- ID:
- ivo://CDS.VizieR/J/MNRAS/453/645
- Title:
- Massive molecular outflows distance-limited sample
- Short Name:
- J/MNRAS/453/645
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have observed 99 mid-infrared-bright, massive young stellar objects and compact HII regions drawn from the Red MSX source survey in the J=3-2 transition of ^12^CO and ^13^CO, using the James Clerk Maxwell Telescope. 89 targets are within 6kpc of the Sun, covering a representative range of luminosities and core masses. These constitute a relatively unbiased sample of bipolar molecular outflows associated with massive star formation. Of these, 59, 17 and 13 sources (66, 19 and 15 percent) are found to have outflows, show some evidence of outflow, and have no evidence of outflow, respectively. The time-dependent parameters of the high-velocity molecular flows are calculated using a spatially variable dynamic time-scale. The canonical correlations between the outflow parameters and source luminosity are recovered and shown to scale with those of low-mass sources. For coeval star formation, we find the scaling is consistent with all the protostars in an embedded cluster providing the outflow force, with massive stars up to ~30M_{sun}_ generating outflows. Taken at face value, the results support the model of a scaled-up version of the accretion-related outflow-generation mechanism associated with discs and jets in low-mass objects with time-averaged accretion rates of ~ 10^-3^M_{sun}_/yr on to the cores. However, we also suggest an alternative model, in which the molecular outflow dynamics are dominated by the entrained mass and are unrelated to the details of the acceleration mechanism. We find no evidence that outflows contribute significantly to the turbulent kinetic energy of the surrounding dense cores.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/834/122
- Title:
- Massive star formation in the LMC. I. N159 & N160
- Short Name:
- J/ApJ/834/122
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present images and spectral energy distributions (SEDs) of massive young stellar objects (YSOs) in three star-forming H II regions of the Large Magellanic Cloud: N159A, N159 Papillon, and N160. We use photometry from SOFIA/FORCAST at 25.3-37.1{mu}m to constrain model fits to the SEDs and determine luminosities, ages, and dust content of the embedded YSOs and their local environments. By placing these sources on mid-infrared color-magnitude and color-color diagrams, we analyze their dust properties and consider their evolutionary status. Since each object in the FORCAST images has an obvious bright near-infrared counterpart in Spitzer Space Telescope images, we do not find any evidence for new, very cool, previously undiscovered Class 0 YSOs. Additionally, based on its mid-infrared colors and model parameters, N159A is younger than N160 and the Papillon. The nature of the first extragalactic protostars in N159, P1, and P2, is also discussed.
- ID:
- ivo://CDS.VizieR/J/ApJ/719/1104
- Title:
- Massive star forming complexes in GLIMPSE
- Short Name:
- J/ApJ/719/1104
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We examine the 13 most luminous sources in the WMAP free-free map using the Spitzer GLIMPSE and Midcourse Space Experiment surveys to identify massive star formation complexes, emitting one-third of the Galactic free-free luminosity. We identify star-forming complexes (SFCs) by a combination of bubble morphology in 8um emission and radio recombination line radial velocities. We find 40 SFCs associated with our WMAP sources and determine unique distances up to 31. We interpret the bubbles as evidence for radial expansion. The radial velocity distribution for each source allows us to measure the intrinsic speed of a complex's expansion. This speed is consistent with the size and age of the bubbles. The high free-free luminosities, combined with negligible synchrotron emission, demonstrate that the bubbles are not driven by supernovae. The kinetic energy of the largest bubbles is a substantial fraction of that measured in the older superbubbles found by Heiles. We find that the energy injected into the interstellar medium by our bubbles is similar to that required to maintain turbulent motion in the gas disk inside 8kpc. We report a number of new SFCs powered by massive (M_*_>10^4^M_{sun}_) star clusters. We measure the scale height of the Galactic O stars to be h_*_=35+/-5pc. We determine an empirical relationship between the 8um and free-free emission of the form F_8um_{propto}F^2^_ff_. Finally, we find that the bubble geometry is more consistent with a spherical shell rather than a flattened disk.
- ID:
- ivo://CDS.VizieR/J/ApJ/864/136
- Title:
- Massive star-forming regions multiwavelength study
- Short Name:
- J/ApJ/864/136
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a multiwavelength study of 28 Galactic massive star-forming HII regions. For 17 of these regions, we present new distance measurements based on Gaia DR2 parallaxes. By fitting a multicomponent dust, blackbody, and power-law continuum model to the 3.6{mu}m through 10mm spectral energy distributions, we find that ~34% of Lyman continuum photons emitted by massive stars are absorbed by dust before contributing to the ionization of HII regions, while ~68% of the stellar bolometric luminosity is absorbed and reprocessed by dust in the HII regions and surrounding photodissociation regions. The most luminous, infrared-bright regions that fully sample the upper stellar initial mass function (ionizing photon rates N_C_>=10^50^s^-1^ and dust-processed L_TIR_>=10^6.8^L_{sun}_) have on average higher percentages of absorbed Lyman continuum photons (~51%) and reprocessed starlight (~82%) compared to less luminous regions. Luminous HII regions show lower average polycyclic aromatic hydrocarbon (PAH) fractions than less luminous regions, implying that the strong radiation fields from early-type massive stars are efficient at destroying PAH molecules. On average, the monochromatic luminosities at 8, 24, and 70{mu}m combined carry 94% of the dust-reprocessed L_TIR_. L70 captures ~52% of L_TIR_, and is therefore the preferred choice to infer the bolometric luminosity of dusty star-forming regions. We calibrate star formation rates (SFRs) based on L24 and L70 against the Lyman continuum photon rates of the massive stars in each region. Standard extragalactic calibrations of monochromatic SFRs based on population synthesis models are generally consistent with our values.
