- ID:
- ivo://CDS.VizieR/J/A+A/552/A123
- Title:
- Far-IR study of G29.96-0.02
- Short Name:
- J/A+A/552/A123
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- G29.96-0.02 is a high-mass star-forming cloud observed at 70, 160, 250, 350, and 500{mu}m as part of the Herschel survey of the Galactic plane (Hi-GAL) during the science demonstration phase. We wish to conduct a far-infrared study of the sources associated with this star-forming region by estimating their physical properties and evolutionary stage, and investigating the clump mass function, the star formation efficiency and rate in the cloud. We have identified the Hi-GAL sources associated with the cloud, searched for possible counterparts at centimeter and infrared wavelengths, fitted their spectral energy distribution and estimated their physical parameters.
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- ID:
- ivo://CDS.VizieR/J/A+A/659/A77
- Title:
- FEEDBACK from the NGC7538 HII region
- Short Name:
- J/A+A/659/A77
- Date:
- 14 Mar 2022 07:43:25
- Publisher:
- CDS
- Description:
- The interaction of expanding HII regions with their environmental cloud is one of the central questions driving the SOFIA legacy program FEEDBACK. We want to understand the interaction of the prototypical NGC7538 HII region with the neighboring molecular cloud hosting several active star-forming regions. Using the Stratospheric Observatory for Infrared Astronomy (SOFIA), we mapped an area of ~210'^2^ (~125pc^2^) around NGC7538 in the velocity-resolved ionized carbon fine-structure line [CII] at 1.9THz (158um). Complementary observed atomic carbon [CI] at 492GHz and high-J CO(8-7) data, as well as the archival near- and far-infrared, cm continuum, CO(3-2), and HI data are folded into the analysis. The ionized carbon [CII] data reveal rich morphological and kinematic structures. While the overall morphology follows the general ionized gas that is also visible in the radio continuum emission, the channel maps show multiple bubble-like structures with sizes on the order of ~80-100'' (~1.0-1.28pc). While at least one of them may be an individual feedback bubble driven by the main exciting sources of the NGC7538 HII region (the O3 and O9 stars IRS6 and IRS5), the other bubble-like morphologies may also be due to the intrinsically porous structure of the HII region. An analysis of the expansion velocities around 10km/s indicates that thermal expansion is not sufficient but that wind-driving from the central O-stars is required. The region exhibits a general velocity gradient across, but we also identify several individual velocity components. The most blue-shifted [CII] component has barely any molecular or atomic counterparts. At the interface to the molecular cloud, we find a typical photon-dominated region (PDR) with a bar-shape. Ionized C+, atomic C0 and molecular carbon CO show a layered structure in this PDR. The carbon in the PDR is dominated by its ionized C+ form with atomic C0 and molecular CO masses of ~0.45+/-0.1M_{sun}_ and ~1.2+/-0.1M_{sun}_, respectively, compared to the ionized carbon C+ in the range of 3.6-9.7M_{sun}_. This bar-shaped PDR exhibits a velocity-gradient across, indicating motions along the line of sight toward the observer. Even if it is shown to be dominated by two nearby exciting sources (IRS6 and IRS5), the NGC7538 HII region exhibits a diverse set of substructures that interact with each other as well as with the adjacent cloud. Compared to other recent [CII] observations of HII regions (e.g., Orion Veil, RCW120, RCW49), the bubble-shape morphologies revealed in [CII] emission that are indicative of expanding shells are recurring structures of PDRs.
