Local Arm Research Articles

Updated Gaia-2MASS 3D maps of Galactic interstellar dust

Aims. Three-dimensional (3D) maps of Galactic interstellar dust are a tool for a wide range of uses. We aim to construct 3D maps of dust extinction in the Local Arm and surrounding regions. Methods. To do this, Gaia EDR3 photometric data were combined with 2MASS measurements to derive extinction towards stars with accurate photometry and relative uncertainties on EDR3 parallaxes of less than 20%. We applied our hierarchical inversion algorithm adapted to inhomogeneous spatial distributions of target stars to this catalogue of individual extinctions. Results. We present the updated 3D dust extinction distribution and provide an estimate of the error on integrated extinctions from the Sun to each area in the 3D map. The full computational area is similar to the one of the previous DR2 map, that is to say with a 6 × 6 × 0.8 kpc3 volume around the Sun. Due to the addition of fainter target stars, the volume in which the clouds can be reconstructed has increased. Due to the improved accuracy of the parallaxes and photometric data in EDR3, extinctions among neighbouring targets are more consistent, allowing one to reach an increased contrast in the dense areas, while cavity contours are more regular. We show several comparisons with recent results on dust and star distributions. The wavy pattern around the Plane of the dust concentrations is better seen and exists over large regions. Its mean vertical peak-to-peak amplitude is of the order of 300 pc; interestingly, it is similar to the vertical period of the spectacular snail-shaped stellar kinematical pattern discovered in Gaia data. Conclusions. The Gaia EDR3 catalogue allows for a significant improvement of the extinction maps to be made, both in extent and quality. The hierarchical technique confirms its efficiency in the inversion of massive datasets. Future comparisons between 3D maps of interstellar matter and stellar distributions may help to understand which mergers or internal perturbations have shaped the Galaxy within the first 3 kpc.

Instability in the System of the Distant Post-AGB Star LS III +52°24 (IRAS 22023+5249)

The optical spectra of the B-supergiant LS III+52 24 (IRAS 22023+5249) obtained at the 6-meter telescope BTA with a resolution R$\ge$60000 in 2010-2021 revealed signs of wind variability and velocity stratification in the extended atmosphere. The H$\alpha$ and H$\beta$ lines have a P Cyg type profile; their wind absorption changes position in the range from $-270$ to $-290$ km/s. The intensity of the H$\alpha$ emission reaches record values with respect to the local continuum: I/Icont $\approx$70. The stationary radial velocity according to the positions of symmetric forbidden emissions and permitted metal emissions was taken as the systemic velocity Vsys=$-149.6\pm$0.6 km/s. Based on the positions of absorptions of NII and OII ions, a time variability of the radial velocity in the range from $-127.2$ to $-178.3$ km/s was found for the first time for this star. This variability indicates the possible presence of a companion and/or atmospheric pulsations. The change of the oxygen triplet profile OI 7775 A due to the occurrence of unstable emission was registered. The set of interstellar absorptions of the NaI D-lines profile in the range from $-10.0$ to $-167.2$ km/s is formed in the Local Arm and subsequent arms of the Galaxy. The distance to the star, d$\ge$5.3 kpc, combined with the high systemic velocity, indicates that the star is located in the Galaxy beyond the Scutum-Crux arm.

Structure and kinematics of the Milky Way galaxy using atomic hydrogen

The present study uses the hyper-fine transition of atomic hydrogen, HI (1420 MHz) to map the structure and kinematics of the Milky Way galaxy. The observation was carried out for galactic longitude 20° ≤ ℓ ≤ 220° and galactic latitude −20° ≤ b ≤ 20° each in 5° steps using the SALSA 2.3m Radio Telescope located at Onsala Space Observatory, Sweden. The velocity components of HI clouds were determined using Gaussian decomposition of the observed spectrum and these values were projected onto the Galactic plane for the identification of spiral structure of the galaxy. The Perseus, Local and Outer arms were identified using the Longitude velocity plots and x-y plots (face-on maps). The rotational velocities of the HI clouds were determined using the tangent-point method and the resulting rotation curve comes out to be consistent with the literature in the range 4 ≤ R ≤ 8 kpc.

