We develop a Bayesian Machine Learning framework called BINGO (Bayesian INference for Galactic archaeOlogy) centred around a Bayesian neural network. After being trained on the APOGEE and \emph{Kepler} asteroseismic age data, BINGO is used to obtain precise relative stellar age estimates with uncertainties for the APOGEE stars. We carefully construct a training set to minimise bias and apply BINGO to a stellar population that is similar to our training set. We then select the 17,305 stars with ages from BINGO and reliable kinematic properties obtained from \textit{Gaia} DR2. By combining the age and chemo-kinematical information, we dissect the Galactic disc stars into three components, namely, the thick disc (old, high-[$α$/Fe], [$α$/Fe] $\gtrsim$ 0.12), the thin disc (young, low-[$α$/Fe]) and the Bridge, which is a region between the thick and thin discs. Our results indicate that the thick disc formed at an early epoch only in the inner region, and the inner disc smoothly transforms to the thin disc. We found that the outer disc follows a different chemical evolution pathway from the inner disc. The outer metal-poor stars only start forming after the compact thick disc phase has completed and the star-forming gas disc extended outwardly with metal-poor gas accretion. We found that in the Bridge region the range of [Fe/H] becomes wider with decreasing age, which suggests that the Bridge region corresponds to the transition phase from the smaller chemically well-mixed thick to a larger thin disc with a metallicity gradient.
We use $Gaia$ eDR3 data and legacy spectroscopic surveys to map the Milky Way disc substructure towards the Galactic Anticenter at heliocentric distances $d\geq10\,\rm{kpc}$. We report the discovery of multiple previously undetected new filaments embedded in the outer disc in highly extincted regions. Stars in these over-densities have distance gradients expected for disc material and move on disc-like orbits with $v_ϕ\sim170-230\,\rm{km\,s^{-1}}$, showing small spreads in energy. Such a morphology argues against a quiescently growing Galactic thin disc. Some of these structures are interprete…
Context. The ZOA does not allow clear optical observations of extragalactic sources behind the Milky Way due to the meaningful extinction of the optical emission of these objects. The observations in NIR wavelengths represent a potential source of astronomical discoveries supporting the detection of new galaxies, completing the picture of the large scale structure in this still little explored area of the sky. Aims. Our aim is to decipher the nature of the overdensity located behind the Milky Way, in the tile b204 of the VVV survey. Methods. We studied an area of six arcmin around a galaxy con…
We demonstrate a new statistical method of determining the global photometric properties of the Milky Way (MW) to an unprecedented degree of accuracy, allowing our Galaxy to be compared directly to objects measured in extragalactic surveys. Capitalizing on the high-quality imaging and spectroscopy dataset from the Sloan Digital Sky Survey (SDSS), we exploit the inherent dependence of galaxies' luminosities and colors on their total stellar mass, $\mathrm{M}_\star$, and star formation rate (SFR), $\mathrm{\dot{M}}_\star$, by selecting a sample of $Milky$ $Way$ $analog$ $galaxies$ designed to re…
The spatial segregation between dSphs and dIrrs in the Local Group has long been regarded as evidence of an interaction with their host galaxies. In this paper, we assume that ram-pressure stripping is the dominant mechanism that removed gas from the dSphs and we use this to derive a lower bound on the density of the corona of the Milky Way at large distances (50-90 kpc) from the Galactic centre. At the same time, we derive an upper bound by demanding that the interstellar medium of the dSphs is in pressure equilibrium with the hot corona. We consider two dwarfs (Sextans and Carina) with well-…
