Recent Submissions

  • 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 < 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 >1 million spectra of LOFAR-selected radio sources; and (viii) trace structures using intergalactic/circumgalactic gas at z > 2. Finally, we describe the WEAVE Operational Rehearsals using the WEAVE Simulator.
  • Exceptional outburst of the blazar CTA 102 in 2012: the GASP-WEBT campaign and its extension

    Astronomical Institute, St.-Petersburg State University, 198504 St.-Petersburg, Russia; Pulkovo Observatory, 196140 St.-Petersburg, Russia; INAF, Osservatorio Astrofisico di Torino, via Osservatorio 20, I-10025 Pino Torinese, Italy; Astronomical Institute, St.-Petersburg State University, 198504 St.-Petersburg, Russia; Institute for Astrophysical Research, Boston University, Boston, MA, 22015 USA; Institute for Astrophysical Research, Boston University, Boston, MA, 22015 USA; Instituto de Astrofisíca de Andalucía, CSIC, E-18080 Granada, Spain; Steward Observatory, University of Arizona, Tucson, AZ 85721, USA; Instituto de Astrofisica de Canarias (IAC), La Laguna, E-38200 Tenerife, Spain; Departamento de Astrofisica, Universidad de La Laguna, La Laguna, Tenerife, Spain; Pulkovo Observatory, 196140 St.-Petersburg, Russia; Institute of Astronomy, Bulgarian Academy of Sciences, BG-1784 Sofia, Bulgaria; Astronomical Institute, St.-Petersburg State University, 198504 St.-Petersburg, Russia; Department of Physics and Institute for Plasma Physics, University of Crete, GR-71003 Heraklion, Greece; Foundation for Research and Technology - Hellas, IESL, Voutes, GR-7110 Heraklion, Greece; et al. (Monthly Notices of the Royal Astronomical Society, 2016-09-01)
    After several years of quiescence, the blazar CTA 102 underwent an exceptional outburst in 2012 September-October. The flare was tracked from γ-ray to near-infrared (NIR) frequencies, including Fermi and Swift data as well as photometric and polarimetric data from several observatories. An intensive Glast-Agile support programme of the Whole Earth Blazar Telescope (GASP-WEBT) collaboration campaign in optical and NIR bands, with an addition of previously unpublished archival data and extension through fall 2015, allows comparison of this outburst with the previous activity period of this blazar in 2004-2005. We find remarkable similarity between the optical and γ-ray behaviour of CTA 102 during the outburst, with a time lag between the two light curves of ≈1 h, indicative of cospatiality of the optical and γ-ray emission regions. The relation between the γ-ray and optical fluxes is consistent with the synchrotron self-Compton (SSC) mechanism, with a quadratic dependence of the SSC γ-ray flux on the synchrotron optical flux evident in the post-outburst stage. However, the γ-ray/optical relationship is linear during the outburst; we attribute this to changes in the Doppler factor. A strong harder-when-brighter spectral dependence is seen both the in γ-ray and optical non-thermal emission. This hardening can be explained by convexity of the UV-NIR spectrum that moves to higher frequencies owing to an increased Doppler shift as the viewing angle decreases during the outburst stage. The overall pattern of Stokes parameter variations agrees with a model of a radiating blob or shock wave that moves along a helical path down the jet.
  • MiNDSTEp differential photometry of the gravitationally lensed quasars WFI 2033-4723 and HE 0047-1756: microlensing and a new time delay