Comparative investigation on ingot evolution and product quality under different arc distributions during vacuum arc remelting process

The arc characteristics especially the arc distribution of the vacuum arc remelting (VAR) process are closely related to the ingot evolution and consequently the final product quality. Taking segregation defects and solidification quality as the indexes to evaluate the final product quality under different arc distributions, a three-dimensional full-scale transient model for predicting segregation defects is developed in this paper. Local solidification time (LST) and secondary dendrite arm spacing (SDAS) are used to characterize the solidification quality. This model is adopted to predict channel segregation (freckle) and macrosegregation defects during VAR process of Ni-5.8 wt.%Al-15.2 wt.%Ta alloy under several typical arc distributions. The results show that the diffuse arc has the shallowest molten pool among several arc distributions. At the early stage of solidification, the solute enrichment channels formed under the Gaussian and diffuse arc are slender and concentrated, while they are relatively sparse and uneven in thickness under the rotating arc. The value of volume-averaged segregation extent is always the smallest under the diffuse arc and the largest under the Gaussian arc, with final values of 67.53% and 69.66%, respectively. The volume-averaged values of LST and SDAS are relatively the largest under the Gaussian arc, about 1599 s and 209 μm, respectively; and they are the smallest under the diffuse arc, about 1520 s and 206 μm, respectively. In the same process conditions, the product quality of VAR ingots prepared under the diffuse arc is the best, followed by the rotating arc, and the worst under the Gaussian arc.

Evidence of a vertical kinematic oscillation beyond the Radcliffe wave

The Radcliffe wave (RW) is a recently discovered sinusoidal vertical feature of dense gas in the proximity of the Sun. In the disk plane, it is aligned with the Local Arm. However, the origin of its vertical undulation is still unknown. This study constrains the kinematics of the RW, using young stars and open clusters as tracers, and explores the possibility of this oscillation being part of a more extended vertical mode. We study the median vertical velocity trends of the young stars and clusters along with the RW and extend it further to the region beyond it. We discovered a kinematic wave in the Galaxy, distinct from the warp, with the amplitude of oscillation depending on the age of the stellar population. We performed a similar analysis in the N-body simulation of a satellite as massive as the Sagittarius dwarf galaxy impacting the galactic disk. When projected in the plane, the spiral density wave induced by the satellite impact is aligned with the RW, suggesting that both may be the response of the disk to an external perturbation. However, the observed kinematic wave is misaligned. It appears as a kinematic wave travelling radially, winding up faster than the density wave matched by the RW, setting its origins into question. If a satellite galaxy is indeed responsible for the presence of this kinematic wave, we predict the existence of a vertical velocity dipole that would be expected to form across the disk. The reality of this prediction may be measurable with the upcoming Gaia DR3 and DR4.

Kinematic footprint of the Milky Way spiral arms in Gaia EDR3

ABSTRACT The Milky Way spiral arms are well established from star counts as well as from the locus of molecular clouds and other young objects; however, they have only recently started to be observed from a kinematics point of view. Using the kinematics of thin disc stars in Gaia EDR3 around the extended solar neighbourhood, we create x–y projections coloured by the radial, residual rotational, and vertical Galactocentric velocities (U, ΔV, W). The maps are rich in substructures and reveal the perturbed state of the Galactic disc. We find that local differences between rotational velocity and the azimuthally averaged velocity, ΔV, display at least five large-scale kinematic spirals; two of them closely follow the locus of the Sagittarius-Carina and Perseus spiral arms, with pitch angles of 9.12° and 7.76°, and vertical thickness of ∼400 pc and ∼600 pc, respectively. Another kinematic spiral is located behind the Perseus arm and appears as a distortion in rotation velocities left by this massive arm but with no known counterpart in gas or stars overdensity. A weaker signal close to the Sun’s position is present in our three velocity maps, and appears to be associated with the Local arm. Our analysis of the stellar velocities in the Galactic disc shows kinematic differences between arms and interarms that are in favour of Milky Way spiral arms that do not corotate with the disc. Moreover, we show that the kinematic spirals are clumpy and flocculent, revealing the underlying nature of the Milky Way spiral arms.