We report 1,656 new star clusters found in the Galactic disk (|b|<20 degrees) beyond 1.2 kpc, using Gaia EDR3 data. Based on an unsupervised machine learning algorithm, DBSCAN, and followed our previous studies, we utilized a unique method to do the data preparation and obtained the clustering coefficients, which proved to be an effective way to search blindly for star clusters. We tabulated the physical parameters and member stars of the new clusters, and presented some interesting examples, including a globular cluster candidate. The cluster parameters and member stars are available at CDS v…
The ALMaQUEST Survey XVII: Unveiling Multiple Quenching Pathways in Green Valley Galaxies via Molecular Gas and Quenching Timescale Analyses
Institute of Astronomy & Astrophysics, Academia Sinica（中央研究院天文及天文物理研究所）；Graduate Institute of Astrophysics and Department of Physics, National Taiwan University（国立台湾大学天体物理研究所暨物理系）；Argelander-Institut für Astronomie, Universität Bonn（波恩大学阿尔兰德天文学研究所）；Stocker AstroScience Center, Dept. of Physics, Florida International University（佛罗里达国际大学斯托克天体科学中心物理系）；Department of Physics, Tamkang University（淡江大学物理系）；Department of Physics & Astronomy, University of Victoria（维多利亚大学物理与天文系）；Space Telescope Science Institute（太空望远镜科学研究所）；William H. Miller III Department of Physics and Astronomy, Johns Hopkins University（约翰斯·霍普金斯大学威廉·H·米勒三世物理与天文系）；Instituto de Astronomía, Universidad Nacional Autónoma de México（墨西哥国立自治大学天文学研究所）
We aim to determine unique features that characterise the past evolution of the progenitor of the Helmi streams through the analysis of star formation histories (SFHs). From the 5D {\it Gaia} EDR3 dataset, we extracted local samples of stars dominated by the Helmi streams, the Galactic (thick and thin) disc, and the local retrograde halo. We did this by identifying regions in a pseudo-Cartesian velocity space (obtained by setting line-of-sight velocities to zero), where stars belonging to these components, as identified in samples with 6D phase-space information, are predominantly found. We ma…
Unveiling the Milky Way with a Gaia DR3 census of OB-type stars within 2 kpc. I. Tracing local Galactic structure, massive star-forming regions and core-collapse supernova progenitors
Observatoire de Paris, Université PSL, Sorbonne Université, Université Paris Cité, CY Cergy Paris Université, CNRS（巴黎天文台，巴黎文理研究大学，索邦大学，巴黎西岱大学，CY塞吉-蓬图瓦兹大学，法国国家科学研究中心）；Max-Planck-Institut für Astronomie（马克斯·普朗克天文学研究所）；INAF – Osservatorio Astrofisico di Torino（意大利国家天体物理研究所都灵天文台）；University of Vienna（维也纳大学）；Keele University（基尔大学）；Instituto de Astrofísica de Canarias（加那利天体物理学研究所）；Universidad de La Laguna（拉古纳大学）；European Southern Observatory（欧洲南方天文台）
The Fermi bubbles, two giant structures above and below the Galactic center (GC), are among the most important discoveries of the Fermi Gamma-ray Space Telescope. Studying their physical origin has been providing valuable insights into cosmic-ray transport, the Galactic magnetic field, and past activity at the GC in the Milky Way galaxy. Despite their importance, the formation mechanism of the bubbles is still elusive. Over the past few years there have been numerous efforts, both observational and theoretical, to uncover the nature of the bubbles. In this article, we present an overview of th…
As nearby neighbors to the Milky Way, the Large and Small Magellanic Clouds (LMC and SMC) provide a unique opportunity to study star formation in the context of their galactic ecosystems. Thousands of young stellar objects (YSOs) have been characterized with large-scale Spitzer and Herschel surveys. In this paper, we present new near-IR spectroscopy of five high-mass YSOs in the LMC and one in the SMC. We detect multiple hydrogen recombination lines, as well as He I 2.058 $μ$m, H$_2$, [Fe II], and [S III] in these highly excited sources. We estimate the internal extinction of each source and f…