- ID:
- ivo://CDS.VizieR/J/ApJ/881/79
- Title:
- Flamingos-2 near-infrared photometry in NGC 2244
- Short Name:
- J/ApJ/881/79
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As part of the ongoing effort to characterize the low-mass (sub)stellar population in a sample of massive young clusters, we have targeted the ~2Myr old cluster NGC2244. The distance to NGC2244 from Gaia DR2 parallaxes is 1.59kpc, with errors of 1% (statistical) and 11% (systematic). We used the Flamingos-2 near-infrared camera at the Gemini-South telescope for deep multi- band imaging of the central portion of the cluster (~2.4pc^2^). We determined membership in a statistical manner, through a comparison of the cluster's color-magnitude diagram to that of a control field. Masses and extinctions of the candidate members are then calculated with the help of evolutionary models, leading to the first initial mass function (IMF) of the cluster extending into the substellar regime, with the 90% completeness limit around 0.02M{sun}. The IMF is well represented by a broken power law (dN/dM{prop}M-{alpha}) with a break at ~0.4M{sun}. The slope on the high- mass side (0.4-7M{sun}) is {alpha}=2.12{+/-}0.08, close to the standard Salpeter slope. In the low-mass range (0.02-0.4M{sun}), we find a slope {alpha}=1.03{+/-}0.02, which is at the high end of the typical values obtained in nearby star-forming regions ({alpha}=0.5-1.0), but still in agreement within the uncertainties. Our results reveal no clear evidence for variations in the formation efficiency of brown dwarfs (BDs) and very low-mass stars due to the presence of OB stars, or for a change in stellar densities. Our finding rules out photoevaporation and fragmentation of infalling filaments as substantial pathways for BD formation.
- ID:
- ivo://CDS.VizieR/J/ApJ/812/39
- Title:
- Fluxes of NGG7793 & NGC4945 with GMOS-S
- Short Name:
- J/ApJ/812/39
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Gas-phase abundances in HII regions of two spiral galaxies, NGC7793 and NGC4945, have been studied to determine their radial metallicity gradients. We used the strong-line method to derive oxygen abundances from spectra acquired with GMOS-S, the multi-object spectrograph on the 8m Gemini South telescope. We found that NGC7793 has a well-defined gas-phase radial oxygen gradient of -0.321+/-0.112dexR_25_^-1^ (or -0.054+/-0.019dex/kpc) in the galactocentric range 0.17<R_G_/R_25_<0.82, not dissimilar from gradients calculated with direct abundance methods in galaxies of similar mass and morphology. We also determined a shallow radial oxygen gradient in NGC 4945, -0.253+/-0.149dexR_25_^-1^ (or -0.019+/-0.011dex/kpc) for 0.04<R_G_/R_25_<0.51, where the larger relative uncertainty derives mostly from the larger inclination of this galaxy. NGC 7793 and NGC 4945 have been selected for this study because they are similar, in mass and morphology, to M33 and the Milky Way, respectively. Since at zeroth order we expect the radial metallicity gradients to depend on mass and galaxy type, we compared our galaxies in the framework of radial metallicity models best suited for M33 and the Galaxy. We found a good agreement between M33 and NGC7793, pointing toward similar evolution for the two galaxies. We notice instead differences between NGC 4945 and the radial metallicity gradient model that best fits the Milky Way. We found that these differences are likely related to the presence of an active galactic nucleus combined with a bar in the central regions of NGC 4945, and to its interacting environment.
