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. The core fragmentation is observed in three massive filaments, one of which shows the oscillations in the velocity and intensity that could be the signature of core-forming gas motions. The gas kinetic temperature is significantly enhanced in the eastern part of OMC1, likely due to the external heating from the high mass stars in M42 and M43. In addition, the filaments are colder than their surrounding regions, suggesting the shielding from the external heating due to the dense gas in the filaments. The OMC1 region consists of three sub-regions, i.e. north, west, and south of Orion KL, having different radial velocities with sharp velocity transitions. There is a north-to-south velocity gradient from the western to the southern regions. The observed velocity pattern suggests that dense gas in OMC1 is collapsing globally toward the high-mass star-forming region, Orion Nebula Cluster.
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{…
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 …
Using a method based on Faraday rotation measurements, Tahani et al. 2018 find the line-of-sight component of magnetic fields in Orion-A and show that their direction changes from the eastern side of this filamentary structure to its western side. Three possible magnetic field morphologies that can explain this reversal across the Orion-A region are toroidal, helical, and bow-shaped morphologies. In this paper we construct simple models to represent these three morphologies and compare them with the available observational data to find the most probable morphology(ies). To compare the observat…
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 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$20 pc length, together with its proximity of 388 pc, the Orion A molecular cloud provides an excellent laboratory for such…
We identify 45 protostellar outflows in CO maps of the Orion A giant molecular cloud from the CARMA-NRO Orion survey. Our sample includes 11 newly detected outflows. We measure the mass and energetics of the outflows, including material at low-velocities by correcting for cloud contributions. The total momentum and kinetic energy injection rates of outflows is comparable to the turbulent dissipation rate of the cloud. We also compare the outflow position angles to the orientation of C$^{18}$O filaments. We find that the full sample of outflows is consistent with being randomly oriented with re…
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…
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
It has recently been suggested that chemical processing can shape the spatial distributions of complex molecules in the Orion-KL region and lead to the nitrogen-oxygen "chemical differentiation" seen in previous observations of this source. Orion-KL is a very dynamic region, and it is therefore also possible that physical conditions can shape the molecular distributions in this source. Only high spatial resolution observations can provide the information needed to disentangle these effects. Here we present millimeter imaging studies of Orion-KL at various beam sizes using the Combined Array fo…
We use the $\mathit{Gaia}$ DR2 distances of about 700 mid-infrared selected young stellar objects in the benchmark giant molecular cloud Orion A to infer its 3D shape and orientation. We find that Orion A is not the fairly straight filamentary cloud that we see in (2D) projection, but instead a cometary-like cloud oriented toward the Galactic plane, with two distinct components: a denser and enhanced star-forming (bent) Head, and a lower density and star-formation quieter $\sim$75 pc long Tail. The true extent of Orion A is not the projected $\sim$40 pc but $\sim$90 pc, making it by far the la…
Stars form in molecular clouds in the interstellar medium (ISM) with a turbulent kinematic state. Newborn stars therefore should retain the turbulent kinematics of their natal clouds. Gaia DR2 and APOGEE-2 surveys in combination provide three-dimensional (3D) positions and 3D velocities of young stars in the Orion Molecular Cloud Complex. Using the full 6D measurements, we compute the velocity structure functions (VSFs) of the stars in six different groups within the Orion Complex. We find that the motions of stars in all diffuse groups exhibit strong characteristics of turbulence. Their first…
Using the IRAM 30m telescope we have surveyed a $1\times0.8^{\circ}$ part of the Orion molecular cloud in the $^{12}$CO and $^{13}$CO (2-1) lines with a maximal spatial resolution of $\sim$11" and spectral resolution of $\sim$ 0.4 km~s$^{-1}$. The cloud appears filamentary, clumpy and with a complex kinematical structure. We derive an estimated mass of the cloud of 7700 M$_{\text{Sun}}$ (half of which is found in regions with visual extinctions $A_V$ below $\sim$10) and a dynamical age for the nebula of the order of 0.2 Myrs. The energy balance suggests that magnetic fields play an important r…
