- ID:
- ivo://CDS.VizieR/J/A+A/417/615
- Title:
- Maser and outflows in UC HII region
- Short Name:
- J/A+A/417/615
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results of a single-dish survey of molecular outflows towards a homogeneous sample of 136 ultracompact HII regions for which we had previously obtained observations in the methanol 6.7GHz and water 22.2GHz maser lines. The line profiles of the ^13^CO J=1-0 and 2-1 transitions have been compared to those of the corresponding lines of the C^18^O isotopomer to reveal the occurrence of line wings and hence of molecular outflows.
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- ID:
- ivo://CDS.VizieR/J/MNRAS/412/223
- Title:
- MASH PNe detected in large-scale radio surveys
- Short Name:
- J/MNRAS/412/223
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an updated and newly compiled radio-continuum data base for Macquarie/AAO/Strasbourg H{alpha} (MASH) planetary nebulae (PNe) detected in the extant large-scale 'blind' radio-continuum surveys [NRAO VLA Sky Survey (NVSS), Sydney University Molonglo Sky Survey/Molonglo Galactic Plane Surveys (SUMSS/MGPS-2) and Parkes-MIT-NRAO (PMN)] and, for a small number of MASH PNe, observed and detected in targeted radio-continuum observations. We found radio counterparts for approximately 250 MASH PNe. In comparison with the percentage of previously known Galactic PNe detected in the NVSS and MGPS-2 radio-continuum surveys and according to their position on the flux density angular diameter and the radio brightness temperature evolutionary diagrams we conclude, unsurprisingly, that the MASH sample presents the radio-faint end of the known Galactic PNe population. Also, we present radio-continuum spectral properties of a small sub-sample of MASH PNe located in the strip between declinations -30{deg} and -40{deg}, that are detected in both the NVSS and MGPS-2 radio surveys.
- ID:
- ivo://CDS.VizieR/J/ApJ/689/108
- Title:
- MASIV survey. II. First four epochs
- Short Name:
- J/ApJ/689/108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the variability of 443 flat-spectrum, compact radio sources monitored using the VLA for 3 days in four epochs at ~4 month intervals at 5GHz as part of the Micro-Arcsecond Scintillation-Induced Variability (MASIV) survey. Over half of these sources exhibited 2%-10% rms variations on timescales over 2 days. We analyzed the variations by two independent methods and find that the rms variability amplitudes of the sources correlate with the emission measure in the ionized interstellar medium along their respective lines of sight. We thus link the variations with interstellar scintillation of components of these sources, with some (unknown) fraction of the total flux density contained within a compact region of angular diameter in the range 10-50{mu}as. We also find that the variations decrease for high mean flux density sources and, most importantly, for high-redshift sources. The decrease in variability is probably due either to an increase in the apparent diameter of the source or to a decrease in the flux density of the compact fraction beyond z~2.
- ID:
- ivo://CDS.VizieR/J/ApJ/767/14
- Title:
- MASIV survey III. Optical identifications
- Short Name:
- J/ApJ/767/14
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Intraday variability (IDV) of the radio emission from active galactic nuclei is now known to be predominantly due to interstellar scintillation (ISS). The MASIV (The Micro-Arcsecond Scintillation-Induced Variability) survey of 443 flat spectrum sources revealed that the IDV is related to the radio flux density and redshift. A study of the physical properties of these sources has been severely handicapped by the absence of reliable redshift measurements for many of these objects. This paper presents 79 new redshifts and a critical evaluation of 233 redshifts obtained from the literature. We classify spectroscopic identifications based on emission line properties, finding that 78% of the sources have broad emission lines and are mainly FSRQs. About 16% are weak lined objects, chiefly BL Lacs, and the remaining 6% are narrow line objects. The gross properties (redshift, spectroscopic class) of the MASIV sample are similar to those of other blazar surveys. However, the extreme compactness implied by ISS favors FSRQs and BL Lacs in the MASIV sample as these are the most compact object classes. We confirm that the level of IDV depends on the 5GHz flux density for all optical spectral types. We find that BL Lac objects tend to be more variable than broad line quasars. The level of ISS decreases substantially above a redshift of about two. The decrease is found to be generally consistent with ISS expected for beamed emission from a jet that is limited to a fixed maximum brightness temperature in the source rest frame.
