Discovery of O stars in the tidal Magellanic Bridge: Stellar parameters, abundances, and feedback of the nearest metal-poor massive stars and their implication for the Magellanic System ecology

Abstract

The Magellanic Bridge stretching between the SMC and LMC is the nearest tidally stripped intergalactic environment and has a low average metallicity of $Z0.1Z_{\odot }$. Here we report the first discovery of three O-type stars in the Bridge using archival spectra collected with FLAMES at ESO/VLT. We analyze the spectra using the PoWR models, which provide the physical parameters, ionizing photon fluxes, and surface abundances. This discovery suggests that the tidally stripped low density gas is capable of producing massive O stars and their ages imply ongoing star formation in the Bridge. The multi-epoch spectra indicate that all three O stars are binaries. Despite their spatial proximity to each other, these O stars are chemically distinct. One of them is a fast-rotating giant with nearly LMC-like abundances. The other two are main-sequence stars that rotate extremely slowly and are strongly metal depleted. This includes the most nitrogen-poor O star known up to date. Taking into account the previous analyses of B stars in the Bridge, we interpret the various metal abundances as the signature of a chemically inhomogeneous interstellar medium, suggesting that the gas might have accreted during multiple episodes of tidal interaction between the Clouds. Attributing the lowest derived metal content to the primordial gas, the time of initial formation of the Bridge may date back to several Gyr. Using the Gaia and Galex color-magnitude diagrams we roughly estimate the total number of O stars in the Bridge and their total ionizing radiation. Comparing with the energetics of the diffuse ISM, we find that the contribution of the hot stars to the ionizing radiation field in the Bridge is less than 10%, and conclude that the main sources of ionizing photons are leaks from the LMC and SMC. We estimate a lower limit for the fraction of ionizing radiation that escapes from these two dwarf galaxies.

arXiv commentto be published in A&A

References in corpus (58)

• The chemical composition of the Sun
• Gaia Data Release 2. Summary of the contents and survey properties
• MESA Isochrones and Stellar Tracks (MIST). I: Solar-Scaled Models
• First stars V - Abundance patterns from C to Zn and supernova yields in the early Galaxy
• Exploring the Milky Way stellar disk. A detailed elemental abundance study of 714 F and G dwarf stars in the Solar neighbourhood
• Pre-Supernova Evolution of Massive Single and Binary Stars
• Are the Magellanic Clouds on their First Passage about the Milky Way?
• Third-Epoch Magellanic Cloud Proper Motions I: HST/WFC3 data and Orbit Implications
• Revised Catalog of GALEX Ultraviolet Sources. I. The All-sky Survey: GUVcat_AIS
• The Role of Dwarf Galaxy Interactions in Shaping the Magellanic System and Implications for Magellanic Irregulars
• N-body Simulations of the Small Magellanic Cloud and the Magellanic Stream
• The IACOB project: I. Rotational velocities in Northern Galactic O and early B-type stars revisited. The impact of other sources of line-broadening
• A coordinated X-ray and Optical Campaign of the Nearest Massive Eclipsing Binary, $\delta$ Orionis Aa: IV. A multiwavelength, non-LTE spectroscopic analysis
• How mergers magnetise massive stars
• The Parkes HI Survey of the Magellanic System
• Surveying the Agents of Galaxy Evolution in the Tidally-Stripped, Low Metallicity Small Magellanic Cloud (SAGE-SMC). I. Overview
• The VLT-FLAMES survey of massive stars: Surface chemical compositions of B-type stars in the Magellanic Clouds
• The Wolf-Rayet stars in the Large Magellanic Cloud: A comprehensive analysis of the WN class
• The Optical Depth of H II Regions in the Magellanic Clouds
• The Magellanic Stream: Circumnavigating the Galaxy
• On the consistent treatment of the quasi-hydrostatic layers in hot star atmospheres
• A Population of Accreted SMC Stars in the LMC
• The VLT-FLAMES Tarantula Survey X: Evidence for a bimodal distribution of rotational velocities for the single early B-type stars
• Rejuvenation of stellar mergers and the origin of magnetic fields in massive stars
• Massive star models with magnetic braking
• Wolf-Rayet stars in the Small Magellanic Cloud: I. Analysis of the single WN stars
• Early magnetic B-type stars: X-ray emission and wind properties
• Testing massive star evolution, star-formation history and feedback at low metallicity : Spectroscopic analysis of OB stars in the SMC Wing
• The Magellanic Bridge: The Nearest Purely Tidal Stellar Population
• Massive stars at low metallicity: Evolution and surface abundances of O dwarfs in the SMC
• An inhomogeneous model for the Galactic halo: a possible explanation for the spread observed in s- and r-process elements
• The formation of the Milky Way halo and its dwarf satellites; a NLTE-1D abundance analysis. II. Early chemical enrichment
• The effects of surface fossil magnetic fields on massive star evolution: I. Magnetic field evolution, mass-loss quenching and magnetic braking
• Mean age gradient and asymmetry in the star formation history of the Small Magellanic Cloud
• The Proper Motion Field Along the Magellanic Bridge: a New Probe of the LMC-SMC Interaction
• Implications of O and Mg abundances in metal-poor halo stars for stellar iron yields
• Chemical Signatures of the First Supernovae in the Sculptor Dwarf Spheroidal Galaxy
• A census of massive stars in NGC 346. Stellar parameters and rotational velocities
• High Resolution \hi observations of the Western Magellanic Bridge
• Chemical compositions of Four B-type Supergiants in the SMC Wing
• Metallicity and Physical Conditions in the Magellanic Bridge
• FUSE Observations of the Magellanic Bridge Gas toward Two Early-Type Stars: Molecules, Physical Conditions, and Relative Abundance
• OGLE-ing the Magellanic System: Stellar populations in the Magellanic Bridge
• Resolved Kinematics of Runaway and Field OB Stars in the Small Magellanic Cloud
• The First Stars in the Universe and Cosmic Reionization
• Warm Ionized Gas Revealed in the Magellanic Bridge Tidal Remnant: Constraining the Baryon Content and the Escaping Ionizing Photons around Dwarf Galaxies
• Observations of the interstellar medium in the Magellanic Bridge
• The VMC survey -- XXXVIII. Proper motion of the Magellanic Bridge
• The effects of stellar winds of fast-rotating massive stars in the earliest phases of the chemical enrichment of the Galaxy
• A non-LTE analysis of the spectra of two narrow lined main sequence stars in the SMC
• Stellar population of the superbubble N206 in the LMC I. Analysis of the Of-type stars
• Exploring Chemical Homogeneity in Dwarf Galaxies: A VLT-MUSE study of JKB 18
• Structured star formation in the Magellanic inter-Cloud region
• Spitzer View of Massive Star Formation in the Tidally Stripped Magellanic Bridge
• The iron abundance of the Magellanic Bridge
• Ha Emission from the Magellanic Bridge
• Magnesium abundances in mildly metal-poor stars from different indicators
• The NGC 346 massive star census: Nitrogen abundances for apparently single, narrow lined, hydrogen core burning B-type stars

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