- ID:
- ivo://CDS.VizieR/J/A+A/532/A127
- Title:
- Inner Galaxy HII regions
- Short Name:
- J/A+A/532/A127
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report simultaneous H110{alpha} and H_2_CO line observations with the 25m radio telescope of Nanshan station toward 251 HII regions. We used the H110{alpha} line to establish the velocity of the HII regions and H_2_CO absorption lines to distinguish between near and far distances. We detected the H110{alpha} RRLs in 28 sources and H_2_CO absorption lines in 59 sources. In the latter case, 43 features had not previously been observed. H_2_CO and H110{alpha} lines were simultaneously detected toward 23 HII regions. We resolved the kinematic distance ambiguities for 14 HII regions and 20 intervening molecular clouds.
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- ID:
- ivo://CDS.VizieR/J/ApJS/154/553
- Title:
- Inner galaxy massive star formation regions
- Short Name:
- J/ApJS/154/553
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report simultaneous H110{alpha} and H_2_CO line observations with the NRAO Green Bank Telescope toward 72HII regions in the Spitzer Space Telescope GLIMPSE survey area (|l|=10{deg}-65{deg} and |b|<=1{deg}). We used the H110{alpha} line to establish the velocity of the HII regions and H_2_CO absorption lines to distinguish between near and far distances. Accurate distances are crucial for the determination of physical properties of massive star formation regions.
- 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.
- 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/AJ/140/462
- Title:
- Intermediate-mass star-forming regions
- Short Name:
- J/AJ/140/462
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In an effort to understand the factors that govern the transition from low- to high-mass star formation, for the first time we identify a sample of intermediate-mass star-forming regions (IM SFRs) where stars up to (but not exceeding) ~8M_{sun}_ are being produced. We use IRAS colors and Spitzer Space Telescope mid-IR images, in conjunction with millimeter continuum and ^13^CO maps, to compile a sample of 50 IM SFRs in the inner Galaxy. These are likely to be precursors to Herbig AeBe stars and their associated clusters of low-mass stars.
- ID:
- ivo://CDS.VizieR/J/BaltA/17/125
- Title:
- Interstellar reddening in 3 HII regions
- Short Name:
- J/BaltA/17/125
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The slope of the interstellar reddening line in the J-H vs. H-Ks diagram of the 2MASS survey in the direction of the North America and Pelican nebulae, the L 935 dust cloud and the Cyg OB2 association is determined. The MK types were either classified by C.J. Corbally or collected from the literature. The ratio E(J-H)/E(H-Ks)=2.0 is obtained by taking the average for the four groups of spectral classes: O3-B1, B2-B6, B7-B9.5 and red clump giants. The obtained ratio is among the largest values of E(J-H)/E(H-Ks) determined till now.
- ID:
- ivo://CDS.VizieR/J/ApJS/241/2
- Title:
- Ionization profiles of 8 Galactic H II regions
- Short Name:
- J/ApJS/241/2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using Green Bank Telescope radio recombination line (RRL) data, we analyze the role of leaking radiation from HII regions in maintaining the ionization of the interstellar medium (ISM). We observed a sample of eight Galactic HII regions of various sizes, morphologies, and luminosities. For each region, the hydrogen RRL intensity decreases roughly as a power-law with the distance from the center of the region. This suggests that radiation leaking from the HII region is responsible for the majority of surrounding ionized gas producing RRL emission. Our results further indicate that the hydrogen RRL intensity appears to be fundamentally related to the HII region sizes traced by their photodissociation regions, such that physically smaller HII regions show a steeper decrease in intensity with an increasing distance from the region centers. As a result, giant HII regions may have a much larger effect in maintaining the ionization of the ISM. For six of the eight observed HII regions, we find a decrease in the ^4^He^+^/H^+^ abundance ratio with an increasing distance, indicating that He-ionizing photons are being absorbed within the ionization front of the HII region. There is enhanced carbon RRL emission toward directions with strong continuum background, suggesting that the carbon emission is amplified by stimulated emission.
- ID:
- ivo://CDS.VizieR/J/A+AS/92/625
- Title:
- Ionized nebulae in M31
- Short Name:
- J/A+AS/92/625
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Deep CCD imagery in H{alpha} and [SII] is presented of the major spiral arms of M31 with particular attention given to the data reduction and the analysis of the [SII]/H{alpha} flux ratios. A diffuse ionized gas noted in the images is analyzed which shows higher [SII]/H{alpha} ratios, and 967 discrete nebulae are listed with gray-scale images, finding charts, and absolute fluxes. The differential H-alpha luminosity function is found to have a slope of -0.95 for brighter objects and flattens out below a critical level. The curve is shown to correspond to the point at which single-star ionization accounts for the H{alpha} luminosities and is consistent with previous observations. The catalog of objects and fluxes is the largest existing sample of this type, and the unresolved objects in the sample are considered to be planetary nebulae.
- ID:
- ivo://CDS.VizieR/J/ApJ/510/104
- Title:
- Ionizing Stars of Extragalactic H II Regions
- Short Name:
- J/ApJ/510/104
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Medium-resolution spectra from 3650 to 10000 {AA} are presented for 96 giant H II regions distributed in 20 spiral galaxies. In order to interpret the data, we have calculated two separate grids of photoionization models, adopting single-star atmospheres (Kurucz) and star clusters synthesized with different initial mass functions (IMFs) as ionizing sources. Additional models were computed with more recent non-LTE stellar atmospheres, in order to check the effects of different stellar ionizing fluxes. We use the radiation softness parameter {eta}'=([O II]/[O III])/([S II]/[S III]) of Vilchez & Pagel (1988MNRAS.231..257V) to test for a metallicity dependence of the effective temperatures of the ionizing stars. Our results are consistent with a significant decrease in mean stellar temperatures of the ionizing stars with increasing metallicity. The magnitude of the effect, combined with the behavior of the He I {lambda}5876/H{beta} ratio, suggest a smaller upper mass limit for star formation at abundances higher than solar, even when considering the effects of metallicity on stellar evolution and atmospheric line blanketing. However, the exact magnitudes of the stellar temperature and IMF variations are dependent on the choice of stellar atmosphere and evolution models used, as well as on uncertainties in the nebular abundance scale at high metallicities. Our results also constrain the systematic behavior of the ionization parameter and the N/O ratio in extragalactic H II regions. The observed spectral sequences are inconsistent with current stellar evolution models, which predict a luminous, hot W-R stellar population in evolved H II regions older than 2-3 Myr. This suggests either that the hardness of the emitted Lyman continuum spectrum has been overestimated in the models or that some mechanism disrupts the H II regions before the W-R phases become important.
- ID:
- ivo://CDS.VizieR/J/MNRAS/407/1170
- Title:
- IRAC photometry of M8
- Short Name:
- J/MNRAS/407/1170
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present photometry and images (3.6, 4.5, 5.8 and 8.0um) from the Spitzer Infrared Array Camera (IRAC) of the star-forming region Messier 8 (M8). The IRAC photometry reveals ongoing star formation in the M8 complex, with 64 class 0/I and 168 class II sources identified in several locations in the vicinity of submm gas cores/clumps.
