- 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.
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- 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.
- ID:
- ivo://CDS.VizieR/J/A+AS/135/437
- Title:
- AGNs with composite spectra. II.
- Short Name:
- J/A+AS/135/437
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have compiled from the literature 88 emission-line galaxies for which the published line-ratios give indication of a "transition spectrum"; selected objects are located north of {delta}~-20{deg}, are brighter than B=17 and have z<0.1. We have observed 53 of these galaxies with the spectrograph CARELEC, attached to the OHP 1.93m telescope. The observations were carried out during several runs in May, June and July 1996 and January, March, October and November 1997. The journal of observations is given in Table 5. The spectra (R~1800) were analysed in terms of Gaussians to search for the presence of multiple line-components, coming from kinematically and spatially distinct regions - "composite spectra". The results of the fitting analysis are given in Table 6.
- ID:
- ivo://CDS.VizieR/J/ApJ/784/53
- Title:
- AKARI NIR spectral atlas of Galactic HII regions
- Short Name:
- J/ApJ/784/53
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using a large collection of near-infrared spectra (2.5-5.4 {mu}m) of Galactic HII regions and HII region-like objects, we perform a systematic investigation of astronomical polycyclic aromatic hydrocarbon (PAH) features. Thirty-six objects were observed using the infrared camera on board the AKARI satellite as a part of a director's time program. In addition to the well known 3.3-3.6 {mu}m features, most spectra show a relatively weak emission feature at 5.22 {mu}m with sufficient signal-to-noise ratios, which we identify as the PAH 5.25 {mu}m band (previously reported).
- ID:
- ivo://CDS.VizieR/J/A+A/626/A36
- Title:
- ALMA continuum fits files of G9.62+0.19
- Short Name:
- J/A+A/626/A36
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We used Band 7 ALMA observations in full polarisation mode to analyse the polarised dust emission of the massive star forming region G9.62+0.19. We estimated the magnetic field strength via the Davis-Chandrasekhar-Fermi and structure function methods. We resolve several protostellar cores embedded in a bright and dusty filamentary structure. The magnetic field is orientated along the filament and appears perpendicular to the direction of the outflows. The polarisation vectors present ordered patterns and the cores showing polarised emission are less fragmented. We suggest an evolutionary sequence of the magnetic field, and the less evolved hot core exhibits a stronger magnetic field than the more evolved hot core. An average magnetic field strength of the order of 11mG was derived, from which we obtain a low turbulent-to-magnetic energy ratio, indicating that turbulence does not significantly contribute to the stability of the clump. We report a detection of linear polarisation from thermal line emission, probably from methanol or carbon dioxide, and we tentatively compared linear polarisation vectors from our observations with previous linearly polarised OH masers observations.
- ID:
- ivo://CDS.VizieR/J/A+A/603/A10
- Title:
- ALMA view of G351.77-0.54
- Short Name:
- J/A+A/603/A10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The fragmentation of high-mass gas clumps and the formation of the accompanying accretion disks lie at the heart of high-mass star formation research. We resolve the small-scale structure around the high-mass hot core G351.77-0.54 to investigate its disk and fragmentation properties. Using the Atacama Large Millimeter Array at 690GHz with baselines exceeding 1.5km, we study the dense gas, dust, and outflow emission at an unprecedented spatial resolution of 0.06" (130AU at 2.2kpc). Within the inner few 1000AU, G351.77 is fragmenting into at least four cores (brightness temperatures between 58 and 201K). The central structure around the main submm source #1 with a diameter of ~0.5" does not show additional fragmentation. While the CO(6-5) line wing emission shows an outflow lobe in the northwestern direction emanating from source #1, the dense gas tracer CH_3_CN shows a velocity gradient perpendicular to the outflow that is indicative of rotational motions. Absorption profile measurements against the submm source #2 indicate infall rates on the order of 10^-4^ to 10^-3^M_{sun}_/yr, which can be considered as an upper limit of the mean accretion rates. The position-velocity diagrams are consistent with a central rotating disk-like structure embedded in an infalling envelope, but they may also be influenced by the outflow. Using the CH_3_CN(37k-36k) k-ladder with excitation temperatures up to 1300K, we derive a gas temperature map for source #1 exhibiting temperatures often in excess of 1000K. Brightness temperatures of the submm continuum barely exceed 200K. This discrepancy between gas temperatures and submm dust brightness temperatures (in the optically thick limit) indicates that the dust may trace the disk mid-plane, whereas the gas could trace a hotter gaseous disk surface layer. We conduct a pixel-by-pixel Toomre gravitational stability analysis of the central rotating structure. The derived high Q values throughout the structure confirm that this central region appears stable against gravitational instability. Resolving for the first time a high-mass hot core at 0.06 resolution at submm wavelengths in the dense gas and dust emission allowed us to trace the fragmenting core and the gravitationally stable inner rotating disk-like structure. A temperature analysis reveals hot gas and comparably colder dust that may be attributed to different disk locations traced by dust emission and gas lines. The kinematics of the central structure #1 reveal contributions from a rotating disk, an infalling envelope, and potentially an outflow as well, whereas the spectral profile toward source #2 can be attributed to infall.