Chronology of our Galaxy from Gaia colour-magnitude diagram fitting (ChronoGal) II. Unveiling the formation and evolution of the kinematically selected Thick and Thin Discs
Universidad de La Laguna（拉古纳大学）；Instituto de Astrofísica de Canarias（加那利天体物理学研究所）；University of Granada（格拉纳达大学）；INAF – Astronomical Observatory of Abruzzo（意大利国家天体物理研究所阿布鲁佐天文台）；INFN, Sezione di Pisa（意大利国家核物理研究所比萨分部）；Kapteyn Astronomical Institute, University of Groningen（格罗宁根大学卡普坦天文研究所）
Milky Way Mapper decoded abundances -- II: From patterns to paths
Research School of Astronomy and Astrophysics, Australian National University（澳大利亚国立大学天文与天体物理研究学院）；Department of Astronomy, Columbia University（哥伦比亚大学天文学系）；Center for Astrophysics and Space Astronomy, Department of Astrophysical and Planetary Sciences, University of Colorado（科罗拉多大学天体物理学与行星科学系天体物理学与空间天文中心）；Department of Physics & Astronomy, University of Utah（犹他大学物理与天文学系）；Department of Physics and Astronomy, Vanderbilt University（范德堡大学物理与天文学系）；Center for Computational Astrophysics, Flatiron Institute（平顿研究所计算天体物理学中心）；School of Physics and Astronomy, Monash University（莫纳什大学物理与天文学院）；Department of Astronomy, The Ohio State University（俄亥俄州立大学天文学系）；Center for Cosmology and Astroparticle Physics (CCAPP), The Ohio State University（俄亥俄州立大学宇宙学与高能粒子物理中心）
Cosmic rays (CRs) are the probes of the deep space. They allow us to study particle acceleration, chemical composition of the interstellar medium, and global properties of our Galaxy. However, until recently studies of CRs were similar to astronomical observations with blurred lenses that capture only the integral brightness of all stars in the field of view. Thanks to the recent technological developments, our "lenses" are now capable of capturing sharp images and making precise measurements of all CR species. We have a full range of unique instrumentation for direct measurements of CRs in sp…
Unveiling star formation at sub-solar metallicity with ALMA2040
INAF-Osservatorio Astrofisico di Arcetri（意大利国家天体物理研究所阿切尔西天文台）；Univ. Grenoble Alpes, CNRS, IPAG（格勒诺布尔阿尔卑斯大学，法国国家科学研究中心，天体物理学与行星学研究所）；University of Hertfordshire, Centre for Astrophysics Research（赫特福德大学天体物理学研究中心）；Niels Bohr Institute, University of Copenhagen（哥本哈根大学尼尔斯·玻尔研究所）；Laboratoire d’astrophysique de Bordeaux, Univ. Bordeaux, CNRS（波尔多大学天体物理学实验室，法国国家科学研究中心）；Centro de Astrobiología (CAB), CSIC-INTA（西班牙国家航空航天技术研究所与高等科学研究委员会天体生物学中心）；Institut de Ciències de l’Espai (ICE-CSIC)（空间科学学院（西班牙高等科学研究委员会））；Institute of Astrophysics, University of Cologne（科隆大学天体物理研究所）；Max Planck Institute for Astronomy（马克斯·普朗克天文学研究所）
We present a comprehensive analysis of different techniques available for the spectroscopic analysis of FGK stars, and provide a recommended methodology which efficiently estimates accurate stellar atmospheric parameters for large samples of stars. Our analysis includes a simultaneous equivalent width analysis of Fe I and Fe II spectral lines, and for the first time, utilises on-the-fly NLTE corrections of individual Fe I lines. We further investigate several temperature scales, finding that estimates from Balmer line measurements provide the most accurate effective temperatures at all metalli…
Most of our knowledge about the structure of the Milky Way has come from the study of variable stars. Among the variables, mimicking the periodic variation of pulsating stars, are the eclipsing binaries. These stars are important in astrophysics because they allow us to directly measure radii and masses of the components, as well as the distance to the system, thus being useful in studies of Galactic structure alongside pulsating RR Lyrae and Cepheids. Using the distinguishing features of their light curves, one can identify them using a semi-automated process. In this work, we present a strat…
