Impact of Distance Determinations on Galactic Structure. I. Young and Intermediate-Age Tracers

Matsunaga, Noriyuki; Bono, G.; Chen, Xiaodian; Grijs, Richard de; Inno, L.; Nishiyama, Shogo

doi:10.1007/s11214-018-0506-5

Cited by 27 publications

(18 citation statements)

References 174 publications

(293 reference statements)

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“…In terms of estimated distance, we find 6 new OCs within 1 kpc (the closest one at around 645 pc) and 30 within 1.8 kpc, to be added to the 23 found by Castro-Ginard et al (2018) and the 31 by Cantat-Gaudin et al (2019) in that distance range, further supporting the claim that more objects are yet to be discovered in this volume, especially with the combination of the excellent Gaia data and ML algorithms in future all-sky searches. This challenges the statement that the OC census is complete up to 1.8 kpc (Kharchenko et al 2013;Matsunaga et al 2018;Piskunov et al 2018).…”

Section: Comments On the Detected Ocsmentioning

confidence: 95%

Hunting for open clusters in Gaia DR2: the Galactic anticentre

Castro-Ginard

Jordi

Luri

et al. 2019

A&A

124

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Context. The Gaia Data Release 2 (DR2) provided an unprecedented volume of precise astrometric and excellent photometric data. In terms of data mining the Gaia catalogue, machine learning methods have shown to be a powerful tool, for instance in the search for unknown stellar structures. Particularly, supervised and unsupervised learning methods combined together significantly improves the detection rate of open clusters. Aims. We systematically scan Gaia DR2 in a region covering the Galactic anticentre and the Perseus arm (120 • ≤ l ≤ 205 • and −10 • ≤ b ≤ 10 • ), with the goal of finding any open clusters that may exist in this region, and fine tuning a previously proposed methodology successfully applied to TGAS data, adapting it to different density regions. Methods. Our methodology uses an unsupervised, density-based, clustering algorithm, DBSCAN, that identifies overdensities in the five-dimensional astrometric parameter space (l, b, , µ α * , µ δ ) that may correspond to physical clusters. The overdensities are separated into physical clusters (open clusters) or random statistical clusters using an artificial neural network to recognise the isochrone pattern that open clusters show in a colour magnitude diagram. Results. The method is able to recover more than 75% of the open clusters confirmed in the search area. Moreover, we detected 53 open clusters unknown previous to Gaia DR2, which represents an increase of more than 22% with respect to the already catalogued clusters in this region. Conclusions. We find that the census of nearby open clusters is not complete. Different machine learning methodologies for a blind search of open clusters are complementary to each other; no single method is able to detect 100% of the existing groups. Our methodology has shown to be a reliable tool for the automatic detection of open clusters, designed to be applied to the full Gaia DR2 catalogue.

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Section: Comments On the Detected Ocsmentioning

confidence: 95%

Hunting for open clusters in Gaia DR2: the Galactic anticentre

Castro-Ginard

Jordi

Luri

et al. 2019

A&A

124

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“…The zero-point uncertainty of the infrared period-luminosity relation is around 0.033 mag 9,44 . The uncertainty in the near-infrared extinction law is the main contributor to the distance error in the Galactic plane; it can be up to 15% for heavily obscured stars 45 . We adopted the infrared extinction law determined using Cepheids in the Galactic Center direction (see Table 2, first row).…”

Section: Methodsmentioning

confidence: 99%

An intuitive 3D map of the Galactic warp’s precession traced by classical Cepheids