We have analyzed new CO($J$ = 1-0) data in the region of a reflection nebula NGC 2023 with a particular focus on the detailed kinematical properties of the molecular gas. The results show that there are two velocity components which indicate signatures of dynamical interaction revealed at a high resolution of 19$''$ (= 0.04 pc). Based on the results we propose a hypothesis that two clouds collided with each other and triggered the formation of the B1.5 star HD 37903 in addition to 20 lower mass stars in two small clusters with a size of 2 pc. Although the previous study favored a scheme of tri…
ALMA Survey of Orion Planck Galactic Cold Clumps (ALMASOP): Discovery of an extremely dense and compact object embedded in the prestellar core G208.68-19.92-N2
We present results from high resolution optical spectra toward 66 young stars in the Orion B molecular cloud to study their kinematics and other properties. Observations of the H$α$ and Li I 6707 Å lines are used to check membership and accretion properties. While the stellar radial velocities of in NGC 2068 and L1622 show good agreement with that of the molecular gas, many of the stars in NGC 2024 show a considerable offset. This could be a signature of either expansion of the cluster, high degree of the ejection of the stars from the cluster through the dynamical interaction, or the accelera…
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…
Using data from the Galactic Arecibo L-band Feed Array Continuum Transit Survey (GALFACTS), we report the discovery of two previously unidentified, very compressed, thin, and straight polarized filaments approximately centred at Galactic coordinates, $(l,b)=(182.5^\circ,-4.0^\circ)$, which we call G182.5--4.0. Using data from the Isaac Newton Telescope Galactic Plane Survey (IGAPS), we also find straight, long, and extremely thin H$α$ filaments coincident with the radio emission. These filaments are positioned in projection at the edge of the Orion-Eridanus superbubble and we find evidence ind…
We present a study of the three dimensional structure, kinematics, and age distribution of the Orion OB association, based on the second data release of the Gaia satellite (Gaia DR2). Our goal is to obtain a complete picture of the star formation history of the Orion complex and to relate our findings to theories of sequential and triggered star formation. We select the Orion population with simple photometric criteria, and we construct a three dimensional map in galactic Cartesian coordinates to study the physical arrangement of the stellar clusters in the Orion region. The map shows structur…
The giant molecular cloud Orion A is the closest massive star-forming region to earth ($d\sim400$ pc). It contains the rich Orion Nebula Cluster (ONC) in the North, and low-mass star-forming regions (L1641, L1647) to the South. To get a better understanding of the differences in star formation activity, we perform an analysis of the gas mass distribution and star formation rate across the cloud. We find that the gas is roughly uniformly distributed, while, oddly, the ONC region produced about a factor of ten more stars compared to the rest of the cloud. For a better interpretation of this phen…
This work extends previous kinematic studies of young stars in the Head of the Orion A cloud (OMC-1/2/3/4/5). It is based on large samples of infrared, optical, and X-ray selected pre-main sequence stars with reliable radial velocities and Gaia-derived parallaxes and proper motions. Stellar kinematic groups are identified assuming they mimic the motion of their parental gas. Several groups are found to have peculiar kinematics: the NGC 1977 cluster and two stellar groups in the Extended Orion Nebula (EON) cavity are caught in the act of departing their birthplaces. The abnormal motion of NGC 1…
We imaged the continuum and molecular line emission from Orion Source I (SrcI) with up to 30 mas (12 AU) resolution at 43, 99, 223, and 340 GHz in an attempt to probe the structure and chemistry of the circumstellar disk and bipolar outflow associated with this high mass protostar. The continuum spectral index ranges from $\sim$2 along the midplane of the disk to $\sim$3 along the edges, consistent with dust that is optically thick in the midplane but becomes optically thin at the periphery. Salt (NaCl) emission is visible where the dust is optically thin; it provides a unique tracer of the ve…