Milky Way Near Twins (MWNeTs). I. A Hierarchical Framework for Identifying Candidate Evolutionary Counterparts of the Milky Way
Main Astronomical Observatory of the NAS of Ukraine（乌克兰国家科学院主天文台）；Institute of Astronomy, V.N. Karazin Kharkiv National University（瓦·尼·卡拉金哈尔科夫国立大学天体物理研究所）；International Centre for Astronomical, Medical, and Ecological Research, National Academy of Sciences of Ukraine（乌克兰国家科学院国际天文、医学和生态研究中心）
Unveiling the Sagittarius Dwarf Spheroidal Galaxy Core with Gaia DR3: A Red Clump Distance Precise to 2%
The University of Texas at Austin（德克萨斯大学奥斯汀分校）；Whitman College（惠特曼学院）；Institute for Astronomy, University of Hawai‘i（夏威夷大学天体物理研究所）；Texas Christian University（得克萨斯基督教大学）；Maunakea Spectroscopic Explorer, Canada-France-Hawaii-Telescope（莫纳克亚光谱巡天项目，加拿大法国夏威夷望远镜）
The Galactic globular cluster system is incomplete, especially in the low latitude regions of the Galactic bulge and disk. We report the physical characterization of twelve star clusters in the Milky Way, most of which are explored here for the first time. Our aim is determining their main physical parameters, such as reddening and extinction, metallicity, age, total luminosity, mean cluster proper motions (PMs), distances, in order to unveil their physical nature. We study the clusters using optical and near-infrared (NIR) datasets. We use the Gaia Early Data Release 3 (EDR3) PMs in order to …
Unveiling the Origins of the Molecular Gas Reservoirs in Recently Quenched Massive Galaxies
University of Florida（佛罗里达大学）；Cosmic Dawn Center (DAWN)（宇宙黎明中心）；University of Pittsburgh（匹兹堡大学）；University of Massachusetts, Amherst（马萨诸塞大学阿默斯特分校）；Department of Astronomy, University of Geneva（日内瓦大学天文系）；Department of Astrophysics, Universität Zürich（苏黎世大学天体物理系）；University of Edinburgh（爱丁堡大学）；Department of Physics and Astronomy, University of the Western Cape（西开普大学物理与天文系）；Texas A&M University（德克萨斯农工大学）
The Milky Way and all other galaxies are missing most of their baryons in that the ratio of the known baryonic mass to the gravitating mass (within the virial radius), is several times less than the cosmic ratio determined from WMAP. This implies that either the baryons never fell into galaxies or that powerful galactic winds removed most of the baryons. It is possible to discriminate between these two pathways if we can discover the missing baryons and measure its properties: spatial distribution; temperature; and metallicity. The missing baryons from galaxies are expected to have temperature…
Spectroscopic surveys of the Milky Way's stars have revealed spatial, chemical and kinematical structures that encode its history. In this work, we study their origins using a cosmological zoom simulation, VINTERGATAN, of a Milky Way-mass disc galaxy. We find that in connection to the last major merger at $z\sim 1.5$, cosmological accretion leads to the rapid formation of an outer, metal-poor, low-[$α$/Fe] gas disc around the inner, metal-rich galaxy containing the old high-[$α$/Fe] stars. This event leads to a bimodality in [$α$/Fe] over a range of [Fe/H]. A detailed analysis of how the galax…
Stellar cluster formation in a Milky Way-sized galaxy at z>4 -- II. A hybrid formation scenario for the nuclear star cluster and its connection to the nuclear stellar ring
Galactic haloes in a $Λ$-CDM universe are predicted to host today a swarm of debris resulting from cannibalised dwarf galaxies. The chemo-dynamical information recorded in their stellar populations helps elucidate their nature, constraining the assembly history of the Galaxy. Using data from APOGEE and \textit{Gaia}, we examine the chemical properties of various halo substructures, considering elements that sample various nucleosynthetic pathways. The systems studied are Heracles, \textit{Gaia}-Enceladus/Sausage (GES), the Helmi stream, Sequoia, Thamnos, Aleph, LMS-1, Arjuna, I'itoi, Nyx, Icar…
