- ID:
- ivo://CDS.VizieR/J/A+A/462/599
- Title:
- JHKs photometry of LMC cluster Cepheids
- Short Name:
- J/A+A/462/599
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This work presents IR photometry for two young clusters known to contain sizeable Cepheid populations: NGC 1866 and NGC 2031. The goal is to determine light curves and period-luminosity (PL) relations in the near-IR, to assess the similarity between cluster and field pulsators, and to examine the predictive capability of current pulsation models. The light curves are obtained from multiwavelength broadband J,H,Ks photometry of Cepheids in both clusters, with periods previously established from optical photometry. Mean magnitudes for the Cepheids are used to construct period-luminosity (PL) relations in the near-IR. The properties in the PL planes are compared with the behavior of field Cepheids in the LMC and with the predictions of recent pulsational models, both canonical and overluminous. Cluster and field Cepheids are homogeneous and the inclusion of the cluster Cepheids in the field sample extends the PL relation. The slope of the PL relation is constant over the whole period range and does not show, at least in the adopted IR bands, the break in slope at P~10d reported by some authors. A comparison with the predictions of pulsation models allows an estimate for the distance moduli of NGC 1866 and NGC 2031. The two clusters are found to lie at essentially the same distance. Fitting of theoretical models to the data gives, for the K filter, (m-M)_0_=18.62+/-0.10 if canonical models are used and (m-M)_0_=18.42+/-0.10 if overluminous models are used.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/132/2653
- Title:
- JHKs photometry of N11 young stellar objects
- Short Name:
- J/AJ/132/2653
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Near-infrared observations have been carried out to survey young stellar objects in the second-largest HII region in the Large Magellanic Cloud, N11. A total area of about 700 arcmin2 is covered in the J, H, and Ks bands. We selected a total of 559 OB and 127 Herbig Ae/Be star candidates out of the detected sources based on their near-infrared colors and magnitudes. The existence of these young stellar objects indicates that star formation activity is underway in the whole N11 region. Many Herbig Ae/Be star candidates are distributed around the periphery of the OB association LH 9. Spatial correlations of the OB and Herbig Ae/Be star candidates with the objects observed at other wavelengths (optical, radio continuum, H{alpha}, CO, and X-ray) suggest that the birth of the young stellar populations in peripheral molecular clouds was triggered originally by LH 9. It is likely that the trigger for this star formation was an expanding supershell blown by the OB association. In N11 a new generation of stars would have been formed in the clouds developed from swept-up interstellar medium.
- ID:
- ivo://CDS.VizieR/J/A+A/453/517
- Title:
- JKs photometry of N159A
- Short Name:
- J/A+A/453/517
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present near-infrared imaging and spectroscopic observations of the HII region N159A (~10pc) in the giant star-forming region N159 (50pc) in the LMC. N159A was observed in the J and Ks bands at high spatial resolution ~0.2" using the ESO Very Large Telescope UT4 (VLT), equipped with the NAOS adaptative optics system. Our data reveal the morphology of this region in unprecedented detail. The protostar P2, one of the first YSOs of Class I identified in the LMC is now resolved in two YSO candidates. The ultracompact HII region LI-LMC 1501W is found to be a tight cluster embedded in a compact HII region ionised by a late O source. A new multiple system composed of a tight star cluster and an YSO candidate, all embedded in compact nebular region (0.4pc) is also detected at the north-east edge of N159A. The stellar population of the whole N159A region appears composed of two main stellar populations, one with an age <3Myr and the other one with a large range of age (300Myr-10Gyr). Using spectroscopy, one of the two exciting O stars in the HII region N159A is classified O5-O6.
- ID:
- ivo://CDS.VizieR/J/MNRAS/341/534
- Title:
- J-type carbon stars in LMC
- Short Name:
- J/MNRAS/341/534
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A sample of 1497 carbon stars in the Large Magellanic Cloud (LMC) has been observed in the red part of the spectrum with the 2dF facility on the Anglo-Australian Telescope. Of these, 156 have been identified as J-type (i.e. ^13^C-rich) carbon stars using a technique which provides a clear distinction between J stars and the normal N-type carbon stars that comprise the bulk of the sample, and yields few borderline cases. A simple two-dimensional classification of the spectra, based on their spectral slopes in different wavelength regions, has been constructed and found to be related to the more conventional c and j indices, modified to suit the spectral regions observed. Most of the J stars form a photometric sequence in the K-(J-K) colour-magnitude diagram, parallel to and 0.6mag fainter than the N-star sequence. A subset of the J stars (about 13 per cent) are brighter than this J-star sequence; most of these are spectroscopically different from the other J stars. The bright J stars have stronger CN bands than the other J stars and are found strongly concentrated in the central regions of the LMC. Most of the rather few stars in common with Hartwick and Cowley's sample (1988ApJ...334..135H) of suspected CH stars are J stars. Overall, the proportion of carbon stars identified as J stars is somewhat lower than has been found in the Galaxy. The Na D lines are weaker in the LMC J stars than in either the Galactic J stars or the LMC N stars, and do not seem to depend on temperature.
