- ID:
- ivo://CDS.VizieR/J/A+A/512/A63
- Title:
- Abundances of M33 HII regions
- Short Name:
- J/A+A/512/A63
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze the spatial distribution of metals in M33 using a new sample and literature data of HII regions, constraining a model of galactic chemical evolution with HII region and planetary nebula (PN) abundances. We consider chemical abundances of a new sample of HII regions complemented with previous literature data-sets. Supported by a uniform sample of nebular spectroscopic observations, we conclude that: i) the metallicity distribution in M33 is very complex, showing a central depression in metallicity probably due to observational bias; ii) the metallicity gradient in the disk of M33 has a slope of -0.037+/-0.009dex/kpc in the whole radial range up to ~8kpc, and -0.044+/-0.009dex/kpc excluding the central kpc; iii) there is a small evolution of the slope with time from the epoch of PN progenitor formation to the present-time. Description: Emission line fluxes, observed and dereddened of 33 HII regions are presented. Physical and chemical properties, such as electron temperatures and density, ionic and total chemical abundances of He, O, N, Ne, Ar, S, are derived.
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- ID:
- ivo://CDS.VizieR/J/AJ/147/131
- Title:
- Abundances of nearby late-type galaxies. I. Data
- Short Name:
- J/AJ/147/131
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the oxygen and nitrogen abundance distributions across the optical disks of 130 nearby late-type galaxies using around 3740 published spectra of HII regions. We use these data in order to provide homogeneous abundance determinations for all objects in the sample, including HII regions in which not all of the usual diagnostic lines were measured. Examining the relation between N and O abundances in these galaxies we find that the abundances in their centers and at their isophotal R_25_ disk radii follow the same relation. The variation in N/H at a given O/H is around 0.3dex. We suggest that the observed spread in N/H may be partly caused by the time delay between N and O enrichment and the different star formation histories in galaxies of different morphological types and dimensions. We study the correlations between the abundance properties (central O and N abundances, radial O and N gradients) of a galaxy and its morphological type and dimension.
- ID:
- ivo://CDS.VizieR/J/A+A/552/A12
- Title:
- Abundances of PNe in NGC 300
- Short Name:
- J/A+A/552/A12
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained deep spectroscopy of 26 planetary nebulae (PNe) and 9 compact HII regions in the nearby spiral galaxy NGC 300, and analyzed them together with the giant HII regions observed by Bresolin et al. (2009ApJ...700..309B). We have determined the physical properties of all those objects and their content in He, N, O, Ne, S and Ar in a consistent way. We find that compact HII regions have abundances similar to those of giant HII regions, while PNe have systematically larger N/O ratios and similar Ne/O and Ar/O ratios. We demonstrate that this nitrogen enhancement in PNe cannot be due to second dredge-up in the progenitor stars, since their initial masses are around 2-2.5M_{sun}_. An extra mixing process is required, perhaps be driven by rotation. Concerning the radial abundance distribution, PNe behave differently from HII regions: In the central parts, they show an average O/H smaller by 0.15dex. Their abundance dispersion at any galactocentric radius is significantly larger than for HII regions and many of them have O/H values higher than HII regions at the same galactocentric distance, suggesting that oxygen production in the PN progenitors in NGC 300 is common. PN abundance gradients in O/H, Ne/H and Ar/He are significantly shallower than those of HII regions. We argue that this indicates a steepening of the metallicity gradient in NGC 300 during the last Gr, rather than the effect of radial stellar motions.
- ID:
- ivo://CDS.VizieR/J/AJ/140/968
- Title:
- A cluster of compact radio sources in W40
- Short Name:
- J/AJ/140/968
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present deep 3.6 cm radio continuum observations of the HII region W40 obtained using the Very Large Array (VLA) in its A and B configurations. We detect a total of 20 compact radio sources in a region of 4'x4', with 11 of them concentrated in a band with 30" of extent. We also present JHK photometry of the W40 cluster taken with the QUIRC instrument on the University of Hawaii 2.2m telescope. These data reveal that 15 of the 20 VLA sources have infrared counterparts, and 10 show radio variability with periods less than 20 days. Based on these combined radio and IR data, we propose that eight of the radio sources are candidate ultracompact HII regions, seven are likely to be young stellar objects, and two may be shocked interstellar gas.