A Vertically Orientated Dark Matter Halo Marks a Flip of the Galactic Disk
Shanghai Astronomical Observatory, Chinese Academy of Sciences（中国科学院上海天文台）；Institute for Astronomy the School of Physics, Zhejiang University（浙江大学物理学院天体物理研究所）；National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）；School of Physics and Optoelectronic Engineering, Hainan University（海南大学物理与电子工程学院）；Department of Astronomy, Westlake University（西湖大学天文系）；Institute for Frontiers in Astronomy and Astrophysics, Beijing Normal University（北京师范大学天文与前沿科学研究中心）
Recent dynamical analysis based on Gaia data have revealed major accretion events in Milky Way's history. Nevertheless, our understanding of the primordial Galaxy is hindered because the bona fide identification of the most metal-poor and correspondently oldest accreted stars remains challenging. Contrary to alpha-elements, neutron-capture elements present unexplained large abundance spreads for low metallicity stars, that could result from a mixture of formation sites. We have analysed the abundances of yttrium, europium, magnesium and iron in Milky Way satellite galaxies, field halo stars an…
We develop a hybrid model of galactic chemical evolution that combines a multi-ring computation of chemical enrichment with a prescription for stellar migration and the vertical distribution of stellar populations informed by a cosmological hydrodynamic disc galaxy simulation. Our fiducial model adopts empirically motivated forms of the star formation law and star formation history, with a gradient in outflow mass loading tuned to reproduce the observed metallicity gradient. With this approach, the model reproduces many of the striking qualitative features of the Milky Way disc's abundance str…
Bulgeless Evolution And the Rise of Discs (BEARD) II. The role of mergers in shaping the Milky Way analogues in TNG50
Donostia International Physics Centre (DIPC)（多诺西亚国际物理中心）；Universidad de Córdoba（科尔多瓦大学）；Universidad de La Laguna（拉帕尔马大学）；Instituto de Astrofísica de Canarias（加那利群岛天体物理学研究所）
In this paper we explore the interplay between intermediate-mass black holes (IMBHs) and their nursing globular clusters (GCs), taking advantage of over 2000 Monte Carlo GC models. We find that the average density of IMBHs sphere of influence can be uniquely connected to the host GCs luminosity and half-light radius via a fundamental plane. We propose a statistical approach to systematically identify potential Galactic GCs harbouring either an IMBH or a massive subsystem comprised of stellar BHs. Our models show that the IMBH is often bound to a stellar companion or a stellar BH, which can lea…
Stars with unusual elemental abundances offer clues about rare astrophysical events or nucleosynthetic pathways. Stars with significantly depleted magnesium and enhanced potassium ([Mg/Fe] < -0.5; [K/Fe] > 1) have to date only been found in the massive globular cluster NGC 2419 and, to a lesser extent, NGC 2808. The origin of this abundance signature remains unknown, as does the reason for its apparent exclusivity to these two globular clusters. Here we present 112 field stars, identified from 454,180 LAMOST giants, that show significantly enhanced [K/Fe] and possibly depleted [Mg/Fe] abundanc…
Bulgeless Evolution And the Rise of Discs (BEARD) III. A numerical simulation view of satellites around Milky-Way analogues
Universidad de La Laguna（拉各拉大学）；Instituto de Astrofísica de Canarias（加那利天体物理研究所）；Donostia International Physics Centre (DIPC)（多诺斯蒂亚国际物理中心）；Universidad de Córdoba（科尔多瓦大学）