We present new Plateau de Bure Interferometer observations of a region in the filamentary infrared-dark cloud (IRDC) G011.11-0.12 containing young, star-forming cores. In addition to the 3.2mm continuum emission from cold dust, we map this region in the N$_2$H$^+$(1-0) line to trace the core kinematics with an angular resolution of 2" and velocity resolution of 0.2km s$^{-1}$. These data are presented in concert with recent {\em Herschel} results, single-dish N$_2$H$^+$(1-0) data, SABOCA 350$μ$m continuum data, and maps of the C$^{18}$O (2-1) transition obtained with the IRAM 30m telescope. We…
The new Gaia data release (EDR3) with improved astrometry has opened a new era in studying our Milky Way in fine detail. We use Gaia EDR3 astrometry together with 2MASS and WISE photometry to study two of the most massive molecular clouds in the solar vicinity: Orion A and California. Despite having remarkable similarities in the plane of the sky in terms of shape, size, and extinction, California has an order of magnitude lower star formation efficiency. We use our state-of-the-art dust mapping technique to derive the detailed three-dimensional (3D) structure of the two clouds, taking into ac…
The "Nessie" Nebula is a filamentary infrared dark cloud (IRDC) with a large aspect ratio of over 150:1 (1.5 degrees x 0.01 degrees, or 80 pc x 0.5 pc at a kinematic distance of 3.1 kpc). Maps of HNC (1-0) emission, a tracer of dense molecular gas, made with the Australia Telescope National Facility Mopra telescope, show an excellent morphological match to the mid-IR extinction. Moreover, because the molecular line emission from the entire nebula has the same radial velocity to within +/- 3.4 km/s, the nebula is a single, coherent cloud and not the chance alignment of multiple unrelated clouds…
Infrared dark clouds (IRDCs) are thought to be potential hosts of the elusive early phases of high-mass star formation. Here we conduct an in-depth kinematic analysis of one such IRDC, G034.43+00.24 (Cloud F), using high sensitivity and high spectral resolution IRAM-30m N$_2$H$^+$ ($1-0$) and C$^{18}$O ($1-0$) observations. To disentangle the complex velocity structure within this cloud we use Gaussian decomposition and hierarchical clustering algorithms. We find that four distinct coherent velocity components are present within Cloud F. The properties of these components are compared to those…
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 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…
To probe the initial conditions for high-mass star and cluster formation, we investigate the properties of dense filaments within the infrared dark cloud G035.39-00.33 (IRDC G035.39) in a combined Very Large Array (VLA) and the Green Bank Telescope (GBT) mosaic tracing the NH3 (1,1) and (2,2) emission down to 0.08 pc scales. Using agglomerative hierarchical clustering on multiple line-of-sight velocity component fitting results, we identify seven extended velocity-coherent components in our data, likely representing spatially coherent physical structures, some exhibiting complex gas motions. T…
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 a high resolution study of the filamentary infrared dark cloud G192.76+00.10 in the S254-S258 OB complex in several molecular species tracing different physical conditions. These include three isotopologues of carbon monoxide (CO), ammonia (NH$_3$), carbon monosulfide (CS). The aim of this work is to study the general structure and kinematics of the filamentary cloud, its fragmentation and physical parameters. The gas temperature is derived from the NH$_3 $ $(J,K) = (1,1), (2,2)$ and $^{12}$CO(2--1) lines and the $^{13}$CO(1--0), $^{13}$CO(2--1) emission is used to invest…
The Orion Molecular Cloud is the nearest massive-star forming region. Massive stars have profound effects on their environment due to their strong radiation fields and stellar winds. Velocity-resolved observations of the [CII] $158\,μ\mathrm{m}$ fine-structure line allow us to study the kinematics of UV-illuminated gas. Here, we present a square-degree-sized map of [CII] emission from the Orion Nebula complex obtained by the upGREAT instrument onboard SOFIA, covering the entire Orion Nebula (M42) plus M43 and the nebulae NGC 1973, 1975, and 1977. We compare the stellar characteristics of these…
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$^{18}$…
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…
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…
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…