- ID:
- ivo://CDS.VizieR/J/MNRAS/474/4396
- Title:
- MASIV Survey. IV. Radio AGNs variability
- Short Name:
- J/MNRAS/474/4396
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the relationship between 5GHz interstellar scintillation (ISS) and 15GHz intrinsic variability of compact, radio-selected active galactic nuclei (AGNs) drawn from the Microarcsecond Scintillation-Induced Variability (MASIV) Survey and the Owens Valley Radio Observatory blazar monitoring program. We discover that the strongest scintillators at 5GHz (modulation index, m_5_>=0.02) all exhibit strong 15GHz intrinsic variability (m_15_>=0.1). This relationship can be attributed mainly to the mutual dependence of intrinsic variability and ISS amplitudes on radio core compactness at ~100{mu}s scales, and to a lesser extent, on their mutual dependences on source flux density, arcsec-scale core dominance and redshift. However, not all sources displaying strong intrinsic variations show high amplitude scintillation, since ISS is also strongly dependent on Galactic line-of-sight scattering properties. This observed relationship between intrinsic variability and ISS highlights the importance of optimizing the observing frequency, cadence, timespan and sky coverage of future radio variability surveys, such that these two effects can be better distinguished to study the underlying physics. For the full MASIV sample, we find that Fermi-detected gamma-ray loud sources exhibit significantly higher 5GHz ISS amplitudes than gamma-ray quiet sources. This relationship is weaker than the known correlation between gamma-ray loudness and the 15GHz variability amplitudes, most likely due to jet opacity effects.
- ID:
- ivo://CDS.VizieR/J/AJ/127/501
- Title:
- 2MASS counterparts for OH/IR stars
- Short Name:
- J/AJ/127/501
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The positions of the IRAS counterparts to the 420 OH/IR stars in the Arecibo sky (0{deg}<{delta}<+38{deg}) are usually accurate to better than 10". But every star has recently been observed by the Two Micron All Sky Survey (2MASS, <II/246>), which provides 0.2" quality positions, while those with |b|<=4.5{deg} have also been observed by the Midcourse Space Experiment (MSX, <V/114>), which provides ~2" quality positions. We use the MSX and/or IRAS coordinates to guide us to 2MASS counterparts for the 134 Arecibo OH/IR stars with images in the second release of the 2MASS Point Source Catalog. An unexpected by-product of having the J-H versus H-K_s_ plot generated from the 2MASS fluxes is the realization that most (~85%) of the redder OH/IR stars have detached circumstellar shells. We identify five objects that probably, by contrast, have "normal" shells, and we confirm the status of AU Vul as a protoplanetary nebula.
- ID:
- ivo://CDS.VizieR/J/A+A/380/665
- Title:
- Massive dense cores with ^13^CO J=1-0 lines
- Short Name:
- J/A+A/380/665
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper reports ^13^CO J=1-0 line observations toward 107 IRAS or H2O maser sources with the 13.7m telescope of the Purple Mountain Observatory (PMO). Parameters of emission components are obtained and the profile characteristics are identified. Table1 lists the observed results. It contains source name and its coordinates. ^13^CO line parameters and profile characteristics are given out. Distance, IRAS color indices and bolometric luminosity are also presented.
