- ID:
- ivo://CDS.VizieR/J/A+A/631/A171
- Title:
- Neutron-capture elements in dwarf galaxies
- Short Name:
- J/A+A/631/A171
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The heavy elements (Z>30) are created in neutron (n)-capture processes which are predicted to happen at vastly different nucleosynthetic sites. To study these processes in an environment different from the Milky Way, we target the n-capture elements in red giant branch stars in the Sculptor dwarf spheroidal galaxy. Using ESO VLT/FLAMES spectra, we measure the chemical abundances of Y, Ba, La, Nd, and Eu, in 98 stars covering the metalliticy range -2.4<[Fe/H]<-0.9. This is the first paper in a series about the n-capture elements in dwarf galaxies, and here we focus on the relative and absolute timescales of the slow (s)- and rapid (r)- processes in Sculptor. From the abundances of the s-process element Ba and the r-process element Eu, it is clear that the r-process enrichment occurred throughout the entire chemical evolution history of Sculptor. Furthermore, there is no evidence for the r-process to have a significant time delay relative to core-collapse supernovae. Neutron star mergers are therefore unlikely the dominant (or only) nucleosynthetic site of the r-process. However, the products of the s-process only become apparent at [Fe/H]~=-2 in Sculptor, and the s-process becomes the dominant source of Ba at [Fe/H]>~-2. We test the use of [Y/Mg] and [Ba/Mg] as chemical clocks in Sculptor. Similarly to what is observed in the Milky Way, [Y/Mg] and [Ba/Mg] increase towards younger ages. However, there is an offset in the trends, where the abundance ratios of [Y/Mg] in Sculptor are significantly lower than those of the Milky Way at any given age. This is most likely caused by metallicity dependence of yields from the s-process, as well as different relative contribution of the s-process to core-collapse supernovae in these galaxies. Comparisons of our data with that of the Milky Way and the Fornax dwarf spheroidal galaxy furthermore show that these chemical clocks are both metallicity and environment dependent.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AZh/81/209
- Title:
- Neutron capture elements in stars: neodymium
- Short Name:
- J/AZh/81/209
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have derived the LTE neodymium abundances in 60 cool stars with [Fe/H] from 0.25 to -1.71 by applying a synthetic-spectrum analysis to spectroscopic observations of NdII lines with a resolution of {lambda}/{Delta}{lambda}~60000 and signal-to noise ratios of 100-200.
- ID:
- ivo://CDS.VizieR/J/A+A/644/A133
- Title:
- New APEX-SEPIA660 observations in OMC-1
- Short Name:
- J/A+A/644/A133
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The star-formation rates and stellar densities found in young massive clusters suggest that these stellar systems originate from gas at densities of n(H_2_)>10^6^cm^-3^. Until today, however, the physical characterization of this ultra high density material remains largely unconstrained in observations. We investigate the density properties of the star-forming gas in the OMC-1 region located in the vicinity of the Orion Nebula Cluster (ONC). Methods. We mapped the molecular emission at 652GHz in OMC-1 as part of the APEX-SEPIA660 Early Science. We detect bright and extended N_2_H^+^ (J=7-6) line emission along the entire OMC-1 region. Comparisons with previous ALMA data of the (J=1-0) transition and radiative transfer models indicate that the line intensities observed in this N_2_H^+^ (7-6) line are produced by large mass reservoirs of gas at densities n(H_2_)>10^7^cm^-3^. The first detection of this N_2_H^+^ (7-6) line at parsec-scales demonstrates the extreme density conditions of the star-forming gas in young massive clusters such as the ONC. Our results highlight the unique combination of sensitivity and mapping capabilities of the new SEPIA660 receiver for the study of the ISM properties at high frequencies.
- ID:
- ivo://CDS.VizieR/J/A+A/585/A64
- Title:
- New atmospheric parameters of MILES cool stars
- Short Name:
- J/A+A/585/A64
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The full spectrum fitting of stellar spectra against a library of empirical spectra is a well-established approach to measure the atmospheric parameters of FGK stars with a high internal consistency. Extending it towards cooler stars still remains a challenge. We address this question by improving the MILES interpolator (Prugniel et al., 2011, Cat. J/A+A/531/A165; hereafter PVK) in the low effective temperature regime (Teff<4800K). We measure the biases of the determined parameters with respect to our updated compilation of parameters. After correcting some systematic effects, we compute a new interpolator that we finally use to redetermine the atmospheric parameters homogeneously and assess the biases. Based on an updated literature compilation, we determine Teff in a more accurate and unbiased manner compared to those determined with the original interpolator. The validity range is extended downwards to about Teff=2900K compared to 3500K previously. The measured parameters are restricted to the current sub sample of MILES, and we have shown that they are generally more reliable than those presented in PVK. But the small discontinuity between the PVK and new measurements is significant, in particular for Teff, and should be corrected if one needs to join the two series.
