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- ID:
- ivo://CDS.VizieR/J/A+A/622/A135
- Title:
- Mid-J CO emission of Top100 clumps
- Short Name:
- J/A+A/622/A135
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- High-mass stars are formed within massive molecular clumps, where a large number of stars form close together. The evolution of the clumps with different masses and luminosities is mainly regulated by their high-mass stellar content and the formation of such objects is still not well understood. In this work, we characterise the mid-J CO emission in a statistical sample of 99 clumps (TOP100) selected from the ATLASGAL survey that are representative of the Galactic proto-cluster population. High-spatial resolution APEX-CHAMP+ maps of the CO (6-5) and CO (7-6) transitions were obtained and combined with additional single-pointing APEX-FLASH+ spectra of the CO (4-3) line. The data were convolved to a common angular resolution of 13.4". We analysed the line profiles by fitting the spectra with up to three Gaussian components, classified as narrow or broad, and computed CO line luminosities for each transition. Additionally, we defined a distance-limited sample of 72 sources within 5kpc to check the robustness of our analysis against beam dilution effects. We have studied the correlations of the line luminosities and profiles for the three CO transitions with the clump properties and investigate if and how they change as a function of the evolution. All sources were detected above 3-{sigma} in all three CO transitions and most of the sources exhibit broad CO emission likely associated with molecular outflows. We find that the extension of the mid-J CO emission is correlated with the size of the dust emission traced by the Herschel-PACS 70um maps. The CO line luminosity (LCO) is correlated with the luminosity and mass of the clumps. However, it does not correlate with the luminosity-to-mass ratio. The dependency of the CO luminosity with the properties of the clumps is steeper for higher-J transitions. Our data seem to exclude that this trend is biased by self-absorption features in the CO emission, but rather suggest that different J transitions arise from different regions of the inner envelope. Moreover, high-mass clumps show similar trends in CO luminosity as lower mass clumps, but are systematically offset towards larger values, suggesting that higher column density and (or) temperature (of unresolved) CO emitters are found inside high-mass clumps.
- ID:
- ivo://CDS.VizieR/J/A+A/587/A96
- Title:
- Mid-J CO shock tracing observations of IRDCs II
- Short Name:
- J/A+A/587/A96
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Infrared dark clouds are kinematically complex molecular structures in the interstellar medium that can host sites of massive star formation. We present maps measuring 4 square arcminutes of the ^12^CO, ^13^CO, and C^18^O J=3 to 2 lines from selected locations within the C and F (G028.37+00.07 and G034.43+00.24) infrared dark clouds (IRDCs), as well as single pointing observations of the ^13^CO and C^18^O J=2 to 1 lines towards three cores within these clouds. We derive CO gas temperatures throughout the maps and find that CO is significantly frozen out within these IRDCs. We find that the CO depletion tends to be the highest near column density peaks with maximum depletion factors between 5 and 9 in IRDC F and between 16 and 31 in IRDC C. We also detect multiple velocity components and complex kinematic structure in both IRDCs. Therefore, the kinematics of IRDCs seem to point to dynamically evolving structures yielding dense cores with considerable depletion factors.
- ID:
- ivo://CDS.VizieR/J/ApJ/883/84
- Title:
- MIKE obs. of 2 metal-poor stars in Sylgr stream
- Short Name:
- J/ApJ/883/84
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We observe two metal-poor main-sequence stars that are members of the recently discovered Sylgr stellar stream. We present radial velocities, stellar parameters, and abundances for 13 elements derived from high-resolution optical spectra collected using the Magellan Inamori Kyocera Echelle spectrograph. The two stars have identical compositions (within 0.13 dex or 1.2{sigma}) among all elements detected. Both stars are very metal-poor ([Fe/H]=-2.92+/-0.06). Neither star is highly enhanced in C ([C/Fe]<+1.0). Both stars are enhanced in the {alpha} elements Mg, Si, and Ca ([{alpha}/Fe]=+0.32+/-0.06), and the ratios among Na, Al, and all Fe-group elements are typical for other stars in the halo and ultra-faint and dwarf spheroidal galaxies at this metallicity. Sr is mildly enhanced ([Sr/Fe]=+0.22+/-0.11), but Ba is not enhanced ([Ba/Fe]{<}-0.4), indicating that these stars do not contain high levels of neutron-capture elements. The Li abundances match those found in metal-poor unevolved field stars and globular clusters (GCs) (log{epsilon}(Li)=2.05+/-0.07), which implies that environment is not a dominant factor in determining the Li content of metal-poor stars. The chemical compositions of these two stars cannot distinguish whether the progenitor of the Sylgr stream was a dwarf galaxy or a GC. If the progenitor was a dwarf galaxy, the stream may originate from a dense region such as a nuclear star cluster. If the progenitor was a GC, it would be the most metal-poor GC known.
