- ID:
- ivo://CDS.VizieR/J/ApJS/63/821
- Title:
- Inner Galaxy Molecular clouds and cloud cores
- Short Name:
- J/ApJS/63/821
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A compilation of CO emission regions and their measured parameters is presented which represents a nearly complete accounting of the molecular clouds in the first quadrant of the Galaxy. Emission regions associated with radio H II regions have systematically brighter CO peaks that are a factor of two to three times larger and have twice the mean velocity dispersion as the general cloud population. Both the H II region clouds and the hot core regions have a Galactic distribution characteristic of a spiral arm population, whereas the colder clouds are much less confined in Galactic azimuthal angle. Virial masses are obtained for the large sample of clouds with assigned kinematic distances. The mean H2 density for a GMC of diameter 40 pc is 180cm^-3^. For these clouds, a linear relationship is found between the H2 column density and the integrated CO emission. The variation in the Z-dispersion of clouds as a function of cloud mass suggests that more massive GMCs have smaller random velocities.
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- ID:
- ivo://CDS.VizieR/J/A+A/609/A102
- Title:
- Inner/outer HII regions: galaxy sample
- Short Name:
- J/A+A/609/A102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using integral field spectroscopy (IFS) observations we aim to perform a systematic study and comparison of two inner and outer HII regions samples. The spatial resolution of the IFS, the number of objects and the homogeneity and coherence of the observations allow a complete characterization of the main observational properties and differences of the regions. We analyzed a sample of 725 inner HII regions and a sample of 671 outer HII regions, all of them detected and extracted from the observations of a sample of 263 nearby, isolated, spiral galaxies observed by the CALIFA survey. We find that inner HII regions show smaller equivalent widths, greater extinction and luminosities, along with greater values of [NII] {lambda}6583/H{alpha} and [OII] {lambda}3727/[OIII] {lambda}5007 emission-line ratios, indicating higher metallicities and lower ionization parameters. Inner regions have also redder colors and higher photometric and ionizing masses, although Mion/Mphot is slightly higher for the outer regions. This work shows important observational differences between inner and outer HII regions in star forming galaxies not previously studied in detail. These differences indicate that inner regions have more evolved stellar populations and are in a later evolution state with respect to outer regions, which goes in line with the inside-out galaxy formation paradigm.
- ID:
- ivo://CDS.VizieR/J/A+A/616/A111
- Title:
- Integral-shaped filament NH_3_ observations
- Short Name:
- J/A+A/616/A111
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recent observations suggest a scenario in which filamentary structures in the interstellar medium represent the first step towards clumps/cores and eventually star formation. The densest filaments would then fragment into prestellar cores owing to gravitational instability. We seek to understand the roles filamentary structures play in high-mass star formation. We mapped the integral-shaped filament (ISF) located at the northern end of the Orion A molecular cloud in NH_3_ (1, 1) and (2, 2). The observations were made using the 25m radio telescope operated by the Xinjiang Astronomical Observatory, Chinese Academy of Sciences. The whole filamentary structure, about 1.2{deg}x0.6{deg}, is uniformly and fully sampled. We investigate the morphology, fragmentation, kinematics, and temperature properties in this region. We find that the morphology revealed by the map of velocity-integrated intensity of the NH_3_ (1, 1) line is closely associated with the dust ridge revealed by the Herschel Space Observatory. We identify 6 "lumps" related to the well known OMC-1 to 5 and 11 "sub-clumps" within the map. The clumps and sub-clumps are separated not randomly but in roughly equal intervals along the ISF. The average spacing of clumps is 11.30'+/-1.31' (1.36+/-0.16pc) and the average spacing of sub-clumps is 7.18'+/-1.19' (0.86+/-0.14pc). These spacings agree well with the predicted values of the thermal (0.86 pc) and turbulent sausage instability (1.43pc) by adopting a cylindric geometry of the ISF with an inclination of 60{deg} with respect to the line of sight. We also find a velocity gradient of about 0.6km/s/pc that runs along the ISF which likely arises from an overall rotation of the Orion A molecular cloud. The inferred ratio between rotational and gravitational energy is well below unity. Furthermore, fluctuations are seen in the centroid velocity diagram along the ISF. The OMC-1 to 5 clouds are located close to the local extrema of the fluctuations, which suggests that there exist gas flows associated with these clumps in the ISF. The derived NH_3_ (1, 1) and (2, 2) rotation temperatures in the OMC-1 are about 30-40K while lower temperatures (below 20K) are obtained in the northern and southern parts of the ISF. In OMC-2, OMC-3, and the northern part of OMC-4, we find higher and lower temperatures at the boundaries and in the interior, respectively.