- ID:
- ivo://CDS.VizieR/J/PASP/124/164
- Title:
- New lithium measurements in metal-poor stars
- Short Name:
- J/PASP/124/164
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We provide {lambda}6708 LiI measurements in 37 metal-poor stars, most of which are poorly studied or have no previous measurements, from high-resolution and high-S/N spectroscopy obtained with the McDonald Observatory 2.1m and 2.7m telescopes.
- ID:
- ivo://CDS.VizieR/J/ApJS/245/32
- Title:
- Newly identified star clusters in Gaia DR2
- Short Name:
- J/ApJS/245/32
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the Star cluster Hunting Pipeline (SHiP) that can identify star clusters in Gaia second data release (DR2) data and establish a star cluster catalog for the Galactic disk. A friend-of-friend-based cluster finder method is used to identify star clusters using five-dimensional stellar parameters, l,b,{omega},{mu}_{alpha}_cos{delta}, and {mu}_{delta}_. Our new catalog contains 2443 star cluster candidates identified from disk stars located within |b|=25{deg} and with G<18mag. An automatic isochrone fitting scheme is applied to all cluster candidates. With a combination of parameters obtained from isochrone fitting, we classify cluster candidates into three classes (Class 1, 2, and 3). Class 1 clusters are the most probable star cluster candidates with the most stringent criteria. Most of these clusters are nearby (within 4kpc). Our catalog is crossmatched with three Galactic star cluster catalogs, Kharchenko+ (2013, J/A+A/558/A53), Cantat-Gaudin+ (2018, J/A+A/618/A93 and 2019, J/A+A/624/A126), and Bica+ (2019, J/AJ/157/12). The proper motion and parallax of matched star clusters are in good agreement with these earlier catalogs. We discover 76 new star cluster candidates that are not listed in these three catalogs. The majority of these are clusters older than log(age/yr)=8.0 and are located in the inner disk with |b|<5{deg}. The recent discovery of new star clusters suggests that current Galactic star cluster catalogs are still incomplete. Among the Class 1 cluster candidates, we find 56 candidates for star cluster groups.
- ID:
- ivo://CDS.VizieR/J/ApJ/900/95
- Title:
- New M87 GCs metallicities from Keck & MMT sp.
- Short Name:
- J/ApJ/900/95
- Date:
- 13 Jan 2022 00:22:24
- Publisher:
- CDS
- Description:
- We present an extensive study of spectroscopically derived chemical abundances for M87 and its globular cluster (GC) system. Using observations from the Mitchell spectrograph at McDonald, LRIS at Keck, and Hectospec on the MMT, we derive new metallicity gradients from ~2 to 140kpc. We use a novel hierarchical statistical framework to simultaneously separate the GC system into subpopulations while measuring the metallicity gradients of those subpopulations. We create physically motivated spectral stacks of the GC subpopulations by leveraging the output of this statistical framework to perform the first application of abundance tagging in a massive early-type galaxy to better constrain the origins of the GC subpopulations and thus the assembly history of M87. We find a metal-poor, {alpha}-enhanced population of GCs in both the inner and outer halos unanticipated by current cosmological simulations of galaxy evolution. We use the remarkably flat metallicity gradients we find for both the metal-rich and metal-poor GC subpopulations in the inner halo as tentative evidence that some amount of the metal-poor GCs formed directly in the halo of M87 at high redshift.
