- ID:
- ivo://CDS.VizieR/J/MNRAS/473/1059
- Title:
- Complete sample of Galactic clump properties
- Short Name:
- J/MNRAS/473/1059
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The APEX Telescope Large Area Survey of the Galaxy (ATLASGAL) is an unbiased 870um submillimetre survey of the inner Galactic plane (|l|<60{deg} with |b|<1.5{deg}). It is the largest and most sensitive ground-based submillimetre wavelength Galactic survey to date and has provided a large and systematic inventory of all massive, dense clumps in the Galaxy (>=1000M_{sun}_ at a heliocentric distance of 20kpc) and includes representative samples of all of the earliest embedded stages of high-mass star formation. Here, we present the first detailed census of the properties (velocities, distances, luminosities and masses) and spatial distribution of a complete sample of ~8000 dense clumps located in the Galactic disc (5{deg}<|l|<60{deg}). We derive highly reliable velocities and distances to ~97 per cent of the sample and use mid- and far-infrared survey data to develop an evolutionary classification scheme that we apply to the whole sample. Comparing the evolutionary subsamples reveals trends for increasing dust temperatures, luminosities and linewidths as a function of evolution indicating that the feedback from the embedded protoclusters is having a significant impact on the structure and dynamics of their natal clumps. We find that the vast majority of the detected clumps are capable of forming a massive star and 88 per cent are already associated with star formation at some level. We find the clump mass to be independent of evolution suggesting that the clumps form with the majority of their mass in situ. We estimate the statistical lifetime of the quiescent stage to be ~5x10^4^yr for clump masses >1000M_{sun}_ decreasing to ~1x10^4^yr for clump masses >10000M_{sun}_. We find a strong correlation between the fraction of clumps associated with massive stars and peak column density. The fraction is initially small at low column densities, but reaching 100 per cent for column densities above 10^23^cm^x2^; there are no clumps with column densities above this value that are not already associated with massive star formation. All of the evidence is consistent with a dynamic view of star formation wherein the clumps form rapidly and are initially very unstable so that star formation quickly ensues.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/469/3738
- Title:
- Complete sample of galaxy clusters
- Short Name:
- J/MNRAS/469/3738
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The X-ray regime, where the most massive visible component of galaxy clusters, the intracluster medium, is visible, offers directly measured quantities, like the luminosity, and derived quantities, like the total mass, to characterize these objects. The aim of this project is to analyse a complete sample of galaxy clusters in detail and constrain cosmological parameters, like the matter density, {Omega}_m_, or the amplitude of initial density fluctuations, {sigma}_8_. The purely X-ray flux-limited sample (HIFLUGCS) consists of the 64 X-ray brightest galaxy clusters, which are excellent targets to study the systematic effects, that can bias results. We analysed in total 196 Chandra observations of the 64 HIFLUGCS clusters, with a total exposure time of 7.7Ms. Here, we present our data analysis procedure (including an automated substructure detection and an energy band optimization for surface brightness profile analysis) that gives individually determined, robust total mass estimates. These masses are tested against dynamical and Planck Sunyaev-Zeldovich (SZ) derived masses of the same clusters, where good overall agreement is found with the dynamical masses. The Planck SZ masses seem to show a mass-dependent bias to our hydrostatic masses; possible biases in this mass-mass comparison are discussed including the Planck selection function. Furthermore, we show the results for the (0.1-2.4)keV luminosity versus mass scaling relation. The overall slope of the sample (1.34) is in agreement with expectations and values from literature. Splitting the sample into galaxy groups and clusters reveals, even after a selection bias correction, that galaxy groups exhibit a significantly steeper slope (1.88) compared to clusters (1.06).
