218.2-222.2 GHz: $^{13}$CO, C$^{18}$O, SO, para-H$_2$CO, and E$_1$-type CH$_3$OH. The on-the-fly mapping observations at 215.1-219.1 GHz revealed that SMM3 is associated with a dense gas core as traced by DCO$^+$ and p-H$_2$CO. Altogether three different p-H$_2$CO transitions were detected with clearly broadened linewidths (8.2-11 km s$^…
Gravity-driven Emergence of Multi-fractal Density Structure in the Orion A Integral Shaped Filament
School of Astronomy and Space Science, Nanjing University（南京大学天文与空间科学学院）；Key Laboratory of Modern Astronomy and Astrophysics (Nanjing University), Ministry of Education（现代天文学和天体物理学教育部重点实验室（南京大学））；South-Western Institute for Astronomy Research, Yunnan University（云南大学西南天文研究所）
The Orion Complex is a notable star forming region, that it is fragmented into several different populations that have substantial difference in their phase space. I propose a model that attempts to explain the how the Complex has evolved to this current configuration. In this model, the large scale expansion can be attributable to a supernova that has exploded 6 Myr ago. The remnant of which can be seen as Barnard's loop, as the center of the expansion is consistent with the geometrical center of the HII bubble. This is similar to the HII bubble and the ballistic expansion that is associated …
The kinematics and dynamics of young stellar populations enable us to test theories of star formation. With this aim, we continue our analysis of the SDSS-III/APOGEE IN-SYNC survey, a high resolution near infrared spectroscopic survey of young clusters. We focus on the Orion A star-forming region, for which IN-SYNC obtained spectra of $\sim2700$ stars. In Paper IV we used these data to study the young stellar population. Here we study the kinematic properties through radial velocities ($v_r$). The young stellar population remains kinematically associated with the molecular gas, following a $\s…
We determine the magnetic field strength in the OMC 1 region of the Orion A filament via a new implementation of the Chandrasekhar-Fermi method using observations performed as part of the James Clerk Maxwell Telescope (JCMT) B-Fields In Star-Forming Region Observations (BISTRO) survey with the POL-2 instrument. We combine BISTRO data with archival SCUBA-2 and HARP observations to find a plane-of-sky magnetic field strength in OMC 1 of $B_{\rm pos}=6.6\pm4.7$ mG, where $δB_{\rm pos}=4.7$ mG represents a predominantly systematic uncertainty. We develop a new method for measuring angular dispersi…
The Orion A molecular cloud is one of the most well-studied nearby star-forming regions, and includes regions of both highly clustered and more dispersed star formation across its full extent. Here, we analyze dense, star-forming cores identified in the 850 μm and 450 μm SCUBA-2 maps from the JCMT Gould Belt Legacy Survey. We identify dense cores in a uniform manner across the Orion A cloud and analyze their clustering properties. Using two independent lines of analysis, we find evidence that clusters of dense cores tend to be mass segregated, suggesting that stellar clusters may have some amo…
We have observed molecular cloud cores in the Orion A giant molecular cloud (GMC) in CCS, HC3N, DNC, and HN13C to study their chemical characteristics. We have detected CCS in the Orion A GMC for the first time. CCS was detected in about a third of the observed cores. The cores detected in CCS are not localized but are widely distributed over the Orion A GMC. The CCS peak intensity of the core tends to be high in the southern region of the Orion A GMC. The HC3N peak intensity of the core also tends to be high in the southern region, while there are HC3N intense cores near Orion KL, which is no…
Abridged. Are all filaments bundles of fibers? To address this question, we have investigated the gas organization within the paradigmatic Integral Shape Filament (ISF). We combined two new ALMA Cycle 3 mosaics with previous IRAM 30m observations to produce a high-dynamic range N$_2$H$^+$(1-0) emission map of the ISF tracing its high-density material and velocity structure down to scales of 0.009 pc. From the analysis of the gas kinematics, we identify a total of 55 dense fibers in the central region of the ISF. Independently of their location, these fibers are characterized by transonic inter…
