- ID:
- ivo://CDS.VizieR/J/ApJ/751/122
- Title:
- Ages and masses for 920 LMC clusters
- Short Name:
- J/ApJ/751/122
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new age and mass estimates for 920 stellar clusters in the Large Magellanic Cloud (LMC) based on previously published broadband photometry and the stellar cluster analysis package, MASSCLEANage. Expressed in the generic fitting formula, d^2^N/dMdt{prop.to}M^{alpha}^t^{beta}^, the distribution of observed clusters is described by {alpha}=-1.5 to -1.6 and {beta}=-2.1 to -2.2. For 288 of these clusters, ages have recently been determined based on stellar photometric color-magnitude diagrams, allowing us to gauge the confidence of our ages. The results look very promising, opening up the possibility that this sample of 920 clusters, with reliable and consistent age, mass, and photometric measures, might be used to constrain important characteristics about the stellar cluster population in the LMC. We also investigate a traditional age determination method that uses a {chi}^2^ minimization routine to fit observed cluster colors to standard infinite-mass limit simple stellar population models. This reveals serious defects in the derived cluster age distribution using this method. The traditional {chi}^2^ minimization method, due to the variation of U, B, V, R colors, will always produce an overdensity of younger and older clusters, with an underdensity of clusters in the log(age/yr)=[7.0,7.5] range. Finally, we present a unique simulation aimed at illustrating and constraining the fading limit in observed cluster distributions that includes the complex effects of stochastic variations in the observed properties of stellar clusters.
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- ID:
- ivo://CDS.VizieR/J/AN/319/201
- Title:
- Alpha Per cluster low-mass members. I.
- Short Name:
- J/AN/319/201
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Following the work of Randich et al. (1996A&A...305..785R) involving a ROSAT raster scan survey of the {alpha} Persei open cluster, we present here the results of a photometric/spectroscopic program examining the possible optical counterparts to a group of 73 X-ray sources in the raster survey which were not matched to catalogued stars. Of the 73 sources investigated, ~40 have an optical counterpart with photometry acceptable for cluster membership and ~20 of these also have radial velocities consistent with membership. We discuss the X-ray properties of these potential new members and why they may not have been identified in earlier membership surveys of this cluster.
- ID:
- ivo://CDS.VizieR/J/AN/319/215
- Title:
- Alpha Per cluster low-mass members. II.
- Short Name:
- J/AN/319/215
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The present investigation examines possible optical counterparts to 130 X-ray sources in the region of the alpha Persei open cluster (d~170pc, age~50Myr) resulting from the analysis of three 22-25ksec ROSAT PSPC pointings. In the same manner as for 73 X-ray sources from a raster survey in alpha Per (Prosser & Randich, 1998, Cat. <J/AN/319/201>), CCD photometry is employed to obtain magnitudes and colors for stars/objects close to the X-ray positions, with additional echelle and low-dispersion Halpha spectra provided for some stars. For almost 60 X-ray sources, an optical counterpart with photometry acceptable for cluster membership is identified, some of which can be excluded from membership on the basis of discrepant radial velocity or X-ray characteristics. On the order of 30 new members or likely members associated with X-ray sources have been identified based on available data. A photometric rotation period has been obtained for one rapid rotator identified in X-rays.
