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  • Disruption of a massive molecular cloud by a supernova in the Galactic Centre: Initial results from the ACES project

    European Southern Observatory (ESO), Karl-Schwarzschild-Straße 2, 85748, Garching, Germany; SUPA, School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews, KY16 9SS, UK; European Southern Observatory (ESO), Karl-Schwarzschild-Straße 2, 85748, Garching, Germany; School of Physics and Astronomy, Cardiff University, The Parade, Cardiff, CF24 3AA, UK; Observatorio Astronómico de Quito, Escuela Politécnica Nacional, Interior del Parque La Alameda, 170136, Quito, Ecuador; Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO, 80389, USA; University of Connecticut, Department of Physics, 196A Hillside Road, Unit 3046, Storrs, CT, 06269-3046, USA; Armagh Observatory and Planetarium, College Hill, Armagh, BT61 9DB, Northern Ireland; National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA, 22903, USA; Centro de Astrobiología (CAB), CSIC-INTA, Carretera de Ajalvir km 4, Torrejón de Ardoz, 28850, Madrid, Spain; Instituto de Astronomía, Universidad Católica del Norte, Av. Angamos 0610, Antofagasta, Chile; Chinese Academy of Sciences South America Center for Astronomy, National Astronomical Observatories, CAS, Beijing, 100101, China; Department of Astronomy, University of Florida, PO Box 112055, Gainesville, FL, 32611, USA; et al. (Astronomy and Astrophysics, 2024-11-01)
    The Milky Way's Central Molecular Zone (CMZ) differs dramatically from our local solar neighbourhood, both in the extreme interstellar medium conditions it exhibits (e.g. high gas, stellar, and feedback density) and in the strong dynamics at play (e.g. due to shear and gas influx along the bar). Consequently, it is likely that there are large-scale physical structures within the CMZ that cannot form elsewhere in the Milky Way. In this paper, we present new results from the Atacama Large Millimeter/submillimeter Array (ALMA) large programme ACES (ALMA CMZ Exploration Survey) and conduct a multi-wavelength and kinematic analysis to determine the origin of the M0.8–0.2 ring, a molecular cloud with a distinct ring-like morphology. We estimate the projected inner and outer radii of the M0.8–0.2 ring to be 79″ and 154″, respectively (3.1 pc and 6.1 pc at an assumed Galactic Centre distance of 8.2 kpc) and calculate a mean gas density &gt;10<SUP>4</SUP> cm<SUP>‑3</SUP>, a mass of ~10<SUP>6</SUP> M<SUB>⊙</SUB>, and an expansion speed of ~20 km s<SUP>‑1</SUP>, resulting in a high estimated kinetic energy (&gt;10<SUP>51</SUP> erg) and momentum (&gt;10<SUP>7</SUP> M<SUB>⊙</SUB> km s<SUP>‑1</SUP>). We discuss several possible causes for the existence and expansion of the structure, including stellar feedback and large-scale dynamics. We propose that the most likely cause of the M0.8–0.2 ring is a single high-energy hypernova explosion. To viably explain the observed morphology and kinematics, such an explosion would need to have taken place inside a dense, very massive molecular cloud, the remnants of which we now see as the M0.8–0.2 ring. In this case, the structure provides an extreme example of how supernovae can affect molecular clouds.
  • JCMT 850 μm Continuum Observations of Density Structures in the G35 Molecular Complex

    School of Physics and Astronomy, Yunnan University, Kunming, 650091, People's Republic of China; National Astronomical Observatories, Chinese Academy of Sciences, Datun Road A20, Beijing, People's Republic of China; CAS Key Laboratory of FAST, NAOC, Chinese Academy of Sciences, Beijing, People's Republic of China; University of Chinese Academy of Sciences, Beijing, People's Republic of China; Indian Institute of Space Science and Technology, Thiruvananthapuram, Kerala 695 547, India; National Astronomical Observatories, Chinese Academy of Sciences, Datun Road A20, Beijing, People's Republic of China; Department of Astronomy, Tsinghua University, Beijing 100084, People's Republic of China; Zhejiang Lab, Hangzhou, Zhejiang 311121, People's Republic of China; Department of Physics, National Sun Yat-Sen University, No. 70, Lien-Hai Road, Kaohsiung City 80424, Taiwan; Center of Astronomy and Gravitation, National Taiwan Normal University, Taipei 116, Taiwan; Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK; Physikalisches Institut, University of Cologne, Zülpicher Str. 77, D-50937 Köln, Germany; National Astronomical Observatories, Chinese Academy of Sciences, Datun Road A20, Beijing, People's Republic of China; CAS Key Laboratory of FAST, NAOC, Chinese Academy of Sciences, Beijing, People's Republic of China; University of Chinese Academy of Sciences, Beijing, People's Republic of China; National Astronomical Observatories, Chinese Academy of Sciences, Datun Road A20, Beijing, People's Republic of China; Key Laboratory of Radio Astronomy and Technology, Chinese Academy of Sciences, A20 Datun Road, Datun Road A20, Beijing, People's Republic of China; Max-Plank-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany; Academia Sinica Institute of Astronomy and Astrophysics, No. 1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan; et al. (The Astrophysical Journal, 2024-10-01)
    Filaments are believed to play a key role in high-mass star formation. We present a systematic study of the filaments and their hosting clumps in the G35 molecular complex using James Clerk Maxwell Telescope SCUBA-2 850 μm continuum data. We identified five clouds in the complex and 91 filaments within them, some of which form 10 hub–filament systems (HFSs), each with at least three hub-composing filaments. We also compiled a catalog of 350 dense clumps, 183 of which are associated with the filaments. We investigated the physical properties of the filaments and clumps, such as mass, density, and size, and their relation to star formation. We find that the global mass–length trend of the filaments is consistent with a turbulent origin, while the hub-composing filaments of high line masses (m <SUB>l</SUB> &gt; 230 M <SUB>⊙</SUB> pc<SUP>‑1</SUP>) in HFSs deviate from this relation, possibly due to feedback from massive star formation. We also find that the most massive and densest clumps (R &gt; 0.2 pc, M &gt; 35 M <SUB>⊙</SUB>, Σ &gt; 0.05 g cm<SUP>‑2</SUP>) are located in the filaments and in the hubs of HFSs, with the latter bearing a higher probability of the occurrence of high-mass star-forming signatures, highlighting the preferential sites of HFSs for high-mass star formation. We do not find significant variation in the clump mass surface density across different evolutionary environments of the clouds, which may reflect the balance between mass accretion and stellar feedback.
  • Atacama Large Aperture Submillimeter Telescope (AtLAST) science: Our Galaxy