- ID:
- ivo://CDS.VizieR/J/A+A/550/A21
- Title:
- Massive star-forming regions radio lines
- Short Name:
- J/A+A/550/A21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Australia Telescope Compact Array (ATCA) observations of the H_2_O maser line and radio continuum at 18.0GHz and 22.8GHz toward a sample of 192 massive star-forming regions containing several clumps already imaged at 1.2mm. The main aim of this study is to investigate the water maser and centimeter continuum emission (that likely traces thermal free-free emission) in sources at different evolutionary stages, using evolutionary classifications previously published. We used the recently comissioned Compact Array Broadband Backend (CABB) at ATCA that obtains images with 20arcsec resolution in the 1.3cm continuum and H_2_O maser emission in all targets. For the evolutionary analysis of the sources we used millimeter continuum emission from the literature and the infrared emission from the MSX Point Source Catalog. We detect centimeter continuum emission in 88% of the observed fields with a typical rms noise level of 0.45mJy/beam. Most of the fields show a single radio continuum source, while in 20% of them we identify multiple components. A total of 214 centimeter continuum sources have been identified, that likely trace optically thin HII regions, with physical parameters typical of both extended and compact HII regions. Water maser emission was detected in 41% of the regions, resulting in a total of 85 distinct components. The low angular (20arcsec) and spectral (14km/s) resolutions do not allow a proper analysis of the water maser emission, but suffice to investigate its association with the continuum sources. We have also studied the detection rate of HII regions in the two types of IRAS sources defined in the literature on the basis of the IRAS colors: High and Low. No significant differences are found, with high detection rates (>90%) for both High and Low sources. We classify the millimeter and infrared sources in our fields in three evolutionary stages following the scheme presented previously: (Type 1) millimeter-only sources, (Type 2) millimeter plus infrared sources, (Type 3) infrared-only sources. We find that HII regions are mainly associated with Type 2 and Type 3 objects, confirming that these are more evolved than Type 1 sources. The HII regions associated with Type 3 sources are slightly less dense and larger in size than those associated with Type 2 sources, as expected if the HII region expands as it evolves, and Type 3 objects are older than Type 2 objects. The maser emission is mostly found to be associated with Type 1 and Type 2 sources, with a higher detection rate toward Type 2, consistent with the results of the literature. Finally, our results on HII region and H_2_O maser association with different evolutionary types confirm the evolutionary classification proposed previously.
- ID:
- ivo://CDS.VizieR/J/MNRAS/473/4130
- Title:
- M31 center emission-line point-like sources
- Short Name:
- J/MNRAS/473/4130
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a detailed description of the wavelength, astrometric and photometric calibration plan for SITELLE, the imaging Fourier transform spectrometer attached to the Canada-France-Hawaii telescope, based on observations of a red (647-685nm) data cube of the central region (11'x11') of the Andromeda galaxy. The first application, presented in this paper, is a radial-velocity catalogue (with uncertainties of ~2-6km/s) of nearly 800 emission-line point-like sources, including ~450 new discoveries. Most of the sources are likely planetary nebulae, although we also detect five novae (having erupted in the first 8 months of 2016) and one new supernova remnant candidate.
287. M16 CO maps
- ID:
- ivo://CDS.VizieR/J/A+A/627/A27
- Title:
- M16 CO maps
- Short Name:
- J/A+A/627/A27
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We aim to investigate the impact of the ionized radiation from the M16 HII region on the surrounding molecular cloud and on its hosted star formation. To present comprehensive multi-wavelength observations towards the M16 HII region, we used new CO data and existing infrared, optical, and submillimeter data. The ^12^CO J=1-0, ^13^CO J=1-0, and C^18^O J=1-0 data were obtained with the Purple Mountain Observatory (PMO) 13.7m radio telescope. To trace massive clumps and extract young stellar objects (YSOs) associated with the M16 HII region, we used the ATLASGAL and GLIMPSE I catalogs, respectively. From CO data, we discern a large-scale filament with three velocity components. Because these three components overlap with each other in both velocity and space, the filament may be made of three layers. The M16 ionized gas interacts with the largescale filament and has reshaped its structure. In the large-scale filament, we find 51 compact cores from the ATLASGAL catalog, 20 of them being quiescent. The mean excitation temperature of these cores is 22.5K, while this is 22.2K for the quiescent cores. This high temperature observed for the quiescent cores suggests that the cores may be heated by M16 and do not experience internal heating from sources in the cores. Through the relationship between the mass and radius of these cores, we obtain that 45% of all the cores are massive enough to potentially form massive stars. Compared with the thermal motion, the turbulence created by the nonthermal motion is responsible for the core formation. For the pillars observed towards M16, the H II region may give rise to the strong turbulence.