- ID:
- ivo://CDS.VizieR/J/ApJ/857/19
- Title:
- ALMA view of GMCs in NGC 300
- Short Name:
- J/ApJ/857/19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have conducted a ^12^CO(2-1) survey of several molecular gas complexes in the vicinity of HII regions within the spiral galaxy NGC300 using the Atacama Large Millimeter Array (ALMA). Our observations attain a resolution of 10pc and 1km/s, sufficient to fully resolve giant molecular clouds (GMCs) and the highest obtained to date beyond the Local Group. We use the CPROPS algorithm to identify and characterize 250 GMCs across the observed regions. GMCs in NGC300 appear qualitatively and quantitatively similar to those in the Milky Way disk: they show an identical scaling relationship between size R and linewidth {Delta}V ({Delta}V{propto}R^0.48+/-0.05^), appear to be mostly in virial equilibrium, and are consistent with having a constant surface density of about 60M_{sun}_/pc^2^. The GMC mass spectrum is similar to those in the inner disks of spiral galaxies (including the Milky Way). Our results suggest that global galactic properties such as total stellar mass, morphology, and average metallicity may not play a major role in setting GMC properties, at least within the disks of galaxies on the star-forming main sequence. Instead, GMC properties may be more strongly influenced by local environmental factors such as the midplane disk pressure. In particular, in the inner disk of NGC 300, we find this pressure to be similar to that in the local Milky Way but markedly lower than that in the disk of M51, where GMCs are characterized by systematically higher surface densities and a higher coefficient for the size-linewidth relation.
- ID:
- ivo://CDS.VizieR/J/ApJS/248/18
- Title:
- 44 and 95GHz observations of class I methanol masers
- Short Name:
- J/ApJS/248/18
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report a simultaneous 44 and 95GHz class I methanol maser survey toward 144 sources from the 95GHz class I methanol maser catalog. The observations were made with the three telescopes of the Korean very long baseline interferometry network operating in single-dish mode. The detection rates are 89% at 44GHz and 77% at 95GHz. There are 106 new discoveries at 44GHz. Comparing the previous 95GHz detections with new observations of the same transitions made using the Purple Mountain Observatory 13.7m radio telescope shows no clear evidence of variability on a timescale of six years. Emission from the 44 and 95GHz transitions shows strong correlations in peak velocity, peak flux density, and integrated flux density, indicating that they are likely cospatial. We found that the peak flux density ratio S_pk,95_/S_pk,44_ decreases as the 44GHz peak flux density increases. We found that some class I methanol masers in our sample might be associated with infrared dark clouds, while others are associated with HII regions, indicating that some sources occur at an early stage of high-mass star formation, while others are located toward more evolved sources.
- ID:
- ivo://CDS.VizieR/J/AJ/142/139
- Title:
- A new catalog of HII regions in M31
- Short Name:
- J/AJ/142/139
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new catalog of HII regions in M31. The full disk of the galaxy (~24kpc from the galaxy center) is covered in a 2.2deg^2^ mosaic of 10 fields observed with the Mosaic Camera on the Mayall 4m telescope as part of the Local Group Galaxies survey.
- ID:
- ivo://CDS.VizieR/J/A+A/565/A103
- Title:
- Anomalous microwave emission in Galactic clouds
- Short Name:
- J/A+A/565/A103
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Anomalous microwave emission (AME) is believed to be due to electric dipole radiation from small spinning dust grains. The aim of this paper is a statistical study of the basic properties of AME regions and the environment in which they emit. We used WMAP and Planck maps, combined with ancillary radio and IR data, to construct a sample of 98 candidate AME sources, assembling SEDs for each source using aperture photometry on 1{deg}-smoothed maps from 0.408GHz up to 3000GHz. Each spectrum is fitted with a simple model of free-free, synchrotron (where necessary), cosmic microwave background (CMB), thermal dust, and spinning dust components. We find that 42 of the 98 sources have significant (>5{sigma}) excess emission at frequencies between 20 and 60GHz. An analysis of the potential contribution of optically thick free-free emission from ultra-compact HII regions, using IR colour criteria, reduces the significant AME sample to 27 regions. The spectrum of the AME is consistent with model spectra of spinning dust. Peak frequencies are in the range 20-35GHz except for the California nebula (NGC1499), which appears to have a high spinning dust peak frequency of (50+/-17)GHz. The AME regions tend to be more spatially extended than regions with little or no AME. The AME intensity is strongly correlated with the sub-millimetre/IR flux densities and comparable to previous AME detections in the literature. AME emissivity, defined as the ratio of AME to dust optical depth, varies by an order of magnitude for the AME regions. The AME regions tend to be associated with cooler dust in the range 14-20K and an average emissivity index, {beta}_d_, of +1.8, while the non-AME regions are typically warmer, at 20-27K. In agreement with previous studies, the AME emissivity appears to decrease with increasing column density. This supports the idea of AME originating from small grains that are known to be depleted in dense regions, probably due to coagulation onto larger grains. We also find a correlation between the AME emissivity (and to a lesser degree the spinning dust peak frequency) and the intensity of the interstellar radiation field, G_0_. Modelling of this trend suggests that both radiative and collisional excitation are important for the spinning dust emission. The most significant AME regions tend to have relatively less ionized gas (free-free emission), although this could be a selection effect. The infrared excess, a measure of the heating of dust associated with HII regions, is typically >4 for AME sources, indicating that the dust is not primarily heated by hot OB stars. The AME regions are associated with known dark nebulae and have higher 12{mu}m/25{mu}m ratios. The emerging picture is that the bulk of the AME is coming from the polycyclic aromatic hydrocarbons and small dust grains from the colder neutral interstellar medium phase.