We present sensitive high angular resolution submillimeter and millimeter observations of torsionally/vibrationally highly excited lines of the CH$_3$OH, HC$_3$N, SO$_2$, and CH$_3$CN molecules and of the continuum emission at 870 and 1300 $μ$m from the Orion KL region, made with the Submillimeter Array (SMA). These observations plus recent SMA CO J=3-2 and J=2-1 imaging of the explosive flow originating in this region, which is related to the non-hierarchical disintegration of a massive young stellar system, suggest that the molecular Orion "Hot Core" is a pre-existing density enhancement hea…
We have investigated the formation and kinematics of sub-mm continuum cores in the Orion A molecular cloud. A comparison between sub-mm continuum and near infrared extinction shows a continuum core detection threshold of $A_V\sim$ 5-10 mag. The threshold is similar to the star formation extinction threshold of $A_V\sim$ 7 mag proposed by recent work, suggesting a universal star formation extinction threshold among clouds within 500 pc to the Sun. A comparison between the Orion A cloud and a massive infrared dark cloud G28.37+0.07 indicates that Orion A produces more dense gas within the extinc…
The Gould Belt Legacy Survey will map star-forming regions within 500 pc, using HARP (Heterodyne Array Receiver Programme), SCUBA-2 (Submillimetre Common-User Bolometer Array 2) and POL-2 (Polarimeter 2) on the James Clerk Maxwell Telescope (JCMT). This paper describes HARP observations of the J = 3-2 transitions of 13CO and C18O towards Orion A. The 1500-resolution observations cover 5 pc of the Orion filament, including OMC1 (inc. BN-KL and Orion Bar), OMC 2/3 and OMC 4, and allow a comparative study of the molecular gas properties throughout the star-forming cloud. The filament shows a velo…
We present results of the classification of cloud structures toward the Orion A Giant Molecular Cloud based on wide-field $^{12}$CO ($J$ = 1--0), $^{13}$CO ($J$ = 1-0), and C$^{18}$O ($J$ = 1-0) observations using the Nobeyama 45 m radio telescope. We identified 78 clouds toward Orion A by applying Spectral Clustering for Interstellar Molecular Emission Segmentation (SCIMES) to the data cube of the column density of $^{13}$CO. Well-known subregions such as OMC-1, OMC-2/3, OMC-4, OMC-5, NGC 1977, L1641-N, and the dark lane south filament (DLSF) are naturally identified as distinct structures in…
During the transition phase from a prestellar to a protostellar cloud core, one or several protostars can form within a single gas core. The detailed physical processes of this transition, however, still remain unclear. We present 1.3 mm dust continuum and molecular line observations with the Atacama Large Millimeter/submillimeter Array (ALMA) toward 43 protostellar cores in the Orion Molecular Cloud Complex ($λ$ Orionis, Orion B, and Orion A) with an angular resolution of $\sim$ 0.35" ($\sim$ 140 au). In total, we detect 13 binary/multiple systems. We derive an overall multiplicity frequency …
Recent observations from the MUSTANG2 instrument on the Green Bank Telescope have revealed evidence of enhanced long-wavelength emission in the dust spectral energy distribution (SED) in the Orion Molecular Cloud (OMC) 2/3 filament on 25" (0.1 pc) scales. Here we present a measurement of the SED on larger spatial scales (map size 0.5-3 degrees or 3-20 pc), at somewhat lower resolution (120", corresponding to 0.25 pc at 400 pc) using data from the Herschel satellite and Atacama Cosmology Telescope (ACT). We then extend the 120"-scale investigation to other regions covered in the Herschel Gould …
We have investigated the global dynamical state of the Integral Shaped Filament in the Orion A cloud using new N$_2$H$^+$ (1-0) large-scale, IRAM30m observations. Our analysis of its internal gas dynamics reveals the presence of accelerated motions towards the Orion Nebula Cluster, showing a characteristic blue-shifted profile centred at the position of the OMC-1 South region. The properties of these observed gas motions (profile, extension, and magnitude) are consistent with the expected accelerations for the gravitational collapse of the OMC-1 region and explain both the physical and kinemat…
We present far-IR (57-196 mu) spectra of 21 protostars in the Orion molecular clouds, obtained with the Photodetector Array Camera and Spectrometer (PACS) onboard the Herschel Space observatory, as part of the Herschel Orion Protostar Survey (HOPS) program. We analyzed the CO emission lines (J_up = 14-46) in the PACS spectra, extracted within a projected distance of <= 2000 AU centered on the protostar. The total luminosity of the CO lines observed with PACS (L(CO)) is found to increase with increasing L_bol. The CO rotational temperature implied by the line ratios increases with J, and at lea…