- ID:
- ivo://CDS.VizieR/J/A+A/650/A142
- Title:
- G24.78+0.08 A1 ALMA images and datacubes
- Short Name:
- J/A+A/650/A142
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Hyper-compact (HC) or ultra-compact HII regions are the first manifestations of the radiation feedback from a newly born massive star. Therefore, their study is fundamental to understanding the process of massive (>=8M_{sun}_) star formation. We employed Atacama Large Millimeter/submillimeter Array (ALMA) 1.4mm Cycle 6 observations to investigate at high angular resolution (~0.050, corresponding to 330au) the HC HII region inside molecular core A1 of the high-mass star-forming cluster G24.78+0.08. We used the H30{alpha} emission and different molecular lines of CH_3_CN and ^13^CH_3_CN to study the kinematics of the ionized and molecular gas, respectively. At the center of the HC HII region, at radii <~500au, we observe two mutually perpendicular velocity gradients, which are directed along the axes at PA=39{deg} and PA=133{deg}, respectively. The velocity gradient directed along the axis at PA=39{deg} has an amplitude of 22km/s/mpc, which is much larger than the other;s, 3km/s/mpc. We interpret these velocity gradients as rotation around, and expansion along, the axis at PA=39{deg}. We propose a scenario where the H30{alpha} line traces the ionized heart of a disk-jet system that drives the formation of the massive star (~20M_{sun}_) responsible for the HC HII region. Such a scenario is also supported by the position-velocity plots of the CH_3_CN and ^13^CH_3_CN lines along the axis at PA=133{deg}, which are consistent with Keplerian rotation around a 20M_{sun}_ star. Toward the HC HII region in G24.78+0.08, the coexistence of mass infall (at radii of ~5000au), an outer molecular disk (from <~4000 au to >~500au), and an inner ionized disk (<~500au) indicates that the massive ionizing star is still actively accreting from its parental molecular core. To our knowledge, this is the first example of a molecular disk around a high-mass forming star that, while becoming internally ionized after the onset of the HII region, continues to accrete mass onto the ionizing star.
- ID:
- ivo://CDS.VizieR/J/MNRAS/487/2771
- Title:
- Gaia-DR2 distance to the W3 Complex
- Short Name:
- J/MNRAS/487/2771
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Perseus Arm is the closest Galactic spiral arm from the Sun, offering an excellent opportunity to study in detail its stellar population. However, its distance has been controversial with discrepancies by a factor of two. Kinematic distances are in the range 3.9-4.2kpc as compared to 1.9-2.3kpc from spectrophotometric and trigonometric parallaxes, reinforcing previous claims that this arm exhibits peculiar velocities. We used the astrometric information of a sample of 31 OB stars from the star-forming W3Complex to identify another 37 W3 members and to derive its distance from their Gaia-DR2 parallaxes with improved accuracy. The Gaia-DR2 distance to the W3Complex, 2.14^+0.08^_-0.07_kpc, coincides with the previous stellar distances of ~2kpc. The Gaia-DR2 parallaxes tentatively show differential distances for different parts of the W3 Complex: W3 Main, located to the NE direction, is at 2.30^+0.19^_-0.16_kpc, the W3 Cluster (IC1795), in the central region of the complex, is at 2.17^+0.12^_-0.11_kpc, and W3(OH) is at 2.00^+0.29^_-0.23_kpc to the SW direction. The W3 Cluster is the oldest region, indicating that it triggered the formation of the other two star-forming regions located at the edges of an expanding shell around the cluster.
- ID:
- ivo://CDS.VizieR/J/MNRAS/473/3671
- Title:
- Galactic bubble infrared fluxes
- Short Name:
- J/MNRAS/473/3671
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we present the first extended catalogue of far-infrared fluxes of Galactic bubbles. Fluxes were estimated for 1814 bubbles, defined here as the 'golden sample', and were selected from the Milky Way Project First Data Release (Simpson et al., 2012MNRAS.424.2442S, Cat. J/MNRAS/424/2442) The golden sample was comprised of bubbles identified within the Wide-field Infrared Survey Explorer (WISE) dataset (using 12- and 22-um images) and Herschel data (using 70-, 160-, 250-, 350- and 500-um wavelength images). Flux estimation was achieved initially via classical aperture photometry and then by an alternative image analysis algorithm that used active contours. The accuracy of the two methods was tested by comparing the estimated fluxes for a sample of bubbles, made up of 126 HII regions and 43 planetary nebulae, which were identified by Anderson et al. The results of this paper demonstrate that a good agreement between the two was found. This is by far the largest and most homogeneous catalogue of infrared fluxes measured for Galactic bubbles and it is a step towards the fully automated analysis of astronomical datasets.
