- ID:
- ivo://CDS.VizieR/J/ApJ/844/138
- Title:
- Optical spectroscopy toward Orion B fields
- Short Name:
- J/ApJ/844/138
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- 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{alpha} and Li I 6707{AA} lines are used to check membership and accretion properties. While the stellar radial velocities of NGC 2068 and L1622 are in 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 the expansion of the cluster, the high degree of the ejection of the stars from the cluster through dynamical interaction, or the acceleration of the gas due to stellar feedback.
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- ID:
- ivo://CDS.VizieR/J/ApJS/217/7
- Title:
- Orion A dense cores based on 1.1mm and C^18^O
- Short Name:
- J/ApJS/217/7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Orion A giant molecular cloud core catalogs, which are based on a 1.1mm map with an angular resolution of 36" (~0.07pc) and C^18^O (J=1-0) data with an angular resolution of 26.4" (~0.05pc). We have cataloged 619 dust cores in the 1.1mm map using the Clumpfind method. The ranges of the radius, mass, and density of these cores are estimated to be 0.01-0.20pc, 0.6-1.2x10^2^M_{sun}_ , and 0.3x10^4^-9.2x10^6^cm^-3^, respectively. We have identified 235 cores from the C^18^O data. The ranges of the radius, velocity width, LTE mass, and density are 0.13-0.34pc, 0.31-1.31km/s, 1.0-61.8M_{sun}_ , and (0.8-17.5)x10^3^cm^-3^, respectively. From the comparison of the spatial distributions between the dust and C^18^O cores, four types of spatial relations were revealed: (1) the peak positions of the dust and C^18^O cores agree with each other (32.4% of the C^18^O cores), (2) two or more C^18^O cores are distributed around the peak position of one dust core (10.8% of the C^18^O cores), (3) 56.8% of the C^18^O cores are not associated with any dust cores, and (4) 69.3% of the dust cores are not associated with any C^18^O cores.
- ID:
- ivo://CDS.VizieR/J/A+A/564/A68
- Title:
- Orion A GMC 13CO and C18O maps
- Short Name:
- J/A+A/564/A68
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We derive physical properties such as the optical depths and the column densities of ^13^CO and C^18^O to investigate the relationship between the far ultraviolet (FUV) radiation and the abundance ratios between ^13^CO and C^18^O.
- ID:
- ivo://CDS.VizieR/J/A+A/617/A77
- Title:
- Orion Bar Herschel/PACS CO maps
- Short Name:
- J/A+A/617/A77
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- With Herschel, we can for the first time observe a wealth of high-J CO lines in the interstellar medium with a high angular resolution. These lines are specifically useful for tracing the warm and dense gas and are therefore very appropriate for a study of strongly irradiated dense photodissocation regions (PDRs). We characterize the morphology of CO J=19-18 emission and study the high-J CO excitation in a highly UV-irradiated prototypical PDR, the Orion Bar. We used fully sampled maps of CO J=19-18 emission with the Photoconductor Array Camera and Spectrometer (PACS) on board the Herschel Space Observatory over an area of ~110"x110" with an angular resolution of 9". We studied the morphology of this high-J CO line in the Orion Bar and in the region in front and behind the Bar, and compared it with lower-J lines of CO from J=5-4 to J=13-12 and ^13^CO from J=5-4 to J=11-10 emission observed with the Herschel Spectral and Photometric Imaging Receiver (SPIRE). In addition, we compared the high-J CO to polycyclic aromatic hydrocarbon (PAH) emission and vibrationally excited H_2_. We used the CO and ^13^CO observations and the RADEX model to derive the physical conditions in the warm molecular gas layers.