- ID:
- ivo://CDS.VizieR/J/MNRAS/457/1028
- Title:
- alpha Per cluster possible members
- Short Name:
- J/MNRAS/457/1028
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained membership probabilities of stars within a field of from the centre of the open cluster alpha Persei using proper motions and photometry from the PPMXL and Wide-field Infrared Survey Explorer catalogues. We have identified 810 possible stellar members of alpha Persei. We derived the global and radial present-day mass function (MF) of the cluster and found that they are well matched by two-stage power-law relations with different slopes at different radii. The global MF of alpha Persei shows a turnover at m=0.62M_{sun}_ with low- and high-mass slopes of {alpha}_low_=0.50+/-0.09 (0.1<m/M_{sun}_<0.62) and {alpha}_high_=2.32+/-0.14 (0.62<=m/M_{sun}_<4.68), respectively. The high-mass slope of the cluster increases from 2.01 inside 110 to 2.63 outside 22, whereas the mean stellar mass decreases from 0.95 to 0.57M_{sun}_ in the same regions, signifying clear evidence of mass segregation in the cluster. From an examination of the high-quality colour-magnitude data of the cluster and performing a series of Monte Carlo simulations, we obtained a binary fraction of fbin=34+/-12 per cent for stars with 0.70<m/M_{sun}_<4.68. This is significantly larger than the observed binary fraction, indicating that this open cluster contains a large population of unresolved binaries. Finally, we corrected the MF slopes for the effect of unresolved binaries and found low- and high-mass slopes of {alpha}_low_=0.89+/-0.11 and {alpha}_high_=2.37+/-0.09 and a total cluster mass of 352M_{sun}_ for alpha Persei.
- ID:
- ivo://CDS.VizieR/J/A+A/395/813
- Title:
- Alpha Per faint stars photometry
- Short Name:
- J/A+A/395/813
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a deep, wide-field optical survey of the young stellar cluster Alpha Per, in which we have discovered a large population of candidate brown dwarfs. Subsequent infrared photometric follow-up shows that the majority of them are probable or possible members of the cluster, reaching to a minimum mass of 0.035M_{sun}_.
- ID:
- ivo://CDS.VizieR/J/A+A/628/A66
- Title:
- alpha Persei, Pleiades and Praesepe clusters
- Short Name:
- J/A+A/628/A66
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Our scientific goal is to provide revised membership lists of the alpha Per, Pleiades, and Praesepe clusters exploiting the second data release of Gaia and produce five-dimensional maps ({alpha}, {delta}, {pi}, {mu}_{alpha}_cos{delta}, {mu}_{delta}_) of these clusters. We implemented the kinematic method combined with the statistical treatment of parallaxes and proper motions to identify astrometric member candidates of three of the most nearby and best studied open clusters in the sky. We cross-correlated the Gaia catalogue with large-scale public surveys to complement the astrometry of Gaia with multi-band photometry from the optical to the mid-infrared. We identified 517, 1248, and 721 bona fide astrometric member candidates inside the tidal radius of alpha Per, the Pleiades, and Praesepe, respectively. We cross-matched our final samples with catalogues from previous surveys to address the level of completeness. We update the main physical properties of the clusters, including mean distance and velocity, as well as core, half-mass, and tidal radii. We infer updated ages from the white dwarf members of the Pleiades and Praesepe. We derive the luminosity and mass functions of the three clusters and compare them to the field mass function. We compute the positions in space of all member candidates in the three regions to investigate their distribution in space. We provide updated distances and kinematics for the three clusters. We identify a list of members in the alpha Per, Pleiades, and Praesepe clusters from the most massive stars all the way down to the hydrogen-burning limit with a higher confidence and better astrometry than previous studies. We produce complete 5D maps of stellar and substellar bona fide members in these three regions. The photometric sequences derived in several colour-magnitude diagrams represent benchmark cluster sequences at ages from 90 to 600Myr. We note the presence of a stream around the Pleiades cluster extending up to 40 pc from the cluster centre.
