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- ID:
- ivo://CDS.VizieR/J/MNRAS/428/3443
- Title:
- PNe and HII regions plasma diagnostics
- Short Name:
- J/MNRAS/428/3443
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We carry out plasma diagnostic analyses for 123 planetary nebulae (PNe) and 42 HII regions using the NII and OII optical recombination lines (ORLs). New effective recombination coefficients for the NII and OII optical recombination spectra are used. These data were calculated under the intermediate coupling scheme for a number of electron temperature (Te) and density (Ne) cases. We use a new method to determine the Te's and Ne's for the nebular sample, combining the ORLs with the most reliable measurements for each ion and the predicted intensities that are based on the new atomic data. Uncertainties of the derived Te and Ne are estimated for each object. The diagnostic results from heavy element ORLs show reasonable agreement with previous calculations in the literature. We compare the electron temperatures derived from the NII and OII ORLs, Te(ORLs), and those from the collisionally excited lines (CELs), Te(CELs), as well as the hydrogen Balmer jump, Te(HIBJ), especially for the PNe with large abundance discrepancies. Temperatures from the HeI recombination lines, Te(HeI), are also used for comparison if available. For all the objects included in our sample, Te(ORLs) are lower than Te(HIBJ), which are in turn systematically lower than Te(CELs). PNe with Te(HeI) available show the relation Te(ORLs)<=Te(HeI)<=Te(HIBJ)<=Te(CELs), which is consistent with predictions from the bi-abundance nebular model postulated by Liu et al. (2000MNRAS.312..585L).
- ID:
- ivo://CDS.VizieR/J/AJ/154/268
- Title:
- Point & compact H{alpha} sources in the inner of M33
- Short Name:
- J/AJ/154/268
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A variety of interesting objects such as Wolf-Rayet stars, tight OB associations, planetary nebulae, X-ray binaries, etc., can be discovered as point or compact sources in H{alpha} surveys. How these objects distribute through a galaxy sheds light on the galaxy star formation rate and history, mass distribution, and dynamics. The nearby galaxy M33 is an excellent place to study the distribution of H{alpha}-bright point sources in a flocculant spiral galaxy. We have reprocessed an archived WIYN continuum-subtracted H{alpha} image of the inner 6.5'x6.5' of M33 and, employing both eye and machine searches, have tabulated sources with a flux greater than approximately 10^-15^ erg/cm^2^/s. We have effectively recovered previously mapped H II regions and have identified 152 unresolved point sources and 122 marginally resolved compact sources, of which 39 have not been previously identified in any archive. An additional 99 H{alpha} sources were found to have sufficient archival flux values to generate a Spectral Energy Distribution. Using the SED, flux values, H{alpha} flux value, and compactness, we classified 67 of these sources.
- ID:
- ivo://CDS.VizieR/J/ApJ/775/84
- Title:
- Polarization from stars behind IC63 nebula
- Short Name:
- J/ApJ/775/84
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the interstellar medium (ISM), molecular hydrogen is expected to form almost exclusively on the surfaces of dust grains. Due to that molecule's large formation energy (-4.5eV), several dynamical effects are likely associated with the process, including the alignment of asymmetric dust grains with the ambient magnetic field. Such aligned dust grains are, in turn, believed to cause the broadband optical/infrared polarization observed in the ISM. Here, we present the first observational evidence for grain alignment driven by H_2_ formation, by showing that the polarization of the light from stars behind the reflection nebula IC 63 appears to correlate with the intensity of H_2_ fluorescence. While our results strongly suggest a role for "Purcell rockets" in grain alignment, additional observations are needed to conclusively confirm their role. By showing a direct connection between H_2_ formation and a probe of the dust characteristics, these results also provide one of the first direct confirmations of the grain-surface formation of H_2_. We compare our observations to ab initio modeling based on Radiative Torque Alignment (RAT) theory.
- ID:
- ivo://CDS.VizieR/J/ApJ/897/90
- Title:
- Polarization measurements of S201 with JCMT
- Short Name:
- J/ApJ/897/90
- Date:
- 11 Mar 2022
- Publisher:
- CDS
- Description:
- We present the properties of magnetic fields (B fields) in two clumps (clump 1 and clump 2), located at the waist of the bipolar HII region Sh2-201, based on James Clerk Maxwell Telescope SCUBA-2/POL-2 observations of 850{mu}m polarized dust emission. We find that B fields in the direction of the clumps are bent and compressed, showing bow-like morphologies, which we attribute to the feedback effect of the HII region on the surface of the clumps. Using the modified Davis-Chandrasekhar-Fermi method, we estimate B-field strengths of 266 and 65{mu}G for clump 1 and clump 2, respectively. From virial analyses and critical mass ratio estimates, we argue that clump 1 is gravitationally bound and could be undergoing collapse, whereas clump 2 is unbound and stable. We hypothesize that the interplay of the thermal pressure imparted by the HII region, the B-field morphologies, and the various internal pressures of the clumps (such as magnetic, turbulent, and gas thermal pressures) has the following consequences: (a) formation of clumps at the waist of the HII region; (b) progressive compression and enhancement of the B fields in the clumps; (c) stronger B fields that will shield the clumps from erosion by the HII region and cause pressure equilibrium between the clumps and the HII region, thereby allowing expanding ionization fronts to blow away from the filament ridge, forming bipolar HII regions; and (d) stronger B fields and turbulence that will be able to stabilize the clumps. A study of a larger sample of bipolar HII regions would help to determine whether our hypotheses are widely applicable.