- ID:
- ivo://CDS.VizieR/J/A+A/623/A129
- Title:
- New satellites of the LMC search
- Short Name:
- J/A+A/623/A129
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A wealth of tiny galactic systems populates the surroundings of the Milky Way. However, some of these objects might have originated as former satellites of the Magellanic Clouds, in particular of the Large Magellanic Cloud (LMC). Examples of the importance of understanding how many systems are genuine satellites of the Milky Way or the LMC are the implications that the number and luminosity-mass function of satellites around hosts of different mass have for dark matter theories and the treatment of baryonic physics in simulations of structure formation. Here we aim at deriving the bulk motions and estimates of the internal velocity dispersion and metallicity properties in four recently discovered distant southern dwarf galaxy candidates, Columba I, Reticulum III, Phoenix II, and Horologium II. We combined Gaia DR2 astrometric measurements, photometry, and new FLAMES/GIRAFFE intermediate-resolution spectroscopic data in the region of the near-IR CaII triplet lines; this combination is essential for finding potential member stars in these low-luminosity systems. We find very likely member stars in all four satellites and are able to determine (or place limits on) the bulk motions and average internal properties of the systems. The systems are found to be very metal poor, in agreement with dwarf galaxies and dwarf galaxy candidates of similar luminosity. Of these four objects, we can only firmly place Phoenix II in the category of dwarf galaxies because of its resolved high velocity dispersion (9.5^+6.8^_-4.4_km/s) and intrinsic metallicity spread (0.33dex). For Columba I we also measure a clear metallicity spread. The orbital pole of Phoenix II is well constrained and close to that of the LMC, suggesting a prior association. The uncertainty on the orbital poles of the other systems is currently very large, so that an association cannot be excluded, except for Columba I. Using the numbers of potential former satellites of the LMC identified here and in the literature, we obtain for the LMC a dark matter mass of M_200_=1.9^+1.3^_-0.9_x10^11^M_{sun}_
- ID:
- ivo://CDS.VizieR/J/AJ/154/57
- Title:
- New SDSS and Washington photometry in Segue 3
- Short Name:
- J/AJ/154/57
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new SDSS and Washington photometry of the young outer-halo stellar system Segue 3. Combined with archival VI-observations, our most consistent results yield Z=0.006+/-0.001, log(Age)=9.42+/-0.08, (m-M)_0_=17.35+/-0.08, and E(B-V)=0.09+/-0.01, with a high binary fraction of 0.39+/-0.05 derived using the Padova models. We confirm that mass-segregation has occurred, supporting the hypothesis that this cluster is being tidally disrupted. A three-parameter King model yields a cluster radius of r_cl_=0.017{deg}+/-0.007{deg}, a core radius of r_c_=0.003{deg}+/-0.001{deg}, and a tidal radius of r_t_=0.04{deg}+/-0.02{deg}. A comparison of Padova and Dartmouth model-grids indicates that the cluster is not significantly {alpha}-enhanced, with a mean [Fe/H]=-0.55_-0.12_^+0.15^dex, and a population age of only 2.6+/-0.4Gyr. We rule out a statistically significant age spread at the main-sequence turnoff because of a narrow subgiant branch, and discuss the role of stellar rotation and cluster age, using Dartmouth and Geneva models: approximately 70% of the Seg 3 stars at or below the main-sequence turnoff have enhanced rotation. Our results for Segue 3 indicate that it is younger and more metal-rich than all previous studies have reported to date. From colors involving Washington C and SDSS-u filters, we identify several giants and a possible blue straggler for future follow-up spectroscopic studies, and we produce spectral energy distributions of previously known members and potential Segue 3 sources with Washington (CT_1_), Sloan (ugri), and VI-filters. Segue 3 shares the characteristics of unusual stellar systems that have likely been stripped from external dwarf galaxies as they are being accreted by the Milky Way, or that have been formed during such an event. Its youth, metallicity, and location are all inconsistent with Segue 3 being a cluster native to the Milky Way.
- ID:
- ivo://CDS.VizieR/J/AJ/158/38
- Title:
- New substellar discoveries from Kepler and K2
- Short Name:
- J/AJ/158/38
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the discoveries of a brown dwarf (BD) and a low-mass star from the Kepler and K2 missions. The newly discovered BD is EPIC 212036875b and the low-mass star is KOI-607b. EPIC 212036875b has a mass of M_b_=52.3+/-1.9 M_J_, a radius of R_b_=0.874+/-0.017 R_J_, and orbits its host star in P=5.169885+/-0.000027 days. Its host star is a late F-type star with M_*_=1.288+/-0.065 M_{sun}_, R_*_= 1.498+/-0.025 R_{sun}_, and T_eff_=6238+/-60 K. KOI-607b has a mass of M_b_=95.1+/-3.4 M_J_, a radius of R_b_=1.089+/-0.089 R_J_, and an orbital period of P=5.89399148+/-0.00000060 days. The primary star in the KOI-607 system is a G dwarf with M_*_=0.993+/-0.052 M_{sun}_, R_*_= 0.915+/-0.031 R_{sun}_, and T_eff_=5418+/-87 K. We also revisit a BD, CWW 89Ab, that was previously published by Nowak et al. 2017AJ....153..131N (under the designation EPIC 219388192b). CWW 89Ab is one of two known transiting BDs associated with a star cluster, which illustrates the need for more BDs with accurate masses, radii, and reliable age determinations to test theoretical models. We find that the newly discovered BD, EPIC 212036875b, falls in the middle of the so-called BD desert, indicating that EPIC 212036875b is either a particularly rare object, or the BD desert may not be so dry after all.