    UK Astronomy Technology Centre, Royal Observatory Edinburgh, Edinburgh, EH9 3HJ, UK; IAPS-INAF, Rome, I-00133, Italy; Osservatorio Astrofisico di Arcetri, INAF, Firenze, 50125, Italy; Department of Physics and Astronomy, University College London, London, England, WC1E 6BT, UK; Center for Astrophysics, Harvard &amp; Smithsonian, Cambridge, MA, 02138-1516, USA; Academia Sinica Institute of Astronomy and Astrophysics, Taipei, 10617, Taiwan; Department of Astrophysics, University of Vienna, Vienna, 1180, Austria; Leiden Observatory, Leiden University, Leiden, South Holland, 2300-RA, The Netherlands; Department of Space, Earth and Environment, Chalmers University of Technology, Gothenburg, SE-412 96, Sweden; Observatoire Astronomique de Strasbourg, Universite de Strasbourg, Strasbourg, Grand Est, F-67000, France; School of Physics and Astronomy, Cardiff University, Cardiff, Wales, CF24 3AA, UK; et al. (Open Research Europe, 2024-06-01)
    As we learn more about the multi-scale interstellar medium (ISM) of our Galaxy, we develop a greater understanding for the complex relationships between the large-scale diffuse gas and dust in Giant Molecular Clouds (GMCs), how it moves, how it is affected by the nearby massive stars, and which portions of those GMCs eventually collapse into star forming regions. The complex interactions of those gas, dust and stellar populations form what has come to be known as the ecology of our Galaxy. Because we are deeply embedded in the plane of our Galaxy, it takes up a significant fraction of the sky, with complex dust lanes scattered throughout the optically recognizable bands of the Milky Way. These bands become bright at (sub-)millimetre wavelengths, where we can study dust thermal emission and the chemical and kinematic signatures of the gas. To properly study such large-scale environments, requires deep, large area surveys that are not possible with current facilities. Moreover, where stars form, so too do planetary systems, growing from the dust and gas in circumstellar discs, to planets and planetesimal belts. Understanding the evolution of these belts requires deep imaging capable of studying belts around young stellar objects to Kuiper belt analogues around the nearest stars. Here we present a plan for observing the Galactic Plane and circumstellar environments to quantify the physical structure, the magnetic fields, the dynamics, chemistry, star formation, and planetary system evolution of the galaxy in which we live with AtLAST; a concept for a new, 50m single-dish sub-mm telescope with a large field of view which is the only type of facility that will allow us to observe our Galaxy deeply and widely enough to make a leap forward in our understanding of our local ecology.
  • Binarity at LOw Metallicity (BLOeM): A spectroscopic VLT monitoring survey of massive stars in the SMC

    The School of Physics and Astronomy, Tel Aviv University, Tel Aviv, 6997801, Israel; ESO – European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748, Garching bei München, Germany; Institute of Astronomy, KU Leuven, Celestijnenlaan 200D, 3001, Leuven, Belgium; Department of Physics &amp; Astronomy, Hounsfield Road, University of Sheffield, Sheffield, S3 7RH, UK; Instituto de Astrofísica de Canarias, C. Vía Láctea, s/n, 38205, La Laguna, Santa Cruz de Tenerife, Spain; Universidad de La Laguna, Dpto. Astrofísica, Av. Astrofśico Francisco Sánchez, 38206, La Laguna, Santa Cruz de Tenerife, Spain; Escola de Ciências e Tecnologia, Universidade Federal do Rio Grande do Norte, Natal, RN, 59072-970, Brazil; Zentrum für Astronomie der Universität Heidelberg, Astronomisches Rechen-Institut, Mönchhofstr. 12–14, 69120, Heidelberg, Germany; School of Mathematics, Statistics and Physics, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK; Institute of Astronomy, KU Leuven, Celestijnenlaan 200D, 3001, Leuven, Belgium; Heidelberger Institut für Theoretische Studien, Schloss-Wolfsbrunnenweg 35, 69118, Heidelberg, Germany; Universität Heidelberg, Department of Physics and Astronomy, Im Neuenheimer Feld 226, 69120, Heidelberg, Germany; Royal Observatory of Belgium, Avenue Circulaire/Ringlaan 3, 1180, Brussels, Belgium; et al. (Astronomy and Astrophysics, 2024-10-01)
    Surveys in the Milky Way and Large Magellanic Cloud have revealed that the majority of massive stars will interact with companions during their lives. However, knowledge of the binary properties of massive stars at low metallicity, and therefore in conditions approaching those of the Early Universe, remain sparse. We present the Binarity at LOw Metallicity (BLOeM) campaign, an ESO large programme designed to obtain 25 epochs of spectroscopy for 929 massive stars in the Small Magellanic Cloud, allowing us to probe multiplicity in the lowest-metallicity conditions to date (Z = 0.2 Z<SUB>⊙</SUB>). BLOeM will provide (i) the binary fraction, (ii) the orbital configurations of systems with periods of P ≲ 3 yr, (iii) dormant black-hole binary candidates (OB+BH), and (iv) a legacy database of physical parameters of massive stars at low metallicity. Main sequence (OB-type) and evolved (OBAF-type) massive stars are observed with the LR02 setup of the GIRAFFE instrument of the Very Large Telescope (3960–4570 Å resolving power R = 6200; typical signal-to-noise ratio(S/N) ≈70–100). This paper utilises the first nine epochs obtained over a three-month time period. We describe the survey and data reduction, perform a spectral classification of the stacked spectra, and construct a Hertzsprung-Russell diagram of the sample via spectral-type and photometric calibrations. Our detailed classification reveals that the sample covers spectral types from O4 to F5, spanning the effective temperature and luminosity ranges 6.5 ≲ T<SUB>eff</SUB>/kK ≲ 45 and 3.7 &lt; log L/L<SUB>⊙</SUB> &lt; 6.1 and initial masses of 8 ≲ M<SUB>ini</SUB> ≲ 80 M<SUB>⊙</SUB>. The sample comprises 159 O-type stars, 331 early B-type (B0–3) dwarfs and giants (luminosity classes V–III), 303 early B-type supergiants (II–I), and 136 late-type BAF supergiants. At least 82 stars are OBe stars: 20 O-type and 62 B-type (13% and 11% of the respective samples). In addition, the sample includes 4 high-mass X-ray binaries, 3 stars resembling luminous blue variables, 2 bloated stripped-star candidates, 2 candidate magnetic stars, and 74 eclipsing binaries.
  • CHIMPS2: <SUP>13</SUP>CO J = 3→2 emission in the central molecular zone

    Astrophysics Research Institute, Liverpool John Moores University, IC2, Liverpool Science Park, 146 Brownlow Hill, Liverpool L3 5RF, UK;; Astrophysics Research Institute, Liverpool John Moores University, IC2, Liverpool Science Park, 146 Brownlow Hill, Liverpool L3 5RF, UK; Armagh Observatory and Planetarium, College Hill, Armagh BT61 9DB, UK;; School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, UK;; Department of Physics, University of Alberta, Edmonton, Alberta T6G 2E1, Canada;; Department of Physics &amp; Astronomy, Kwantlen Polytechnic University, 12666 72nd Avenue, Surrey BC V3W 2M8, Canada; Purple Mountain Observatory and Key Laboratory of Radio Astronomy, Chinese Academy of Sciences, Nanjing 210034, China; Xinjiang Astronomical Observatory, 150 Science 1-Street, Urumqi, Xinjiang 830011, China; School of Physics and Astronomy, Cardiff University, 5 The Parade, Newport Road, Cardiff CF24 3AA, UK;; Shanghai Astronomical Observatory, 80 Nandan Road, Xuhui District, Shanghai 200030, China; et al. (Monthly Notices of the Royal Astronomical Society, 2024-09-01)
    We present the initial data for the $(J = 3 \rightarrow 2)$ transition of $^{13}\text{CO}$ obtained from the central molecular zone (CMZ) of the Milky Way as part of the CO Heterodyne Inner Milky Way Plane Survey 2 (CHIMPS2). Covering $359^{\circ } \le l \le 1^{\circ }$ and $|b| \le 0.5^{\circ }$ with an angular resolution of 19 arcsec, velocity resolution of 1 km s$^{-1}$, and rms $\Delta {T_{\rm A}^{*}} = 0.59\, \mathrm{K}$ at these resolutions, our observations unveil the complex structure of the CMZ molecular gas in improved detail. Complemented by the $\rm {^{12}CO}$ CHIMPS2 data, we estimate a median optical depth of $\tau _{13} = 0.087$. The preliminary analysis yields a median $^{13}\text{CO}$ column-density range equal to $N(^{13}{\rm CO}) = 2{\!-\!}5 \times 10^{18}\, \mathrm{cm}^{-2}$, median H$_{2}$ column density equal to $N(\mathrm{H_{2}}) = 4 \times 10^{22}\, \mathrm{cm}^{-2}$ to $1 \times 10^{23}\, \mathrm{cm}^{-2}$. We derive $N({\rm H_{2}})$-based total mass estimates of $M({\rm H}_{2}) = 2{\!-\!}6 \times 10^{7}\, \mathrm{M}_{\odot }$, in agreement with previous studies. We analyse the relationship between the integrated intensity of $^{13}\text{CO}$ and the surface density of compact sources identified by Herschel Hi-GAL, and find that younger Hi-GAL sources detected at 500 $\rm{\mu m}$ but not at 70 $\rm{\mu m}$ follow the dense gas of the CMZ more closely than those that are bright at 70 $\rm{\mu m}$. The latter, actively star-forming sources appear to be more associated with material in the foreground spiral arms.
  • X-Shooting ULLYSES: Massive stars at low metallicity: V. Effect of metallicity on surface abundances of O stars