et al. 2019

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The Milky Way's neutral hydrogen (HI) disk is warped and flared 1, 2 . However, a dearth of accurate HI-based distances has thus far prevented the development of an accurate Galactic disk model. Moreover, the extent to which our Galaxy's stellar and gas disk morphologies are mutually consistent is also unclear. Classical Cepheids, primary distance indicators with distance accuracies of 3-5% 3 , offer a unique opportunity to develop an intuitive and accurate three-dimensional picture. Here, we establish a robust Galactic disk model based on 1339 classical Cepheids. We provide strong evidence that the warp's line of nodes is not oriented in the Galactic Center-Sun direction. Instead, it subtends a mean angle of 17.5 • ± 1 • (formal) ±3 • (systematic) and exhibits a leading spiral pattern. Our Galaxy thus follows Briggs' rule for spiral galaxies 4 , which suggests that the origin of the warp is associated with torques forced by the massive inner disk 5 . The stellar disk traced by Cepheids follows the gas disk in terms of their amplitudes; the stellar disk extends to at least 20 kpc 6,7 . This morphology provides a crucial, updated map for studies of the kinematics and archaeology of the Galactic disk.We have compiled samples of classical Cepheids from the Wide-field Infrared Survey Explorer (WISE) catalogue of periodic variables 8 (our 'WISE Cepheid sample') as well as from a number of optical surveys (collectively referred to as our 'optical Cepheid sample'). We will discuss both samples separately, because the catalogues' optical and infrared passbands are characterised by significantly different photometric and extinction sensitivities. Highly accurate Cepheid distances can be estimated using their well-established wavelength-dependent period-luminosity relations. To mitigate the influence of extinction in the Galactic plane and of photometric uncertainties at infrared wavelengths, we adopted the 'infrared multi-passband optimal distance method' 9 to determine accurate Cepheid distances. Contaminants, including Type-II Cepheids, long-period eclipsing binaries and quasi-periodic variables were removed using Gaia Data Release 2 parallaxes 10 .Cepheids located in areas centered on the Magellanic Clouds were also excluded. Careful sample selection resulted in a tally of 2330 classical Cepheids for further analysis.Distances were converted to 3D XY z and spherical Rφz coordinates by adopting a reference frame centered on the Galactic Center and a solar Galactocentric distance R 0 = 8.0 kpc. Here, φ is the Galactocentric angle in the anticlockwise direction (aligned with the disk's rotation axis) with respect to the solar position (φ = 0 • ). Since Gaia parallaxes are reliable within ∼5 kpc, we only selected Cepheids within the volume R < 20, |z| < 2 kpc to avoid significant contamination by Type-II Cepheids. Our downselection included 1459 Cepheids with distances accurate to <5%, corresponding to a distance modulus standard deviation <0.108 mag. Cepheids located clearly away from the best-fitting warp model (∆ > 1 kp...

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“…Studies of variables in the infrared view can benefit our understanding of infrared extinction, since the universality (or otherwise) of the infrared extinction law is still being debated (e.g. Matsunaga et al 2018). Studies using the red clump as a diagnostic tool imply a relatively universal extinction law in the NIR but a variable mid-infrared (MIR) extinction law (Wang & Jiang 2014;Zasowski et al 2009).…”

Section: Introductionmentioning

confidence: 99%

Wide-field Infrared Survey Explorer ( WISE ) Catalog of Periodic Variable Stars

Chen

Wang

Deng

et al. 2018

ApJS

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118

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We have compiled the first all-sky mid-infrared variable-star catalog based on Wide-field Infrared Survey Explorer (WISE) five-year survey data. Requiring more than 100 detections for a given object, 50,282 carefully and robustly selected periodic variables are discovered, of which 34,769 (69%) are new. Most are located in the Galactic plane and near the equatorial poles. A method to classify variables based on their mid-infrared light curves is established using known variable types in the General Catalog of Variable Stars. Careful classification of the new variables results in a tally of 21,427 new EW-type eclipsing binaries, 5654 EA-type eclipsing binaries, 1312 Cepheids, and 1231 RR Lyraes. By comparison with known variables available in the literature, we estimate that the misclassification rate is 5% and 10% for short-and long-period variables, respectively. A detailed comparison of the types, periods, and amplitudes with variables in the Catalina catalog shows that the independently obtained classifications parameters are in excellent agreement. This enlarged sample of variable stars will not only be helpful to study Galactic structure and extinction properties, they can also be used to constrain stellar evolution theory and as potential candidates for the James Webb Space Telescope.

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Impact of Distance Determinations on Galactic Structure. I. Young and Intermediate-Age Tracers

Cited by 27 publications

References 174 publications

Hunting for open clusters in Gaia DR2: the Galactic anticentre

Hunting for open clusters in Gaia DR2: the Galactic anticentre

An intuitive 3D map of the Galactic warp’s precession traced by classical Cepheids

Wide-field Infrared Survey Explorer ( WISE ) Catalog of Periodic Variable Stars

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