- 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.
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- 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/A+A/586/A37
- Title:
- M33 center and BCLMP302 [CII] spectroscopy
- Short Name:
- J/A+A/586/A37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The forbidden fine structure transition of [CII] at 158 micron is one of the major cooling lines of the interstellar medium (ISM). We aim to understand the contribution of the ionized, atomic and molecular phases of the ISM to the [CII] emission from clouds near the dynamical center and the BCLMP302 HII region in the north of the nearby galaxy M33 at a spatial resolution of 50pc. We combine high resolution [CII] spectra taken with the Herschel/HIFI spectrometer onboard the Herschel satellite with [CII] Herschel-PACS maps and ground-based observations of CO(2-1) with IRAM 30m and HI with VLA, all at the same spatial resolution. We decomposed the [CII] spectra in terms of contribution from molecular and atomic gas detected in CO(2-1) and HI, respectively. Typically, the [CII] lines have widths intermediate between the narrower CO(2-1) and broader HI line profiles. Comparison of spectra show that the relative contribution of molecular and atomic gas traced by CO(2-1) and HI varies substantially between positions and depends mostly on the local physical conditions and geometry. In both regions a larger fraction of the molecular gas is traced by [C II] than by the canonical tracer CO. These results emphasize the need for velocity-resolved observations to discern the contribution of different components of the ISM to [C II] emission.
- 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.
325. 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.
- ID:
- ivo://CDS.VizieR/J/other/IJAA/4.571
- Title:
- Methanol masers in HII regions
- Short Name:
- J/other/IJAA/4.5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As the recent publication by Breen et al. (2013MNRAS.435..524B) found, Class II methanol masers are exclusively associated with high mass star forming regions. Based on the positions of the Class I and II methanol and H_2_O masers, UC HII regions and 4.5um infrared sources, and the center velocities (vLSR) of the Class I methanol and H_2_O masers, compared to the vLSR of the Class II methanol masers, we propose three disk-outflow models that may be traced by methanol masers. In all three models, we have located the Class II methanol maser near the protostar, and the Class I methanol maser in the outflow, as is known from observations during the last twenty years. In our first model, the H_2_O masers trace the linear extent of the outflow. In our second model, the H_2_O masers are located in a circumstellar disk. In our third model, the H_2_O masers are located in one or more outflows near the terminating shock where the outflow impacts the ambient interstellar medium. Together, these models reiterate the utility of coordinated high angular resolution observations of high mass star forming regions in maser lines and associated star formation tracers.
- ID:
- ivo://CDS.VizieR/J/A+A/633/A155
- Title:
- M8, G333.6-0.2 and NGC6357 young stars
- Short Name:
- J/A+A/633/A155
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The identification and characterisation of populations of young massive stars in (giant) HII regions provides important constraints on i) the formation process of massive stars and their early feedback on the environment, and ii) the initial conditions for population synthesis models predicting the evolution of ensembles of stars. We identify and characterise the stellar populations of the following young giant HII regions: M8, G333.6-0.2, and NGC6357. We have acquired H- and K-band spectra of around 200 stars using The K-band Multi Object Spectrograph (KMOS) on the ESO Very Large Telescope. The targets for M8 and NGC6357 were selected from the Massive Young Star-Forming Complex Study in Infrared and X-ray (MYStIX), which combines X-ray observations with near-infrared and mid-infrared data. For G333.6-0.2, the sample selection is based on the near-infrared colours combined with X-ray data. We introduce an automatic spectral classification method in order to obtain temperatures and luminosities for the observed stars. We analysed the stellar populations using their photometric, astrometric, and spectroscopic properties and compared the position of the stars in the Hertzprung-Russell diagram with stellar evolution models to constrain their ages and mass ranges. We confirm the presence of candidate ionising sources in the three regions and report new ones, including the first spectroscopically identified O stars in G333.6-0.2. In M8 and NGC6357, two populations are identified: (i) OB main-sequence stars (M>5M_{sun}_) and (ii) pre-main sequence stars (M~=0.5-5M_{sun}_). The ages of the clusters are ~1-3Myr, <3Myr, and 0.5-3Myr for M8, G333.6-0.2, and NGC6357, respectively. We show that MYStIX selected targets have >90% probability of being members of the HII region, whereas a selection based on near infrared (NIR) colours leads to a membership probability of only 70%.