    LUPM, Université de Montpellier, CNRS, Place Eugène Bataillon, 34095, Montpellier, France;; Aix-Marseille Univ, CNRS, CNES, LAM, Marseille, France; Department of Physics and Astronomy &amp; Pittsburgh Particle Physics, Astrophysics and Cosmology Center (PITT PACC), University of Pittsburgh, 3941 O'Hara Street, Pittsburgh, PA, 15260, USA; Astronomical Institute Anton Pannekoek, University of Amsterdam, Science Park 904, 1098, XH, Amsterdam, The Netherlands;; Department of Physics &amp; Astronomy, University of Sheffield, Hounsfield Road, Sheffield, S3 7RH, UK;; Instituto de Astrofísica de Canarias, C. Vía Láctea, s/n, 38205, La Laguna, Tenerife, Spain; Departamento de Astrofísica, Universidad de La Laguna, Avenida Astrofísico Francisco Sánchez, s/n, 38205, La Laguna, Tenerife, Spain;; Departamento de Astrofísica, Centro de Astrobiología (CSIC-INTA), Ctra. Torrejón a Ajalvir km 4, 28850, Torrejón de Ardoz, Spain; Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Str. 24/25, 14476, Potsdam, Germany;; LMU München, Universitäts-Sternwarte, Scheinerstr. 1, 81679, München, Germany;; Zentrum für Astronomie der Universität Heidelberg, Astronomisches Rechen-Institut, Mönchhofstr. 12–14, 69120, Heidelberg, Germany;; et al. (Astronomy and Astrophysics, 2024-09-01)
    Context. Massive stars rotate faster, on average, than lower mass stars. Stellar rotation triggers hydrodynamical instabilities which transport angular momentum and chemical species from the core to the surface. Models of high-mass stars that include these processes predict that chemical mixing is stronger at lower metallicity. Aims. We aim to test this prediction by comparing the surface abundances of massive stars at different metallicities. Methods. We performed a spectroscopic analysis of single O stars in the Magellanic Clouds (MCs) based on the ULLYSES and XShootU surveys. We determined the fundamental parameters and helium, carbon, nitrogen, and oxygen surface abundances of 17 LMC and 17 SMC non-supergiant O6–9.5 stars. We complemented these determinations by literature results for additional MCs and also Galactic stars to increase the sample size and metallicity coverage. We investigated the differences in the surface chemical enrichment at different metallicities and compared them with predictions of three sets of evolutionary models. Results. Surface abundances are consistent with CNO-cycle nucleosynthesis. The maximum surface nitrogen enrichment is stronger in MC stars than in Galactic stars. Nitrogen enrichment is also observed in stars with higher surface gravities in the SMC than in the Galaxy. This trend is predicted by models that incorporate chemical transport caused by stellar rotation. The distributions of projected rotational velocities in our samples are likely biased towards slow rotators. Conclusions. A metallicity dependence of surface abundances is demonstrated. The analysis of larger samples with an unbiased distribution of projected rotational velocities is required to better constrain the treatment of chemical mixing and angular momentum transport in massive single and binary stars.
  • X-Shooting ULLYSES: Massive stars at low metallicity. II. DR1: Advanced optical data products for the Magellanic Clouds

    Institute of Astronomy, KU Leuven, Celestijnlaan 200D, 3001, Leuven, Belgium; ESO - European Organisation for Astronomical Research in the Southern Hemisphere, Alonso de Cordova 3107, Vitacura, Santiago de Chile, Chile; Instituto de Astrofísica de Canarias, C. Vía Láctea, s/n, 38205, La Laguna, Santa Cruz de Tenerife, Spain; Universidad de La Laguna, Dpto. Astrofísica, Av. Astrofísico Francisco Sánchez, 38206, La Laguna, Santa Cruz de Tenerife, Spain; Royal Observatory of Belgium, Avenue Circulaire/Ringlaan 3, 1180, Brussels, Belgium; Institute of Astronomy, KU Leuven, Celestijnlaan 200D, 3001, Leuven, Belgium; Université Libre de Bruxelles, Av. Franklin Roosevelt 50, 1050, Brussels, Belgium; IAASARS, National Observatory of Athens, 15236, Penteli, Greece; Institute of Astrophysics FORTH, 71110, Heraklion, Greece; NAT - Universidade Cidade de São Paulo, Rua Galvão Bueno 868, São Paulo, Brazil; ESO - European Organisation for Astronomical Research in the Southern Hemisphere, Alonso de Cordova 3107, Vitacura, Santiago de Chile, Chile; Instituto de Astronomía, Universidad Nacional Autónoma de México, Unidad Académica en Ensenada, Km 103 Carr. Tijuana-Ensenada, Ensenada, B.C., C.P. 22860, Mexico; Centro Universitário da FEI, Dept. de Física, Av. Humberto Alencar de Castelo Branco, 3972, São Bernardo do Campo-SP, CEP 09850-901, Brazil; Department of Physics &amp; Astronomy, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield, S3 7RH, UK; et al. (Astronomy and Astrophysics, 2024-08-01)
    Context. The XShootU project aims to obtain ground-based optical to near-infrared spectroscopy of all targets observed by the Hubble Space Telescope (HST) under the Director's Discretionary program ULLYSES. Using the medium-resolution spectrograph X-shooter, spectra of 235 OB and Wolf-Rayet (WR) stars in subsolar metallicity environments have been secured. The bulk of the targets belong to the Large and Small Magellanic Clouds, with the exception of three stars in NGC 3109 and Sextans A. <BR /> Aims: This second paper in the series focuses on the optical observations of Magellanic Clouds targets. It describes the uniform reduction of the UVB (300-560 nm) and VIS (550-1020 nm) XShootU data as well as the preparation of advanced data products that are suitable for homogeneous scientific analyses. <BR /> Methods: The data reduction of the RAW data is based on the ESO CPL X-shooter pipeline. We paid particular attention to the determination of the response curves. This required equal flat-fielding of the science and flux standard star data and the derivation of improved flux standard models. The pipeline products were then processed with our own set of routines to produce a series of advanced data products. In particular, we implemented slit-loss correction, absolute flux calibration, (semi-)automatic rectification to the continuum, and a correction for telluric lines. The spectra of individual epochs were further corrected for the barycentric motion, re-sampled and co-added, and the spectra from the two arms were merged into a single flux-calibrated spectrum covering the entire optical range with maximum signal-to-noise ratio. <BR /> Results: We identify and describe an undocumented recurrent ghost visible on the RAW data. We present an improved flat-fielding strategy that limits artifacts when the SCIENCE and FLUX standard stars are observed on different nights. The improved FLUX standard models and the new grid of anchor points limit artifacts of the response curve correction, for example on the shape of the wings of the Balmer lines, from a couple of per cent of the continuum level to less than 0.5%. We confirm the presence of a radial velocity shift of about 3.5 km s<SUP>−1</SUP> between the UVB and the VIS arm of X-shooter and that there are no short term variations impacting the RV measurements. RV precision better than 1 km s<SUP>-1</SUP> can be obtained on sharp telluric lines while RV precision on the order of 2 to 3 km s<SUP>-1</SUP> is obtained on data with the best S/N. <BR /> Conclusions: For each target observed by XShootU, we provide three types of data products: (i) two-dimensional spectra for each UVB and VIS exposure before and after correction for the instrument response; (ii) one-dimensional UVB and VIS spectra as produced by the X-shooter pipeline before and after response-correction, and applying various processing, including absolute flux calibration, telluric removal, normalization and barycentric correction; and (iii) co-added flux-calibrated and rectified spectra over the full optical range, for which all available XShootU exposures were combined. For the large majority of the targets, the final signal-to-noise ratio per resolution element is above 200 in the UVB and in the VIS co-added spectra. The reduced data and advanced scientific data products are made available to the community. Together with the HST UV ULLYSES data, they should enable various science goals, from detailed stellar atmosphere and stellar wind studies, and empirical libraries for population synthesis, to the study of the local nebular environment and feedback of massive stars in subsolar metallicity environments. <P />Full Tables 1, 2 and C.1 are available at the CDS via anonymous ftp to <A href=https://cdsarc.cds.unistra.fr>cdsarc.cds.unistra.fr</A> (ftp://130.79.128.5) or via <A href=https://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/688/A104>https://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/688/A104</A> <P />The DR1 data and an accompanying release documentation are made available on Zenodo <A href=https://doi.org/10.5281/zenodo.11122188>https://doi.org/10.5281/zenodo.11122188</A> <P />Based on observations collected at the European Southern Observatory under ESO program ID 106.211Z.001.
  • X-Shooting ULLYSES: Massive stars at low metallicity. III. Terminal wind speeds of ULLYSES massive stars