- ID:
- ivo://CDS.VizieR/J/PAZh/38/776
- Title:
- Complete sample of OB stars within 350pc
- Short Name:
- J/PAZh/38/776
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The sample of 37485 suspected OB stars selected by Gontcharov (2008AstL...34....7G) from the Tycho-2 catalogue has been cleaned of the stars that are not of spectral types OV-A0V. For this purpose, the apparent magnitude VT from Tycho-2, the absolute magnitude MVT calibrated as a function of the dereddened color index (BT-VT)0, the interstellar extinction AVT calculated from the 3D analytical model by Gontcharov (2009AstL...35..780G) as a function of the Galactic coordinates, and the photometric distance Rph calculated as a function of VT, M_VT_, and A_VT_ have been reconciled in an iterative process. The 20514 stars that passed the iterations have (BT-VT)_0_<0 and M_VT_>-5 and are considered as a sample of OV-A0V stars complete within 350 pc of the Sun. Based on the theoretical relation between the dereddened color and age of the stars, the derived sample has been divided into three subsamples: (BT-VT)_0_< -0.2, -0.2<(BT-VT)_0_< -0.1, and -0.1<(BT-VT)_0_<0, younger than 100, 100-200, and 200-400 Myr, respectively. The spatial distribution of all 20514 stars and the kinematics analyzed for more than 1500 stars with radial velocities from the PCRV and RAVE catalogues are different for the subsamples, showing smooth rotations, shears, and deformations of the layer of gas producing stars with the formation of the Gould Belt, the Great Tunnel, the Local Bubble, and other structures within the last 200 Myr. The detected temporal variations of the velocity dispersions, solar motion components, Ogorodnikov-Milne model parameters, and Oort constants are significant, agree with the results of other authors, and show that it is meaningless to calculate the kinematic parameters for samples of stars with uncertain ages or with a wide range of ages.
- ID:
- ivo://CDS.VizieR/J/other/BSAO/46.28
- Title:
- Complete sample of PMN survey spectra
- Short Name:
- J/other/BSAO/46.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this report we present the results of observations of a complete sample of sources from the PMN Survey. The adopted selection criteria were: flux density >200mJy at the PMN Survey frequency 4.8GHz; 0h<RA<24h; -21{deg}<=Dec<=-17{deg}; |b|>=10(deg} to exclude the galactic plane. Five runs of observations were accomplished in 1995-1996. The observations were made at 0.96, 2.3, 3.9, 7.7 and 11.2GHz at the RATAN-600 radio telescope. For all sources of the sample, flux densities at five frequencies and their simultaneous spectra were determined, accuracies in RA were improved 5-10 times. Identifications with data from the Texas Survey were performed.
- ID:
- ivo://CDS.VizieR/J/ApJ/714/476
- Title:
- Complete spectrum of ethyl cyanide
- Short Name:
- J/ApJ/714/476
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- There is a general consensus that many of the unidentified features in astrophysical spectra are due to low lying excited vibrational and torsional states of a few molecules -commonly referred to as the astrophysical weeds. This is a challenging spectroscopic problem not only because there are many such states, but also because these states are often highly perturbed and difficult to analyze. We have previously described an alternative approach based on experimental, intensity-calibrated spectra taken at many temperatures. In this paper, we describe the procedures and results obtained with this approach for ethyl cyanide, strategies for archiving and disseminating these results, and the prospects for using these results to reduce the confusion limit in the powerful new observatories that are coming online.
- ID:
- ivo://CDS.VizieR/J/ApJ/782/75
- Title:
- Complete spectrum of methanol
- Short Name:
- J/ApJ/782/75
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The complete spectrum of methanol (CH_3_OH) has been characterized over a range of astrophysically significant temperatures in the 560.4-654.0GHz spectral region. Absolute intensity calibration and analysis of 166 experimental spectra recorded over a slow 248-398K temperature ramp provide a means for the simulation of the complete spectrum of methanol as a function of temperature. These results include contributions from v_t_=3 and other higher states that are difficult to model via quantum mechanical (QM) techniques. They also contain contributions from the ^13^C isotopologue in terrestrial abundance. In contrast to our earlier work on semi-rigid species, such as ethyl cyanide and vinyl cyanide, significant intensity differences between these experimental values and those calculated by QM methods were found for many of the lines. Analysis of these differences shows the difficulty of the calculation of dipole matrix elements in the context of the internal rotation of the methanol molecule. These results are used to both provide catalogs in the usual line frequency, linestrength, and lower state energy format, as well as in a frequency point-by-point catalog that is particularly well suited for the characterization of blended lines.