Distribution of the diffuse interstellar band λ6614 in the NGC 2264, Rosette Nebula, and S147 regions

ABSTRACT Diffuse interstellar bands (DIBs) are absorption features arising from the interstellar medium, for which the carriers remain unclear. In this work, a total of 3115 stars in the regions of NGC 2264, the Rosette Nebula, and S147 are selected from LAMOST-MRS to study the spatial and velocity distributions of the DIB λ6614 carrier. From the spatial distribution, we find that DIB λ6614 carrier clouds appear to be widely and inhomogeneously distributed in the three target regions. They are either closer or further in distance, or much wider than the three nebulae, and there are gaps within them. The radial velocities of the DIB λ6614 carrier clouds are on average about 13, 20, and 10 km s−1 slower than the radial velocities of the nebulae in the NGC 2264, Rosette Nebula, and S147 regions, respectively. Furthermore, there is probably a high-extinction region from 0.6 to 0.8 kpc in the NGC 2264 direction, where the DIB λ6614 carrier vanishes. In the S147 region, the DIB λ6614 cloud is possibly discontinuous, and the tomographic evidence suggests that there are two DIB λ6614 clouds. The first cloud is at 0.3–0.9 kpc, which is in or near the Local Arm, while the second one emerges at about 1.8 kpc from the Sun and may be associated with S147 and in the Perseus Arm.

Eptifibatida y vasodilatadores intracoronarios para prevenir la ausencia de reperfusión en el IAMCEST con diabetes y alta carga de trombos. Un ensayo aleatorizado

Introduction and objectivesTo study the impact of injecting intracoronary eptifibatide plus vasodilators via thrombus aspiration catheter vs thrombus aspiration alone in reducing the risk of no-reflow in acute ST-elevation myocardial infarction (STEMI) with diabetes and high thrombus burden. MethodsThe study involved 413 diabetic STEMI patients with high thrombus burden, randomized to intracoronary injection (distal to the occlusion) of eptifibatide, nitroglycerin and verapamil after thrombus aspiration and prior to balloon inflation (n=206) vs thrombus aspiration alone (n=207). The primary endpoint was post procedural myocardial blush grade and corrected Thrombolysis in Myocardial Infarction (TIMI) frame count (cTFC). Major adverse cardiovascular events were reported at 6 months. ResultsThe intracoronary eptifibatide and vasodilators arm was superior to thrombus aspiration alone regarding myocardial blush grade-3 (82.1% vs 31.4%; P=.001). The local intracoronary eptifibatide and vasodilators arm had shorter cTFC (18.16±6.54 vs 29.64±5.53, P=.001), and better TIMI 3 flow (91.3% vs 61.65%; P=.001). Intracoronary eptifibatide and vasodilators improved ejection fraction at 6 months (55.2±8.13 vs 43±6.67; P=.005). There was no difference in the rates of major adverse cardiovascular events at 6 months. ConclusionsAmong diabetic patients with STEMI and high thrombus burden, intracoronary eptifibatide plus vasodilators injection was beneficial in preventing no-reflow compared with thrombus aspiration alone. Larger studies are encouraged to investigate the benefit of this strategy in reducing the risk of adverse clinical events.