    Institute of Astronomy, KU Leuven, Celestijnenlaan 200D, 3001, Leuven, Belgium; Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD, 21218, USA; Institute of Astronomy, KU Leuven, Celestijnenlaan 200D, 3001, Leuven, Belgium; Royal Observatory of Belgium, Avenue Circulaire 3, 1180, Brussels, Belgium; Astronomical Institute Anton Pannekoek, Amsterdam University, Science Park 904, 1098 XH, Amsterdam, The Netherlands; Institute of Astronomy, KU Leuven, Celestijnenlaan 200D, 3001, Leuven, Belgium; Department of Physics and Astronomy, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield, S3 7RH, UK; Astronomical Institute Anton Pannekoek, Amsterdam University, Science Park 904, 1098 XH, Amsterdam, The Netherlands; Department of Physics and Astronomy, Howard University, Washington, DC 20059, USA; Center for Research and Exploration in Space Science and Technology, and X-ray Astrophysics Laboratory, NASA/GSFC, Greenbelt, MD, 20771, USA; Department of Physics &amp; Astronomy, East Tennessee State University, Johnson City, TN, 37614, USA; Centro de Astrobiología, CSIC-INTA, Crtra. de Torrejón a Ajalvir km 4, 28850 Torrejón de Ardoz, Madrid, Spain; Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Str. 24/25, 14476, Potsdam, Germany; et al. (Astronomy and Astrophysics, 2024-08-01)
    Context. The winds of massive stars have a significant impact on stellar evolution and on the surrounding medium. The maximum speed reached by these outflows, the terminal wind speed v<SUB>∞</SUB>, is a global wind parameter and an essential input for models of stellar atmospheres and feedback. With the arrival of the ULLYSES programme, a legacy UV spectroscopic survey with the Hubble Space Telescope, we have the opportunity to quantify the wind speeds of massive stars at sub-solar metallicity (in the Large and Small Magellanic Clouds, 0.5 Z<SUB>⊙</SUB> and 0.2 Z<SUB>⊙</SUB>, respectively) at an unprecedented scale. <BR /> Aims: We empirically quantify the wind speeds of a large sample of OB stars, including supergiants, giants, and dwarfs at sub-solar metallicity. Using these measurements, we investigate trends of v<SUB>∞</SUB> with a number of fundamental stellar parameters, namely effective temperature (T<SUB>eff</SUB>), metallicity (Z), and surface escape velocity v<SUB>esc</SUB>. <BR /> Methods: We empirically determined v<SUB>∞</SUB> for a sample of 149 OB stars in the Magellanic Clouds either by directly measuring the maximum velocity shift of the absorption component of the C IV λλ1548-1550 line profile, or by fitting synthetic spectra produced using the Sobolev with exact integration method. Stellar parameters were either collected from the literature, obtained using spectral-type calibrations, or predicted from evolutionary models. <BR /> Results: We find strong trends of v<SUB>∞</SUB> with T<SUB>eff</SUB> and v<SUB>esc</SUB> when the wind is strong enough to cause a saturated P Cygni profile in C IV λλ1548-1550. We find evidence for a metallicity dependence on the terminal wind speed v<SUB>∞</SUB> ∝ Z<SUP>0.22±0.03</SUP> when we compared our results to previous Galactic studies. <BR /> Conclusions: Our results suggest that T<SUB>eff</SUB> rather than v<SUB>esc</SUB> should be used as a straightforward empirical prediction of v<SUB>∞</SUB> and that the observed Z dependence is steeper than suggested by earlier works.
  • X-Shooting ULLYSES: Massive stars at low metallicity: IV. Spectral analysis methods and exemplary results for O stars

    Zentrum für Astronomie der Universität Heidelberg, Astronomisches Rechen-Institut, Mönchhofstr. 12–14, 69120, Heidelberg, Germany;; Aix Marseille Univ, CNRS, CNES, LAM, Marseille, France;; LMU München, Universitätssternwarte, Scheinerstr. 1, 81679, München, Germany;; Anton Pannekoek Institute for Astronomy, Universiteit van Amsterdam, Science Park 904, 1098 XH, Amsterdam, The Netherlands;; Instituto de Astrofísica de Canarias, 38200, La Laguna, Tenerife, Spain; Departamento de Astrofísica, Universidad de La Laguna, 38205, La Laguna, Tenerife, Spain; Department of Physics &amp; Astronomy, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield, S3 7RH, UK;; Instituto de Astrofísica de Canarias, 38200, La Laguna, Tenerife, Spain; Departamento de Astrofísica, Universidad de La Laguna, 38205, La Laguna, Tenerife, Spain;; LUPM, Université de Montpellier, CNRS, Place Eugène Bataillon, 34095, Montpellier, France;; Astronomical Institute of the Czech Academy of Sciences, Fričova 298, 25165, Ondřejov, Czech Republic; Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Str. 24/25, 14476, Potsdam, Germany;; et al. (Astronomy and Astrophysics, 2024-09-01)
    Context. The spectral analysis of hot, massive stars is a fundamental astrophysical method of determining their intrinsic properties and feedback. With their inherent, radiation-driven winds, the quantitative spectroscopy for hot, massive stars requires detailed numerical modeling of the atmosphere and an iterative treatment in order to obtain the best solution within a given framework. Aims. We present an overview of different techniques for the quantitative spectroscopy of hot stars employed within the X-Shooting ULLYSES collaboration, ranging from grid-based approaches to tailored spectral fits. By performing a blind test for selected targets, we gain an overview of the similarities and differences between the resulting stellar and wind parameters. Our study is not a systematic benchmark between different codes or methods; our aim is to provide an overview of the parameter spread caused by different approaches. Methods. For three different stars from the XShooting ULLYSES sample (SMC O5 star AzV 377, LMC O7 star Sk -69° 50, and LMC O9 star Sk-66° 171), we employ different stellar atmosphere codes (CMFGEN, FASTWIND, PoWR) and different strategies to determine their best-fitting model solutions. For our analyses, UV and optical spectroscopy are used to derive the stellar and wind properties with some methods relying purely on optical data for comparison. To determine the overall spectral energy distribution, we further employ additional photometry from the literature. Results. The effective temperatures found for each of the three different sample stars agree within 3 kK, while the differences in log g can be up to 0.2 dex. Luminosity differences of up to 0.1 dex result from different reddening assumptions, which seem to be systematically larger for the methods employing a genetic algorithm. All sample stars are found to be enriched in nitrogen. The terminal wind velocities are surprisingly similar and do not strictly follow the u<SUB>∞</SUB>‑T<SUB>eff</SUB> relation. Conclusions. We find reasonable agreement in terms of the derived stellar and wind parameters between the different methods. Tailored fitting methods tend to be able to minimize or avoid discrepancies obtained with coarser or increasingly automatized treatments. The inclusion of UV spectral data is essential for the determination of realistic wind parameters. For one target (Sk -69° 50), we find clear indications of an evolved status.
  • The maximum black hole mass at solar metallicity

