The extended population associated with W40

Abstract

W40 is a heavily obscured bipolar HII region projected in the direction of the Aquila Rift and ionized by hot stars in a central, partly embedded cluster. The study of the cluster and its surroundings has been greatly hampered thus far by the strong extinction in the region. We use the Gaia eDR3 catalog to establish astrometric membership criteria based on the population of the W40 central cluster, reassess the distance of the region, and identify in this way new members, both inside and outside the cluster. We obtain visible spectroscopy in the red spectral region to classify both known and new members, complemented with Gaia and Spitzer photometry to assess the evolutionary status of the stellar population. We derive a high-confidence geometric distance to the W40 region of 502 pc $\pm$ 4 pc and confirm the presence of a comoving extended population of stars at the same distance, spreading over the whole projected area of the HII region and beyond. Spectral classifications are presented for 21 members of the W40 region, 10 of them belonging to the central cluster. One of the newly identified B stars in the extended population is clearly interacting with the shell surrounding the HII region, giving rise to a small arc-shaped nebula that traces a bow shock. The infrared excess properties suggest that the extended population is significantly older ($\sim 3$ Myr) than the W40 central cluster ($<1$ Myr). The area currently occupied by the W40 HII region and its surroundings has a history of star formation extending at least several million years in the past, of which the formation of the W40 central cluster and the subsequent HII region is one of the latest episodes. The newly determined distance suggests that W40 is behind, and physically detached from, a pervasive large dust layer which is some 60 pc foreground to it as determined by previous studies.

arXiv commentSubmitted to Astronomy and Astrophysics

References in corpus (30)

• Modules for Experiments in Stellar Astrophysics (MESA)
• Modules for Experiments in Stellar Astrophysics (MESA): Giant Planets, Oscillations, Rotation, and Massive Stars
• Modules for Experiments in Stellar Astrophysics (MESA): Binaries, Pulsations, and Explosions
• MESA Isochrones and Stellar Tracks (MIST). I: Solar-Scaled Models
• Intrinsic Colors, Temperatures, and Bolometric Corrections of Pre-Main Sequence Stars
• Gaia Data Release 2: The astrometric solution
• MESA Isochrones and Stellar Tracks (MIST) 0: Methods for the construction of stellar isochrones
• Gaia Early Data Release 3: Parallax bias versus magnitude, colour, and position
• The Optical to Mid-Infrared Extinction Law Based on the APOGEE, Gaia DR2, Pan-STARRS1, SDSS, APASS, 2MASS and WISE Surveys
• Young Stellar Objects in the Gould Belt
• Protoplanetary disk lifetimes vs stellar mass and possible implications for giant planet populations
• The Disk Population of the Upper Scorpius Association
• The Spitzer Gould Belt Survey of Large Nearby Interstellar Clouds: Discovery of a Dense Embedded Cluster in the Serpens-Aquila Rift
• The Herschel first look at protostars in the Aquila Rift
• Gaia-DR2 confirms VLBA parallaxes in Ophiuchus, Serpens and Aquila
• Overview of the Massive Young Star-Forming Complex Study in Infrared and X-ray (MYStIX) Project
• The Gould's Belt Distances Survey (GOBELINS) III. The distance to the Serpens/Aquila Molecular Complex
• Circumstellar Disk Lifetimes In Numerous Galactic Young Stellar Clusters
• Age Gradients in the Stellar Populations of Massive Star Forming Regions Based on a New Stellar Chronometer
• The MYStIX InfraRed-Excess Source Catalog
• Internal dynamics and membership of the NGC 3603 Young Cluster from microarcsecond astrometry
• From Birth to Death of Protoplanetary Disks: Modeling Their Formation, Evolution, and Dispersal
• Star Formation In Nearby Clouds (SFiNCs): X-ray And Infrared Source Catalogs And Membership
• A Chandra Observation of the Obscured Star-Forming Complex W40
• W40 region in the Gould Belt : An embedded cluster and H II region at the junction of filaments
• An initial overview of the extent and structure of recent star formation within the Serpens Molecular Cloud using Gaia Data Release 2
• Internal motions in OB-associations with Gaia DR2
• Intracluster Age Gradients In Numerous Young Stellar Clusters
• Spectral classification of the brightest objects in the galactic star forming region W40
• IN-SYNC. VIII. Primordial Disk Frequencies in NGC 1333, IC 348, and the Orion A Molecular Cloud

Cited by in corpus (3)

• Understanding star formation in molecular clouds IV. Column density PDFs from quiescent to massive molecular clouds
• Description of turbulent dynamics in the interstellar medium: Multifractal microcanonical analysis: II. Sparse filtering of Herschel observation maps and visualization of filamentary structures at different length scales
• FIRESTORM I: Stellar Feedback and Gas Kinematics in the Evolved W40 Hub-Filament System