Intracoronary eptifibatide with vasodilators to prevent no-reflow in diabetic STEMI with high thrombus burden. A randomized trial

Introduction and objectivesTo study the impact of injecting intracoronary eptifibatide plus vasodilators via thrombus aspiration catheter vs thrombus aspiration alone in reducing the risk of no-reflow in acute ST-elevation myocardial infarction (STEMI) with diabetes and high thrombus burden. MethodsThe study involved 413 diabetic STEMI patients with high thrombus burden, randomized to intracoronary injection (distal to the occlusion) of eptifibatide, nitroglycerin and verapamil after thrombus aspiration and prior to balloon inflation (n=206) vs thrombus aspiration alone (n=207). The primary endpoint was post procedural myocardial blush grade and corrected Thrombolysis in Myocardial Infarction (TIMI) frame count (cTFC). Major adverse cardiovascular events were reported at 6 months. ResultsThe intracoronary eptifibatide and vasodilators arm was superior to thrombus aspiration alone regarding myocardial blush grade-3 (82.1% vs 31.4%; P=.001). The local intracoronary eptifibatide and vasodilators arm had shorter cTFC (18.16±6.54 vs 29.64±5.53, P=.001), and better TIMI 3 flow (91.3% vs 61.65%; P=.001). Intracoronary eptifibatide and vasodilators improved ejection fraction at 6 months (55.2±8.13 vs 43±6.67; P=.005). There was no difference in the rates of major adverse cardiovascular events at 6 months. ConclusionsAmong diabetic patients with STEMI and high thrombus burden, intracoronary eptifibatide plus vasodilators injection was beneficial in preventing no-reflow compared with thrombus aspiration alone. Larger studies are encouraged to investigate the benefit of this strategy in reducing the risk of adverse clinical events.

Gas Dynamics in the Galaxy: Total Mass Distribution and the Bar Pattern Speed

Abstract Gas morphology and kinematics in the Milky Way contain key information for understanding the formation and evolution of our Galaxy. We present hydrodynamical simulations based on realistic barred Milky Way potentials constrained by recent observations. Our model can reproduce most features in the observed longitude–velocity diagram, including the Central Molecular Zone, the Near and Far 3 kpc arms, the Molecular Ring, and the spiral arm tangents. It can also explain the noncircular motions of masers from the recent BeSSeL2 survey. The central gas kinematics are consistent with a mass of 6.9 × 108 M ⊙ in the Nuclear Stellar Disk. Our model predicts the formation of an elliptical gaseous ring surrounding the bar, which is composed of the 3 kpc arms, the Norma arm, and the bar-spiral interfaces. This ring is similar to those “inner” rings in some Milky Way analogs with a boxy/peanut-shaped bulge (e.g., NGC 4565 and NGC 5746). The kinematics of gas near the solar neighborhood are governed by the Local arm. The bar pattern speed constrained by our gas model is 37.5–40 km s−1 kpc−1, corresponding to a corotation radius of R CR = 6.0–6.4 kpc. The rotation curve of our model rises gently within the central ∼ 5 kpc, significantly less steep than those predicted by some recent zoom-in cosmological simulations.

A 12.2 GHz Methanol Maser Survey toward the 6.7 GHz Counterparts Associated with/without UC H ii Regions

Abstract We report a new survey of the 12.2 GHz Class II methanol masers toward a sample of 367 sources with the 6.7 GHz methanol masers conducted with the Shanghai 65 m Tianma Radio Telescope. This sample has been previously made with observations of the radio continuum emission of UC H ii regions by the VLA. A total of 176 sources were detected with the 12.2 GHz methanol maser, with a detection rate of 48%, including 8 new detections. A lower detection rate (<10%) was determined toward the sources in the Galactic longitude ranges of 60°–180°, revealing that the physical environments from those sources in the Local arm or the tails of Galactic arms do not easily excite the 12.2 GHz masers. In addition, two detections of highly excited-state OH masers at the 13.4 GHz transition were made, one of which is a new detection. Compared to previous surveys, one-third of the detected 12.2 GHz masers show considerable flux variations, implying the possible changes of their physical environments associated with variable radiation fields from their host high-mass young stellar objects. A positive log–log correlation is found between the luminosities of the 6.7 and 12.2 GHz masers in our observed sample, suggesting that both the transition masers have similar excitation conditions. The statistical analysis for the relationships between the methanol maser luminosity and UC H ii region spatial size indicates that the maser luminosities of both the 6.7 and 12.2 GHz transitions have a decreasing trend with the spatial sizes of the associated UC H ii regions, indicating that the Class II methanol masers might fade away with the H ii region evolution.