- ID:
- ivo://CDS.VizieR/J/AJ/156/94
- Title:
- APOGEE and Gaia DR2 analysis of IC 166
- Short Name:
- J/AJ/156/94
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- IC 166 is an intermediate-age open cluster (OC) (~1 Gyr) that lies in the transition zone of the metallicity gradient in the outer disk. Its location, combined with our very limited knowledge of its salient features, make it an interesting object of study. We present the first high-resolution spectroscopic and precise kinematical analysis of IC 166, which lies in the outer disk with R_GC_~12.7 kpc. High-resolution H-band spectra were analyzed using observations from the SDSS-IV Apache Point Observatory Galactic Evolution Experiment survey. We made use of the Brussels Automatic Stellar Parameter code to provide chemical abundances based on a line-by-line approach for up to eight chemical elements (Mg, Si, Ca, Ti, Al, K, Mn, and Fe). The {alpha}-element (Mg, Si, Ca, and whenever available Ti) abundances, and their trends with Fe abundances have been analyzed for a total of 13 high-likelihood cluster members. No significant abundance scatter was found in any of the chemical species studied. Combining the positional, heliocentric distance, and kinematic information, we derive, for the first time, the probable orbit of IC 166 within a Galactic model including a rotating boxy bar, and found that it is likely that IC 166 formed in the Galactic disk, supporting its nature as an unremarkable Galactic OC with an orbit bound to the Galactic plane.
- ID:
- ivo://CDS.VizieR/J/A+A/556/A26
- Title:
- Arches cluster: IR phot., extinction and masses
- Short Name:
- J/A+A/556/A26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Galactic Center is the most active site of star formation in the Milky Way Galaxy, where particularly high-mass stars have formed very recently and are still forming today. However, since we are looking at the Galactic Center through the Galactic disk, knowledge of extinction is crucial to study this region. The Arches cluster is a young, massive starburst cluster near the Galactic Center. We observed the Arches cluster out to its tidal radius using Ks-band imaging obtained with NAOS/CONICA at the VLT combined with Subaro/Cisco J-band data to gain a full understanding of the cluster mass distribution. We show that the determination of the mass of the most massive star in the Arches cluster, which had been used in previous studies to establish an upper-mass limit for the star formation process in the Milky Way, strongly depends on the assumed slope of the extinction law. Assuming the two regimes of widely used infrared extinction laws, we show that the difference can reach up to 30% for individually derived stellar masses and {Delta}AKs~1 magnitude in acquired Ks-band extinction, while the present mass function slope changes by ~0.17dex. The present-day mass function slope derived assuming the Nishiyama et al. (2009) extinction law increases from a flat slope of {alpha}-Nishi=-1.50+/-0.35 in the core (r<0.2pc) to {alpha}-Nishi=-2.21+/-0.27 in the intermediate annulus (0.2<r<0.4pc), where the Salpeter slope is -2.3. The present-day mass function steepens to {alpha}-Nishi=-3.21+/-0.30 in the outer annulus (0.4<r<1.5pc), indicating that the outer cluster region is depleted of high mass stars. This picture is consistent with mass segregation due to the dynamical evolution of the cluster.
- ID:
- ivo://CDS.VizieR/J/AJ/138/1116
- Title:
- A Spitzer view of NGC 2264
- Short Name:
- J/AJ/138/1116
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have performed mid-IR photometry of the young open cluster NGC 2264 using the images obtained with the Spitzer Space Telescope Infrared Array Camera and Multiband Imaging Photometer for Spitzer instruments and presented a normalized classification scheme of young stellar objects in various color-color diagrams to make full use of the information from multicolor photometry. These results are compared with the classification scheme based on the slope of the spectral energy distribution (SED). From the spatial distributions of Class I and II stars, we have identified two subclusterings of Class I objects in the CONE region of Sung et al. (Cat. J/AJ/135/441). The disked stars in the other star-forming region S Mon are mostly Class II objects. In addition, we have derived a somewhat higher value of the primordial disk fraction for NGC 2264 members located below the main pre-main-sequence locus (so-called BMS stars). This result supports the idea that BMS stars are young stars with nearly edge-on disks.
- ID:
- ivo://CDS.VizieR/J/PASP/116/1012
- Title:
- A star catalog for the open cluster NGC 188
- Short Name:
- J/PASP/116/1012
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new BVRI broadband photometry for the old open cluster NGC 188, based on an analysis of 299 CCD images either obtained by us, donated by colleagues, or retrieved from public archives.