- ID:
- ivo://CDS.VizieR/J/MNRAS/456/3655
- Title:
- Masses and ages of red giants
- Short Name:
- J/MNRAS/456/3655
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We show that the masses of red giant stars can be well predicted from their photospheric carbon and nitrogen abundances, in conjunction with their spectroscopic stellar labels logg, Teff, and [Fe/H]. This is qualitatively expected from mass-dependent post-main-sequence evolution. We here establish an empirical relation between these quantities by drawing on 1475 red giants with asteroseismic mass estimates from Kepler that also have spectroscopic labels from Apache Point Observatory Galactic Evolution Experiment (APOGEE) DR12. We assess the accuracy of our model, and find that it predicts stellar masses with fractional rms errors of about 14 percent (typically 0.2M_{sun}_). From these masses, we derive ages with rms errors of 40 percent. This empirical model allows us for the first time to make age determinations (in the range 1-13Gyr) for vast numbers of giant stars across the Galaxy. We apply our model to ~52000 stars in APOGEE DR12, for which no direct mass and age information was previously available. We find that these estimates highlight the vertical age structure of the Milky Way disc, and that the relation of age with [{alpha}/M] and metallicity is broadly consistent with established expectations based on detailed studies of the solar neighbourhood.
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Search Results
- ID:
- ivo://CDS.VizieR/V/19
- Title:
- Masses and Ages of Stars in 68 Open Clusters
- Short Name:
- V/19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalog contains the evolutionary masses and ages of about 7000 stars in 68 open clusters, as derived from their positions in the theoretical HR diagram. Cluster ages range from 10^6^ to some 10^9^ years, and their population varies from 30 to 700 members. For each cluster we have a table with ages and masses of stars. The file, clusters.dat may include for each cluster, the name (or NGC/IC number), cluster class, assumed color index E(B-V), true distance modulus (V-M_V)_0, evolutionary tracks used for given cluster and reference to the source of UBV data. The data in data.dat consists of star serial number, color index, V magnitude, luminosity, effective temperature, and ages and masses of stars.
- ID:
- ivo://CDS.VizieR/J/AJ/150/95
- Title:
- Masses and ages of YSOs in Per OB2
- Short Name:
- J/AJ/150/95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have performed a Wide-Field Infrared Survey Explorer based study to identify and characterize young stellar objects (YSOs) in the 12{deg}x12{deg} Perseus OB2 association. A spectral energy distribution (SED) slope in the range of 3.4-12{mu}m and 5{sigma} selection criteria were used to select our initial sample. Further manual inspection reduced our final catalog to 156 known and 119 YSO candidates. The spatial distribution of newly found YSOs all over the field shows an older generation of star formation in which most of its massive members have evolved into main-sequence stars. In contrast, the majority of younger members lie within the Perseus molecular cloud and currently active star-forming clusters such as NGC 1333 and IC 348. We also identified an additional 66 point sources that passed YSO selection criteria but are likely AGB stars. However, their spatial distribution suggests that they may contain a fraction of the YSOs. Comparing our results with the commonly used color-color selections, we found that while the color selection method fails in picking up bright but evolved weak disks, our SED fitting method can identify such sources, including transitional disks. In addition, we have less contamination with background sources such as galaxies, but at a price of losing fainter (J_mag_>12) YSOs. Finally, we employed a Bayesian Monte Carlo SED fitting method to determine the characteristics of each YSO candidate. Distribution of SED slopes and model-driven age and mass confirms separated YSO populations with three suggested age groups of younger than 1Myr old, 1-5Myr old, and older than 5Myr, which agrees with the age of the Per OB2 association and currently star-forming sites within the cloud.
- ID:
- ivo://CDS.VizieR/J/MNRAS/457/3743
- Title:
- 104 massive quiescent galaxies SFHs
- Short Name:
- J/MNRAS/457/3743
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present star formation histories (SFHs) for a sample of 104 massive (stellar mass M>10^10^M_{sun}_) quiescent galaxies (MQGs) at z=1.0-1.5 from the analysis of spectrophotometric data from the Survey for High-z Absorption Red and Dead Sources (SHARDS) and HST/WFC3 G102 and G141 surveys of the GOODS-North field, jointly with broad-band observations from ultraviolet (UV) to far-infrared (far-IR). The sample is constructed on the basis of rest-frame UVJ colours and specific star formation rates (sSFRs=SFR/Mass). The spectral energy distributions (SEDs) of each galaxy are compared to models assuming a delayed exponentially declining SFH. A Monte Carlo algorithm characterizes the degeneracies, which we are able to break taking advantage of the SHARDS data resolution, by measuring indices such as MgUV and D4000. The population of MQGs shows a duality in their properties. The sample is dominated (85 per cent) by galaxies with young mass-weighted ages, <t_M_><2Gyr, short star formation time-scales, <{tau}>~60-200MYr, and masses log(M/M_{sun}_)~10.5. There is an older population (15 per cent) with <t_M_>=2-4Gyr, longer star formation time-scales, <{tau}>~400Myr, and larger masses, log(M/M_{sun}_)~10.7. The SFHs of our MQGs are consistent with the slope and the location of the main sequence of star-forming galaxies at z>1.0, when our galaxies were 0.5-1.0Gyr old. According to these SFHs, all the MQGs experienced a luminous infrared galaxy phase that lasts for ~500Myr, and half of them an ultraluminous infrared galaxy phase for ~100Myr. We find that the MQG population is almost assembled at z~1, and continues evolving passively with few additions to the population.