Nobeyama 45 m Local Spur CO survey. I. Giant molecular filaments and cluster formation in the Vulpecula OB association

Abstract We have performed new large-scale 12CO, 13CO, and C18O J = 1–0 observations toward the Vulpecula OB association (l ∼ 60°) as part of the Nobeyama 45 m Local Spur CO survey project. Molecular clouds are distributed over ∼100 pc, with local peaks at the Sh 2-86, Sh 2-87, and Sh 2-88 high-mass star-forming regions in the Vulpecula complex. The molecular gas is associated with the Local Spur, which corresponds to the nearest inter-arm region located between the Local Arm and the Sagittarius Arm. We discovered new giant molecular filaments (GMFs) in Sh 2-86, with a length of ∼30 pc, width of ∼5 pc, and molecular mass of $\sim\!\! 4 \times 10^4\, M_{\odot }$. We also found that Sh 2-86 contains the three velocity components at 22, 27, and 33 km s−1. These clouds and GMFs are likely to be physically associated with Sh 2-86 because they have high 12CO J = 2–1 to J = 1–0 intensity ratios and coincide with the infrared dust emission. The open cluster NGC 6823 exists at the common intersection of these clouds. We argue that the multiple cloud interaction scenario, including GMFs, can explain cluster formation in the Vulpecula OB association.

The Proliferation of Small Arms and Light Weapons in Nigeria: Corruption a Major Challenge

The proliferation of small arms and light weapons (SALW) is gradually and perilously becoming a transnational organized crime. In Nigeria, this peril assumed its delicate stage with incessant killings by Boko Haram insurgents, herdsmen-farmers clashes, kidnappings, communal and religious crisis, and armed robbery. The drift of this threat is the availability of weapons that are trafficked through Nigeria’s porous borders. Regulating the proliferation of small arms and light weapons has been challenged by several factors such as border porosity, inadequate personnel, lack of equipment, lack of data, weak enforcement, stockpile management, local arms manufacturers. Corruption takes center stage and is the focus of this paper. Corruption directly or indirectly is related to other challenges. The paper recommends that corruption must be addressed if all legal and institutional measures for border security and curtailing the spread of weapons in Nigeria are to achieve their objectives.

A Unified Model for the Fan Region and the North Polar Spur: A Bundle of Filaments in the Local Galaxy

Abstract We present a simple, unified model that can explain two of the brightest, large-scale, diffuse, polarized radio features in the sky, the North Polar Spur (NPS) and the Fan Region, along with several other prominent loops. We suggest that they are long, magnetized, and parallel filamentary structures that surround the Local arm and/or Local Bubble, in which the Sun is embedded. We show that this model is consistent with the large number of observational studies on these regions and is able to resolve an apparent contradiction in the literature that suggests that the high-latitude portion of the NPS is nearby, while lower-latitude portions are more distant. Understanding the contributions of this local emission is critical to developing a complete model of the Galactic magnetic field. These very nearby structures also provide context to help understand similar nonthermal, filamentary structures that are increasingly being observed with modern radio telescopes.