    Armagh Observatory and Planetarium, College Hill, BT61 9DG, Armagh, Northern Ireland, UK; Vink, Jorick S.; Sabhahit, Gautham N.; Higgins, Erin R. (Astronomy and Astrophysics, 2024-08-01)
    We analyse the current knowledge and uncertainties in detailed stellar evolution and wind modelling to evaluate the mass of the most massive stellar black hole (BH) at solar metallicity. Contrary to common expectations that it is the most massive stars that produce the most massive BHs, we find that the maximum M<SUB>BH</SUB><SUP>Max</SUP> ≃ 30 ± 10 M<SUB>⊙</SUB> is found in the canonical intermediate range between M<SUB>ZAMS</SUB> ≃ 30 and 50 M<SUB>⊙</SUB> instead. The prime reason for this seemingly counter-intuitive finding is that very massive stars (VMS) have increasingly high mass-loss rates that lead to substantial mass evaporation before they expire as stars and end as lighter BHs than their canonical O-star counterparts.
  • Molecular gas scaling relations for local star-forming galaxies in the low-M<SUB>*</SUB> regime

    Institute of Theoretical Astrophysics, University of Oslo, PO Box 1029, Blindern, 0315, Oslo, Norway; Armagh Observatory and Planetarium, College Hill, Armagh, BT61 9DG, UK; Department of Physics and Astronomy, University College London, London, WC1E 6BT, UK; INAF - Osservatorio Astronomico di Brera, Via Brera 28, 20121, Milano, Italy; Dipartimento di Fisica e Astronomia Augusto Righi, Università degli Studi di Bologna, Via Gobetti 93/2, 40129, Bologna, Italy; INAF - Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Gobetti 93/3, 40129, Bologna, Italy; Hagedorn, B.; Cicone, C.; Sarzi, M.; Saintonge, A.; Severgnini, P.; et al. (Astronomy and Astrophysics, 2024-07-01)
    We derived molecular gas fractions (f<SUB>mol</SUB> = M<SUB>mol</SUB>/M<SUB>*</SUB>) and depletion times (τ<SUB>mol</SUB> = M<SUB>mol</SUB>/SFR) for 353 galaxies representative of the local star-forming population with 10<SUP>8.5</SUP> M<SUB>⊙</SUB> &lt; M<SUB>*</SUB> &lt; 10<SUP>10.5</SUP> M<SUB>⊙</SUB> drawn from the ALLSMOG and xCOLDGASS surveys of CO(2−1) and CO(1−0) line emission. By adding constraints from low-mass galaxies and upper limits for CO non-detections, we find the median molecular gas fraction of the local star-forming population to be constant at log f<SUB>mol</SUB> = −0.99<SUB>−0.19</SUB><SUP>+0.22</SUP>, challenging previous reports of increased molecular gas fractions in low-mass galaxies. Above M<SUB>*</SUB> ∼ 10<SUP>10.5</SUP> M<SUB>⊙</SUB>, we find the f<SUB>mol</SUB> versus M<SUB>*</SUB> relation to be sensitive to the selection criteria for star-forming galaxies. We tested the robustness of our results against different prescriptions for the CO-to-H<SUB>2</SUB> conversion factor and different selection criteria for star-forming galaxies. The depletion timescale τ<SUB>mol</SUB> weakly depends on M<SUB>*</SUB>, following a power law with a best-fit slope of 0.16 ± 0.03. This suggests that small variations in specific star formation rate (sSFR = SFR/M<SUB>*</SUB>) across the local main sequence of star-forming galaxies with M<SUB>*</SUB> &lt; 10<SUP>10.5</SUP> M<SUB>⊙</SUB> are mainly driven by differences in the efficiency of converting the available molecular gas into stars. We tested these results against a possible dependence of f<SUB>mol</SUB> and τ<SUB>mol</SUB> on the surrounding (group) environment of the targets by splitting them into centrals, satellites, and isolated galaxies, and find no significant variation between these populations. We conclude that the group environment is unlikely to have a large systematic effect on the molecular gas content of star-forming galaxies in the local Universe.
  • A study of Galactic Plane Planck Galactic cold clumps observed by SCOPE and the JCMT Plane Survey

    Armagh Observatory and Planetarium, College Hill, Armagh BT61 9DB, UK;; Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030, People's Republic of China; Astrophysics Research Institute, Liverpool John Moores University, Liverpool Science Park, iC2, 146 Brownlow Hill. Liverpool L3 5RF, UK; NRC Herzberg Astronomy and Astrophysics, 5071 West Saanich Rd, Victoria, BC V9E 2E7, Canada; Department of Physics and Astronomy, University of Victoria, Victoria, BC V8W 2Y2, Canada; Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, The University of Manchester, Oxford Road, Manchester M13 9PL, UK;; Korea Astronomy and Space Science Institute, 776 Daedeokdae-ro, Yuseong-gu, Daejon 34055, Republic of Korea; University of Science and Technology, Korea (UST), 217 Gajeong-ro, Yuseong-gu, Daejeon 34113, Republic of Korea; National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China; Key Laboratory of Radio Astronomy, Chinese Academy of Science, Nanjing 210008, China;; Academia Sinica Institute of Astronomy and Astrophysics, 11F of AS/NTU Astronomy - Mathematics, Building, No.1, Section 4, Roosevelt Rd, Taipei 10617, Taiwan; Department of Physics and Astronomy, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada; Nobeyama Radio Observatory, National Astronomical Observatory of Japan, National Institutes of Natural Sciences, Nobeyama, Minamimaki, Minamisaku, Nagano 384-1305, Japan; Astronomical Science Program, Graduate Institute for Advanced Studies, SOKENDAI, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan;; et al. (Monthly Notices of the Royal Astronomical Society, 2024-06-01)
    We have investigated the physical properties of Planck Galactic Cold Clumps (PGCCs) located in the Galactic Plane, using the JCMT Plane Survey (JPS) and the SCUBA-2 Continuum Observations of Pre-protostellar Evolution (SCOPE) survey. By utilizing a suite of molecular-line surveys, velocities, and distances were assigned to the compact sources within the PGCCs, placing them in a Galactic context. The properties of these compact sources show no large-scale variations with Galactic environment. Investigating the star-forming content of the sample, we find that the luminosity-to-mass ratio (L/M) is an order of magnitude lower than in other Galactic studies, indicating that these objects are hosting lower levels of star formation. Finally, by comparing ATLASGAL sources that are associated or are not associated with PGCCs, we find that those associated with PGCCs are typically colder, denser, and have a lower L/M ratio, hinting that PGCCs are a distinct population of Galactic Plane sources.
  • The impact of shear on the rotation of Galactic plane molecular clouds

