OGLE-ing the Magellanic System: Three-Dimensional Structure of the Clouds and the Bridge Using Classical Cepheids
Anna M. Jacyszyn-Dobrzeniecka, D. M. Skowron, P. Mróz, J. Skowron, I. Soszyński, A. Udalski, P. Pietrukowicz, S. Kozłowski, Ł. Wyrzykowski, R. Poleski, M. Pawla… 展开作者
Anna M. Jacyszyn-Dobrzeniecka, D. M. Skowron, P. Mróz, J. Skowron, I. Soszyński, A. Udalski, P. Pietrukowicz, S. Kozłowski, Ł. Wyrzykowski, R. Poleski, M. Pawlak, M. K. Szymański, K. Ulaczyk
备注：
48 pages, 19 figures. A new version of the paper contains substantial changes and is consistent with Acta Astron. 2016, 66, 149
We analyzed a sample of 9418 fundamental-mode and first-overtone Classical Cepheids from the OGLE-IV Collection of Classical Cepheids. The distance to each Cepheid was calculated using the period-luminosity relation for the Wesenheit magnitude, fitted to our data.
The classical Cepheids in the LMC are situated mainly in the bar and in the northern arm. The eastern part of the LMC is closer to us and the plane fit to the whole LMC sample yields the inclination $i=24.2\pm0.7$ deg and position angle ${\rm P.A.}=151.4\pm1.7$ deg. We redefined the LMC bar by extending it in the western direction and found no offset from the plane of the LMC contrary to previous studies. On the other hand, we found that the northern arm is offset from a plane by about $-0.5$ kpc, which was not observed before. The age distribution of the LMC Cepheids shows one maximum at about 100 Myr.
We demonstrate that the SMC has a non-planar structure and can be described as an extended ellipsoid. We identified two large ellipsoidal off-axis structures in the SMC. The northern one is located closer to us and is younger, while the south-western is farther and older. The age distribution of the SMC Cepheids is bimodal with one maximum at 110 Myr, and another one at 220 Myr. Younger stars are located in the closer part of this galaxy while older ones are more distant.
We classified nine Cepheids from our sample as Magellanic Bridge objects. These Cepheids show a large spread in three-dimensions although five of them form a connection between the Clouds. The closest one is closer than any of the LMC Cepheids, while the farthest one -- farther than any SMC Cepheid. All but one Cepheids in the Magellanic Bridge are younger than 300 Myr. The oldest one can be associated with the SMC Wing.
We present the final release of the OGLE collection of classical pulsators (Cepheids and RR Lyr stars) in the Large and Small Magellanic Clouds. The sky coverage has been increased from 670 to 765 square degrees compared to the previous edition of the collection. We also add some Cepheids and RR Lyr stars found by the Gaia team and reclassify three Cepheids. Ultimately, our collection consists of 9650 classical Cepheids, 343 type II Cepheids, 278 anomalous Cepheids, and 47828 RR Lyr stars inside and toward the Magellanic System.
In the present study, we examine reddening distribution across the LMC and SMC through largest data on Classical Cepheids provided by the OGLE Phase IV survey. The V and I band photometric data of 2476 fundamental mode (FU) and 1775 first overtone mode (FO) Cepheids in the LMC and 2753 FU and 1793 FO Cepheids in the SMC are analyzed for their Period-Luminosity (P-L) relations. We convert period of FO Cepheids to corresponding period of FU Cepheids before combining the two modes of Cepheids. The reddening analysis is performed on 133 segments covering a total area of about 154.6 deg^2 in the LM…
We present results from the Large Magellanic Cloud Near-infrared Synoptic Survey (LMCNISS) for classical and type II Cepheid variables that were identified by the Optical Gravitational Lensing Experiment (OGLE-III) catalogue. Multiwavelength time-series data for classical Cepheid variables are used to study light-curve structures as a function of period and wavelength. We exploit a sample of $\sim$1400 classical and $\sim$80 type II Cepheid variables to derive Period--Wesenheit relations that combine both optical and near-infrared data. The new Period--Luminosity and Wesenheit relations are us…
We present a study of a recently discovered stellar overdensity near the northern edge of the Small Magellanic Cloud (SMCNOD). We exploited variable stars from the fourth release of the Optical Gravitational Lensing Experiment (OGLE). We used mainly pulsating variable stars and investigated their potential association with the SMCNOD using their spatial distribution and distances. We found four rather spatially concentrated anomalous Cepheids and eight evenly dispersed RR~Lyrae stars to be most likely members of this overdensity. The anomalous Cepheids inside the SMCNOD trace possible intermed…