- ID:
- ivo://CDS.VizieR/J/MNRAS/447/2307
- Title:
- Galactic HII region IRAS 16148-5011 content
- Short Name:
- J/MNRAS/447/2307
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- An investigation of the IRAS 16148-5011 region - a cluster at a distance of 3.6kpc - is presented here, carried out using multiwavelength data in near-infrared (NIR) from the 1.4m Infrared Survey Facility telescope, mid-infrared (MIR) from the archival Spitzer GLIMPSE (Galactic Legacy Infrared Midplane Survey Extraordinaire) survey, far-infrared (FIR) from the Herschel archive, and low-frequency radio continuum observations at 1280 and 843MHz from the Giant Metrewave Radio Telescope and Molonglo Survey archive, respectively. A combination of NIR and MIR data is used to identify 7 Class I and 133 Class II sources in the region. Spectral energy distribution (SED) analysis of selected sources reveals a 9.6M_{sun}_ high-mass source embedded in nebulosity. However, Lyman continuum luminosity calculation using radio emission - which shows a compact HII region - indicates the spectral type of the ionizing source to be earlier than B0-O9.5. Free-free emission SED modelling yields the electron density as 138cm^-3^, and thus the mass of the ionized hydrogen as ~16.4M_{sun}_. Thermal dust emission modelling, using the FIR data from Herschel and performing modified blackbody fits, helped us construct the temperature and column density maps of the region, which show peak values of 30K and 3.3x10^22^cm^-2^, respectively. The column density maps reveal an A_V_>20mag extinction associated with the nebular emission, and weak filamentary structures connecting dense clumps. The clump associated with this IRAS object is found to have dimensions of ~1.1pcx0.8pc, and a mass of 10^23^M_{sun}_.
109. Galactic HII regions
- ID:
- ivo://CDS.VizieR/J/A+A/397/213
- Title:
- Galactic HII regions
- Short Name:
- J/A+A/397/213
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Master Catalog collects the information from 24 previously published lists and catalogs for 1442 Galactic HII regions. For each object, the Master Catalog quotes the original fluxes and diameters as well as the available information on radio line velocities, line widths and line temperatures and the errors on these quantities. The Synthetic Catalog at 2.7GHz summarizes the basic information of flux density and angular diameter for each of these objects. The catalog can be used for detailed studies of Galactic HII regions and, by extrapolation, for investigations of HII regions up to millimetric wavelengths.
- ID:
- ivo://CDS.VizieR/J/AJ/150/147
- Title:
- Galactic HII regions. I. Stellar distances
- Short Name:
- J/AJ/150/147
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new catalog of spectrophotometric distances and line of sight systemic velocities to 103 HII regions between 90{deg}{<=}l<=195{deg} (longitude quadrants II and part of III). Two new velocities for each region are independently measured using 1 arcmin resolution 21cm HI and 2.6mm^12^CO line maps (from the Canadian Galactic Plane Survey and Five College Radio Astronomy Observatory Outer Galaxy Surveys) that show where gaseous shells are observed around the periphery of the ionized gas. Known and neighboring O- and B-type stars with published UBV photometry and MK classifications are overlaid onto 21cm continuum maps, and those stars observed within the boundary of the HII emission (and whose distance is not more than three times the standard deviation of the others) are used to calculate new mean stellar distances to each of the 103 nebulae. Using this approach of excluding distance outliers from the mean distance to a group of many stars in each HII region lessens the impact of anomalous reddening for certain individuals. The standard deviation of individual stellar distances in a cluster is typically 20% per stellar distance, and the error in the mean distance to the cluster is typically +/-10%. Final mean distances of nine common objects with very long baseline interferometry parallax distances show a 1:1 correspondence. Further, comparison with previous catalogs of HII regions in these quadrants shows a 50% reduction in scatter for the distance to Perseus spiral arm objects in the same region, and a reduction by ~1/2^0.5^ in scatter around a common angular velocity relative to the Sun {Omega}-{Omega}_0_(km/s/kpc). The purpose of the catalog is to provide a foundation for more detailed large-scale Galactic spiral structure and dynamics (rotation curve, density wave streaming) studies in the 2nd and 3rd quadrants, which from the Sun's location is the most favorably viewed section of the Galaxy.