- ID:
- ivo://CDS.VizieR/J/AJ/150/71
- Title:
- Metal abundances of KISS galaxies. V.
- Short Name:
- J/AJ/150/71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present high signal-to-noise ratio spectroscopy of 15 emission-line galaxies cataloged in the KPNO International Spectroscopic Survey, selected for their possession of high equivalent width [OIII] lines. The primary goal of this study was to attempt to derive direct-method (T_e_) abundances for use in constraining the upper-metallicity branch of the R_23_ relation. The spectra cover the full optical region from [OII]{lambda}{lambda}3726,3729 to [SIII]{lambda}{lambda}9069,9531 and include the measurement of [OIII]{lambda}4363 in 13 objects. From these spectra, we determine abundance ratios of helium, nitrogen, oxygen, neon, sulfur, and argon. We find these galaxies to predominantly possess oxygen abundances in the range of 8.0<~12+log(O/H)<~8.3. We present a comparison of direct-method abundances with empirical strong-emission-line techniques, revealing several discrepancies. We also present a comparison of direct-method oxygen abundance calculations using electron temperatures determined from emission lines of O^++^ and S^++^, finding a small systematic shift to lower T_e_(~1184K) and higher metallicity (~0.14dex) for sulfur-derived T_e_ compared to oxygen-derived T_e_. Finally, we explore in some detail the different spectral activity types of targets in our sample, including regular star-forming galaxies, those with suspected AGN contamination, and a local pair of low-metallicity, high-luminosity compact objects.
- ID:
- ivo://CDS.VizieR/J/ApJ/758/133
- Title:
- Metallicity profile of M31 HII regions and PNe
- Short Name:
- J/ApJ/758/133
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The oxygen abundance gradients among nebular emission line regions in spiral galaxies have been used as important constraints for models of chemical evolution. We present the largest-ever full-wavelength optical spectroscopic sample of emission line nebulae in a spiral galaxy (M31). We have collected spectra of 253 HII regions and 407 planetary nebulae (PNe) with the Hectospec multi-fiber spectrograph of the MMT. We measure the line-of-sight extinction for 199 HII regions and 333 PNe; we derive oxygen abundance directly, based on the electron temperature, for 51 PNe; and we use strong-line methods to estimate oxygen abundance for 192 HII regions and nitrogen abundance for 52 HII regions. The relatively shallow oxygen abundance gradient of the more extended HII regions in our sample is generally in agreement with the result of Zaritsky et al. (1994ApJ...420...87Z), based on only 19 M31 HII regions, but varies with the strong-line diagnostic employed. Our large sample size demonstrates that there is significant intrinsic scatter around this abundance gradient, as much as ~3 times the systematic uncertainty in the strong-line diagnostics. The intrinsic scatter is similar in the nitrogen abundances, although the gradient is significantly steeper. On small scales (deprojected distance <0.5kpc), HII regions exhibit local variations in oxygen abundance that are larger than 0.3dex in 33% of neighboring pairs. We do not identify a significant oxygen abundance gradient among PNe, but we do find a significant gradient in the [NII] ratio that varies systematically with surface brightness. Our results underscore the complex and inhomogeneous nature of the interstellar medium of M31, and our data set illustrates systematic effects relevant to future studies of the metallicity gradients in nearby spiral galaxies.
- ID:
- ivo://CDS.VizieR/J/MNRAS/291/261
- Title:
- Methanol maser of IRAS-selected sources
- Short Name:
- J/MNRAS/291/261
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A survey of ultracompact (UC) HII regions has been carried out by searching for 6.669-GHz methanol maser emission from a sample of 535 IRAS-selected candidates. A total of 201 candidates exhibit methanol emission. These sources have been used, in conjunction with previously identified UC HII regions, to provide a base for further studies of such regions. Estimates of distances have indicated that the identified UC HII regions tend to have some Galactic structure but it is not clear whether they lie in or between the spiral arms of the Galaxy. The regions are tightly constrained to the plane of the Galaxy. Comparison of identified regions and IRAS sources selected by Wood & Churchwell indicates that there there is some degree of contamination, which could be due to an older phase in the life on an UC HII region where methanol maser emission is not apparent. Luminosities and spectral types have been derived for many of the regions. The maximum number of maser spots observed seems to increase with increasing peak maser luminosity, which indicates that the maser emission is more dependent on the abundance of methanol than the availability of far-infrared radiation.