    Astronomisches Rechen-Institut, Zentrum für Astronomie, Universität Heidelberg, Mönchhofstraße 12-14, 69120, Heidelberg, Germany; Qatar Environment and Energy Research Institute (QEERI), HBKU, Qatar Foundation, Doha, Qatar; Department of Astronomy, Boston University, 725 Commonwealth Avenue, Boston, MA, 02215, USA; Niels Bohr Institute & Centre for Star and Planet Formation, University of Copenhagen Øster Voldgade 5, 1350, Copenhagen, Denmark; Departamento de Ciencias Físicas, Universidad Andres Bello, Avenida República 220, Santiago, Chile; Millennium Institute of Astrophysics, Chile; Dipartimento di Fisica E. R. Caianiello, Università di Salerno, via Giovanni Paolo II 132, 84084, Fisciano (SA), Italy; Istituto Nazionale di Fisica Nucleare, Sezione di Napoli, 80126, Napoli, Italy; SUPA, University of St Andrews, School of Physics & Astronomy, North Haugh, St Andrews, KY16 9SS, UK; Dipartimento di Fisica E. R. Caianiello, Università di Salerno, via Giovanni Paolo II 132, 84084, Fisciano (SA), Italy; Istituto Internazionale per gli Alti Studi Scientifici (IIASS), Vietri Sul Mare (SA), Italy; NASA Exoplanet Science Institute, MS 100-22, California Institute of Technology, Pasadena, CA, 91125, USA; Institut d'Astrophysique et de Géophysique, Université de Liège, Allée du 6 Août, Bât. B5c, 4000, Liège, Belgium; Astronomisches Rechen-Institut, Zentrum für Astronomie, Universität Heidelberg, Mönchhofstraße 12-14, 69120, Heidelberg, Germany; Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, 21029, Hamburg, Germany; Institut d'Astrophysique et de Géophysique, Université de Liège, Allée du 6 Août, Bât. B5c, 4000, Liège, Belgium; Main Astronomical Observatory, Academy of Sciences of Ukraine, Zabolotnoho 27, 03680, Kyiv, Ukraine; Dipartimento di Fisica e Astronomia, Università di Bologna, viale Berti Pichat 6/2, 40127, Bologna, Italy; et al. (Astronomy and Astrophysics, 2017-01-01)
    <BR /> Aims: We present V and R photometry of the gravitationally lensed quasars WFI 2033-4723 and HE 0047-1756. The data were taken by the MiNDSTEp collaboration with the 1.54 m Danish telescope at the ESO La Silla observatory from 2008 to 2012. <BR /> Methods: Differential photometry has been carried out using the image subtraction method as implemented in the HOTPAnTS package, additionally using GALFIT for quasar photometry. <BR /> Results: The quasar WFI 2033-4723 showed brightness variations of order 0.5 mag in V and R during the campaign. The two lensed components of quasar HE 0047-1756 varied by 0.2-0.3 mag within five years. We provide, for the first time, an estimate of the time delay of component B with respect to A of Δt = (7.6 ± 1.8) days for this object. We also find evidence for a secular evolution of the magnitude difference between components A and B in both filters, which we explain as due to a long-duration microlensing event. Finally we find that both quasars WFI 2033-4723 and HE 0047-1756 become bluer when brighter, which is consistent with previous studies. <P />Based on data collected by MiNDSTEp with the Danish 1.54 m telescope at the ESO La Silla observatory.
  • 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, Marseille, France; INAF - Osservatorio Astronomico di Padova, Vicolo Osservatorio 5, 35122 Padova, Italy; et al. (Monthly Notices of the Royal Astronomical Society, 2023-03-01)
    WEAVE, the new wide-field, massively multiplexed spectroscopic survey facility for the William Herschel Telescope, will see first light in late 2022. WEAVE comprises a new 2-degree 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 ~ 20 000. After summarising the design and implementation of WEAVE and its data systems, we present the organisation, 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 ionised gas in z &lt; 0.5 cluster galaxies; (vi) survey stellar populations and kinematics in ~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; (viii) trace structures using intergalactic/circumgalactic gas at z &gt; 2. Finally, we describe the WEAVE Operational Rehearsals using the WEAVE Simulator.
  • Sensitivity of the Cherenkov Telescope Array for probing cosmology and fundamental physics with gamma-ray propagation