- ID:
- ivo://CDS.VizieR/J/MNRAS/404/1639
- Title:
- MILES base models & new line index system
- Short Name:
- J/MNRAS/404/1639
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present synthetic spectral energy distributions (SEDs) for single-age, single-metallicity stellar populations (SSPs) covering the full optical spectral range at moderately high resolution [full width at half-maximum (FWHM)=2.3{AA}]. These SEDs constitute our base models, as they combine scaled-solar isochrones with an empirical stellar spectral library [Medium resolution INT Library of Empirical Spectra (MILES)], which follows the chemical evolution pattern of the solar neighbourhood. The models rely as much as possible on empirical ingredients, not just on the stellar spectra, but also on extensive photometric libraries, which are used to determine the transformations from the theoretical parameters of the isochrones to observational quantities. The unprecedented stellar parameter coverage of the MILES stellar library allowed us to safely extend our optical SSP SED predictions from intermediate- to very-old-age regimes and the metallicity coverage of the SSPs from super-solar to [M/H]=-2.3. SSPs with such low metallicities are particularly useful for globular cluster studies. We have computed SSP SEDs for a suite of initial mass function shapes and slopes. We provide a quantitative analysis of the dependence of the synthesized SSP SEDs on the (in)complete coverage of the stellar parameter space in the input library that not only shows that our models are of higher quality than those of other works, but also in which range of SSP parameters our models are reliable.
- ID:
- ivo://CDS.VizieR/J/MNRAS/371/703
- Title:
- MILES library of empirical spectra
- Short Name:
- J/MNRAS/371/703
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A new stellar library developed for stellar population synthesis modelling is presented. The library consists of 985 stars spanning a large range in atmospheric parameters. The spectra were obtained at the 2.5-m Isaac Newton Telescope and cover the range 3525-7500{AA} at 2.3{AA} (full width at half-maximum) spectral resolution. The spectral resolution, spectral-type coverage, flux-calibration accuracy and number of stars represent a substantial improvement over previous libraries used in population-synthesis models.
- ID:
- ivo://CDS.VizieR/J/A+A/649/A83
- Title:
- Milky Way nuclear disk KMOS survey
- Short Name:
- J/A+A/649/A83
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- In the central few degrees of the bulge of the Milky Way there is a flattened structure of gas, dust, and stars, known as the central molecular zone, that is similar to nuclear disks in other galaxies. As a result of extreme foreground extinction, we possess only sparse information about the (mostly old) stellar population of the nuclear disk. In this work we present our KMOS spectroscopic survey of the stars in the nuclear disk reaching the old populations. To obtain an unbiased data set, we sampled stars in the full extinction range along each line of sight. We also observed reference fields in neighboring regions of the Galactic bulge. We describe the design and execution of the survey and present first results. We obtain spectra and five spectral indices of 3113 stars with a median S/N of 67 and measure radial velocities for 3051 stars. Of those, 2735 sources have sufficient S/N to estimate temperatures and metallicities from indices. We derive metallicities using the CO 2-0 and Na I K-band spectral features, where we derive our own empirical calibration using metallicities obtained with higher-resolution observations.We use 183 giant stars for calibration spanning in metallicity from -2.5 to 0.6dex and covering temperatures of up to 5500K. The derived index based metallicities deviate from the calibration values with a scatter of 0.32dex. The internal uncertainty of our metallicities is likely smaller. We use these metallicity measurements, together with the CO index, to derive effective temperatures using literature relations. We publish the catalog in this paper. Our data set complements Galactic surveys such as Gaia and APOGEE for the inner 200pc radius of the Milky Way, which is not readily accessible by those surveys owing to extinction. We will use the derived properties in future papers for further analysis of the nuclear disk.