We present a detailed analysis of Magellanic Bridge Cepheid sample constructed using the OGLE Collection of Variable Stars. Our updated Bridge sample contains 10 classical and 13 anomalous Cepheids. We calculate their individual distances using optical period--Wesenheit relations and construct three-dimensional maps. Classical Cepheids on-sky locations match very well neutral hydrogen and young stars distributions, thus they add to the overall Bridge young population. In three dimensions, eight out of ten classical Cepheids form a bridge-like connection between the Magellanic Clouds. The other…
Multi-mode Cepheids pulsate simultaneously in more than one mode of oscillation. They provide an independent means to test stellar models and pulsation theories. They can also be used to derive metallicities. In recent years, the number of known multi-mode Cepheids has increased dramatically with the discovery of a large number of Galactic double-mode Cepheids. To date, 209 double-mode Cepheids have been detected in the Galactic bulge and disk, mostly based on the Optical Gravitational Lensing Experiment's (OGLE) catalog. In this paper, we conduct a comprehensive search for double-mode Cepheid…
We have analysed Optical Gravitational Lensing Experiment photometry for first overtone classical Cepheids in the Large and Small Magellanic Clouds in search for additional periodicities beyond radial modes. We have used standard consecutive prewhitening technique in some cases followed by time-dependent prewhitening. We report new candidates for double-mode radial pulsations. However, majority of signals we have detected cannot be interpreted in terms of radial modes. We report 516 double-periodic stars with period ratios, $P_{\rm x}/P_{\rm 1O}$, in the range 0.60 and 0.65. We study the prope…
We present candidates for non-pulsating stars lying in the classical Cepheid instability strip based on OGLE photometric maps combined with Strömgren photometry obtained with the 4.1-m SOAR telescope, and Gaia DR2 data in four fields in the Large Magellanic Cloud. We selected 19 candidates in total. After analysis of their light curves from OGLE surveys we found that all these stars appear to be photometrically stable at the level of a few mmag. Our results show that non-pulsating stars might constitute to about 21%-30% of the whole sample of giant stars located in the classical instability st…
We present a three-dimensional structure of the Magellanic System using over 9 000 Classical Cepheids and almost 23 000 RR Lyrae stars from the OGLE Collection of Variable Stars. Given the vast coverage of the OGLE-IV data and very high completeness of the sample, we were able to study the Magellanic System in great details. We very carefully studied the distribution of both types of pulsators in the Magellanic Bridge area. We show that there is no evident physical connection between the Clouds in RR Lyrae stars distribution. We only see the two extended structures overlapping. There are few c…
We present an updated three dimensional map of the Milky Way based on a sample of 2431 classical Cepheid variable stars, supplemented with about 200 newly detected classical Cepheids from the OGLE survey. The new objects were discovered as a result of a dedicated observing campaign of the ~280 square degree extension of the OGLE footprint of the Galactic disk during 2018-2019 observing seasons. These regions cover the main part of the northern Galactic warp that has been deficient in Cepheids so far. We use direct distances to the sample of over 2390 classical Cepheids to model the distributio…
The Cepheid Leavitt Law (LL), also known as the Period-Luminosity relation, is a crucial tool for assembling the cosmic distance ladder. By combining data from the OGLE-IV catalogue with mid-infrared photometry from the Spitzer Space Telescope, we have determined the $3.6$ $μ$m and $4.5$ $μ$m LLs for the Magellanic Clouds using around 5000 fundamental-mode Classical Cepheids. Mean magnitudes were determined using a Monte Carlo Markov Chain (MCMC) template fitting procedure, with template light curves constructed from a subsample of these Cepheids with fully-phased, well-sampled light curves. T…
The latest Gaia Data Release 3 provides an opportunity to expand the census of Galactic open clusters harboring classical Cepheid variables, thereby bolstering the cosmic distance scale. A comprehensive analysis yielded a total of 50 classical Cepheids associated with 45 open clusters, of which 39 open cluster-classical Cepheid pairs are considered probable, with the remaining 11 pairs considered improbable but worth following up. Two previously identified clusters by us possibly host classical Cepheids (OC-0125/V1788 Cyg and OC-0675/OGLE-BLG-CEP-114). In addition, we identify 38 new open clus…
