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1611. Methane partition function
ID:
ivo://CDS.VizieR/J/ApJ/789/2
Title:
Methane partition function
Short Name:
J/ApJ/789/2
Date:
21 Oct 2021
Publisher:
CDS
Description:
The paper describes the construction of complete sets of hot methane lines based on accurate ab initio potential and dipole moment surfaces and extensive first-principle calculations. Four line lists spanning the [0-5000]/cm infrared region were built at T = 500, 1000, 1500, and 2000 K. For each of these four temperatures, we have constructed two versions of line lists: a version for high-resolution applications containing strong and medium lines and a full version appropriate for low-resolution opacity calculations. A comparison with available empirical databases is discussed in detail for both cold and hot bands giving a very good agreement for line positions, typically <0.1-0.5/cm and ~5% for intensities of strong lines. Together with numerical tests using various basis sets, this confirms the computational convergence of our results for the most important lines, which is the major issue for theoretical spectra predictions. We showed that transitions with lower state energies up to 14,000/cm could give significant contributions to the methane opacity and have to be systematically taken into account. Our list at 2000 K calculated up to J = 50 contains 11.5 billion transitions for I > 10^-29^ cm/mol. These new lists are expected to be quantitatively accurate with respect to the precision of available and currently planned observations of astrophysical objects with improved spectral resolution.
1612. Methyl isocyanate in Orion
ID:
ivo://CDS.VizieR/J/A+A/587/L4
Title:
Methyl isocyanate in Orion
Short Name:
J/A+A/587/L4
Date:
21 Oct 2021
Publisher:
CDS
Description:
The recent analysis of the composition of the frozen surface of comet 67P/Churyumov-Gerasimenko has revealed a significant number of complex organic molecules. Methyl isocyanate (CH_3_NCO) is one of the more abundant species detected on the comet surface. In this work we report extensive characterization of its rotational spectrum resulting in a list of 1269 confidently assigned laboratory lines and its detection in space towards the Orion clouds where 399 lines of the molecule have been unambiguously identified. We find that the limited mm-wave laboratory data reported prior to our work require some revision. The abundance of CH_3_NCO in Orion is only a factor of ten below those of HNCO and CH_3_CN. Unlike the molecular abundances in the coma of comets, which correlate with those of warm molecular clouds, molecular abundances in the gas phase in Orion are only weakly correlated with those measured on the comet surface. We also compare our abundances wit those derived recently for this molecule towards Sgr B2 (Halfen et al., 2015ApJ...812L...5H). A more accurate abundance of CH_3_NCO is provided for this cloud based on our extensive laboratory work.
1613. M2FS stellar spectroscopy of Reticulum 2
ID:
ivo://CDS.VizieR/J/ApJ/808/108
Title:
M2FS stellar spectroscopy of Reticulum 2
Short Name:
J/ApJ/808/108
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present results from spectroscopic observations with the Michigan/Magellan Fiber System (M2FS) of 182 stellar targets along the line of sight (LOS) to the newly discovered "ultrafaint" object Reticulum 2 (Ret 2). For 37 of these targets, the spectra are sufficient to provide simultaneous estimates of LOS velocity ({nu}i_los_, median random error {delta}_{nu}los_=1.4km/s), effective temperature (T_eff_, {delta}_Tef_=478K), surface gravity (logg, {delta}_logg_=0.63dex), and iron abundance ([Fe/H], {delta}_[Fe/H]_=0.47dex). We use these results to confirm 17 stars as members of Ret 2. From the member sample we estimate a velocity dispersion of {sigma}_{nu}los_=3.6_-0.7_^+1.0^km/s about a mean of <{nu}_los_>=64.3_1.2_^+1.2^km/s in the solar rest frame (~-90.9km/s in the Galactic rest frame), and a metallicity dispersion of {sigma}_[Fe/H]_=0.49_-0.14_^+0.19^dex about a mean of <[Fe/H]_>=-2.58_-0.33_^+0.34^. These estimates marginalize over possible velocity and metallicity gradients, which are consistent with zero. Our results place Ret 2 on chemodynamical scaling relations followed by the Milky Way's dwarf-galactic satellites. Under assumptions of dynamic equilibrium and negligible contamination from binary stars --both of which must be checked with deeper imaging and repeat spectroscopic observations-- the estimated velocity dispersion suggests a dynamical mass of M(R_h_)~5R_h_{sigma}_{nu}los_^2^/(2G)=2.4_-0.8_^+1.4^x10^5^M_{sun}_ enclosed within projected halflight radius R_h_~32pc, with mass-to-light ratio ~2M(R_h_)/L_V_=467_-168_^+286^ in solar units.
1614. M8, G333.6-0.2 and NGC6357 young stars
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%.
