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11. Ages of SMC young clusters and field stars
ID:
ivo://CDS.VizieR/J/A+A/452/179
Title:
Ages of SMC young clusters and field stars
Short Name:
J/A+A/452/179
Date:
21 Oct 2021
Publisher:
CDS
Description:
In this paper we discuss the cluster and field star formation in the central part of the Small Magellanic Cloud. The main goal is to study the correlation between young objects and their interstellar environment. The ages of about 164 associations and 311 clusters younger than 1Gyr are determined using isochrone fitting. The spatial distribution of the clusters is compared with the HI maps, with the HI velocity dispersion field, with the location of the CO clouds and with the distribution of young field stars.
12. Ages of star clusters in SMC
ID:
ivo://CDS.VizieR/J/ApJ/853/104
Title:
Ages of star clusters in SMC
Short Name:
J/ApJ/853/104
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a new study of the spatial distribution and ages of the star clusters in the Small Magellanic Cloud (SMC). To detect and estimate the ages of the star clusters we rely on the new fully automated method developed by Bitsakis+ (2017, J/ApJ/845/56). Our code detects 1319 star clusters in the central 18deg^2^ of the SMC we surveyed (1108 of which have never been reported before). The age distribution of those clusters suggests enhanced cluster formation around 240Myr ago. It also implies significant differences in the cluster distribution of the bar with respect to the rest of the galaxy, with the younger clusters being predominantly located in the bar. Having used the same setup, and data from the same surveys as for our previous study of the LMC, we are able to robustly compare the cluster properties between the two galaxies. Our results suggest that the bulk of the clusters in both galaxies were formed approximately 300Myr ago, probably during a direct collision between the two galaxies. On the other hand, the locations of the young (<=50Myr) clusters in both Magellanic Clouds, found where their bars join the HI arms, suggest that cluster formation in those regions is a result of internal dynamical processes. Finally, we discuss the potential causes of the apparent outside-in quenching of cluster formation that we observe in the SMC. Our findings are consistent with an evolutionary scheme where the interactions between the Magellanic Clouds constitute the major mechanism driving their overall evolution.
13. A global model for MC and Galactic Cepheids
ID:
ivo://CDS.VizieR/J/ApJ/748/107
Title:
A global model for MC and Galactic Cepheids
Short Name:
J/ApJ/748/107
Date:
21 Oct 2021
Publisher:
CDS
Description:
We perform a global fit to ~5000 radial velocity and ~177000 magnitude measurements in 29 photometric bands covering 0.3{mu}m to 8.0{mu}m distributed among 287 Galactic, Large Magellanic Cloud, and Small Magellanic Cloud Cepheids with P>10 days. We assume that the Cepheid light curves and radial velocities are fully characterized by distance, reddening, and time-dependent radius and temperature variations. We construct phase curves of radius and temperature for periods between 10 and 100 days, which yield light-curve templates for all our photometric bands and can be easily generalized to any additional band. With only four to six parameters per Cepheid, depending on the existence of velocity data and the amount of freedom in the distance, the models have typical rms light and velocity curve residuals of 0.05mag and 3.5km/s. The model derives the mean Cepheid spectral energy distribution and its derivative with respect to temperature, which deviate from a blackbody in agreement with metal-line and molecular opacity effects. We determine a mean reddening law toward the Cepheids in our sample, which is not consistent with standard assumptions in either the optical or near-IR. Based on stellar atmosphere models, we predict the biases in distance, reddening, and temperature determinations due to the metallicity and quantify the metallicity signature expected for our fit residuals.