- ID:
- ivo://CDS.VizieR/J/A+A/459/L13
- Title:
- A composite HII region luminosity function
- Short Name:
- J/A+A/459/L13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Statistical properties of HII region populations in disk galaxies yield important clues to the physics of massive star formation. We present a set of HII region catalogues and luminosity functions for a sample of 56 spiral galaxies in order to derive the most general form of their luminosity function. HII region luminosity functions were derived for individual galaxies which, after photometric calibration, were summed to form a total luminosity function comprising 17797 HII regions from 53 galaxies.
- ID:
- ivo://CDS.VizieR/J/A+AS/115/81
- Title:
- A CS(2-1) survey of UC HII regions
- Short Name:
- J/A+AS/115/81
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have made a complete survey of the CS(2-1) emission toward IRAS point sources in the galactic plane. The sources observed were selected according to their far infrared (FIR) colors, which are characteristic of UC HII regions. They have 25{mu}m/12{mu}m flux ratios larger than 3.7 and 60{mu}m/12{mu}m flux ratios larger than 19.3. The survey covered a region from b=-2deg to b=2deg from l=300deg to l=0deg and from l=0deg to l=60deg, and from b=-4deg to b=4deg elsewhere. We detected 843 sources out of 1427 sources observed. The distributions of detected and undetected sources in a FIR color-color diagram show some differences, suggesting that more than one type of object is present in our observed sample.
- ID:
- ivo://CDS.VizieR/J/A+A/551/A43
- Title:
- AFGL 2591 multi-wavelength maps
- Short Name:
- J/A+A/551/A43
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- While it is currently unclear from a theoretical standpoint which forces and processes dominate the formation of high-mass stars, and hence determine the mode in which they form, much of the recent observational evidence suggests that massive stars are born in a similar manner to their low-mass counterparts. This paper aims to investigate the hypothesis that the embedded luminous star AFGL 2591-VLA 3 (2.3E+5L_{sun}_ at 3.33kpc) is forming according to a scaled-up version of a low-mass star formation scenario. We present multi-configuration Very Large Array 3.6cm and 7mm, as well as Combined Array for Research in Millimeter Astronomy C^18^O and 3mm continuum observations to investigate the morphology and kinematics of the ionized gas, dust, and molecular gas around AFGL 2591. We also compare our results to ancillary Gemini North near-IR images, and model the near-IR to sub-mm Spectral Energy distribution (SED) and Two Micron All Sky Survey (2MASS) image profiles of AFGL 2591 using a Monte-Carlo dust continuum radiative transfer code. The observed 3.6 cm images uncover for the first time that the central powering source AFGL 2591-VLA 3 has a compact core plus collimated jet morphology, extending 4000AU eastward from the central source with an opening angle of <10{deg} at this radius. However, at 7mm VLA 3 does not show a jet morphology, but instead compact (< 500AU) emission, some of which (<0.57mJy of 2.9mJy) is estimated to be from dust emission. The spectral index of AFGL 2591-VLA 3 between 3.6cm and 7mm was found to be between 0.4 and 0.5, similar to that of an ionized wind. If the 3.6cm emission is modelled as an ionized jet, the jet has almost enough momentum to drive the larger-scale flow. However, assuming a shock efficiency of 10%, the momentum rate of the jet is not sufficient to ionize itself via only shocks, and thus a significant portion of the emission is instead likely created in a photoionized wind. The C18O emission uncovers dense entrained material in the outflow(s) from these young stars. The main features of the SED and 2MASS images of AFGL 2591-VLA 3 are also reproduced by our model dust geometry of a rotationally flattened envelope with and without a disk. The above results are consistent with a picture of massive star formation similar to that seen for low-mass protostars. However, within its envelope, AFGL 2591-VLA 3 contains at least four other young stars, constituting a small cluster. Therefore it appears that AFGL 2591-VLA 3 may be able to source its accreting material from a shared gas reservoir while still exhibiting the phenomena expected during the formation of low-mass stars.