- ID:
- ivo://CDS.VizieR/J/ApJ/729/82
- Title:
- Integrated column densities vs shock age
- Short Name:
- J/ApJ/729/82
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- I present computations of the integrated column densities produced in the post-shock cooling layers and in the radiative precursors of partially cooled fast shocks as a function of the shock age. The results are applicable to the shock-heated warm/hot intergalactic medium which is expected to be a major baryonic reservoir and contain a large fraction of the so-called missing baryons. My computations indicate that readily observable amounts of intermediate and high ions, such as CIV, NV, and OVI, are created in the precursors of young shocks, for which the shocked gas remains hot and difficult to observe. I suggest that such precursors may provide a way to identify and estimate the "missing" baryonic mass associated with the shocks. The absorption-line signatures predicted here may be used to construct ion-ratio diagrams, which will serve as diagnostics for the photoionized gas in the precursors. In my numerical models, the time evolution of the shock structure, self-radiation, and associated metal-ion column densities are computed by a series of quasi-static models, each appropriate for a different shock age. The shock code used in this work calculates the non-equilibrium ionization and cooling, follows the radiative transfer of the shock self-radiation through the post-shock cooling layers, takes into account the resulting photoionization and heating rates, follows the dynamics of the cooling gas, and self-consistently computes the photoionization states in the precursor gas. I present a complete set of the age-dependent post-shock and precursor columns for all ionization states of the elements H, He, C, N, O, Ne, Mg, Si, S, and Fe as functions of the shock velocity, gas metallicity, and magnetic field.
- ID:
- ivo://CDS.VizieR/J/A+A/572/A63
- Title:
- Intensity maps in the star-forming complex W33
- Short Name:
- J/A+A/572/A63
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The object W33 is a giant molecular cloud that contains star forming regions at various evolutionary stages from quiescent clumps to developed HII regions. Since its star forming regions are located at the same distance and the primary material of the birth clouds is probably similar, we conducted a comparative chemical study to trace the chemical footprint of the different phases of evolution. We observed six clumps in W33 with the Atacama Pathfinder Experiment (APEX) telescope at 280GHz and the Submillimeter Array (SMA) at 230GHz. We detected 27 transitions of 10 different molecules in the APEX data and 52 transitions of 16 different molecules in the SMA data. The chemistry on scales larger than ~0.2pc, which are traced by the APEX data, becomes more complex and diverse the more evolved the star forming region is. On smaller scales traced by the SMA data, the chemical complexity and diversity increase up to the hot core stage. In the HII region phase, the SMA spectra resemble the spectra of the protostellar phase. Either these more complex molecules are destroyed or their emission is not compact enough to be detected with the SMA. Synthetic spectra modelling of the H_2_CO transitions, as detected with the APEX telescope, shows that both a warm and a cold component are needed to obtain a good fit to the emission for all sources except for W33 Main1. The temperatures and column densities of the two components increase during the evolution of the star forming regions. The integrated intensity ratios N_2_H^+^(3-2)/CS(6-5) and N_2_H^+^(3-2)/H_2_CO(4_2,2_-3_2,1_) show clear trends as a function of evolutionary stage, luminosity, luminosity-to-mass ratio, and H_2_ peak column density of the clumps and might be usable as chemical clocks.
- ID:
- ivo://CDS.VizieR/J/A+A/541/A98
- Title:
- Interacting planetary nebulae
- Short Name:
- J/A+A/541/A98
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We discuss the classification and orientation of planetary nebulae that interact with the interstellar medium throughout the Milky Way. A sample of 117 confirmed interacting planetary nebulae is used for this purpose. Our results indicate that the majority of interacting objects are located close to the Galactic plane, and ~77% of them are located inside the Galactic thin disk.
- ID:
- ivo://CDS.VizieR/J/AJ/131/1501
- Title:
- Intermediate-velocity clouds in the CGPS
- Short Name:
- J/AJ/131/1501
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present observations of intermediate-velocity clouds (IVCs) found at positive velocities in the Canadian Galactic Plane Survey Phase I region (74{deg}<l<148{deg},-3.5{deg}<b<+5.6{deg}). A catalog of 138 distinct IVCs and 13 IVC complexes has been compiled.
- ID:
- ivo://CDS.VizieR/J/A+A/414/949
- Title:
- Interstellar bands and H2, CH, CO column densities
- Short Name:
- J/A+A/414/949
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Mutual relations between column densities of H_2_, CH and CO molecules as well as between the latter and strengths of the major 5780 and 5797 diffuse bands are presented and discussed.
- ID:
- ivo://CDS.VizieR/J/ApJS/147/61
- Title:
- Interstellar Ca I absorption
- Short Name:
- J/ApJS/147/61
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present high-resolution (FWHM~0.3-1.5km/s) spectra, obtained with the AAT UHRF, the McDonald Observatory 2.7m coude spectrograph, and/or the KPNO coude feed, of interstellar Ca I absorption toward 30 Galactic stars. Comparisons of the column densities of Ca I, Ca II, K I, and other species - for individual components identified in the line profiles and also when integrated over entire lines of sight - yield information on relative electron densities and depletions (dependent on assumptions regarding the ionization equilibrium).
- ID:
- ivo://CDS.VizieR/J/ApJ/634/451
- Title:
- Interstellar Ca II line equivalent widths
- Short Name:
- J/ApJ/634/451
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We show that the equivalent widths of the well-known interstellar CaII H and K lines can be used to determine the distances to OB stars in our Galaxy. The equivalent widths, measured in the spectra of 147 early-type stars, are strongly related to the Hipparcos parallaxes of those objects. The lines fitted to the parallax-equivalent width data are given by the formulae {pi}=1/[2.78EW(K)+95] and {pi}=1/[4.58EW(H)+102], where {pi} is in arcseconds and EW is in milliangstroms.