The Spiral Structure in the Solar Neighborhood

The spiral structure in the solar neighborhood is an important issue in astronomy. In the past few years, there has been significant progress in observation. The distances for a large number of good spiral tracers, i.e., giant molecular clouds, high-mass star-formation region masers, HII regions, O-type stars, and young open clusters, have been accurately estimated, making it possible to depict the detailed properties of nearby spiral arms. In this work, we first give an overview about the research status for the Galaxy’s spiral structure based on different types of tracers. Then the objects with distance uncertainties better than 15% and <0.5 kpc are collected and combined together to depict the spiral structure in the solar neighborhood. Five segments related with the Perseus, Local, Sagittarius-Carina, Scutum-Centaurus, and Norma arms are traced. With the large dataset, the parameters of the nearby arm segments are fitted and updated. Besides the dominant spiral arms, some substructures probably related to arm spurs or feathers are also noticed and discussed.

Evolution of the local spiral structure of the Milky Way revealed by open clusters

The structure and evolution of the spiral arms of our Milky Way are basic but long-standing questions in astronomy. In particular, the lifetime of spiral arms is still a puzzle and has not been well constrained from observations. In this work, we aim to inspect these issues using a large catalogue of open clusters. We compiled a catalogue of 3794 open clusters based on Gaia EDR3. A majority of these clusters have accurately determined parallaxes, proper motions, and radial velocities. The age parameters for these open clusters are collected from references or calculated in this work. In order to understand the nearby spiral structure and its evolution, we analysed the distributions, kinematic properties, vertical distributions, and regressed properties of subsamples of open clusters. We find evidence that the nearby spiral arms are compatible with a long-lived spiral pattern and might have remained approximately stable for the past 80 million years. In particular, the Local Arm, where our Sun is currently located, is also suggested to be long-lived in nature and probably a major arm segment of the Milky Way. The evolutionary characteristics of nearby spiral arms show that the dynamic spiral mechanism might be not prevalent for our Galaxy. Instead, density wave theory is more consistent with the observational properties of open clusters.

Milky Way spiral arms from open clusters in Gaia EDR3

Context. The physical processes driving the formation of Galactic spiral arms are still under debate. Studies using open clusters favour the description of the Milky Way spiral arms as long-lived structures following the classical density wave theory. Current studies comparing the Gaia DR2 field stars kinematic information of the solar neighbourhood to simulations, find a better agreement with short-lived arms with a transient behaviour. Aims. Our aim is to provide an observational, data-driven view of the Milky Way spiral structure and its dynamics using open clusters as the main tracers, and to contrast it with simulation-based approaches. We used the most complete catalogue of Milky Way open clusters, with astrometric Gaia EDR3 updated parameters, estimated astrophysical information, and radial velocities, to revisit the nature of the spiral pattern of the Galaxy. Methods. We used a Gaussian mixture model to detect overdensities of open clusters younger than 30 Myr that correspond to the Perseus, Local, Sagittarius, and Scutum spiral Arms, respectively. We used the birthplaces of the open cluster population younger than 80 Myr to trace the evolution of the different spiral arms and compute their pattern speed. We analysed the age-distribution of the open clusters across the spiral arms to explore the differences in the rotational velocity of stars and spiral arms. Results. We are able to increase the range in Galactic azimuth where present-day spiral arms are described, better estimating its parameters by adding 264 young open clusters to the 84 high-mass star-forming regions used so far, thus increasing the number of tracers by 314%. We used the evolution of the open clusters from their birth positions to find that spiral arms nearly co-rotate with field stars at any given radius, discarding a common spiral pattern speed for the spiral arms explored. Conclusions. The derivation of different spiral pattern speeds for the different spiral arms disfavours classical density waves as the main drivers for the formation of the Milky Way spiral structure, and it is in better agreement with simulation-based approaches that tend to favour transient spirals. The increase in the number of known open clusters, as well as in their derived properties, allows us to use them as effective spiral structure tracers and homogenise the view from open clusters and field stars on the nature of the Galactic spiral arms.