14. 5000 AGNs behind the Magellanic clouds
ID:
ivo://CDS.VizieR/J/ApJ/701/508
Title:
5000 AGNs behind the Magellanic clouds
Short Name:
J/ApJ/701/508
Date:
21 Oct 2021
Publisher:
CDS
Description:
We show that using mid-IR color selection to find active galactic nuclei (AGNs) is as effective in dense stellar fields such as the Magellanic Clouds as it is in extragalactic fields with low stellar densities using comparisons between the Spitzer Deep Wide Field Survey data for the NOAO Deep Wide Field Survey Bootes region and the SAGE Survey of the Large Magellanic Cloud. We use this to build high-purity catalogs of ~5000 AGN candidates behind the Magellanic Clouds. Once confirmed, these quasars will expand the available astrometric reference sources for the Clouds and the numbers of quasars with densely sampled, long-term (>decade) monitoring light curves by well over an order of magnitude and potentially identify sufficiently bright quasars for absorption line studies of the interstellar medium of the Clouds.
15. AKARI-LMC Near-infrared Spectroscopic Catalog
ID:
ivo://CDS.VizieR/J/AJ/145/32
Title:
AKARI-LMC Near-infrared Spectroscopic Catalog
Short Name:
J/AJ/145/32
Date:
21 Oct 2021
Publisher:
CDS
Description:
We performed a near-infrared spectroscopic survey toward an area of ~10deg^2^ of the Large Magellanic Cloud (LMC) with the infrared satellite AKARI. Observations were carried out as part of the AKARI Large-area Survey of the Large Magellanic Cloud (LSLMC). The slitless multi-object spectroscopic capability of the AKARI/IRC enabled us to obtain low-resolution (R~20) spectra in 2-5{mu}m for a large number of point sources in the LMC. As a result of the survey, we extracted about 2000 infrared spectra of point sources. The data are organized as a near-infrared spectroscopic catalog. The catalog includes various infrared objects such as young stellar objects (YSOs), asymptotic giant branch (AGB) stars, supergiants, and so on. It is shown that 97% of the catalog sources have corresponding photometric data in the wavelength range from 1.2 to 11{mu}m, and 67% of the sources also have photometric data up to 24{mu}m. The catalog allows us to investigate near-infrared spectral features of sources by comparison with their infrared spectral energy distributions. In addition, it is estimated that about 10% of the catalog sources are observed at more than two different epochs. This enables us to study a spectroscopic variability of sources by using the present catalog. Initial results of source classifications for the LSLMC samples are presented. We classified 659 LSLMC spectra based on their near-infrared spectral features by visual inspection. As a result, it is shown that the present catalog includes 7 YSOs, 160 C-rich AGBs, 8 C-rich AGB candidates, 85 O-rich AGBs, 122 blue and yellow supergiants, 150 red super giants, and 128 unclassified sources. Distributions of the classified sources on the color-color and color-magnitude diagrams are discussed in the text. Continuous wavelength coverage and high spectroscopic sensitivity in 2-5{mu}m can only be achieved by space observations. This is an unprecedented large-scale spectroscopic survey toward the LMC in the near-infrared. A large number of near-infrared spectral data provided by the survey possess scientific potential that can be applied to various studies. In this paper, we present the details of the spectroscopic survey and the catalog, and discuss its scientific applications.