- ID:
- ivo://CDS.VizieR/J/ApJS/234/33
- Title:
- A GBT survey of large Galactic HII regions
- Short Name:
- J/ApJS/234/33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As part of our ongoing HII Region Discovery Survey (HRDS), we report the Green Bank Telescope detection of 148 new angularly large Galactic HII regions in radio recombination line (RRL) emission. Our targets are located at a declination of {delta}>-45{deg}, which corresponds to 266{deg}>l>-20{deg} at b=0{deg}. All sources were selected from the Wide-field Infrared Survey Explorer Catalog of Galactic HII Regions, and have infrared angular diameters >=260". The Galactic distribution of these "large" HII regions is similar to that of the previously known sample of Galactic HII regions. The large HII region RRL line width and peak line intensity distributions are skewed toward lower values, compared with that of previous HRDS surveys. We discover seven sources with extremely narrow RRLs <10km/s. If half the line width is due to turbulence, these seven sources have thermal plasma temperatures <1100K. These temperatures are lower than any measured for Galactic HII regions, and the narrow-line components may arise instead from partially ionized zones in the HII region photodissociation regions. We discover G039.515+00.511, one of the most luminous HII regions in the Galaxy. We also detect the RRL emission from three HII regions with diameters >100pc, making them some of the physically largest known HII regions in the Galaxy. This survey completes the HRDS HII region census in the Northern sky, where we have discovered 887 HII regions and more than doubled the size of the previously known census of Galactic HII regions.
- ID:
- ivo://CDS.VizieR/J/ApJS/248/3
- Title:
- A 4-6GHz RRL survey in the Milky Way
- Short Name:
- J/ApJS/248/3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We performed a radio recombination line (RRL) survey to construct a high-mass star-forming region (HMSFR) sample in the Milky Way based on the all-sky Wide-Field Infrared Survey Explorer point-source catalog. The survey was observed with the Shanghai 65m Tianma radio telescope covering 10 hydrogen RRL transitions ranging from H98{alpha} to H113{alpha} (corresponding to the rest frequencies of 4.5-6.9GHz) simultaneously. Out of 3348 selected targets, we identified an HMSFR sample consisting of 517 sources traced by RRLs; a large fraction of this sample (486) is located near the Galactic Plane (|b|<2{deg}). In addition to the hydrogen RRLs, we also detected helium and carbon RRLs toward 49 and 23 sources, respectively. We crossmatch the RRL detections with the 6.7 methanol maser sources built up in previous works for the same target sample. As a result, 103 HMSFR sources were found to harbor both emissions. In this paper, we present the HMSFR catalog accompanied by the measured RRL line properties and a correlation with our methanol maser sample, which is believed to trace massive stars at earlier stages. The construction of an HMSFR sample consisting of sources in various evolutionary stages indicated by different tracers is fundamental for future studies of high-mass star formation in such regions.
- ID:
- ivo://CDS.VizieR/J/ApJS/91/347
- Title:
- A 5-GHz VLA Survey of the Galactic Plane
- Short Name:
- J/ApJS/91/347
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used the VLA to survey the inner Galaxy (|b|<0.4{deg}, l=350-40{deg}) at 5GHz to a limiting sensitivity of between 2.5 and 10mJy. The survey has resulted in a catalog of 1272 discrete sources (including 100 sources outside the formal survey area) of which we have tentatively identified ~450 as ultracompact H II regions and ~45 as planetary nebulae. Approximately 30% of the radio sources are detected in the IRAS Point Source Catalog. The results confirm a scale height of only 30pc for ultracompact H II regions. We show that source lists generated from the IRAS Point Source Catalog alone suffer serious effects; the combination of the IRAS and radio surveys allows us to produce a much more complete census of the regions of massive star formation in our Galaxy.