    Centre for Space Research, North-West University, Potchefstroom, 2520, South Africa; Institute for Cosmic Ray Research, University of Tokyo, 5-1-5, Kashiwa-no-ha, Kashiwa, Chiba 277-8582, Japan; AIM, CEA, CNRS, Université Paris-Saclay, Université Paris Diderot, Sorbonne Paris Cité, CEA Paris-Saclay, IRFU/DAp, Bat 709, Orme des Merisiers, 91191 Gif-sur-Yvette, France; Centre for Advanced Instrumentation, Dept. of Physics, Durham University, South Road, Durham DH1 3LE, United Kingdom; Laboratoire Leprince-Ringuet, École Polytechnique (UMR 7638, CNRS/IN2P3, Institut Polytechnique de Paris), 91128 Palaiseau, France; Instituto de Astrofísica de Andalucía-CSIC, Glorieta de la Astronomía s/n, 18008, Granada, Spain; Instituto de Física Teórica UAM/CSIC and Departamento de Física Teórica, Universidad Autónoma de Madrid, c/ Nicolás Cabrera 13-15, Campus de Cantoblanco UAM, 28049 Madrid, Spain; Universidad Nacional Autónoma de México, Delegación Coyoacán, 04510 Ciudad de México, Mexico; Pontificia Universidad Católica de Chile, Av. Libertador Bernardo O'Higgins 340, Santiago, Chile; University of Geneva - Département de physique nucléaire et corpusculaire, 24 rue du Général-Dufour, 1211 Genave 4, Switzerland; et al. (Journal of Cosmology and Astroparticle Physics, 2021-02-01)
    The Cherenkov Telescope Array (CTA), the new-generation ground-based observatory for γ astronomy, provides unique capabilities to address significant open questions in astrophysics, cosmology, and fundamental physics. We study some of the salient areas of γ cosmology that can be explored as part of the Key Science Projects of CTA, through simulated observations of active galactic nuclei (AGN) and of their relativistic jets. Observations of AGN with CTA will enable a measurement of γ absorption on the extragalactic background light with a statistical uncertainty below 15% up to a redshift z=2 and to constrain or detect γ halos up to intergalactic-magnetic-field strengths of at least 0.3 pG . Extragalactic observations with CTA also show promising potential to probe physics beyond the Standard Model. The best limits on Lorentz invariance violation from γ astronomy will be improved by a factor of at least two to three. CTA will also probe the parameter space in which axion-like particles could constitute a significant fraction, if not all, of dark matter. We conclude on the synergies between CTA and other upcoming facilities that will foster the growth of γ cosmology.
  • Galaxy And Mass Assembly (GAMA): Data Release 4 and the z &lt; 0.1 total and z &lt; 0.08 morphological galaxy stellar mass functions

    International Centre for Radio Astronomy Research (ICRAR), University of Western Australia, Crawley, WA 6009, Australia; Astrophysics Research Institute, Liverpool John Moores University, 146 Brownlow Hill, Liverpool L3 5RF, UK; Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, D-21029 Hamburg, Germany; Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Hawthorn, VIC 3122, Australia; Faculty of Physics and Astronomy, Astronomical Institute (AIRUB), Ruhr University Bochum, D-44780 Bochum, Germany; Imagen Technologies, 151 W 26th St, New York, NY 10001, USA; School of Physics and Astronomy, University of Nottingham, University Park, Nottingham NG7 2RD, UK; Vera C. Rubin Observatory, 950 N Cherry Ave, Tucson, AZ 85719, USA; Sydney Astrophotonic Instrumentation Labs, School of Physics, the University of Sydney, Sydney NSW 2006, Australia; Centre for Theoretical Physics, Polish Academy of Sciences, al. Lotnikow 32/46, PL-02-668 Warsaw, Poland; et al. (Monthly Notices of the Royal Astronomical Society, 2022-06-01)
    In Galaxy And Mass Assembly Data Release 4 (GAMA DR4), we make available our full spectroscopic redshift sample. This includes 248 682 galaxy spectra, and, in combination with earlier surveys, results in 330 542 redshifts across five sky regions covering ~250 deg<SUP>2</SUP>. The redshift density, is the highest available over such a sustained area, has exceptionally high completeness (95 per cent to r<SUB>KiDS</SUB> = 19.65 mag), and is well-suited for the study of galaxy mergers, galaxy groups, and the low redshift (z &lt; 0.25) galaxy population. DR4 includes 32 value-added tables or Data Management Units (DMUs) that provide a number of measured and derived data products including GALEX, ESO KiDS, ESO VIKING, WISE, and HerschelSpace Observatory imaging. Within this release, we provide visual morphologies for 15 330 galaxies to z &lt; 0.08, photometric redshift estimates for all 18 million objects to r<SUB>KiDS</SUB> ~ 25 mag, and stellar velocity dispersions for 111 830 galaxies. We conclude by deriving the total galaxy stellar mass function (GSMF) and its sub-division by morphological class (elliptical, compact-bulge and disc, diffuse-bulge and disc, and disc only). This extends our previous measurement of the total GSMF down to 10<SUP>6.75</SUP> M$_{\odot } \, h_{70}^{-2}$ and we find a total stellar mass density of ρ<SUB>*</SUB> = (2.97 ± 0.04) × 10<SUP>8</SUP> M$_{\odot } \, h_{70}$ Mpc<SUP>-3</SUP> or $\Omega _*=(2.17 \pm 0.03) \times 10^{-3} \, h_{70}^{-1}$. We conclude that at z &lt; 0.1, the Universe has converted 4.9 ± 0.1 per cent of the baryonic mass implied by big bang Nucleosynthesis into stars that are gravitationally bound within the galaxy population.
  • The Variation of the Gas Content of Galaxy Groups and Pairs Compared to Isolated Galaxies

