- ID:
- ivo://CDS.VizieR/J/MNRAS/448/1314
- Title:
- Line list for seven target PAndAS clusters
- Short Name:
- J/MNRAS/448/1314
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Detailed chemical abundances are presented for seven M31 outer halo globular clusters (with projected distances from M31 greater than 30 kpc), as derived from high-resolution integrated light spectra taken with the Hobby-Eberly Telescope. Five of these clusters were recently discovered in the Pan-Andromeda Archaeological Survey (PAndAS) - this paper presents the first determinations of integrated Fe, Na, Mg, Ca, Ti, Ni, Ba, and Eu abundances for these clusters. Four of the target clusters (PA06, PA53, PA54, and PA56) are metal poor ([Fe/H]< -1.5), {alpha}-enhanced (though they are possibly less {alpha}-enhanced than Milky Way stars at the 1{sigma} level), and show signs of star-to-star Na and Mg variations. The other three globular clusters (H10, H23, and PA17) are more metal rich, with metallicities ranging from [Fe/H]=-1.4 to -0.9. While H23 is chemically similar to Milky Way field stars, Milky Way globular clusters, and other M31 clusters, H10 and PA17, have moderately low [Ca/Fe], compared to Milky Way field stars and clusters. Additionally, PA17's high [Mg/Ca] and [Ba/Eu] ratios are distinct from Milky Way stars, and are in better agreement with the stars and clusters in the Large Magellanic Cloud. None of the clusters studied here can be conclusively linked to any of the identified streams from PAndAS; however, based on their locations, kinematics, metallicities, and detailed abundances, the most metal-rich PAndAS clusters H23 and PA17 may be associated with the progenitor of the Giant Stellar Stream, H10 may be associated with the SW cloud, and PA53 and PA56 may be associated with the eastern cloud.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/446/3319
- Title:
- Line list for the NGC 1851 stars
- Short Name:
- J/MNRAS/446/3319
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We measure the C+N+O abundance sum in red giant stars in two Galactic globular clusters, NGC 1851 and NGC 6752. NGC 1851 has a split subgiant branch which could be due to different ages or C+N+O content while NGC 6752 is representative of the least complex globular clusters. For NGC 1851 and NGC 6752, we obtain average values of A(C+N+O)=8.16+/-0.10 ({sigma}=0.34) and 7.62+/-0.02 ({sigma}=0.06), respectively. When taking into account the measurement errors, we find a constant C+N+O abundance sum in NGC 6752. The C+N+O abundance dispersion is only 0.06 dex, and such a result requires that the source of the light element abundance variations does not increase the C+N+O sum in this cluster. For NGC 1851, we confirm a large spread in C+N+O. In this cluster, the anomalous RGB has a higher C+N+O content than the canonical RGB by a factor of 4 (~0.6 dex). This result lends further support to the idea that the two subgiant branches in NGC 1851 are roughly coeval, but with different CNO abundances.
- ID:
- ivo://CDS.VizieR/J/A+A/632/A55
- Title:
- Line list from Pal 13 sample stars
- Short Name:
- J/A+A/632/A55
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- At a Galactocentric distance of 27kpc, Palomar 13 is an old globular cluster (GC) belonging to the outer halo. We present a chemical abundance analysis of this remote system from high-resolution spectra obtained with the Keck/HIRES spectrograph. Owing to the low signal-to-noise ratio of the data, our analysis is based on a coaddition of the spectra of 18 member stars. We are able to determine integrated abundance ratios for 16 species of 14 elements, of {alpha}-elements (Mg, Si, Ca, and Ti), Fe-peak (Sc, Mn, Cr, Ni, Cu, and Zn), and neutron-capture elements (Y and Ba). While the mean Na abundance is found to be slightly enhanced and halo-like, our method does not allow us to probe an abundance spread that would be expected in this light element if multiple populations are present in Pal 13. We find a metal-poor mean metallicity of -1.91+/-0.05 (statistical) +/-0.22 (systematic), confirming that Pal 13 is a typical metal-poor representative of the outer halo. While there are some differences between individual {alpha}-elements, such as halo-like Mg and Si versus the mildly lower Ca and Ti abundances, the mean [{alpha}/Fe] of 0.34+/-0.06 is consistent with the marginally lower {alpha} component of the halo field and GC stars at similar metallicity. We discuss our results in the context of other objects in the outer halo and consider which of these objects were likely accreted. We also discuss the properties of their progenitors. While chemically, Pal 13 is similar to Gaia-Enceladus and some of its GCs, this is not supported by its kinematic properties within the Milky Way system. Moreover, its chemodynamical similarity with NGC 5466, a purported progeny of the Sequoia accretion event, might indicate a common origin in this progenitor. However, the ambiguities in the full abundance space of this comparison emphasize the difficulties in unequivocally labeling a single GC as an accreted object, let alone assigning it to a single progenitor.