- ID:
- ivo://CDS.VizieR/J/ApJ/724/L113
- Title:
- Polarization of IRAS 18089-1732
- Short Name:
- J/ApJ/724/L113
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To characterize the magnetic field structure of the outflow and core region within a prototypical high-mass star-forming region, we analyzed polarized CO(3-2) -for the first time observed with the Submillimeter Array- as well as 880um submillimeter continuum emission from the high-mass outflow/disk system IRAS 18089-1732. Both emission features with polarization degrees at a few percent level indicate that the magnetic field structure is largely aligned with the outflow/jet orientation from small core scales to larger outflow scales. Although quantitative estimates are crude, the analysis indicates that turbulent energy dominates over magnetic energy. The data also suggest a magnetic field strength increase from the lower-density envelope to the higher-density core.
- ID:
- ivo://CDS.VizieR/J/MNRAS/403/2012
- Title:
- PopStar II. Giant HII regions models
- Short Name:
- J/MNRAS/403/2012
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is the second paper of a series reporting the results from the popstar evolutionary synthesis models. Here, we present synthetic emission-line spectra of HII regions photoionized by young star clusters, for seven values of cluster masses and for ages between 0.1 and 5.2Myr. The ionizing spectral energy distributions (SEDs) are those obtained by the popstar code for six different metallicities, with a very low-metallicity set, Z=0.0001 , not included in previous similar works. We assume that the radius of the HII region is the distance at which the ionized gas is deposited by the action of the mechanical energy of the winds and supernovae from the central ionizing young cluster.
- ID:
- ivo://CDS.VizieR/J/ApJS/209/32
- Title:
- Probable young stars in the MYStIX project
- Short Name:
- J/ApJS/209/32
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Massive Young star-forming complex Study in Infrared and X-rays (MYStIX) project requires samples of young stars that are likely members of 20 nearby Galactic massive star-forming regions. Membership is inferred from statistical classification of X-ray sources, from detection of a robust infrared excess that is best explained by circumstellar dust in a disk or infalling envelope and from published spectral types that are unlikely to be found among field stars. We present the MYStIX membership lists here, and describe in detail the statistical classification of X-ray sources via a "Naive Bayes Classifier."
- ID:
- ivo://CDS.VizieR/J/A+A/623/A105
- Title:
- Radio catalogue of Galactic HII regions
- Short Name:
- J/A+A/623/A105
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Large-scale radio continuum surveys provide data to get insights into the physical properties of radio sources. HII regions are prominent radio sources produced by thermal emission of ionised gas around young massive stars. We identify and analyse HII regions in the Sino-German {lambda}6cm polarisation survey of the Galactic plane. Objects with flat radio continuum spectra together with infrared and/or H{alpha} emission were identified to be HII regions. For HII regions with small apparent sizes, we cross-matched the {lambda}6cm small-diameter source catalogue with the radio HII region catalogue compiled by Paladini and the infrared HII region catalogue based on the WISE data. Effelsberg {lambda}21cm and {lambda}11cm continuum survey data were used to determine source spectra. High angular resolution data from the Canadian Galactic Plane Survey and the NVSS were used to solve the confusion when low angular resolution observations are not sufficient. Extended HII regions were identified by overlaying the Paladini and the WISE HII regions onto the {lambda}6cm survey images for coincidences by eye. The TT-plot method was employed for spectral index verification. 401 HII regions were identified and their flux densities were determined with the Sino-German {lambda}6cm survey data. In the surveyed area, 76 pairs of sources are found to be duplicated in the Paladini HII region catalogue mainly due to the non-distinction of previous observations with different angular resolutions, and 78 objects in their catalogue are misclassified as HII regions, being actually planetary nebulae, supernova remnants or extragalactic sources that have steep spectra. More than 30 HII regions and HII region candidates from our {lambda}6cm survey data, especially extended ones, do not have counterparts in the WISE HII region catalogue, among which 9 are identified for the first time. Our results imply that some more Galactic HII regions still await to be discovered and the combination of multi-domain observations is important for HII region identification. Based on the newly derived radio continuum spectra and the evidence of infrared emission, the previously identified SNRs G11.1-1.0, G20.4+0.1 and G16.4-0.5 are believed to be HII regions.
- ID:
- ivo://CDS.VizieR/J/AJ/129/348
- Title:
- Radio compact HII regions in the Milky Way
- Short Name:
- J/AJ/129/348
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use new VLA Galactic plane catalogs at 5 and 1.4 GHz covering the first Galactic quadrant (350{deg}<=l<=42{deg}, |b|<=0.4{deg}) in conjunction with the MSX6C Galactic plane catalog (Cat. <V/114>) to construct a large sample of ultracompact H II regions. A radio catalog of this region was first published by Becker et al. (Cat. <J/ApJS/91/347>, but we have added new observations and rereduced the data with significantly improved calibration and mosaicking procedures, resulting in a tripling of the number of 5GHz sources detected. Comparison of the new 5GHz catalog and the MSX6C Galactic plane catalog resulted in a sample of 687 matches, out of which we estimate only 15 to be chance coincidences.