    Center of Astronomy and Gravitation, Department of Earth Sciences, National Taiwan Normal University, 88, Sec. 4, Ting-Chou Road, Wenshan District, Taipei 116, Taiwan, ROC&lt;IDsystem=ORCID&gt;0000-0002-6747-0838; Institute of Astronomy, National Tsing Hua University, Hsinchu 30013, Taiwan, ROC; Astrophysics Research Institute, Liverpool John Moores University, IC2, Liverpool Science Park, 146 Brownlow Hill, Liverpool L3 5RF, UK; Armagh Observatory and Planetarium, College Hill, Armagh BT61 9DB, UK&lt;IDsystem=ORCID&gt;0000-0002-5881-3229; School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, UK&lt;IDsystem=ORCID&gt;0000-0002-3351-2200; Telepix Co., Ltd, 17, Techno 4-ro, Yuseong-gu, Daejeon 34013, Republic of Korea; Research Institute of Natural Sciences, Chungnam National University, 99 Daehak-ro, Yuseong-gu, Daejeon 34134, Republic of Korea; Korea Astronomy and Space Science Institute, 776 Daedeokdae-ro, Yuseong-gu, Daejeon 34055, Republic of Korea; Center of Astronomy and Gravitation, Department of Earth Sciences, National Taiwan Normal University, 88, Sec. 4, Ting-Chou Road, Wenshan District, Taipei 116, Taiwan, ROC&lt;IDsystem=ORCID&gt;0000-0003-3497-2329; Rani, Raffaele; Li, Jia-Lun; Moore, Toby J. T.; et al. (Monthly Notices of the Royal Astronomical Society, 2024-08-01)
    Stars form in the densest regions of molecular clouds; however, there is no universal understanding of the factors that regulate cloud dynamics and their influence on the gas-to-star conversion. This study considers the impact of Galactic shear on the rotation of giant molecular clouds (GMCs) and its relation to the solenoidal modes of turbulence. We estimate the direction of rotation for a large sample of clouds in the $\mathrm{^{13}CO}$/$\mathrm{C^{18}O}$(3-2) Heterodyne Inner Milky Way Plane Survey (CHIMPS) and their corresponding sources in a new segmentation of the $\mathrm{^{12}CO}$(3-2) High-Resolution Survey. To quantify the strength of shear, we introduce a parameter that describes the shear's ability to disrupt growing density perturbations within the cloud. Although we find no correlation between the direction of cloud rotation, the shear parameter, and the magnitude of the velocity gradient, the solenoidal fraction of the turbulence in the CHIMPS sample is positively correlated with the shear parameter and behaves similarly when plotted over Galactocentric distance. GMCs may thus not be large or long-lived enough to be affected by shear to the point of showing rotational alignment. In theory, Galactic shear can facilitate the rise of solenoidal turbulence and thus contribute to suppressing star formation. These results also suggest that the rotation of clouds is not strictly related to the overall rotation of the disc, but is more likely to be the imprint of Kelvin-Helmholtz instabilities in the colliding flows that formed the clouds.
  • The S-PLUS Fornax Project (S+FP): A first 12-band glimpse of the Fornax galaxy cluster

    Instituto de Astrofísica de La Plata, CONICET-UNLP, Paseo del Bosque s/n, La Plata, B1900FWA, Argentina; Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, Paseo del Bosque s/n, La Plata, B1900FWA, Argentina; Valongo Observatory, Federal University of Rio de Janeiro, Ladeira Pedro Antonio 43, Saude Rio de Janeiro, RJ 20080-090, Brazil; Instituto de Fisica, Universidade Federal do Rio de Janeiro, 21941-972, Rio de Janeiro, RJ, Brazil; Instituto de Astrofísica de La Plata, CONICET-UNLP, Paseo del Bosque s/n, La Plata, B1900FWA, Argentina; Departamento de Física, CFM, Universidade Federal de Santa Catarina, PO Box 476, 88040-900, Florianópolis, SC, Brazil; Valongo Observatory, Federal University of Rio de Janeiro, Ladeira Pedro Antonio 43, Saude Rio de Janeiro, RJ 20080-090, Brazil; Centro Brasileiro de Pesquisas Físicas, Rua Dr Xavier Sigaud 150, CEP 22290-180, Rio de Janeiro, RJ, Brazil; IAG, Universidade de São Paulo, Rua do Matão 1226, São Paulo, SP, Brazil; Facultad de Ciencias Exactas y Naturales y Ciclo Básico Común, Universidad de Buenos Aires, Buenos Aires, Argentina; Instituto de Astronomía y Física del Espacio (IAFE), CONICET-Universidad de Buenos Aires, Buenos Aires, Argentina; Cambridge Survey Astronomical Unit (CASU), Institute of Astronomy, Madingley Road, Cambridge CB3 0HA, UK; Observatório Nacional, Rua General José Cristino, 77, São Cristóvão, 20921-400 Rio de Janeiro, RJ, Brazil; et al. (Monthly Notices of the Royal Astronomical Society, 2024-06-01)
    The Fornax galaxy cluster is the richest nearby (D ~ 20 Mpc) galaxy association in the southern sky. As such, it provides a wealth of opportunities to elucidate on the processes where environment holds a key role in transforming galaxies. Although it has been the focus of many studies, Fornax has never been explored with contiguous homogeneous wide-field imaging in 12 photometric narrow and broad bands like those provided by the Southern Photometric Local Universe Survey (S-PLUS). In this paper, we present the S-PLUS Fornax Project (S+FP) that aims to comprehensively analyse the galaxy content of the Fornax cluster using S-PLUS. Our data set consists of 106 S-PLUS wide-field frames (FoV~1.4 × 1.4 deg<SUP>2</SUP>) observed in five Sloan Digital Sky Survey-like ugriz broad bands and seven narrow bands covering specific spectroscopic features like [O II], Ca II H+K, Hδ, G band, Mg b triplet, Hα, and the Ca II triplet. Based on S-PLUS specific automated photometry, aimed at correctly detecting Fornax galaxies and globular clusters in S-PLUS images, our data set provides the community with catalogues containing homogeneous 12-band photometry for ~3 × 10<SUP>6</SUP> resolved and unresolved objects within a region extending over ~208 deg<SUP>2</SUP> (~5 R<SUB>vir</SUB> in RA) around Fornax' central galaxy, NGC 1399. We further explore the EAGLE and ILLUSTRISTNG cosmological simulations to identify 45 Fornax-like clusters and generate mock images on all 12 S-PLUS bands of these structures down to galaxies with M<SUB>⋆</SUB> ≥ 10<SUP>8</SUP> M<SUB>⊙</SUB>. The S+FP data set we put forward in this first paper of a series will enable a variety of studies some of which are briefly presented.
  • A 500 pc volume-limited sample of hot subluminous stars. I. Space density, scale height, and population properties