- ID:
- ivo://CDS.VizieR/J/A+A/510/A19
- Title:
- K-band spectra of 6 LMC globular clusters
- Short Name:
- J/A+A/510/A19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Current stellar population models have arguably the largest uncertainties in the near-IR wavelength range, partly due to a lack of large and well calibrated empirical spectral libraries. In this paper we present a project whose aim it is to provide the first library of luminosity weighted integrated near-IR spectra of globular clusters to be used to test the current stellar population models and serve as calibrators for future ones. Our pilot study presents spatially integrated K-band spectra of three old (>=10Gyr) and metal poor ([Fe/H]~-1.4), and three intermediate age (1-2Gyr) and more metal rich ([Fe/H]~-0.4) globular clusters in the LMC.
- ID:
- ivo://CDS.VizieR/J/A+AS/122/507
- Title:
- Kinematics of SMC carbon stars
- Short Name:
- J/A+AS/122/507
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a radial velocity survey of a sample of the field population of carbon stars in the outer parts of the Small Magellanic Cloud (SMC). This first set of results includes radial velocities for 71 carbon stars, with an individual precision of +/-2-5km/s. The mean heliocentric velocity of the stars (excluding one very high velocity star) is 149.3+/-3.0km/s with a velocity dispersion of 25.2+/-2.1km/s. These values drop to 145.5+/-2.7km/s and 20.6+/-1.9km/s respectively, if we exclude the stars belonging to the Outer Wing. The velocity distribution does not show the multiple peaks seen in some samples of Population I objects. The mass of the SMC as inferred from the above velocity dispersion (without the outer Wing stars) is =~1.2x10^9^M_{sun}_.
- ID:
- ivo://CDS.VizieR/J/A+A/469/459
- Title:
- K magnitudes of N159-5 (LMC)
- Short Name:
- J/A+A/469/459
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present high-resolution near-infrared imaging of the compact HII region N159-5 and its immediate environment in the giant-star forming region N159 in the LMC. N159-5 was observed at high spatial resolution ~0.11"-0.25" in the K-band using the ESO Very Large Telescope UT4 (VLT), equipped with the NAOS adaptive optics system. Our data reveal that N159-5 has a complex morphology formed mainly by two wings and probably a single central bright star, embedded in diffuse emission of ~4.5" diameter. A remarkable embedded tight cluster of approximatively the same size, containing at least 38 faint stars coinciding with N159-5, is also detected. Such clusters can be found in galactic HII regions like the star-forming regions SH2 269 or M42. At the location of the radio peak, especially in the bright western wing, this cluster is rich in stars. Spectroscopic observations reveal that the diffuse region is constituted mainly of dust continuum and that the bright star #2-55 could be of type O8 V. A comparison with the radio observation flux of N159-5 published in the literature seems to show that the bright star #2-55 is not the only ionization source of N159-5. Towards N159-5 molecular H_2_ emission is detected. A model of the region is proposed.
- ID:
- ivo://CDS.VizieR/J/MNRAS/459/1687
- Title:
- Ks light curve of 299 SMC new Cepheids
- Short Name:
- J/MNRAS/459/1687
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present K_s_-band light curves for 299 Cepheids in the Small Magellanic Cloud (SMC) of which 288 are new discoveries that we have identified using multi-epoch near-infrared photometry obtained by the VISTA survey of the Magellanic Clouds system (VMC). The new Cepheids have periods in the range from 0.34 to 9.1d and cover the magnitude interval 12.9<=<K_s_><=17.6mag. Our method was developed using variable stars previously identified by the optical microlensing survey OGLE. We focus on searching new Cepheids in external regions of the SMC for which complete VMC K_s_-band observations are available and no comprehensive identification of different types of variable stars from other surveys exists yet.
- ID:
- ivo://CDS.VizieR/J/ApJ/777/82
- Title:
- Ks luminosity of AGB stars in LMC clusters
- Short Name:
- J/ApJ/777/82
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of K_s_-band luminosity evolution of the asymptotic giant branch (AGB) population in simple stellar systems using star clusters in the Large Magellanic Cloud (LMC). We determine physical parameters of LMC star clusters including center coordinates, radii, and foreground reddenings. Ages of 83 star clusters are derived from isochrone fitting with the Padova models, and those of 19 star clusters are taken from the literature. The AGB stars in 102 star clusters with log(age)=7.3-9.5 are selected using near-infrared color-magnitude diagrams based on Two Micron All Sky Survey photometry. Then we obtain the K_s_-band luminosity fraction of AGB stars in these star clusters as a function of ages. The K_s_-band luminosity fraction of AGB stars increases, on average, as age increases from log(age)~8.0, reaching a maximum at log(age)~8.5, and it decreases thereafter. There is a large scatter in the AGB luminosity fraction for given ages, which is mainly due to stochastic effects. We discuss this result in comparison with five simple stellar population models. The maximum K_s_-band AGB luminosity fraction for bright clusters is reproduced by the models that expect the value of 0.7-0.8 at log(age)=8.5-8.7. We discuss the implication of our results with regard to the study of size and mass evolution of galaxies.
- ID:
- ivo://CDS.VizieR/J/A+A/502/505
- Title:
- Ks photometry of LMC RR Lyrae
- Short Name:
- J/A+A/502/505
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- RR Lyrae variable stars are the primary Population II distance indicator. Likewise, the LMC constitutes a key step in the extragalactic distance scale. By combining near-IR photometry and spectroscopically measured metallicities for a homogeneous sample of 50 RR Lyr stars in the Large Magellanic Cloud (LMC), we investigate the metallicity dependence of the period-luminosity relation in the near-infrared (IR), use the newly derived relations to re-derive the distance to the LMC, and compare the distance moduli obtained from RR Lyr and red clump stars.