- ID:
- ivo://CDS.VizieR/J/A+A/632/A8
- Title:
- Orion Bar photon-dominated region water lines
- Short Name:
- J/A+A/632/A8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The ortho-to-para ratio (OPR) of water in the interstellar medium (ISM) is often assumed to be related to the formation temperature of water molecules, making it a potentially interesting tracer of the thermal history of interstellar gas. A very low OPR of 0.1-0.5 was previously reported in the Orion Bar photon-dominated region (PDR), based on observations of two optically thin H_2_^18^O lines which were analyzed by using a single-slab large velocity gradient (LVG) model. The corresponding spin temperature does not coincide with the kinetic temperature of the molecular gas in this UV-illuminated region. This was interpreted as an indication of water molecules being formed on cold icy grains which were subsequently released by UV photodesorption. A more complete set of water observations in the Orion Bar, including seven H_2_^16^O lines and one H_2_^18^O line, carried out using Herschel/HIFI instrument, was reanalyzed using the Meudon PDR code to derive gas-phase water abundance and the OPR. The model takes into account the steep density and temperature gradients present in the region. The model line intensities are in good agreement with the observations assuming that water molecules formed with an OPR corresponding to thermal equilibrium conditions at the local kinetic temperature of the gas and when solely considering gas-phase chemistry and water gas-grain exchanges through adsorption and desorption. Gas-phase water is predicted to arise from a region deep into the cloud, corresponding to a visual extinction of A_V_~9, with a H_2_^16^O fractional abundance of ~2x10^-7^ and column density of (1.4+/-0.8)x10^15^cm^-2^ for a total cloud depth of A_V_=15. A line-of-sight average OPR of 2.8+/-0.2 is derived. The observational data are consistent with a nuclear spin isomer repartition corresponding to the thermal equilibrium at a temperature of 36+/-2K, much higher than the spin temperature previously reported for this region and close to the gas kinetic temperature in the water-emitting gas.
- ID:
- ivo://CDS.VizieR/J/A+A/538/A137
- Title:
- Orion B9 dense cores maps
- Short Name:
- J/A+A/538/A137
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We aim to further constrain the properties and evolutionary stages of dense cores in Orion B9. The central part of Orion B9 was mapped at 350 micron with APEX/SABOCA. A sample of nine cores in the region were observed in C^17^O(2-1), H^13^CO^+^(4-3) (towards 3 sources), DCO^+^(4-3), N_2_H^+^(3-2), and N_2_D^+^(3-2) with APEX/SHFI. These data are used in conjunction with our previous APEX/LABOCA 870-micron dust continuum data. Many of the LABOCA cores show evidence of substructure in the higher-resolution SABOCA image.
- ID:
- ivo://CDS.VizieR/J/A+A/645/A27
- Title:
- Orion B in 18 molecular tracers maps
- Short Name:
- J/A+A/645/A27
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Molecular hydrogen being unobservable in cold molecular clouds, the column density measurements of molecular gas currently rely either on dust emission observation in the far-IR or on star counting. (Sub-)millimeter observations of numerous trace molecules are effective from ground based telescopes, but the relationships between the emission of one molecular line and the H_2_ column density (NH_2_) is non-linear and sensitive to excitation conditions, optical depths, abundance variations due to the underlying physico-chemistry. We aim to use multi-molecule line emission to infer NH_2_ from radio observations. We propose a data-driven approach to determine NH_2_ from radio molecular line observations. We use supervised machine learning methods (Random Forests) on wide-field hyperspectral IRAM-30m observations of the Orion B molecular cloud to train a predictor of NH_2_, using a limited set of molecular lines as input, and the Herschel-based dust-derived NH_2_ as ground truth output. For conditions similar to the Orion B molecular cloud, we obtain predictions of NH_2_ within a typical factor of 1.2 from the Herschel-based estimates. An analysis of the contributions of the different lines to the predictions show that the most important lines are ^13^CO(1-0), ^12^CO(1-0), C^18^O(1-0), and HCO+(1-0). A detailed analysis distinguishing between diffuse, translucent, filamentary, and dense core conditions show that the importance of these four lines depends on the regime, and that it is recommended to add the N_2_H+(1-0) and CH_3_OH(2_0_-1_0_) lines for the prediction of NH_2_ in dense core conditions. This article opens a promising avenue to directly infer important physical parameters from the molecular line emission in the millimeter domain. The next step will be to try to infer several parameters simultaneously (e.g., NH_2_ and far-UV illumination field) to further test the method.