Filaments are an important part of star-forming interstellar clouds. Theie properties hold clues to their formation mechanisms and role in the star-formation process. We compare the properties of filaments in the Orion Molecular Cloud 3 (OMC-3), as seen in mid-infrared (MIR) absorption and far-infrared (FIR) dust emission. We calculated optical depth maps of the OMC-3 filaments based on the MIR absorption seen in Spitzer data and FIR dust emission observed with Herschel and the ArTéMiS instrument. The widths of the selected OMC-3 filament segments are in the range 0.03-0.1 pc, with similar ave…
We study the structure and kinematics of nine 0.1 pc-scale cores in Orion with the IRAM 30-m telescope and at higher resolution eight of the cores with CARMA, using CS(2-1) as the main tracer. The single-dish moment zero maps of the starless cores show single structures with central column densities ranging from 7 to 42 times 10^23 cm^-2 and LTE masses from 20 solar masses to 154 solar masses. However, at the higher CARMA resolution (5 arcsec), all of the cores except one fragment into 3 - 5 components. The number of fragments is small compared to that found in some turbulent fragmentation mod…
Complex Organic Molecules (COMs) are believed to form in the ice mantle of dust grains and are released to the gas by thermal sublimation when grain mantles are heated to temperatures of $T_{\rm d}\gtrsim 100\,\rm K$. However, some COMs are detected in regions with temperatures below 100 K. Recently, a new mechanism of rotational desorption due to centrifugal stress induced by radiative torques (RATs) is proposed by Hoang & Tram 2020 that can desorb COMs at low temperatures. In this paper, we report observational evidence for rotational desorption of COMs toward the nearest massive star-formin…
We present $^{29}$SiO(J=8--7) $ν$=0, SiS (J=19--18) $ν$=0, and $^{28}$SiO (J=8--7) $ν$=1 molecular line archive observations made with the Atacama Large Millimeter/Submillimeter Array (ALMA) of the molecular outflow associated with Orion Source I. The observations show velocity asymmetries about the flow axis which are interpreted as outflow rotation. We find that the rotation velocity ($\sim$4--8 km s$^{-1}$) decreases with the vertical distance to the disk. In contrast, the cylindrical radius ($\sim$100--300 au), the expansion velocity ($\sim$2--15 km s$^{-1}$), and the axial velocity $v_{\r…
We present numerical simulations of reorienting oblique shocks that form in the collision layer between magnetized colliding flows. Reorientation aligns parsec-scale post-shock filaments normal to the background magnetic field. We find that reorientation begins with pressure gradients between the collision region and the ambient medium. This drives a lateral expansion of post-shock gas, which reorients the growing filament from the outside-in (i.e. from the flow-ambient boundary, toward the colliding flows axis). The final structures of our simulations resemble polarization observations of fil…
The Orion Bar is one of the nearest and best-studied photodissociation or photon-dominated regions (PDRs). Observations reveal the presence of H2 lines from vibrationally or rotationally excited upper levels that suggest warm gas temperatures (400 to 700 K). However, standard models of PDRs are unable to reproduce such warm rotational temperatures. In this paper we attempt to explain these observations with new comprehensive models which extend from the H+ region through the Bar and include the magnetic field in the equation of state. We adopt the model parameters from our previous paper which…
We have analyzed the angular momentum of the molecular cloud cores in the Orion A giant molecular cloud observed in the N2H+ J = 1-0 line with the Nobeyama 45 m radio telescope. We have measured the velocity gradient using position velocity diagrams passing through core centers, and made sinusoidal fitting against the position angle. 27 out of 34 N2H+ cores allowed us to measure the velocity gradient without serious confusion. The derived velocity gradient ranges from 0.5 to 7.8 km/s/pc. We marginally found that the specific angular momentum J/M (against the core radius R) of the Orion N2H+ co…