    International Centre for Radio Astronomy Research (ICRAR), University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia; ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), Australia; European Southern Observatory, Karl Schwarzschild Straße 2, D-85748 Garching, Germany; International Centre for Radio Astronomy Research (ICRAR), University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia; International Centre for Radio Astronomy Research (ICRAR), University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia; SUPA, School of Physics &amp; Astronomy, University of St Andrews, North Haugh, St Andrews KY16 9SS, UK; ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), Australia; Sydney Institute for Astronomy, School of Physics, University of Sydney, NSW 2006, Australia; Physics and Astronomy Department, University of Louisville, Louisville KY 40292, USA; Australian Astronomical Optics, Macquarie University, 105 Delhi Rd, North Ryde, NSW 2113, Australia; Armagh Observatory and Planetarium, College Hill, Armagh, BT61 DG, UK; ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), Australia; Australian Astronomical Optics, Macquarie University, 105 Delhi Rd, North Ryde, NSW 2113, Australia; Department of Physics and Astronomy, Macquarie University, NSW 2109, Australia; International Centre for Radio Astronomy Research (ICRAR), University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia; ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), Australia; Faculty of Physics, Ludwig-Maximilians-Universität, Scheinerstr. 1, D-81679 Munich, Germany; et al. (The Astrophysical Journal, 2022-03-01)
    We measure how the atomic gas (H I) fraction $\left({f}_{{\rm{H}}\,{\rm\small{I}}}=\tfrac{{M}_{{\rm{H}}\,{\rm\small{I}}}}{{M}_{* }}\right)$ of groups and pairs taken as single units vary with average stellar mass (&lt;M <SUB>*</SUB>&gt;) and average star formation rate (&lt;SFR&gt;), compared to isolated galaxies. The H I 21 cm emission observation are from (i) archival ALFALFA survey data covering three fields from the GAMA survey (provides environmental and galaxy properties), and (ii) DINGO pilot survey data of one of those fields. The mean f <SUB>H I </SUB> for different units (groups/pairs/isolated galaxies) are measured in regions of the log(&lt;M <SUB>*</SUB>&gt;)-log(&lt;SFR&gt;) plane, relative to the z ~ 0 star-forming main sequence (SFMS) of individual galaxies, by stacking f <SUB>H I </SUB> spectra of individual units. For ALFALFA, f <SUB>H I </SUB> spectra of units are measured by extracting H I spectra over the full groups/pair areas and dividing by the total stellar mass of member galaxies. For DINGO, f <SUB>H I </SUB> spectra of units are measured by co-adding H I spectra of individual member galaxies, followed by division by their total stellar mass. For all units, the mean f <SUB>H I </SUB> decreases as we move to higher &lt;M <SUB>*</SUB>&gt; along the SFMS and as we move from above the SFMS to below it at any &lt;M <SUB>*</SUB>&gt;. From the DINGO-based study, mean f <SUB>H I </SUB> in groups appears to be lower compared to isolated galaxies for all &lt;M <SUB>*</SUB>&gt; along the SFMS. From the ALFALFA-based study, we find substantially higher mean f <SUB>H I </SUB> in groups compared to isolated galaxies (values for pairs being intermediate) for &lt;M <SUB>*</SUB>&gt; ≲ 10<SUP>9.5</SUP> M <SUB>⊙</SUB>, indicating the presence of substantial amounts of H I not associated with cataloged member galaxies in low mass groups.
  • Winds from stripped low-mass helium stars and Wolf-Rayet stars

    Armagh Observatory and Planetarium, College Hill, Armagh, BT61 9DG, UK; Vink, Jorick S. (Astronomy and Astrophysics, 2017-11-01)
    We present mass-loss predictions from Monte Carlo radiative transfer models for helium (He) stars as a function of stellar mass, down to 2 M<SUB>⊙</SUB>. Our study includes both massive Wolf-Rayet (WR) stars and low-mass He stars that have lost their envelope through interaction with a companion. For these low-mass He stars we predict mass-loss rates that are an order of magnitude smaller than by extrapolation of empirical WR mass-loss rates. Our lower mass-loss rates make it harder for these elusive stripped stars to be discovered via line emission, and we should attempt to find these stars through alternative methods instead. Moreover, lower mass-loss rates make it less likely that low-mass He stars provide stripped-envelope supernovae (SNe) of type Ibc. We express our mass-loss predictions as a function of L and Z and not as a function of the He abundance, as we do not consider this physically astute given our earlier work. The exponent of the M⊙ versus Z dependence is found to be 0.61, which is less steep than relationships derived from recent empirical atmospheric modelling. Our shallower exponent will make it more challenging to produce "heavy" black holes of order 40 M<SUB>⊙</SUB>, as recently discovered in the gravitational wave event GW 150914, making low metallicity for these types of events even more necessary.
  • Very massive stars and nitrogen-emitting galaxies