16. AKARI-LMC Point-source catalog
ID:
ivo://CDS.VizieR/J/AJ/144/179
Title:
AKARI-LMC Point-source catalog
Short Name:
J/AJ/144/179
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a near- to mid-infrared point-source catalog of five photometric bands at 3.2, 7, 11, 15, and 24{mu}m for a 10deg^2^ area of the Large Magellanic Cloud (LMC) obtained with the Infrared Camera on board the AKARI satellite. To cover the survey area the observations were carried out at three separate seasons from 2006 May to June, 2006 October to December, and 2007 March to July. The 10{sigma} limiting magnitudes of the present survey are 17.9, 13.8, 12.4, 9.9, and 8.6mag at 3.2, 7, 11, 15, and 24{mu}m, respectively. The photometric accuracy is estimated to be about 0.1mag at 3.2{mu}m and 0.06-0.07 mag in the other bands. The position accuracy is 0.3" at 3.2, 7, and 11{mu}m and 1.0" at 15 and 24{mu}m. The sensitivities at 3.2, 7, and 24{mu}m are roughly comparable to those of the Spitzer SAGE LMC point-source catalog, while the AKARI catalog provides the data at 11 and 15 {mu}m, covering the mid-infrared spectral range contiguously. Two types of catalog are provided: a Catalog and an Archive. The Archive contains all the detected sources, while the Catalog only includes the sources that have a counterpart in the Spitzer SAGE point-source catalog. The Archive contains about 650,000, 140,000, 97,000, 43,000, and 52,000 sources at 3.2, 7, 11, 15, and 24{mu}m, respectively. Based on the catalog, we discuss the luminosity functions at each band, the color-color diagram, and the color-magnitude diagram using the 3.2, 7, and 11{mu}m band data. Stars without circumstellar envelopes, dusty C-rich and O-rich stars, young stellar objects, and background galaxies are located at distinct regions in the diagrams, suggesting that the present catalog is useful for the classification of objects toward the LMC.
17. AKARI observations of SMC Cepheids
ID:
ivo://CDS.VizieR/J/MNRAS/420/585
Title:
AKARI observations of SMC Cepheids
Short Name:
J/MNRAS/420/585
Date:
21 Oct 2021
Publisher:
CDS
Description:
In this work we matched the AKARI archival data to the Optical Gravitational Lensing Experiment III (OGLE-III) catalogue to derive the mid-infrared period-luminosity (PL) relations for Small Magellanic Cloud (SMC) Cepheids. Mismatched AKARI sources were eliminated using random-phase colours obtained from the full I-band light curves from OGLE-III. It was possible to derive PL relations in the N3 and N4 bands only, although the S7-, S11-, L15- and L24-band data were also tested. Random-phase correction was included when deriving the PL relation in the N3 and N4 bands using the available time of observations from AKARI data. The final adopted PL relations were N3=-3.370logP+16.527 and N4=-3.402logP+16.556. However, these PL relations may be biased due to the small number of Cepheids in the sample.
18. AKARI SMC photometry
ID:
ivo://CDS.VizieR/J/PASJ/62/273
Title:
AKARI SMC photometry
Short Name:
J/PASJ/62/273
Date:
21 Oct 2021
Publisher:
CDS
Description:
We carried out near- to mid-infrared imaging and spectroscopic observations of patchy areas in the Small Magellanic Cloud using the Infrared Camera aboard AKARI. Two 100arcmin^2^ areas were imaged in 3.2, 4.1, 7, 11, 15, and 24um, and also spectroscopically observed in the wavelength range continuously from 2.5 to 13.4um. The spectral resolving power, {lambda}{Delta}{lambda}, values were about 20, 50, and 50 at 3.5, 6.6, and 10.6um, respectively. Other than the two 100arcmin^2^ areas, some patchy areas were imaged and/or spectroscopically observed as well. In this paper, we overview the observations and present a list of near- to mid-infrared photometric results, which lists ~12000 near-infrared and ~1800 mid-infrared bright point sources detected in the observed areas. The 10{sigma} limits are 16.50, 16.12, 13.28, 11.26, 9.62, and 8.76 in Vega magnitudes at 3.2, 4.1, 7, 11, 15, and 24um bands, respectively.