- ID:
- ivo://CDS.VizieR/J/A+A/592/A43
- Title:
- Millimeter wave spectra of carbonyl cyanide
- Short Name:
- J/A+A/592/A43
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- More than 30 cyanide derivatives of simple organic molecules have been detected in the interstellar medium, but only one dicarbonitrile has been found and that very recently. There is still a lack of high-resolution spectroscopic data particularly for dinitriles derivatives. The carbonyl cyanide molecule is a new and interesting candidate for astrophysical detection. It could be formed by the reaction of CO and CN radicals, or by substitution of the hydrogen atom by a cyano group in cyanoformaldehyde, HC(=O)CN, that has already been detected in the interstellar medium. The available data on the rotational spectrum of carbonyl cyanide is limited in terms of quantum number values and frequency range, and does not allow accurate extrapolation of the spectrum into the millimeter-wave range. To provide a firm basis for astrophysical detection of carbonyl cyanide we studied its millimeter-wave spectrum. Methods. The rotational spectrum of carbonyl cyanide was measured in the frequency range 152-308GHz and analyzed using Watson's A- and S-reduction Hamiltonians. The ground and first excited state of v5 vibrational mode were assigned and analyzed. More than 1100 distinct frequency lines of the ground state were fitted to produce an accurate set of rotational and centrifugal distortion constants up to the eighth order. The frequency predictions based on these constants should be accurate enough for astrophysical searches in the frequency range up to 500GHz and for transition involving energy levels with J<100 and Ka<42. Based on the results we searched for interstellar carbonyl cyanide in available observational data without success. Thus, we derived upper limits to its column density in different sources.
- ID:
- ivo://CDS.VizieR/J/A+A/591/A75
- Title:
- Millimeter wave spectrum of methyl cyanate
- Short Name:
- J/A+A/591/A75
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The recent discovery of methyl isocyanate (CH_3_NCO) in Sgr B2(N) and Orion KL makes methyl cyanate (CH_3_OCN) a potential molecule in the interstellar medium. The aim of this work is to fulfill the first requirement for its unequivocal identification in space, i.e. the availability of transition frequencies with high accuracy. The room-temperature rotational spectrum of methyl cyanate was recorded in the millimeter wave domain from 130 to 350GHz. All rotational transitions revealed A-E splitting owing to methyl internal rotation and were globally analyzed using the ERHAM program. The data set for the ground torsional state of methyl cyanate exceeds 700 transitions within J"=10-35 and K"a=0-13 and newly derived spectroscopic constants reproduce the spectrum close to the experimental uncertainty. Spectral features of methyl cyanate were then searched for in Orion KL, Sgr B2(N), B1-b, and TMC-1 molecular clouds. Upper limits to the column density of methyl cyanate are provided.
- ID:
- ivo://CDS.VizieR/J/A+A/577/A91
- Title:
- Millimeter wave spectrum of vinyl acetate
- Short Name:
- J/A+A/577/A91
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The recent discovery of methyl acetate in Orion KL makes vinyl acetate, CH3-(C=O)-O-CH=CH2, a potential molecule in the interstellar medium.We obtained very accurate spectroscopic constants in a comprehensive laboratory analysis of its rotational spectra which can be used to predict those transition frequencies towards interstellar sources. We present the experimental study and theoretical analysis of the ground torsional state of vinyl acetate in a large spectral range for astrophysical use. The room-temperature rotational spectrum of vinyl acetate has been measured from 125 to 305GHz to provide direct frequencies to the astronomical community. Additional measurements have also been made using a broadband CP-FTMWspectrometer in the region of 6 - 18 GHz. Transition lines, corresponding to the most stable conformer, have been observed and assigned. All the rotational transitions revealed the A-E splitting due to the methyl internal rotation and had to be treated with a specific internal rotation code (BELGI-Cs). We analyzed 2508 transitions up to J"=75 for vt=0 for the most stable conformer of vinyl acetate. The new lines were globally fitted with previously published data and 24 parameters of the Hamiltonian were accurately determined. The spectral features of vinyl acetate were then searched for in Orion KL. Using the whole line survey of Orion KL (80-280GHz) obtained with the IRAM 30m radio telescope we can provide only an upper limit to the column density of vinyl acetate. However, using the ALMA Science Verification data we obtain a tentative detection of this species that will require further search at other frequencies to confirm its presence in this high mass star forming region.
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