    Institute for Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24/25, 14476, Potsdam, Germany; Dr. Remeis-Sternwarte and ECAP, Astronomical Institute, University of Erlangen-Nürnberg, Sternwartstr. 7, 96049, Bamberg, Germany; Department of Physics, University of Warwick, Gibet Hill Road, Coventry, CV4 7AL, UK; Institute for Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24/25, 14476, Potsdam, Germany; Institute for Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24/25, 14476, Potsdam, Germany; Dr. Remeis-Sternwarte and ECAP, Astronomical Institute, University of Erlangen-Nürnberg, Sternwartstr. 7, 96049, Bamberg, Germany; Thüringer Landessternwarte Tautenburg, Sternwarte 5, 07778, Tautenburg, Germany; Institute for Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24/25, 14476, Potsdam, Germany; Zentrum für Astronomie der Universität Heidelberg, Landessternwarte, Königstuhl 12, 69117, Heidelberg, Germany; Institute for Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24/25, 14476, Potsdam, Germany; Astronomical Institute of the Czech Academy of Sciences, 251 65, Ondřejov, Czech Republic; Institute for Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24/25, 14476, Potsdam, Germany; Institute for Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24/25, 14476, Potsdam, Germany; Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482, Potsdam, Germany; Institute of Astronomy, KU Leuven, Celestijnenlaan 200D, 3001, Leuven, Belgium; Instituto de Física y Astronomía, Universidad de Valparaíso, Gran Bretaña 1111, Playa Ancha, Valparaíso, 2360102, Chile; European Southern Observatory, Alonso de Cordova 3107, Santiago, Chile; Instituto de Física y Astronomía, Universidad de Valparaíso, Gran Bretaña 1111, Playa Ancha, Valparaíso, 2360102, Chile; et al. (Astronomy and Astrophysics, 2024-06-01)
    We present the first volume-limited sample of spectroscopically confirmed hot subluminous stars out to 500 pc, defined using the accurate parallax measurements from the Gaia space mission data release 3 (DR3). The sample comprises a total of 397 members, with 305 (~77%) identified as hot subdwarf stars, including 83 newly discovered systems. Of these, we observe that 178 (~58%) are hydrogen-rich sdBs, 65 are sdOBs (~21%), 32 are sdOs (~11%), and 30 are He-sdO/Bs (~10%). Among them, 48 (~16%) exhibit an infrared excess in their spectral energy distribution fits, suggesting a composite binary system. The hot subdwarf population is estimated to be 90% complete, assuming that most missing systems are these composite binaries located within the main sequence (MS) in the Gaia colour-magnitude diagram. The remaining sources in the sample include cataclysmic variables, blue horizontal branch stars, hot white dwarfs, and MS stars. We derived the mid-plane density ρ<SUB>0</SUB> and scale height h<SUB>z</SUB> for the non-composite hot subdwarf star population using a hyperbolic sechant profile (sech<SUP>2</SUP>). The best-fit values are ρ<SUB>0</SUB> = 5.17 ± 0.33 × 10<SUP>−7</SUP> stars pc<SUP>−3</SUP> and h<SUB>z</SUB> = 281 ± 62 pc. When accounting for the composite-colour hot subdwarfs and their estimated completeness, the mid-plane density increases to ρ<SUB>0</SUB> = 6.15<SUB>−0.53</SUB><SUP>+1.16</SUP> × 10<SUP>−7</SUP> stars pc<SUP>−3</SUP>. This corrected space density is an order of magnitude lower than predicted by population synthesis studies, supporting previous observational estimates. <P />Tables A.1-A.3 are available at the CDS ftp to <A href=https://cdsarc.cds.unistra.fr>cdsarc.cds.unistra.fr</A> (ftp://130.79.128.5) or via <A href=https://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/686/A25>https://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/686/A25</A>
  • X-Shooting ULLYSES: Massive Stars at Low Metallicity

    Armagh Observatory and Planetarium, UK; Department of Physics &amp; Astronomy, University of Sheffield, UK; Space Telescope Science Institute, Baltimore, USA; Centre for Astrobiology (CSIC-INTA), Torrejón de Ardoz, Madrid, Spain; Montpellier Universe and Particles Laboratory, Montpellier University, France; Las Campanas Observatory, Carnegie Observatories, Chile; Institute for Physics and Astronomy, University of Potsdam, Germany; Department of Physics, University of Montreal, Canada; Penn State Scranton, Dunmore, PA, USA; Astronomy Centre, Heidelberg University, Germany; et al. (The Messenger, 2024-03-01)
    The Hubble Space Telescope has devoted 500 orbits to observing 250 massive stars with low metallicity in the ultraviolet (UV) range within the framework of the ULLYSES program. The X-Shooting ULLYSES (XShootU) project enhances the legacy value of this UV dataset by providing high-quality optical and near-infrared spectra, which are acquired using the wide-wavelength- coverage X-shooter spectrograph at ESO's Very Large Telescope. XShootU emphasises the importance of combining UV with optical spectra for the consistent determination of key stellar parameters such as effective temperature, surface gravity, luminosity, abundances, and wind characteristics including mass-loss rates as a function of metallicity. Since uncertainties in these parameters have implications across various branches of astrophysics, the data and modelling generated by the XShootU project are poised to significantly advance our understanding of massive stars at low metallicity. This is particularly crucial for confidently interpreting James Webb Space Telescope (JWST) data of the earliest stellar generations, making XShootU a unique resource for comprehending individual spectra of low-metallicity stars.
  • A study of galactic plane Planck galactic cold clumps observed by SCOPE and the JCMT plane survey

    Armagh Observatory and Planetarium, College Hill, Armagh, BT61 9DB, UK; Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030, People's Republic of China; Astrophysics Research Institute, Liverpool John Moores University, Liverpool Science Park, iC2, 146 Brownlow Hill. Liverpool, L3 5RF, UK; NRC Herzberg Astronomy and Astrophysics, 5071 West Saanich Rd, Victoria, BC V9E 2E7, Canada; Department of Physics and Astronomy, University of Victoria, Victoria, BC V8W 2Y2, Canada; Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, The University of Manchester, Oxford Road, Manchester M13 9PL, UK; Korea Astronomy and Space Science Institute, 776 Daedeokdae-ro, Yuseong-gu, Daejon 34055, Republic of Korea; University of Science and Technology, Korea (UST), 217 Gajeong-ro, Yuseong-gu, Daejeon 34113, Republic of Korea; National Astronomical Observatories, Chinese Academy of Sciences, Beijing, 100012, China; Key Laboratory of Radio Astronomy, Chinese Academy of Science, Nanjing 210008, China; Academia Sinica Institute of Astronomy and Astrophysics, 11F of AS/NTU Astronomy-Mathematics Building, No.1, Section 4, Roosevelt Rd, Taipei 10617, Taiwan; Department of Physics and Astronomy, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada; Nobeyama Radio Observatory, National Astronomical Observatory of Japan, National Institutes of Natural Sciences, Nobeyama, Minamimaki, Minamisaku, Nagano 384-1305, Japan; Astronomical Science Program, Graduate Institute for Advanced Studies, SOKENDAI, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; et al. (Monthly Notices of the Royal Astronomical Society, 2024-05-01)
    We have investigated the physical properties of Planck Galactic Cold Clumps (PGCCs) located in the Galactic Plane, using the JCMT Plane Survey (JPS) and the SCUBA-2 Continuum Observations of Pre-protostellar Evolution (SCOPE) survey. By utilising a suite of molecular-line surveys, velocities and distances were assigned to the compact sources within the PGCCs, placing them in a Galactic context. The properties of these compact sources show no large-scale variations with Galactic environment. Investigating the star-forming content of the sample, we find that the luminosity-to-mass ratio (L/M) is an order of magnitude lower than in other Galactic studies, indicating that these objects are hosting lower levels of star formation. Finally, by comparing ATLASGAL sources that are associated or are not associated with PGCCs, we find that those associated with PGCCs are typically colder, denser, and have a lower L/M ratio, hinting that PGCCs are a distinct population of Galactic Plane sources.
  • The wide-field, multiplexed, spectroscopic facility WEAVE: Survey design, overview, and simulated implementation