- ID:
- ivo://CDS.VizieR/J/A+A/587/A6
- Title:
- Linelist of 14 Galactic post-AGB stars
- Short Name:
- J/A+A/587/A6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper is part of a larger project in which we systematically study the chemical abundances of Galactic and extragalactic post-asymptotic giant branch (post-AGB) stars. The goal at large is to provide improved observational constraints to the models of the complex interplay between the AGB s-process nucleosynthesis and the associated mixing processes. Aims. Lead (Pb) is the final product of the s-process nucleosynthesis and is predicted to have large overabundances with respect to other s-process elements in AGB stars of low metallicities. However, Pb abundance studies of s-process enriched post-AGB stars in the Magellanic Clouds show a discrepancy between observed and predicted Pb abundances. The determined upper limits based on spectral studies are much lower than what is predicted. In this paper, we focus specifically on the Pb abundance of 14 Galactic s-process enhanced post-AGB stars to check whether the same discrepancy is present in the Galaxy as well. Among these 14 objects, two were not yet subject to a detailed abundance study in the literature. We apply the same method to obtain accurate abundances for the 12 others. Our homogeneous abundance results provide the input of detailed spectral synthesis computations in the spectral regions where Pb lines are located. We used high-resolution UVES and HERMES spectra for detailed spectral abundance studies of our sample of Galactic post-AGB stars. None of the sample stars display clear Pb lines, and we only deduced upper limits of the Pb abundance by using spectrum synthesis in the spectral ranges of the strongest Pb lines.
- ID:
- ivo://CDS.VizieR/J/ApJ/812/146
- Title:
- Line-of-sight velocities from bar simulations
- Short Name:
- J/ApJ/812/146
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We extract the resonant orbits from an N-body bar that is a good representation of the Milky Way, using the method recently introduced by Molloy et al. (2015ApJ...804...80M). By decomposing the bar into its constituent orbit families, we show that they are intimately connected to the boxy-peanut shape of the density. We highlight the imprint due solely to resonant orbits on the kinematic landscape toward the Galactic center. The resonant orbits are shown to have distinct kinematic features and may be used to explain the cold velocity peak seen in the Apache Point Observatory Galactic Evolution Experiment commissioning data. We show that high velocity peaks are a natural consequence of the motions of stars in the 2:1 orbit family and that stars on other higher order resonances can contribute to the peaks. The locations of the peaks vary with bar angle and, with the tacit assumption that the observed peaks are due to the 2:1 family, we find that the locations of the high velocity peaks correspond to bar angles in the range 10{deg}<~{theta}_bar_<~25{deg}. However, some important questions about the nature of the peaks remain, such as their apparent absence in other surveys of the Bulge and the deviations from symmetry between equivalent fields in the north and south. We show that the absence of a peak in surveys at higher latitudes is likely due to the combination of a less prominent peak and a lower number density of bar supporting orbits at these latitudes.
- ID:
- ivo://CDS.VizieR/J/ApJ/691/1862
- Title:
- Line-strength indices for 74 early-type galaxies
- Short Name:
- J/ApJ/691/1862
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present line-strength measurements for 74 early-type galaxies in the core of the Coma cluster reaching down to velocity dispersions, {sigma}, of 30km/s. The index-{sigma} relations for our sample, including galaxies with {sigma}<100km/s (low-{sigma}), differ in shape depending on which index is used. We note two types of relations for the metallic indices: one showing a break in the slope around ~100km/s and another group with strong linear relations between an index and log {sigma}. We find no connection between the behavior of index-{sigma} relations with either {alpha}- or Fe-peak elements. However, we find indications that the relations are tighter for indices which do not depend on the microturbulent velocities of stellar atmospheres.
- ID:
- ivo://CDS.VizieR/J/A+A/395/431
- Title:
- Line-strength indices for 148 early-type galaxies
- Short Name:
- J/A+A/395/431
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have derived high quality line-strength indices and velocity dispersions for a sample of 148 early-type galaxies in different environments. The wavelength region covered by the observations (lambda~4600 to 6600{AA}) includes the Lick/IDS indices Hbeta, Mg_1_, Mg_2_, Mgb, Fe5015, Fe5270, Fe5335, Fe5406, Fe5709, Fe5782, NaD, TiO_1_ and TiO_2_. The data are intended to address possible differences of the stellar populations of early-type galaxies in low- and high-density environments. This paper describes the sample properties, explains the data reduction and presents the complete list of all the measurements. Most galaxies of the sample (85%) had no previous measurements of any Lick/IDS indices and for 30% of the galaxies we present first-time determinations of their velocity dispersions. Special care is taken to identify galaxies with emission lines. We found that 62 per cent of the galaxies in the sample have emission lines, as measured by the equivalent width of the [0III]5007{AA} line, EW[OIII]~>~0.3{AA}.