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 the ALMA Band 3 and Band 6 results of 12CO(2-1), 13$CO(2-1), H30alpha recombination line, free-free emission around 98 GHz, and the dust thermal emission around 230 GHz toward the N159 East Giant Molecular Cloud (N159E) in the Large Magellanic Cloud (LMC). LMC is the nearest active high-mass star forming face-on galaxy at a distance of 50 kpc and is the best target for studing high-mass star formation. ALMA observations show that N159E is the complex of filamentary clouds with the width and length of ~1 pc and 5 pc - 10 pc, respectively. The total molecular mass is 0.92 x 10^5 Msun …
This paper analyses images from 43 to 340 GHz to trace the structure of the Source I disk in Orion-KL with $\sim$12 AU resolution. The data reveal an almost edge-on disk with an outside diameter $\sim$ 100 AU which is heated from the inside. The high opacity at 220-340 GHz hides the internal structure and presents a surface temperature $\sim$500 K. Images at 43, 86 and 99 GHz reveal structure within the disk. At 43 GHz there is bright compact emission with brightness temperature $\sim$1300 K. Another feature, most prominent at 99 GHz, is a warped ridge of emission. The data can be explained by…
We present the results of the SDSS APOGEE INfrared Spectroscopy of Young Nebulous Clusters program (IN-SYNC) survey of the Orion A molecular cloud. This survey obtained high resolution near infrared (NIR) spectroscopy of about 2700 young pre-main sequence stars throughout the region, acquired across five distinct fields spanning 6deg field of view (FOV). With these spectra, we have measured accurate stellar parameters (T_eff, log g, v sin i) and extinctions, and placed the sources in the Hertzsprung-Russel Diagram (HRD). We have also extracted radial velocities for the kinematic characterizati…
The kinematics of the bipolar planetary nebulae Hb~5 and K 3-17 are investigated in detail by means of a comprehensive set of spatially resolved high spectral resolution, long-slit spectra. Both objects share particularly interesting characteristics, such as a complex filamentary, rosette-type nucleus, axial point-symmetry and very fast bipolar outflows. The kinematic information of Hb~5 is combined with {\it HST} imagery to construct a detailed 3D model of the nebula using the code SHAPE. The model shows that the large scale lobes are growing in a non-homologous way. The filamentary loops in …
The kinematics and dynamics of stellar and substellar populations within young, still-forming clusters provides valuable information for constraining theories of formation mechanisms. Using Keck II NIRSPEC+AO data, we have measured radial velocities for 56 low-mass sources within 4' of the core of the Orion Nebula Cluster (ONC). We also re-measure radial velocities for 172 sources observed with SDSS/APOGEE. These data are combined with proper motions measured using $HST$ ACS/WFPC2/WFC3IR and Keck II NIRC2, creating a sample of 135 sources with all three velocity components. The velocities meas…
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…
The Palomar Cosmic Web Imager (PCWI), an integral field spectrograph designed to detect and map low surface brightness emission, has obtained imaging spectroscopic maps of Ly-alpha from the circum-QSO medium (CQM) of QSO HS1549+19 at redshift of 2.843. Extensive extended emission is detected from the CQM, consistent with fluorescent and pumped Ly-alpha produced by the ionizing and Ly-alpha continuum of the QSO. Many features present in PCWI spectral images match those detected in narrow-band images. Filamentary structures with narrow line profiles are detected in several cases as long as 250-4…
Star formation in molecular clouds is intimately linked to their internal mass distribution. We present an unprecedentedly detailed analysis of the column density structure of a high-mass, filamentary molecular cloud, namely IRDC G11.11-0.12 (G11). We use two novel column density mapping techniques: high-resolution (FWHM=2", or ~0.035 pc) dust extinction mapping in near- and mid-infrared, and dust emission mapping with the Herschel satellite. These two completely independent techniques yield a strikingly good agreement, highlighting their complementarity and robustness. We first analyze the de…
We assemble a census of the most massive stars in Orion, then use stellar isochrones to estimate their masses and ages, and use these results to establish the stellar content of Orion's individual OB associations. From this, our new population synthesis code is utilized to derive the history of the emission of UV radiation and kinetic energy of the material ejected by the massive stars, and also follow the ejection of the long-lived radioactive isotopes 26Al and 60Fe. In order to estimate the precision of our method, we compare and contrast three distinct representations of the massive stars. …