- ID:
- ivo://CDS.VizieR/J/A+A/638/A105
- Title:
- 8 massive proto-cluster clumps NH2D & NH3 cubes
- Short Name:
- J/A+A/638/A105
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The initial stage of star formation is very difficult to study because of its high density (n_H_2> 10^6^cm^-3^) and low temperature (T_dust_<18K). Under such conditions, many molecules become depleted from the gas phase by freezing out onto dust grains. However, the deuterated species could remain gaseous under these extreme conditions and are thus ideal tracers. We investigate the gas dynamics and NH_2_D chemistry in eight massive pre/protocluster clumps (G18.17, G18.21, G23.97N, G23.98, G23.44, G23.97S, G25.38, and G25.71). We present NH_2_D 1_11-1_01 (at 85.926GHz), NH_3_ (1,1) and (2,2) observations in the eight clumps using the PdBI and the VLA, respectively. We use 3D GAUSSCLUMPS to extract NH_2_D cores and provide a statistical view of their deuterium chemistry. We use NH_3_ (1,1) and (2,2) data to investigate the temperature and dynamics of dense and cold objects. We find that the distribution between deuterium fractionation and kinetic temperature shows a number density peak at around T_kin_=16.1K, and the NH_2_D cores are mainly located at a temperature range of 13.0 to 22.0K. The 3.5mm continuum cores have a kinetic temperature with the median width of 22.1+/-4.3K, which is obviously higher than the temperature in NH_2_D cores. We detect seven extremely high deuterium fractionation of 1.0<=D_frac_<=1.41. We find that the NH_2_D emission does not appear to coincide exactly with either dust continuum or NH3 peak positions, but often surrounds the star-formation active regions. This suggests that the NH_2_D has been destroyed by the central young stellar object (YSO) due to its heating. The detected NH_2_D lines are very narrow with a median width of 0.98+/-0.02km/s, which is dominated by non-thermal broadening. The extracted NH_2_D cores are gravitationally bound ({alpha}_vir_<1), are likely prestellar or starless, and can potentially form intermediate-mass or high-mass stars in future. Using NH3 (1,1) as a dynamical tracer, we find very complicated dynamical movement in all the eight clumps, which can be explained by a combined process with outflow, rotation, convergent flow, collision, large velocity gradient, and rotating toroids. High deuterium fractionation strongly depends on the temperature condition. NH_2_D is a poor evolutionary indicator of high-mass star formation in evolved stages, but a useful tracer in the starless and prestellar cores.
- ID:
- ivo://CDS.VizieR/J/A+A/627/A85
- Title:
- 8 massive proto-cluster clumps observations
- Short Name:
- J/A+A/627/A85
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Massive clumps tend to fragment into clusters of cores and condensations, some of which form high-mass stars. In this work, we study the structure of massive clumps at different scales, analyze the fragmentation process, and investigate the possibility that star formation is triggered by nearby HII regions. We present a high angular resolution study of a sample of 8 massive proto-cluster clumps. Combining infrared data, we use few-arcsecond resolution radio- and millimeter interferometric data to study their fragmentation and evolution. Our sample is unique in the sense that all the clumps have neighboring HII regions. Taking advantage of that, we test triggered star formation using a novel method where we study the alignment of the centres of mass traced by dust emission at multiple scales. The eight massive clumps have masses ranging from 228 to 2279M_{sun}_. The brightest compact structures within infrared bright clumps are typically associated with embedded compact radio continuum sources. The smaller scale structures of Reff~0.02pc observed within each clump are mostly gravitationally bound and massive enough to form at least a B3-B0 type star. Many condensations have masses larger than 8M_{sun}_ at small scale of Reff~0.02pc. Although the clumps are mostly infrared quiet, the dynamical movements are active at clump scale (~1pc). We studied the spatial distribution of the gas conditions detected at different scales. For some sources we find hints of external triggering, whereas for others we find no significant pattern that indicates triggering is dynamically unimportant. This probably indicates that the different clumps go through different evolutionary paths. In this respect, studies with larger samples are highly desired.
- ID:
- ivo://CDS.VizieR/J/A+A/432/921
- Title:
- Massive protostellar candidates
- Short Name:
- J/A+A/432/921
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have observed two rotational transitions of both CS and C^17^O, and the 1.2mm continuum emission towards a sample of 130 high-mass protostellar candidates with DE<-30{deg}. This work represents the first step of the extension to the southern hemisphere of a project started more than a decade ago aimed at the identification of massive protostellar candidates. Following the same approach adopted for sources with DE>=-30{deg}, we have selected from the IRAS Point Source Catalogue 429 sources which potentially are compact molecular clouds on the basis of their IR colours. The sample has then been divided into two groups according to the colour indices [25-12] and [60-12]: the 298 sources with [25-12]>=0.57 and [60-12]>=1.30 have been called High sources, the remaining 131 have been called Low sources. In this paper, we check the association with dense gas and dust in 130 Low sources. We have obtained a detection rate of ~85% in CS, demonstrating a tight association of the sources with dense molecular clumps.