- ID:
- ivo://CDS.VizieR/J/other/Sci/359.69
- Title:
- Massive stars in 30 Dor
- Short Name:
- J/other/Sci/359.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The 30 Doradus star-forming region in the Large Magellanic Cloud is a nearby analog of large star-formation events in the distant universe. We determined the recent formation history and the initial mass function (IMF) of massive stars in 30 Doradus on the basis of spectroscopic observations of 247 stars more massive than 15 solar masses (M_{sun}_). The main episode of massive star formation began about 8 million years (My) ago, and the star-formation rate seems to have declined in the last 1My. The IMF is densely sampled up to 200 Embedded Image and contains 32+/-12% more stars above 30M_{sun}_ than predicted by a standard Salpeter IMF. In the mass range of 15 to 200M_{sun}_, the IMF power-law exponent is 190^+0.37^_-0.26_, shallower than the Salpeter value of 2.35.
- ID:
- ivo://CDS.VizieR/J/A+A/640/A40
- Title:
- 1002 mCP stars from LAMOST DR4
- Short Name:
- J/A+A/640/A40
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The present work is aimed at identifying new mCP stars using spectra collected by the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST). Suitable candidates were selected by searching LAMOST DR4 spectra for the presence of the characteristic 5200{AA} flux depression. Spectral classification was carried out with a modified version of the MKCLASS code and the accuracy of the classifications was estimated by comparison with results from manual classification and the literature. Using parallax data and photometry from Gaia DR2, we investigated the space distribution of our sample stars and their properties in the colour-magnitude diagram. Our final sample consists of 1002 mCP stars, most of which are new discoveries (only 59 common entries with the Catalogue of Ap, HgMn and Am stars). Traditional mCP star peculiarities have been identified in all but 36 stars, highlighting the efficiency of the code's peculiarity identification capabilities. The derived temperature and peculiarity types are in agreement with manually derived classifications and the literature. Our sample stars are between 100Myr and 1Gyr old, with the majority having masses between 2M_{sun}_ and 3M_{sun}_. Our results could be considered as strong evidence for an inhomogeneous age distribution among low-mass (M<3M_{sun}_) mCP stars; however, we caution that our sample has not been selected on the basis of an unbiased, direct detection of a magnetic field. We identified several astrophysically interesting objects: the mCP stars LAMOST J122746.05+113635.3 and LAMOST J150331.87+093125.4 have distances and kinematical properties in agreement with halo stars; LAMOST J034306.74+495240.7 is an eclipsing binary system (Porb=5.1435+/-0.0012d) hosting an mCP star component; and LAMOST J050146.85+383500.8 was found to be an SB2 system likely comprising of an mCP star and a supergiant component. With our work, we significantly increase the sample size of known Galactic mCP stars, paving the way for future in-depth statistical studies.
- ID:
- ivo://CDS.VizieR/J/MNRAS/435/1325
- Title:
- Membership of the {epsilon} Cha association
- Short Name:
- J/MNRAS/435/1325
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a comprehensive investigation of the {epsilon} Chamaeleontis association, one of several young moving groups spread across the southern sky. We re-assess the putative membership of {epsilon} Cha using the best available proper motion and spectroscopic measurements, including new ANU 2.3-m/Wide Field Spectrograph observations. After applying a kinematic analysis, our final membership comprises 35-41 stars from B9 to mid-M spectral types. Theoretical evolutionary models suggest {epsilon} Cha is 3-5Myr old, distinguishing it as the youngest moving group in the solar neighbourhood. 15 members show 3-22um spectral energy distributions attributable to circumstellar discs, including 11 stars which appear to be actively accreting. {epsilon} Cha's disc and accretion fractions are both consistent with a typical 3-5Myr old population. Multi-epoch spectroscopy reveals three M-type members with broad and highly variable Ha emission as well as several new spectroscopic binaries. We reject 11 stars proposed as members in the literature and suggest they may belong to the background Cha I and II clouds or other nearby young groups. Our analysis underscores the importance of a holistic and conservative approach to assigning young stars to kinematic groups, many of which have only subtly different properties and ill-defined memberships. We conclude with a brief discussion of {epsilon} Cha's connection to the young open cluster eta Cha and the Scorpius- Centaurus OB association. Contrary to earlier studies which assumed eta and {epsilon} Cha are coeval and were born in the same location, we find the groups were separated by ~30pc when eta Cha formed 4-8Myr ago in the outskirts of Sco-Cen, 1-3Myr before the majority of {epsilon} Cha members.
