- 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.
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- 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/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/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.
- ID:
- ivo://CDS.VizieR/J/A+A/629/A112
- Title:
- Complex refractive index of CO ice
- Short Name:
- J/A+A/629/A112
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Reliable, directly measured optical properties of astrophysical ice analogs in the infrared (IR) and terahertz (THz) range are missing. These parameters are of great importance to model the dust continuum radiative transfer in dense and cold regions, where thick ice mantles are present, and are necessary for the interpretation of future observations planned in the far-IR region. Coherent THz radiation allows direct measurement of the complex dielectric function (refractive index) of astrophysically relevant ice species in the THz range. The time-domain waveforms and the frequency-domain spectra of reference samples of CO ice, deposited at a temperature of 28.5K and annealed to 33K at different thicknesses, have been recorded. A new algorithm is developed to reconstruct the real and imaginary parts of the refractive index from the time-domain THz data. The complex refractive index in the wavelength range of 1mm-150um (0.3-2.0THz) has been determined for the studied ice samples, and compared with available data found in the literature. The developed algorithm of reconstructing the real and imaginary parts of the refractive index from the time-domain THz data enables, for the first time, the determination of optical properties of astrophysical ice analogs without using the Kramers-Kronig relations. The obtained data provide a benchmark to interpret the observational data from current ground based facilities as well as future space telescope missions, and have been used to estimate the opacities of the dust grains in presence of CO ice mantles.
- ID:
- ivo://CDS.VizieR/J/ApJ/897/83
- Title:
- Component structure in the neightborhood of IC 443
- Short Name:
- J/ApJ/897/83
- Date:
- 11 Mar 2022
- Publisher:
- CDS
- Description:
- We present the results of a detailed investigation into the physical conditions in interstellar material interacting with the supernova remnant (SNR) IC443. Our analysis is based on a comprehensive examination of high-resolution far-ultraviolet spectra obtained with the Space Telescope Imaging Spectrograph onboard the Hubble Space Telescope of two stars behind IC443. One of our targets (HD43582) probes gas along the entire line of sight through the SNR, while the other (HD254755) samples material located ahead of the primary supernova shock front. We identify low-velocity quiescent gas in both directions and find that the densities and temperatures in these components are typical of diffuse atomic and molecular clouds. Numerous high- velocity components are observed in the absorption profiles of neutral and singly ionized atomic species toward HD43582. These components exhibit a combination of greatly enhanced thermal pressures and significantly reduced dust-grain depletions. We interpret this material as cooling gas in a recombination zone far downstream from shocks driven into neutral gas clumps. The pressures derived for a group of ionized gas components at high positive velocity toward HD43582 are lower than those of the other shocked components, pointing to pressure inhomogeneities across the remnant. A strong, very high velocity component near -620km/s is seen in the absorption profiles of highly ionized species toward HD43582. The velocity of this material is consistent with the range of shock velocities implied by observations of soft thermal X-ray emission from IC443. Moderately high velocity gas toward HD254755 may represent shocked material from a separate foreground SNR.
- ID:
- ivo://CDS.VizieR/J/AJ/131/1288
- Title:
- Composite spectra of early-type galaxies
- Short Name:
- J/AJ/131/1288
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Chemical abundance indicators are studied using composite spectra, which we provide in tabular form. Tables of line strengths measured from these spectra and parameters derived from these line strengths are also provided. All the objects we analyze were selected from the SDSS database. We selected all objects targeted as galaxies and having Petrosian apparent magnitude 14.5<=r_Pet_<=17.75. To extract a sample of early-type galaxies, we then chose the subset with the spectroscopic parameter eclass<0, which classifies the spectral type based on a principal component analysis, and the photometric parameter fracDev_r_>0.8, which is a seeing-corrected indicator of morphology.
- ID:
- ivo://CDS.VizieR/J/ApJ/725/1252
- Title:
- Confirmed members of RX J0152.7-1357
- Short Name:
- J/ApJ/725/1252
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a spectrophotometric analysis of galaxies belonging to the dynamically young, massive cluster RX J0152.7-1357 at z~0.84, aimed at understanding the effects of the cluster environment on the star formation history (SFH) of cluster galaxies and the assembly of the red sequence (RS). We use VLT/FORS spectroscopy, ACS/WFC optical, and NTT/SofI near-IR data to characterize SFHs as a function of color, luminosity, morphology, stellar mass, and local environment from a sample of 134 spectroscopic members. In order to increase the signal-to-noise ratio, individual galaxy spectra are stacked according to these properties. Moreover, the D4000, Balmer, CN3883, Fe4383, and C4668 indices are also quantified.
- ID:
- ivo://CDS.VizieR/J/A+A/608/A46
- Title:
- Constraining cosmic scatter
- Short Name:
- J/A+A/608/A46
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the stellar parameters, abundances, associated errors and the linelist of a set of 23 metal-poor and very metal-poor halo stars. Stellar parameters and chemical abundances were derived in a line-by-line differential analysis from equivalent widths of UVES/VLT spectra. The differential analysis provided us unprecedented small data scatter and errors. Our sample, along with data from different authors in different metallicity ranges, allowed us to do an extensive comparison of the chemical abundances with the predictions of a Galaxy chemical evolution model.
- ID:
- ivo://CDS.VizieR/J/ApJ/866/133
- Title:
- Continuum-H{beta} light curves of 5 Seyfert 1
- Short Name:
- J/ApJ/866/133
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first results from a reverberation-mapping campaign undertaken during the first half of 2012, with additional data on one active galactic nucleus (AGN) (NGC 3227) from a 2014 campaign. Our main goals are (1) to determine the black hole masses from continuum-H{beta} reverberation signatures, and (2) to look for velocity-dependent time delays that might be indicators of the gross kinematics of the broad-line region. We successfully measure H{beta} time delays and black hole masses for five AGNs, four of which have previous reverberation mass measurements. The values measured here are in agreement with earlier estimates, though there is some intrinsic scatter beyond the formal measurement errors. We observe velocity-dependent H{beta} lags in each case, and find that the patterns have changed in the intervening five years for three AGNs that were also observed in 2007.