    Armagh Observatory and Planetarium, College Hill, BT61 9DG, Armagh, Northern Ireland, UK; Vink, Jorick S. (Astronomy and Astrophysics, 2023-11-01)
    Recent studies of high-redshift galaxies with James Webb Space Telescope (JWST), such as GN-z11 at z = 10.6, show unexpectedly significant amounts of nitrogen (N) in their spectra. As this phenomenology appears to extend to gravitionally lensed galaxies at Cosmic noon such as the Sunburst Arc at z = 2.37, as well as globular clusters overall, we suggest that the common ingredient among them are very massive stars (VMSs) with zero-age main sequence (ZAMS) masses in the range of 100-1000 M<SUB>⊙</SUB>. The He II in the Sunburst Arc might also be the result of the disproportionally large contribution of VMS to the total stellar contribution. We analyse the pros and cons of the previous suggestions, including classical Wolf-Rayet (cWR) stars and supermassive stars (SMSs), to conclude that only our VMS alternative ticks all the relevant boxes. We discuss the VMS mass-loss history via their peculiar vertical evolution in the HR diagram resulting from a self-regulatory effect of these wind-dominated VMSs and we estimate that the large amounts of N present in star-forming galaxies may indeed result from VMSs. We conclude that VMSs should be included in population synthesis and chemical evolution models. Moreover, that it is critical for this to be done self-consistently, as a small error in their mass-loss rates would have dramatic consequences for their stellar evolution, as well as their ionising and chemical feedback.
  • Bringing Stellar Evolution and Feedback Together: Summary of Proposals from the Lorentz Center Workshop

    Anton Pannekoek Institute for Astronomy, Universiteit van Amsterdam, Science Park 904, 1098 XH Amsterdam, Netherlands; Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, Netherlands; Institute of Astronomy, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Grudziądzka 5, 87-100 Toruń, Poland; Kapteyn Astronomical Institute, University of Groningen, P.O. Box 800, 9700 AV Groningen, Netherlands; McWilliams Center for Cosmology, Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213, USA; Physics &amp; Astronomy, University of Sheffield, Hounsfield Road, Sheffield, S3 7RH, UK; Department of Physics and Material Science, The University of Memphis, Memphis, TN 38152, USA; Zentrum für Astronomie der Universität Heidelberg, Astronomisches Rechen-Institut, Mönchhofstr. 12-14, D-69120 Heidelberg, Germany; Anton Pannekoek Institute for Astronomy, Universiteit van Amsterdam, Science Park 904, 1098 XH Amsterdam, Netherlands; Institute of Astronomy, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven, Belgium; Anton Pannekoek Institute for Astronomy, Universiteit van Amsterdam, Science Park 904, 1098 XH Amsterdam, Netherlands; Center for Computational Astrophysics, Division of Science, National Astronomical Observatory of Japan, 2-21-1, Osawa, Mitaka, Tokyo 181-8588, Japan; Cardiff Hub for for Astrophysics Research and Technology, School of Physics and Astronomy, Cardiff University, Queen's Buildings, The Parade, Cardiff CF24 3AA, UK; Department of Physics and Astronomy, University of Exeter, Stocker Road, Exeter EX4 4QL, UK; Anton Pannekoek Institute for Astronomy, Universiteit van Amsterdam, Science Park 904, 1098 XH Amsterdam, Netherlands; SOFIA Science Center, USRA, NASA Ames Research Center, Moffett Field, CA 94045, USA; et al. (Publications of the Astronomical Society of the Pacific, 2023-02-01)
    Stars strongly impact their environment, and shape structures on all scales throughout the universe, in a process known as "feedback." Due to the complexity of both stellar evolution and the physics of larger astrophysical structures, there remain many unanswered questions about how feedback operates and what we can learn about stars by studying their imprint on the wider universe. In this white paper, we summarize discussions from the Lorentz Center meeting "Bringing Stellar Evolution and Feedback Together" in 2022 April and identify key areas where further dialog can bring about radical changes in how we view the relationship between stars and the universe they live in.
  • Maximum black hole mass across cosmic time