- ID:
- ivo://CDS.VizieR/J/A+A/604/A32
- Title:
- Orion BN-KL ALMA view
- Short Name:
- J/A+A/604/A32
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We wish to improve our understanding of the Orion central star formation region (Orion-KL) and disentangle its complexity. We collected data with ALMA during cycle 2 in 16GHz of total bandwidth spread between 215.1 and 252.0GHz with a typical sensitivity of 5mJy/beam (2.3mJy/beam from 233.4 to 234.4GHz) and a typical beam size of 1.7"x1.0" (average position angle of 89). We produced a continuum map and studied the emission lines in nine remarkable infrared spots in the region including the Hot Core and the Compact Ridge, plus the recently discovered Ethylene Glycol Peak. We present the data, and report the detection of several species not previously seen in Orion, including n- and i-propyl cyanide (C_3_H_7_CN), and the tentative detection of a number of other species including glycolaldehyde (CH_2_(OH)CHO). The first detections of gGg' ethylene glycol (gGg' (CH_2_OH)_2_) and of acetic acid (CH_3_COOH) in Orion are presented in a companion paper. We also report the possible detection of several vibrationally excited states of cyanoacetylene (HC_3_N), and of its ^13^C isotopologues. We were not able to detect the ^16^O^18^O line predicted by our detection of O_2_ with Herschel, due to blending with a nearby line of vibrationally excited ethyl cyanide. We do not confirm the tentative detection of hexatriynyl (C_6_H) and cyanohexatriyne (HC_7_N) reported previously, or of hydrogen peroxide (H_2_O_2_) emission. We report a complex velocity structure only partially revealed before. Components as extreme as -7 and +19km/s are detected inside the hot region. Thanks to different opacities of various velocity components, in some cases we can position these components along the line of sight. We propose that the systematically redshifted and blueshifted wings of several species observed in the northern part of the region are linked to the explosion that occurred ~500 years ago. The compact ridge, noticeably farther south displays extremely narrow lines (~1km/s) revealing a quiescent region that has not been acted by this explosion. This probably indicates that the compact ridge is either over 10,000 au in front of or behind the rest of the region. Many lines remain unidentified, and only a detailed modeling of all known species, including vibrational states of isotopologues combined with the detailed spatial analysis offered by ALMA enriched with zero-spacing data, will allow new species to be detected.
- ID:
- ivo://CDS.VizieR/J/A+A/610/A77
- Title:
- Orion Integral Filament ALMA+IRAM30m N2H+(1-0) data
- Short Name:
- J/A+A/610/A77
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have investigated the gas organization within the paradigmatic Integral Shape Filament (ISF) in Orion in order to decipher whether or not all filaments are bundles of fibers. We combined two new ALMA Cycle 3 mosaics with previous IRAM 30m observations to produce a high-dynamic range N2H+ (1-0) emission map of the ISF tracing its high-density material and velocity structure down to scales of 0.009pc (or ~2000AU). 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 in the cloud, these fibers are characterized by transonic internal motions, lengths of ~0.15pc, and masses per unit length close to those expected in hydrostatic equilibrium. The ISF fibers are spatially organized forming a dense bundle with multiple hub-like associations likely shaped by the local gravitational potential. Within this complex network, the ISF fibers show a compact radial emission profile with a median FWHM of 0.035pc systematically narrower than the previously proposed universal 0.1pc filament width. Our ALMA observations reveal complex bundles of fibers in the ISF, suggesting strong similarities between the internal substructure of this massive filament and previously studied lower-mass objects. The fibers show identical dynamic properties in both low- and high-mass regions, and their widespread detection in nearby clouds suggests a preferred organizational mechanism of gas in which the physical fiber dimensions (width and length) are self-regulated depending on their intrinsic gas density. Combining these results with previous works in Musca, Taurus, and Perseus, we identify a systematic increase of the surface density of fibers as a function of the total mass per-unit-length in filamentary clouds. Based on this empirical correlation, we propose a unified star-formation scenario where the observed differences between low- and high-mass clouds, and the origin of clusters, emerge naturally from the initial concentration of fibers.
- ID:
- ivo://CDS.VizieR/J/ApJS/160/511
- Title:
- Orion Nebula Cluster proplyd candidates
- Short Name:
- J/ApJS/160/511
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the X-ray and near-infrared emission properties of a sample of pre-main-sequence (PMS) stellar systems in the Orion Nebula Cluster (ONC) that display evidence for circumstellar disks ("proplyds") and optical jets in Hubble Space Telescope (HST) imaging. Our study uses X-ray data acquired during Chandra Orion Ultradeep Program (COUP) observations, as well as complementary optical and near-infrared data recently acquired with HST and the Very Large Telescope (VLT), respectively.