- ID:
- ivo://CDS.VizieR/J/AJ/135/2424
- Title:
- Line strengths of early-type galaxies
- Short Name:
- J/AJ/135/2424
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we present measurements of velocity dispersions and Lick indices for 509 galaxies in the local universe, based on high signal-to-noise, long-slit spectra obtained with the 1.52m ESO telescope at La Silla.
- ID:
- ivo://CDS.VizieR/J/A+A/657/A70
- Title:
- Linking high- and low-mass star formation
- Short Name:
- J/A+A/657/A70
- Date:
- 21 Mar 2022 09:28:51
- Publisher:
- CDS
- Description:
- Astronomers have yet to establish whether high-mass protostars form from high-mass prestellar cores, similar to their lower-mass counterparts, or from lower-mass fragments at the heart of a pre-protostellar cluster undergoing large-scale collapse. Part of the uncertainty is due to a shortage of envelope structure data on protostars of a few tens of solar masses, where we expect to see a transition from intermediate-mass star formation to the high-mass process. We sought to derive the masses, luminosities, and envelope density profiles for eight sources in Cygnus-X, whose mass estimates in the literature placed them in the sampling gap. Combining these sources with similarly evolved sources in the literature enabled us to perform a meta-analysis of protostellar envelope parameters over six decades in source luminosity. We performed spectral energy distribution (SED) fitting on archival broadband photometric continuum data from 1.2 to 850 microns, to derive bolometric luminosities for our eight sources plus initial mass and radius estimates for modelling density and temperature profiles with the radiative transfer package Transphere. The envelope masses, densities at 1000AU, outer envelope radii, and density power law indices as functions of bolometric luminosity all follow established trends in the literature spanning six decades in luminosity. Most of our sources occupy an intermediate to moderately high range of masses and luminosities, which helps more firmly establish the continuity between low- and high-mass star formation mechanisms. Our density power law indices are consistent with observed values in literature, which show no discernible trends with luminosity. Finally, we show that the trends in all of the envelope parameters for high-mass protostars are statistically indistinguishable from trends in the same variables for low- and intermediate-mass protostars.
- ID:
- ivo://CDS.VizieR/J/A+A/643/A48
- Title:
- Linking ice and gas. Serpens SVS4
- Short Name:
- J/A+A/643/A48
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The interaction between dust, ice, and gas during the formation of stars produces complex organic molecules. While observations indicate that several species are formed on ice-covered dust grains and are released into the gas phase, the exact chemical interplay between solid and gas phases and their relative importance remain unclear. Our goal is to study the interplay between dust, ice, and gas in regions of low-mass star formation through ice- and gas- mapping and by directly measuring gas-to-ice ratios. This provides constraints on the routes that lead to the chemical complexity that is observed in solid and gas phases. We present observations of gas-phase methanol (CH_3_OH) and carbon monoxide (^13^CO and C^18^O) at 1.3mm towards ten low-mass young protostars in the Serpens SVS4 cluster from the SubMillimeter Array (SMA) and the Atacama Pathfinder EXperiment (APEX) telescope. We used archival data from the Very Large Telescope (VLT) to derive abundances of ice H_2_O, CO, and CH_3_OH towards the same region. Finally, we constructed gas-ice maps of SVS4 and directly measured CO and CH_3_OH gas-to-ice ratios. The SVS4 cluster is characterised by a global temperature of 15+/-5K. At this temperature, the chemical behaviours of CH_3_OH and CO are anti-correlated: larger variations are observed for CH_3_OH gas than for CH_3_OH ice, whereas the opposite is seen for CO. The gas-to-ice ratios (N_gas_/N_ice_) range from 1-6 for CO and 1.4x10^-4^-3.7x10^-3^for CH_3_OH. The CO gas-maps trace an extended gaseous component that is not sensitive to the effect of freeze-out. Because of temperature variations and dust heating around 20K, the frozen CO is efficiently desorbed. The CH_3_OH gas-maps, in contrast, probe regions where methanol is predominantly formed and present in ices and is released into the gas phase through non-thermal desorption mechanisms. Combining gas- and ice-mapping techniques, we measure gas-to-ice ratios of CO and CH_3_OH in the SVS4 cluster. The CH_3_OH gas-to-ice ratio agrees with values that were previously reported for embedded Class 0/I low-mass protostars. We find that there is no straightforward correlation between CO and CH_3_OH gas with their ice counterparts in the cluster. This is likely related to the complex morphology of SVS4: the Class 0 protostar SMM4 and its envelope lie in the vicinity, and the outflow associated with SMM4 intersects the cluster. This study serves as a pathfinder for future observations with ALMA and the James Webb Space Telescope (JWST) that will provide high-sensitivity gas-ice maps of molecules more complex than methanol. Such comparative maps will be essential to constrain the chemical routes that regulate the chemical complexity in star-forming regions.