    Armagh Observatory and Planetarium, College Hill, Armagh BT61 9DG, UK; Vink, Jorick S.; Higgins, Erin R.; Sander, Andreas A. C.; Sabhahit, Gautham N. (Monthly Notices of the Royal Astronomical Society, 2021-06-01)
    At the end of its life, a very massive star is expected to collapse into a black hole (BH). The recent detection of an 85 M<SUB>⊙</SUB> BH from the gravitational wave event GW 190521 appears to present a fundamental problem as to how such heavy BHs exist above the approximately 50 M<SUB>⊙</SUB> pair-instability (PI) limit where stars are expected to be blown to pieces with no remnant left. Using MESA, we show that for stellar models with non-extreme assumptions, 90-100 M<SUB>⊙</SUB> stars at reduced metallicity ($Z/\mbox{ $\mathrm{Z}_{\odot }$}\le 0.1$) can produce blue supergiant progenitors with core masses sufficiently small to remain below the fundamental PI limit, yet at the same time lose an amount of mass via stellar winds that is small enough to end up in the range of an 'impossible' 85 M<SUB>⊙</SUB> BH. The two key points are the proper consideration of core overshooting and stellar wind physics with an improved scaling of mass-loss with iron (Fe) contents characteristic for the host galaxy metallicity. Our modelling provides a robust scenario that not only doubles the maximum BH mass set by PI, but also allows us to probe the maximum stellar BH mass as a function of metallicity and cosmic time in a physically sound framework.
  • X-Shooting ULLYSES: Massive stars at low metallicity. I. Project description

    Armagh Observatory and Planetarium, College Hill, BT61 9DG, Armagh, UK; ESO - European Organisation for Astronomical Research in the Southern Hemisphere, Alonso de Cordova 3107, Vitacura, Santiago de Chile, Chile; Dept of Physics &amp; Astronomy, University of Sheffield, Hounsfield Road, Sheffield, S3 7RH, UK; Space Telescope Science Institute, 3700 San Martin Dr, Baltimore, MD, 21218, USA; Centro de Astrobiología (CAB), CSIC-INTA, Ctra. Torrejón a Ajalvir km 4., 28850, Torrejón de Ardoz, Madrid, Spain; LUPM, Université de Montpellier, CNRS, Place Eugène Bataillon, 34095, Montpellier, France; Las Campanas Observatory, Carnegie Observatories, Casilla 601, La Serena, Chile; Institute for Physics and Astronomy, University Potsdam, 14476, Potsdam, Germany; Département de physique, Université de Montréal, Campus MIL, 1375 Thérèse-Lavoie-Roux, Montréal, (QC), H2V 0B3, Canada; Penn State Scranton, 120 Ridge View Drive, Dunmore, PA, 18512, USA; et al. (Astronomy and Astrophysics, 2023-07-01)
    Observations of individual massive stars, super-luminous supernovae, gamma-ray bursts, and gravitational wave events involving spectacular black hole mergers indicate that the low-metallicity Universe is fundamentally different from our own Galaxy. Many transient phenomena will remain enigmatic until we achieve a firm understanding of the physics and evolution of massive stars at low metallicity (Z). The Hubble Space Telescope has devoted 500 orbits to observing ∼250 massive stars at low Z in the ultraviolet (UV) with the COS and STIS spectrographs under the ULLYSES programme. The complementary X-Shooting ULLYSES (XShootU) project provides an enhanced legacy value with high-quality optical and near-infrared spectra obtained with the wide-wavelength coverage X-shooter spectrograph at ESO's Very Large Telescope. We present an overview of the XShootU project, showing that combining ULLYSES UV and XShootU optical spectra is critical for the uniform determination of stellar parameters such as effective temperature, surface gravity, luminosity, and abundances, as well as wind properties such as mass-loss rates as a function of Z. As uncertainties in stellar and wind parameters percolate into many adjacent areas of astrophysics, the data and modelling of the XShootU project is expected to be a game changer for our physical understanding of massive stars at low Z. To be able to confidently interpret James Webb Space Telescope spectra of the first stellar generations, the individual spectra of low-Z stars need to be understood, which is exactly where XShootU can deliver. <P />Table B.1 and full Table B.2 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/675/A154">https://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/675/A154</A> <P />Based on observations collected at the European Southern Observatory under ESO programme 106.211Z.001.