1615. MGGPOD Monte Carlo suite
ID:
ivo://CDS.VizieR/J/ApJS/156/69
Title:
MGGPOD Monte Carlo suite
Short Name:
J/ApJS/156/69
Date:
21 Oct 2021
Publisher:
CDS
Description:
Intense and complex instrumental backgrounds, against which the much smaller signals from celestial sources have to be discerned, are a notorious problem for low- and intermediate-energy {gamma}-ray astronomy (~50keV-10MeV). Therefore, a detailed qualitative and quantitative understanding of instrumental line and continuum backgrounds is crucial for most stages of {gamma}-ray astronomy missions, ranging from the design and development of new instrumentation through performance prediction to data reduction. We have developed MGGPOD, a user-friendly suite of Monte Carlo codes built around the widely used GEANT (ver. 3.21) package, to simulate ab initio the physical processes relevant for the production of instrumental backgrounds. These include the build-up and delayed decay of radioactive isotopes as well as the prompt de-excitation of excited nuclei, both of which give rise to a plethora of instrumental {gamma}-ray background lines in addition to continuum backgrounds. The MGGPOD package and documentation are publicly available online (http://sigma-2.cesr.fr/spi/MGGPOD/). We demonstrate the capabilities of the MGGPOD suite by modeling high-resolution {gamma}-ray spectra recorded by the Transient Gamma-Ray Spectrometer (TGRS) on board Wind during 1995. The TGRS is a Ge spectrometer operating in the 40keV-8MeV range. Because of its fine energy resolution, these spectra reveal the complex instrumental background in formidable detail, particularly the many prompt and delayed {gamma}-ray lines. We evaluate the successes and failures of the MGGPOD package in reproducing TGRS data and provide identifications for the numerous instrumental lines.
1616. MgH in the A^2^{Pi}-X^2^{Sigma}^+^ system
ID:
ivo://CDS.VizieR/J/ApJS/207/26
Title:
MgH in the A^2^{Pi}-X^2^{Sigma}^+^ system
Short Name:
J/ApJS/207/26
Date:
21 Oct 2021
Publisher:
CDS
Description:
Using laboratory hollow cathode spectra we have identified lines of the less common magnesium isotopologues of MgH, ^25^MgH and ^26^MgH, in the A^2^{Pi}-X^2^{Sigma}^+^ system. Based on the previous analysis of ^24^MgH, molecular lines have been measured and molecular constants derived for ^25^MgH and ^26^MgH. Term values and linelists, in both wavenumber and wavelength units, are presented. The A^2^{Pi}-X^2^{Sigma}^+^ system of MgH is important for measuring the magnesium isotope ratios in stars.
1617. MgI and sTiO index definitions
ID:
ivo://CDS.VizieR/J/MNRAS/396/1895
Title:
MgI and sTiO index definitions
Short Name:
J/MNRAS/396/1895
Date:
21 Oct 2021
Publisher:
CDS
Description:
Using the near-infrared spectral stellar library of Cenarro et al. (J/MNRAS/326/959), the behaviour of the MgI line at 8807{AA} and nearby TiO bands is analyzed in terms of the effective temperature, surface gravity and metallicity of the library stars. New spectroscopic indices for both spectral features - namely MgI and sTiO - are defined, and their sensitivities to different signal-to-noise ratios, spectral resolutions, flux calibrations and sky emission-line residuals are characterized. The two new indices exhibit interesting properties. In particular, MgI is a good indicator of the Mg abundance, whereas sTiO is a powerful dwarf-to-giant discriminator for cold spectral types. Empirical fitting polynomials that reproduce the strength of the new indices as a function of the stellar atmospheric parameters are computed, and a fortran routine with the fitting function predictions is made available. A thorough study of several error sources, non-solar [Mg/Fe] ratios and their influence on the fitting function residuals is also presented. From this analysis, an [Mg/Fe] underabundance of ~-0.04 is derived for the Galactic open cluster M67.
1618. M giants spectra and photometry
ID:
ivo://CDS.VizieR/J/A+AS/105/311
Title:
M giants spectra and photometry
Short Name:
J/A+AS/105/311
Date:
21 Oct 2021
Publisher:
CDS
Description:
From a sample of 97 very bright M-giant stars in the Solar neighbourhood, high-quality `intrinsic' spectra in the spectral range [380-900]nm for all M-spectral subclasses of the Case and MK classification systems are obtained. The results are fitted to photospheric synthetic spectra in the range [99-12500]nm in order to infer the corresponding continua. The synthetic spectra are also compared to the intrinsic spectra. The effective temperatures are derived and mathematical spectral classification criteria are found. The (UB)j(VRI)c(JHKLM)eso photometric data of the sample are also given.
1619. M giant stars in the Sagittarius dwarf galaxy. V.
ID:
ivo://CDS.VizieR/J/ApJ/670/346
Title:
M giant stars in the Sagittarius dwarf galaxy. V.
Short Name:
J/ApJ/670/346
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present reliable measurements of the metallicity distribution function (MDF) at different points along the tidal stream of the Sagittarius (Sgr) dwarf spheroidal (dSph) galaxy, based on high-resolution, echelle spectroscopy of candidate M giant members of the Sgr system.
1620. MgII absorbing gas around galaxies
ID:
ivo://CDS.VizieR/J/ApJ/724/L176
Title:
MgII absorbing gas around galaxies
Short Name:
J/ApJ/724/L176
Date:
21 Oct 2021
Publisher:
CDS
Description:
We study the connections between ongoing star formation, galaxy mass, and extended halo gas, in order to distinguish between starburst-driven outflows and infalling clouds that produce the majority of observed MgII absorbers at large galactic radii (>~10h^-1^kpc) and to gain insights into halo gas contents around galaxies. We present new measurements of total stellar mass (M_star_), H{alpha} emission line strength (EW(H{alpha})), and specific star formation rate (sSFR) for the 94 galaxies described by Chen et al.'s 2010 paper (Cat. J/ApJ/714/1521).

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