19. ALMA Magellanic Bridge A molecular clouds
ID:
ivo://CDS.VizieR/J/A+A/641/A97
Title:
ALMA Magellanic Bridge A molecular clouds
Short Name:
J/A+A/641/A97
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Magellanic Bridge is a tidal feature located between both Magellanic Clouds, containing young stars formed in situ. Its proximity allows high-resolution studies of molecular gas, dust and star formation in a tidal, low metallicity environment. Our goal is to characterize gas and dust emission in Magellanic Bridge A, the source with the highest 870um excess of emission found in single dish surveys. Using the ALMA telescope including the Morita Array, we mapped with sub-parsec resolution a 3arcmin, field of view centered on the Magellanic Bridge A molecular cloud, in 1.3mm continuum emission and ^12^CO(2-1 line emission. This region was also mapped in continuum at 870um and in ^12^CO(2-1) line emission at ~6pc resolution with the APEX telescope. To study its dust properties, we also use archival Herschel and Spitzer data. We combine the ALMA and APEX ^12^CO(2-1) line cubes to study the molecular gas emission. Magallanic Bridge A breaks up into two distinct molecular clouds in dust and ^12^CO(2-1) emission, which we call North and South. Dust emission in the North source, according to our best parameters from fitting the far-infrared fluxes, is ~3K colder than in the South source in correspondence to its less developed star formation. Both dust sources present large submillimeter excesses in LABOCA data: according to our best fits the excess over the modified blackbody (MBB) fit to the Spitzer/Herschel continuum is E(870um)~7 and E(870um)~3 for the North and South sources respectively. Nonetheless, we do not detect the corresponding 1.3mm continuum with ALMA. Our limits are compatible with the extrapolation of the MBB fits and therefore we cannot independently confirm the excess at this longer wavelength. The ^12^CO(2-1) emission is concentrated in two parsec-sized clouds with virial masses around 400 and 700M_{sun}_ each. Their bulk volume densities are n(H_2_)~0.7-2.6x10^3^cm^-3^, larger than typical bulk densities of Galactic molecular clouds. The ^12^CO luminosity to H_2_ mass conversion factor {alpha}_CO_ is 6.5 and 15.3M_{sun}_/(K.(km/s)pc^2^) for the North and South clouds, calculated using their respective virial masses and ^12^CO(2-1) luminosities. Gas mass estimates from our MBB fits to dust emission yields masses M~1.3x10^3^M_{sun}_ and 2.9x10^3^M_{sun}_ for North and South respectively, a factor of ~4 larger than the virial masses we infer from ^12^CO.
20. Anomalous RRd stars in Magellanic Clouds
ID:
ivo://CDS.VizieR/J/MNRAS/463/1332
Title:
Anomalous RRd stars in Magellanic Clouds
Short Name:
J/MNRAS/463/1332
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report the discovery of a new subclass of double-mode RR Lyrae stars in the Large and Small Magellanic Clouds. The sample of 22 pulsating stars has been extracted from the latest edition of the Optical Gravitational Lensing Experiment collection of RR Lyrae variables in the Magellanic System. The stars pulsating simultaneously in the fundamental (F) and first-overtone (1O) modes have distinctly different properties than regular double-mode RR Lyrae variables (RRd stars). The P_1O_/P_F_ period ratios of our anomalous RRd stars are within a range of 0.725-0.738, while 'classical' double-mode RR Lyrae variables have period ratios in the range of 0.742-0.748. In contrast to the typical RRd stars, in the majority of the anomalous pulsators, the F-mode amplitudes are higher than the 1O-mode amplitudes. The light curves associated with the F-mode in the anomalous RRd stars show different morphology than the light curves of, both, regular RRd stars and single-mode RRab stars. Most of the anomalous double-mode stars show long-term modulations of the amplitudes (Blazhko-like effect). Translating the period ratios into the abundance parameter, Z, we find for our stars Z{in}(0.002, 0.005) - an order of magnitude higher values than typical for RR Lyrae stars. The mass range of the RRd stars inferred from the W_I_ versus P_F_ diagram is (0.55-0.75)M_{sun}_. These parameters cannot be accounted for with single star evolution assuming a Reimers-like mass-loss. Much greater mass-loss caused by interaction with other stars is postulated. We blame the peculiar pulsation properties of our stars to the parametric resonance instability of the 1O-mode to excitation of the F- and 2O-modes as with the inferred parameters of the stars 2{omega}_1O_~={omega}_F_+{omega}_2O_.

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