Galactic spiral structure revealed byGaiaEDR3

Using the astrometry and integrated photometry from theGaiaEarly Data Release 3, we map the density variations in the distribution of young upper main sequence (UMS) stars, open clusters, and classical Cepheids in the Galactic disc within several kiloparsecs of the Sun. We derive maps of relative over- and under-dense regions for UMS stars in the Galactic disc using both bivariate kernel density estimators and wavelet transformations. The resulting overdensity maps exhibit large-scale arches that extend in a clumpy but coherent way over the entire sampled volume, indicating the location of the spiral arm segments in the vicinity of the Sun. Peaks in the UMS overdensity are well matched by the distribution of young and intrinsically bright open clusters. By applying a wavelet transformation to a sample of classical Cepheids, we find that their overdensities possibly extend the spiral arm segments on a larger scale (≃10 kpc from the Sun). While the resulting map based on the UMS sample is generally consistent with previous models of the Sagittarius-Carina spiral arm, the geometry of the arms in the III quadrant (galactic longitudes 180° <l < 270°) differs significantly from that suggested by many previous models. In particular, we find that our maps favour a larger pitch angle for the Perseus arm, and that the Local Arm extends into the III quadrant at least 4 kpc past the position of the Sun, giving it a total length of at least 8 kpc.

SPICY: The Spitzer/IRAC Candidate YSO Catalog for the Inner Galactic Midplane

Abstract We present ∼120,000 Spitzer/IRAC candidate young stellar objects (YSOs) based on surveys of the Galactic midplane between ℓ ∼ 255° and 110°, including the GLIMPSE I, II, and 3D, Vela-Carina, Cygnus X, and SMOG surveys (613 square degrees), augmented by near-infrared catalogs. We employed a classification scheme that uses the flexibility of a tailored statistical learning method and curated YSO data sets to take full advantage of Spitzer’s spatial resolution and sensitivity in the mid-infrared ∼3–9 μm range. Multiwavelength color/magnitude distributions provide intuition about how the classifier separates YSOs from other red IRAC sources and validate that the sample is consistent with expectations for disk/envelope-bearing pre–main-sequence stars. We also identify areas of IRAC color space associated with objects with strong silicate absorption or polycyclic aromatic hydrocarbon emission. Spatial distributions and variability properties help corroborate the youthful nature of our sample. Most of the candidates are in regions with mid-IR nebulosity, associated with star-forming clouds, but others appear distributed in the field. Using Gaia DR2 distance estimates, we find groups of YSO candidates associated with the Local Arm, the Sagittarius–Carina Arm, and the Scutum–Centaurus Arm. Candidate YSOs visible to the Zwicky Transient Facility tend to exhibit higher variability amplitudes than randomly selected field stars of the same magnitude, with many high-amplitude variables having light-curve morphologies characteristic of YSOs. Given that no current or planned instruments will significantly exceed IRAC’s spatial resolution while possessing its wide-area mapping capabilities, Spitzer-based catalogs such as ours will remain the main resources for mid-infrared YSOs in the Galactic midplane for the near future.

The Gaia view of the Cepheus flare

ABSTRACT We present a new census of candidate pre-main-sequence stars in the Cepheus flare star-forming region, based on Gaia EDR3 parallaxes, proper motions, and colour–magnitude diagrams. We identified new candidate members of the previously known young stellar groups associated with NGC 7023, L1177, L1217/L1219, L1228, L1235, and L1251. We studied the 3D structure of the star-forming complex and the distribution of tangential velocities of the young stars. The young stellar groups are located between 330 and 368 pc from the Sun, divided into three kinematic subgroups, and have ages between 1 and 5 million yr. The results confirm the scenario of propagating star formation, suggested by previous studies. In addition to the bulk pre-main-sequence star population between 330 and 370 pc, there is a scattered and more evolved pre-main-sequence population around 150–180 pc. We found new candidate members of the nearby Cepheus Association, and identified a new moving group of 46, 15–20 million yr old pre-main-sequence stars located at a distance of 178 pc, around the A0-type star HD 190833. A few pre-main-sequence stars are located at 800–900 pc, indicative of star-forming regions associated with the Galactic local arm above the Galactic latitude of +10°.