We characterize the stellar and gas volume density, potential, and gravitational field profiles in the central $\sim$ 0.5 pc of the Orion Nebula Cluster (ONC), the nearest embedded star cluster (or rather, proto-cluster) hosting massive star formation available for detailed observational scrutiny. We find that the stellar volume density is well characterized by a Plummer profile $ρ_{stars}(r) = 5755\,{\rm M}_{\odot}\,{\rm pc}^{-3}\,(1+(r/a)^2)^{-5/2}$, where $a = 0.36$ pc. The gas density follows a cylindrical power law $ρ_{gas}(R) = 25.9\,{\rm M}_{\odot}\,{\rm pc}^{-3}\,(R/{\rm pc})^{-1.775}$…
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 performed a multi-wavelength study toward the filamentary cloud G47.06+0.26 to investigate the gas kinematics and star formation. We present the 12CO (J=1-0), 13CO (J=1-0) and C18O (J=1-0) observations of G47.06+0.26 obtained with the Purple Mountain Observation (PMO) 13.7 m radio telescope to investigate the detailed kinematics of the filament. The 12CO (J=1-0) and 13CO (J=1-0) emission of G47.06+0.26 appear to show a filamentary structure. The filament extends about 45 arcmin (58.1 pc) along the east-west direction. The mean width is about 6.8 pc, as traced by the 13CO (J=1-0) emission. G…
We present a comparative study of the physical properties and the spatial distribution of column density peaks in two Giant Molecular Clouds (GMC), the Pipe Nebula and Orion A, which exemplify opposite cases of star cluster formation stages. The density peaks were extracted from dust extinction maps constructed from Herschel/SPIRE farinfrared images. We compare the distribution functions for dust temperature, mass, equivalent radius and mean volume density of peaks in both clouds, and made a more fair comparison by isolating the less active Tail region in Orion A and by convolving the Pipe Neb…
Our main goal is to derive a new extinction map of the OMC-1, obtaining information about the structure of the OMC-1 and the Orion Nebula Cluster. The most recent near-infrared catalog of stars is used to study the distribution of reddening across a ~0.3 deg^2 area covering the Orion Nebula Cluster. On the basis of the observed (H,H-K_S) diagram, we establish a criterion for disentangling contaminants from bona-fide cluster members. For contaminant stars, interstellar reddenings are estimated by comparison with a synthetic galactic model. A statistical analysis is then performed to consistentl…
We present the stability analysis of two regions, OMC-3 and OMC-4, in the massive and long molecular cloud complex of Orion A. We obtained $214~μ$m HAWC+/SOFIA polarization data, and we make use of archival data for the column density and C$^{18}$O (1-0) emission line. We find clear depolarization in both observed regions and that the polarization fraction is anti-correlated with the column density and the polarization-angle dispersion function. We find that the filamentary cloud and dense clumps in OMC-3 are magnetically supercritical and strongly subvirial. This region should be in the gravi…
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）
Massive stars born in star clusters terminate star cluster formation by ionizing the surrounding gas. This process is considered to be prevalent in young star clusters containing massive stars. The Orion Nebula is an excellent example associated with a forming star cluster including several massive stars (the Orion Nebula Cluster; ONC) and a 2-pc size H{\sc ii} region (ionized bubble) opening toward the observer; however, the other side is still covered with dense molecular gas. Recent astrometric data acquired by the Gaia satellite revealed the stellar kinematics in this region. By comparing …
We present Atacama Large Millimeter Array CO(3$-$2) and HCO$^+$(4$-$3) observations covering the central $1\rlap{.}'5$$\times$$1\rlap{.}'5$ region of the Orion Nebula Cluster (ONC). The unprecedented level of sensitivity ($\sim$0.1 mJy beam$^{-1}$) and angular resolution ($\sim$$0\rlap{.}''09 \approx 35$ AU) of these line observations enable us to search for gas-disk detections towards the known positions of submillimeter-detected dust disks in this region. We detect 23 disks in gas: 17 in CO(3$-$2), 17 in HCO$^+$(4$-$3), and 11 in both lines. Depending on where the sources are located in the …
We present an analysis of spectrosopic and astrometric data from APOGEE-2 and Gaia DR2 to identify structures towards the Orion Complex. By applying a hierarchical clustering algorithm to the 6-dimensional stellar data, we identify spatially and/or kinematically distinct groups of young stellar objects with ages ranging from 1 to 12 Myr. We also investigate the star forming history within the Orion Complex, and identify peculiar sub-clusters. With this method we reconstruct the older populations in the regions that are presently largely devoid of molecular gas, such as Orion C (which includes …