- ID:
- ivo://CDS.VizieR/J/MNRAS/466/2614
- Title:
- Complex cluster Abell 1758 stars
- Short Name:
- J/MNRAS/466/2614
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a weak-lensing and dynamical study of the complex cluster Abell 1758 (A1758, {bar}z=0.278) supported by hydrodynamical simulations. This cluster is composed of two main structures called A1758N and A1758S. The northern structure is composed of A1758NW and A1758NE, with lensing determined masses of 7.90_-1.55_^+1.89^x10^14^M_{sun}_ and 5.49_-1.33_^+1.67^x10^14^M_{sun}_, respectively. They show a remarkable feature: while in A1758NW, there is a spatial agreement among weak-lensing mass distribution, intracluster medium and its brightest cluster galaxy (BCG), in A1758NE, the X-ray peak is located 96_-15_^+14^ arcsec away from the mass peak and BCG positions. Given the detachment between gas and mass, we could use the local surface mass density to estimate an upper limit for the dark matter self-interaction cross-section: {sigma}/m<5.83cm^2^/g. Combining our velocity data with hydrodynamical simulations, we have shown that A1758 NW and NE had their closest approach 0.27Gyr ago and their merger axis is 21+/-12{deg} from the plane of the sky. In the A1758S system, we have measured a total mass of 4.96_-1.19_^+1.08^x10^14^M_{sun}_ and, using radial velocity data, we found that the main merger axis is located at 70+/-4{deg} from the plane of the sky, therefore closest to the line of sight.
- ID:
- ivo://CDS.VizieR/J/A+A/629/A83
- Title:
- Complexity of magnetic fields on red dwarfs
- Short Name:
- J/A+A/629/A83
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Generation, amplification, and evolution of magnetic fields in cool stars can be investigated by measuring the Zeeman effect in atomic and molecular lines observed in their spectra. In particular, Zeeman line broadening and polarization have been used for detecting magnetic fields in stellar atmospheres. Similar to the Sun, these fields are complex and height-dependent (i.e., comprise 3D structures) and require advanced diagnostics. Fortunately, many molecular lines dominating M-dwarf spectra, such as FeH, CaH, MgH, and TiO, are temperature- and Zeeman- sensitive and form at different atmospheric heights, which makes them excellent probes of magnetic fields on M dwarfs. Our goal is to analyze the complexity of magnetic fields in M dwarfs. We investigate how magnetic fields vary with the stellar temperature (i.e., mass) and how "surface" inhomogeneities are distributed in height - the dimension that is usually neglected in stellar magnetic studies. This is achieved by including many atomic and molecular species in our study. We have determined effective temperatures of the photosphere and of magnetic features, magnetic field strengths and filling factors for nine M dwarfs (M1-M7). Our chi^2^ analysis is based on a comparison of observed and synthetic intensity and circular polarization profiles (Stokes I and V) of many magnetically sensitive atomic and molecular lines in ten wavelength regions. Stokes profiles were calculated by solving polarized radiative transfer equations under the local thermodynamic equilibrium using model atmospheres. We have found that properties of magnetic structures depend on the analyzed atomic or molecular species and their formation heights within the atmosphere. Two types of magnetic features similar to those on the Sun have been found: one is cooler (starspots), while the other one is hotter (network, small-scale magnetic features). The magnetic field strength in both starspots and network is within 3kG to 6kG, on average it is 5kG for the M1-M7 spectral class range. These fields occupy a large fraction of M dwarf atmospheres at all heights, up to 100%. The plasma beta is less than one throughout the entire M dwarf atmospheres, implying that they are highly magnetized stars. A combination of many molecular and atomic species and a simultaneous analysis of intensity and circular polarization spectra have allowed us to better decipher the complexity of magnetic fields on M dwarfs, including their dependence on the height within the atmosphere. This work provides an opportunity to investigate a larger sample of M dwarfs as well as L-type brown dwarfs.
