- ID:
- ivo://CDS.VizieR/J/ApJ/728/104
- Title:
- Optical polarization for 878 Hipparcos stars
- Short Name:
- J/ApJ/728/104
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Sun is located inside an extremely low density and quite irregular volume of the interstellar medium, known as the Local Cavity (LC). It has been widely believed that some kind of interaction could be occurring between the LC and Loop I, a nearby superbubble seen in the direction of the Galactic center. As a result of such interaction, a wall of neutral and dense material, surrounded by a ring-shaped feature, would be formed at the interaction zone. Evidence of this structure was previously observed by analyzing the soft X-ray emission in the direction of Loop I. Our goal is to investigate the distance of the proposed annular region and map the geometry of the Galactic magnetic field in these directions. On that account, we have conducted an optical polarization survey of 878 stars from the Hipparcos catalog. Our results suggest that the structure is highly twisted and fragmented, showing very discrepant distances along the annular region: ~100pc on the left side and 250pc on the right side, independently confirming the indication from a previous photometric analysis. In addition, the polarization vectors' orientation pattern along the ring also shows a widely different behavior toward both sides of the studied feature, running parallel to the ring contour on the left side and showing no relation to its direction on the right side. Altogether, these evidences suggest a highly irregular nature, casting some doubt on the existence of a unique large-scale ring-like structure.
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- ID:
- ivo://CDS.VizieR/J/A+AS/101/551
- Title:
- Optical polarization of 1000 stars
- Short Name:
- J/A+AS/101/551
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have prepared a catalogue of optical polarization measurements for 1000 stars closer than 50 parsecs from the Sun. The distances, which are presently those given in the Sky Catalogue 2000.0, 2nd Edition (Hirshfeld et al., 1991skca.book.....H) are provisional: they will be replaced later by the much safer parallaxes which will result from the Hipparcos mission. The polarization data have been compiled, for 60% in various catalogues with due care to their accuracy; for 40% they are new, unpublished, measurements obtained at Pic du Midi Observatory. We expect that this new data base will allow a better understanding of the interstellar medium around the Sun.
- ID:
- ivo://CDS.VizieR/J/MNRAS/452/715
- Title:
- Optical polarization of the Polaris Flare
- Short Name:
- J/MNRAS/452/715
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The stages before the formation of stars in molecular clouds are poorly understood. Insights can be gained by studying the properties of quiescent clouds, such as their magnetic field structure. The plane-of-the-sky orientation of the field can be traced by polarized starlight. We present the first extended, wide-field (~10deg^2^) map of the Polaris Flare cloud in dust-absorption induced optical polarization of background stars, using the Robotic Polarimeter (RoboPol) polarimeter at the Skinakas Observatory. This is the first application of the wide-field imaging capabilities of RoboPol. The data were taken in the R band and analysed with the automated reduction pipeline of the instrument. We present in detail optimizations in the reduction pipeline specific to wide-field observations. Our analysis resulted in reliable measurements of 641 stars with median fractional linear polarization 1.3%. The projected magnetic field shows a large-scale ordered pattern. At high longitudes it appears to align with faint striations seen in the Herschel-Spectral and Photometric Imaging Receiver (SPIRE) map of dust emission (250um), while in the central 4.5 deg2 it shows an eddy-like feature. The overall polarization pattern we obtain is in good agreement with large-scale measurements by Planck of the dust emission polarization in the same area of the sky.
- ID:
- ivo://CDS.VizieR/J/ApJS/151/313
- Title:
- Optical spectra in star-forming regions
- Short Name:
- J/ApJS/151/313
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present high-resolution optical spectra (at ~0.6-1.8km/s) of interstellar CN, CH, CH+, CaI, KI, and CaII absorption toward 29 lines of sight in three star-forming regions, {rho} Oph, Cep OB2, and Cep OB3. The observations and data reduction are described. The agreement between earlier measurements of the total equivalent widths and our results is quite good. However, our higher resolution spectra reveal complex structure and closely blended components in most lines of sight. The velocity component structure of each species is obtained by analyzing the spectra of the six species for a given sight line together. The tabulated column densities and Doppler parameters of individual components are determined by using the method of profile fitting. Total column densities along lines of sight are computed by summing results from profile fitting for individual components and are compared with column densities from the apparent optical depth method. A more detailed analysis of these data and their implications will be presented in a companion paper.
- 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.
- 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.