- ID:
- ivo://CDS.VizieR/J/AJ/159/166
- Title:
- Membership & properties of moving groups with Gaia
- Short Name:
- J/AJ/159/166
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze the membership probability of young stars belonging to nearby moving groups with Gaia DR2 data. The sample of 1429 stars was identified from "The Catalog of Suspected Nearby Young Moving Group Stars" (CSNYMGS; see Riedel+, J/AJ/153/95). Good-quality parallax and proper motion values were retrieved for 890 stars from the Gaia DR2 database. The analysis for membership probability is performed in the framework of the LACEwING algorithm (Riedel 2016IAUS..314...33R). From the analysis it is confirmed that 279 stars do not belong to any of the known moving groups. We estimated the U, V, W space velocity values for 250 moving group members, which were found to be more accurate than previous values listed in the literature. The velocity ellipses of all the moving groups are well constrained within the "good box," a widely used criterion to identify moving group members. The age of moving group members are uniformly estimated from the analysis of the Gaia color-magnitude diagram with MIST isochrones. We found a spread in the age distribution of stars belonging to some moving groups, which needs to be understood from further studies.
- ID:
- ivo://CDS.VizieR/J/MNRAS/493/5195
- Title:
- Milky Way halo stars ages and kinematics
- Short Name:
- J/MNRAS/493/5195
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We exploit the [Mg/Mn]-[Al/Fe] chemical abundance plane to help identify nearby halo stars in the 14th data release from the APOGEE survey that have been accreted on to the Milky Way. Applying a Gaussian Mixture Model, we find a 'blob' of 856 likely accreted stars, with a low disc contamination rate of about 7 percent. Cross-matching the sample with the second data release from Gaia gives us access to parallaxes and apparent magnitudes, which place constraints on distances and intrinsic luminosities. Using a Bayesian isochrone pipeline, this enables us to estimate new ages for the accreted stars, with typical uncertainties of 20 percent. Our new catalogue is further supplemented with estimates of orbital parameters. The blob stars span a metallicities between -0.5 to -2.5, and [Mg/Fe] between -0.1 to 0.5. They constitute 30 percent of the metal-poor ([Fe/H]<-0.8) halo at metallicities of -1.4. Our new ages are mainly range between 8 to 13Gyr, with the oldest stars the metal-poorest, and with the highest [Mg/Fe] abundance. If the blob stars are assumed to belong to a single progenitor, the ages imply that the system merged with our Milky Way around 8 Gyr ago and that star formation proceeded for 5Gyr. Dynamical arguments suggest that such a single progenitor would have a total mass of 10^11^M_{sun}_, similar to that found by other authors using chemical evolution models and simulations. Comparing the scatter in the [Mg/Fe]-[Fe/H] plane of the blob stars to that measured for stars belonging to the Large Magellanic Cloud suggests that the blob does indeed contain stars from only one progenitor.
- ID:
- ivo://CDS.VizieR/J/ApJ/810/158
- Title:
- M,L,T dwarfs fundamental parameters and SEDs
- Short Name:
- J/ApJ/810/158
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We combine optical, near-infrared, and mid-infrared spectra and photometry to construct expanded spectral energy distributions for 145 field age (>500 Myr) and 53 young (lower age estimate <500 Myr) ultracool dwarfs (M6-T9). This range of spectral types includes very low mass stars, brown dwarfs, and planetary mass objects, providing fundamental parameters across both the hydrogen and deuterium burning minimum masses for the largest sample assembled to date. A subsample of 29 objects have well constrained ages as probable members of a nearby young moving group. We use 182 parallaxes and 16 kinematic distances to determine precise bolometric luminosities (L_bol_) and radius estimates from evolutionary models give semi-empirical effective temperatures (T_eff_) for the full range of young and field age late-M, L, and T dwarfs. We construct age-sensitive relationships of luminosity, temperature, and absolute magnitude as functions of spectral type and absolute magnitude to disentangle the effects of degenerate physical parameters such as T_eff_, surface gravity, and clouds on spectral morphology. We report bolometric corrections in J for both field age and young objects and find differences of up to a magnitude for late-L dwarfs. Our correction in Ks shows a larger dispersion but not necessarily a different relationship for young and field age sequences. We also characterize the NIR-MIR reddening of low gravity L dwarfs and identify a systematically cooler T_eff_ of up to 300 K from field age objects of the same spectral type and 400 K cooler from field age objects of the same M_H_ magnitude.