Variable stars have been used for over one hundred years as probes for determining astronomical distances; these distances can be used to map the three-dimensional (3D) structure of nearby galaxies. Exploiting the effect that moving to the mid-infrared has on Cepheid magnitudes and light curves, we can now map our nearest galaxies in 3D at fidelities never before achievable. Combining data from the OGLE-IV catalogue with mid-infrared photometry from the Spitzer Space Telescope, around 5000 fundamental mode Cepheids are being used to trace the 3D structure of the Magellanic Clouds. An automated…
The Cepheid variables in SMC, LMC, the Milky Way, M33 and M31 are used to examine the dependence of pulsation mode on metallicity which was previously found in red supergiants. The initial samples of Cepheids are collected from the Cepheid catalogs identified from the OGLE, PS1, DIRECT, WISE and ZTF surveys. The contaminants are removed with the help of the Gaia/EDR3 astrometric information for extra galaxies or by comparing the geometric distance and the distance from the P-L relation for the Milky Way. The division of fundamental and first-overtone mode is refined according to the gap betwee…
We use the extended and updated OGLE Collection of Variable Stars to thoroughly analyze distribution of RR Lyrae stars in the Magellanic Bridge. We use photometric metallicities to derive absolute Wesenheit magnitude and then individual distance of each RR Lyr star. We confirm results from our earlier study showing that RR Lyr stars are present in between the Magellanic Clouds, though their three-dimensional distribution rather resembles two extended overlapping structures than a strict bridge-like connection. The contours do connect in the southern parts of the Bridge, albeit on a too low lev…
Estimating metallicity of classical Cepheids is of prime importance for studying metallicity effect on stellar evolution, chemical evolution of galaxies, and ultimately its impact on period-luminosity relation used in the extragalactic distance scale. We aim at establishing new empirical relations for estimating the iron content of classical Cepheids for short and long-periods based on Fourier parameters from the $V$-band light curves. We calibrate new interrelations of Fourier parameters to convert $V$-band empirical relations into the $I$-band. Then we apply these relation in $V$ and $I$-ban…
The nature of type II Cepheids and anomalous Cepheids is still not well known and their evolutionary channels leave many unanswered questions. We use complete collection of classical pulsating stars in the Magellanic Clouds discovered by the OGLE project, to compare their spatial distributions, which are one of the characteristic features directly related to the star formation history. In this analysis we use 9649 classical Cepheids, 262 anomalous Cepheids, 338 type II Cepheids and 46 443 RR Lyr stars from both Magellanic Clouds. We compute three-dimensional Kolmogorov-Smirnov tests for every …
We present the results of the light curve model fitting technique applied to optical and near-infrared photometric data for a sample of 18 Classical Cepheids (11 fundamentals and 7 first overtones) in the Large Magellanic Cloud (LMC). We use optical photometry from the OGLE III database and near--infrared photometry obtained by the European Southern bservatory public survey "VISTA near--infrared survey of the Magellanic Clouds system". Iso--periodic nonlinear convective model sequences have been computed for each selected Cepheid in order to reproduce the multi--filter light curve amplitudes a…
We present the most extensive and detailed reddening maps of the Magellanic Clouds (MCs) derived from the color properties of Red Clump (RC) stars. The analysis is based on the deep photometric maps from the fourth phase of the Optical Gravitational Lensing Experiment (OGLE-IV), covering approximately 670 deg2 of the sky in the Magellanic System region. The resulting maps provide reddening information for 180 deg2 in the Large Magellanic Cloud (LMC) and 75 deg2 in the Small Magellanic Cloud (SMC), with a resolution of 1.7x1.7 arcmin in the central parts of the MCs, decreasing to approximately …
The period-change rate (PCR) of pulsating variable stars is a useful probe of changes in their interior structure, and thus of their evolutionary stages. So far, the PCRs of Classical Cepheids in the Large Magellanic Cloud (LMC) have been explored in a limited sample of the total population of these variables. Here we use a template-based method to build observed minus computed (O-C) period diagrams, from which we can derive PCRs for these stars by taking advantage of the long time baseline afforded by the Digital Access to a Sky Century @ Harvard (DASCH) light curves, combined with additional…