- ID:
- ivo://CDS.VizieR/J/ApJ/845/36
- Title:
- Complex network for solar active regions
- Short Name:
- J/ApJ/845/36
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we developed a complex network of solar active regions (ARs) to study various local and global properties of the network. The values of the Hurst exponent (0.8-0.9) were evaluated by both the detrended fluctuation analysis and the rescaled range analysis applied on the time series of the AR numbers. The findings suggest that ARs can be considered as a system of self-organized criticality (SOC). We constructed a growing network based on locations, occurrence times, and the lifetimes of 4227 ARs recorded from 1999 January 1 to 2017 April 14. The behavior of the clustering coefficient shows that the AR network is not a random network. The logarithmic behavior of the length scale has the characteristics of a so-called small-world network. It is found that the probability distribution of the node degrees for undirected networks follows the power law with exponents of about 3.7-4.2. This indicates the scale-free nature of the AR network. The scale-free and small-world properties of the AR network confirm that the system of ARs forms a system of SOC. Our results show that the occurrence probability of flares (classified by GOES class C>5, M, and X flares) in the position of the AR network hubs takes values greater than that obtained for other nodes.
- ID:
- ivo://CDS.VizieR/J/A+A/641/A54
- Title:
- Complex organic molecules in high-mass SFRs
- Short Name:
- J/A+A/641/A54
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have studied four complex organic molecules (COMs), the oxygen-bearing methyl formate (CH_3_OCHO) and dimethyl ether (CH_3_OCH_3_) as well as the nitrogen-bearing formamide (NH_2_CHO) and ethyl cyanide (C_2_H_5_CN), towards a large sample of 39 high-mass star-forming regions representing different evolutionary stages, from early to evolved phases. We aim to identify potential correlations and chemical links between the molecules and to trace their evolutionary sequence through the star formation process. We analysed spectra obtained at 3, 2, and 0.9mm with the IRAM-30m telescope. We derived the main physical parameters for each species by fitting the molecular lines. We compared them and evaluated their evolution while also taking several other interstellar environments into account. We report detections in 20 sources, revealing a clear dust absorption effect on column densities. Derived abundances range between ~10^-10^-10^-7^ for CH_3_OCHO and CH_3_OCH_3_, ~10^-12^-10^-10^ for NH_2_CHO, and ~10^-11^-10^-9^ for C_2_H_5_CN. The abundances of CH3OCHO, CH3OCH3, and C2H5CN are very strongly correlated (r>=0.92) across 4 orders of magnitude.We note that CH_3_OCHO and CH_3_OCH_3_ show the strongest correlations in most parameters, and a nearly constant ratio (1) over a remarkable 9 orders of magnitude in luminosity for the following wide variety of sources: pre-stellar to evolved cores, low- to high-mass objects, shocks, Galactic clouds, and comets. This indicates that COMs chemistry is likely early developed and then preserved through evolved phases. Moreover, the molecular abundances clearly increase with evolution, covering 6 orders of magnitude in the luminosity/mass ratio. We consider CH_3_OCHO and CH_3_OCH_3_ to be most likely chemically linked. They could, for example, share a common precursor, or be formed one from the other. Based on correlations, ratios, and the evolutionary trend, we propose a general scenario for all COMs, involving a formation in the cold, earliest phases of star formation and a following increasing desorption with the progressive thermal and shock-induced heating of the evolving core.