    Oxford Astrophysics, University of Oxford, Keble Road, Oxford OX1 3RH, UK; Kapteyn Astronomical Institute, Rijksuniversiteit Groningen, Landleven 12, 9747 AD Groningen, The Netherlands; RALSpace, STFC, Harwell, Didcot OX11 0QX, UK; SRON - Netherlands Institute for Space Research, Landleven 12, 9747 AD Groningen, The Netherlands; Kapteyn Astronomical Institute, Rijksuniversiteit Groningen, Landleven 12, 9747 AD Groningen, The Netherlands; Oxford Astrophysics, University of Oxford, Keble Road, Oxford OX1 3RH, UK; RALSpace, STFC, Harwell, Didcot OX11 0QX, UK; Instituto de Astrofísica de Canarias, Calle Vía Láctea s/n, 38205 La Laguna, Santa Cruz de Tenerife, Spain; Departamento de Astrofísica, Universidad de La Laguna, 38206 La Laguna, Tenerife, Spain; Centre for Astrophysics Research, University of Hertfordshire, Hatfield, Hertfordshire AL10 9AB, UK; Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK; Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK; Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Laboratoire Lagrange, Bd de l'Observatoire, CS 34229, 06304 Nice Cedex 4, France; INAF - Osservatorio Astronomico di Brera, Via Brera, 28, 20121 Milano, Italy; Aix Marseille Univ, CNRS, CNES, LAM, Laboratoire d'Astrophysique de Marseille, 13388 Marseille, France; INAF - Osservatorio Astronomico di Padova, Vicolo Osservatorio 5, 35122 Padova, Italy; et al. (Monthly Notices of the Royal Astronomical Society, 2024-05-01)
    WEAVE, the new wide-field, massively multiplexed spectroscopic survey facility for the William Herschel Telescope, saw first light in late 2022. WEAVE comprises a new 2-deg field-of-view prime-focus corrector system, a nearly 1000-multiplex fibre positioner, 20 individually deployable 'mini' integral field units (IFUs), and a single large IFU. These fibre systems feed a dual-beam spectrograph covering the wavelength range 366-959 nm at R ~ 5000, or two shorter ranges at $R\sim 20\, 000$. After summarizing the design and implementation of WEAVE and its data systems, we present the organization, science drivers, and design of a five- to seven-year programme of eight individual surveys to: (i) study our Galaxy's origins by completing Gaia's phase-space information, providing metallicities to its limiting magnitude for ~3 million stars and detailed abundances for ~1.5 million brighter field and open-cluster stars; (ii) survey ~0.4 million Galactic-plane OBA stars, young stellar objects, and nearby gas to understand the evolution of young stars and their environments; (iii) perform an extensive spectral survey of white dwarfs; (iv) survey ~400 neutral-hydrogen-selected galaxies with the IFUs; (v) study properties and kinematics of stellar populations and ionized gas in z &lt; 0.5 cluster galaxies; (vi) survey stellar populations and kinematics in ${\sim} 25\, 000$ field galaxies at 0.3 ≲ z ≲ 0.7; (vii) study the cosmic evolution of accretion and star formation using &gt;1 million spectra of LOFAR-selected radio sources; and (viii) trace structures using intergalactic/circumgalactic gas at z &gt; 2. Finally, we describe the WEAVE Operational Rehearsals using the WEAVE Simulator.
  • The S-PLUS Fornax Project (S+FP): A first 12-band glimpse of the Fornax galaxy cluster

    Instituto de Astrofísica de La Plata, CONICET-UNLP, Paseo del Bosque s/n, B1900FWA, Argentina; Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, Paseo del Bosque s/n, B1900FWA, Argentina; Valongo Observatory, Federal University of Rio de Janeiro, Ladeira Pedro Antonio 43, Saude Rio de Janeiro, RJ, 20080-090, Brazil; Instituto de Fisica, Universidade Federal do Rio de Janeiro, 21941-972, Rio de Janeiro, RJ, Brazil; Instituto de Astrofísica de La Plata, CONICET-UNLP, Paseo del Bosque s/n, B1900FWA, Argentina; Departamento de Física - CFM - Universidade Federal de Santa Catarina, PO BOx 476, 88040-900, Florianópolis, SC, Brazil; Valongo Observatory, Federal University of Rio de Janeiro, Ladeira Pedro Antonio 43, Saude Rio de Janeiro, RJ, 20080-090, Brazil; Centro Brasileiro de Pesquisas Físicas, Rua Dr Xavier Sigaud 150, CEP 22290-180, Rio de Janeiro, RJ, Brazil; Universidade de São Paulo, IAG, Rua do Matão 1226, Sao Paulo, SP, Brazil; Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales y Ciclo Básico Común, Buenos Aires, Argentina; CONICET-Universidad de Buenos Aires, Instituto de Astronomía y Física del Espacio (IAFE), Buenos Aires, Argentina; Cambridge Survey Astronomical Unit (CASU), Institute of Astronomy, Madingley Road, Cambridge CB3 0HA, UK; Observatório Nacional, Rua General José Cristino, 77, São Cristóvão, 20921-400 Rio de Janeiro, RJ, Brazil; et al. (Monthly Notices of the Royal Astronomical Society, 2024-03-01)
    The Fornax galaxy cluster is the richest nearby (D ~ 20 Mpc) galaxy association in the southern sky. As such, it provides a wealth of oportunities to elucidate on the processes where environment holds a key role in transforming galaxies. Although it has been the focus of many studies, Fornax has never been explored with contiguous homogeneous wide-field imaging in 12 photometric narrow- and broad-bands like those provided by the Southern Photometric Local Universe Survey (S-PLUS). In this paper we present the S-PLUS Fornax Project (S+FP) that aims to comprehensively analyse the galaxy content of the Fornax cluster using S-PLUS. Our data set consists of 106 S-PLUS wide-field frames (FoV~1.4 ×1.4 deg<SUP>2</SUP>) observed in five SDSS-like ugriz broad-bands and seven narrow-bands covering specific spectroscopic features like [OII], CaII H+K, Hδ, G-band, Mg b triplet, Hα, and the CaII triplet. Based on S-PLUS specific automated photometry, aimed at correctly detecting Fornax galaxies and globular clusters in S-PLUS images, our dataset provides the community with catalogues containing homogeneous 12-band photometry for ~3 × 10<SUP>6</SUP> resolved and unresolved objects within a region extending over ~208 deg<SUP>2</SUP> (~5 R<SUB>vir</SUB> in RA) around Fornax' central galaxy, NGC 1399. We further explore the EAGLE and ILLUSTRISTNG cosmological simulations to identify 45 Fornax-like clusters and generate mock images on all 12 S-PLUS bands of these structures down to galaxies with M<SUB>⋆</SUB> ≥ 10<SUP>8</SUP> M<SUB>⊙</SUB>. The S+FP dataset we put forward in this first paper of a series will enable a variety of studies some of which are briefly presented.
  • EC 19529-4430: SALT identifies the most carbon- and metal-poor extreme helium star

    Armagh Observatory and Planetarium, College Hill, Armagh BT61 9DG, UK; Armagh Observatory and Planetarium, College Hill, Armagh BT61 9DG, UK; School of Mathematics and Physics, Queen's University Belfast, Belfast BT7 1NN, UK; Australian Astronomical Optics - Macquarie, Faculty of Science and Engineering, Macquarie University, North Ryde, NSW 2113, Australia; Physics Department, University of Nebraska at Omaha, 6001 Dodge St, Omaha, NE 68182, USA; Jeffery, C. S.; Scott, L. J. A.; Philip Monai, A.; Miszalski, B.; Woolf, V. M. (Monthly Notices of the Royal Astronomical Society, 2024-05-01)
    EC 19529-4430 was identified as a helium-rich star in the Edinburgh-Cape (EC) Survey of faint-blue objects and subsequently resolved as a metal-poor extreme helium (EHe) star in the Southern African Large Telescope (SALT) survey of chemically peculiar hot subdwarfs. This paper presents a fine analysis of the SALT high-resolution spectrum. EC 19529-4430 has $T_{\rm eff} = 20\, 700 \pm 250$ K, $\log g /{\rm cm\, s^{-2}} = 3.49\pm 0.03$, and an overall metallicity some 1.3 dex below solar; surface hydrogen is $\approx 0.5~{{\ \rm per\ cent}}$ by number. The surface CNO ratio 1:100:8 implies that the surface consists principally of CNO-processed helium and makes EC 19529-4430 the coolest known carbon-poor and nitrogen-rich EHe star. Metal-rich analogues include V652 Her and GALEX J184559.8-413827. Kinematically, its retrograde orbit indicates membership of the Galactic halo. No pulsations were detected in TESS photometry and there is no evidence for a binary companion. EC 19529-4430 most likely formed from the merging of two helium white dwarfs, which themselves formed as a binary system some 11 Gyr ago.

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