Red Eyes on Wolf-Rayet Stars: 60 New Discoveries via Infrared Color Selection

Abstract

We have spectroscopically identified 60 Galactic Wolf-Rayet (WR) stars, including 38 nitrogen types (WN) and 22 carbon types (WC). Using photometry from the Spitzer/GLIMPSE and 2MASS databases, the WRs were selected via a method we have established that exploits their unique infrared colors, which is mainly the result of excess radiation from free-free scattering within their dense ionized winds. The selection criteria has been refined since our last report, and now yields WRs at a rate of ~20% in spectroscopic follow-up of candidates that comprise a broad color space defined by the color distribution of all known WRs having B>14 mag. However, there are subregions within the broad color space which yield WRs at a rate of >50%. Cross-correlation of WR candidates with archival X-ray point-source catalogs increases the WR detection rate of the broad color space to ~40%; ten new WR X-ray sources have been found, in addition to a previously unrecognized X-ray counterpart to a known WR. The extinction values, distances, and galactocentric radii of all new WRs are calculated using the method of spectroscopic parallax. Although the majority of the new WRs have no obvious association with stellar clusters, two WC8 stars reside in a previously unknown massive-star cluster that lies near the intersection of the Scutum-Centaurus Arm and the Galaxy's bar, in which five OB supergiants were also identified. In addition, two WC and four WN stars were identified in association with the stellar clusters Danks 1 and 2. A WN9 star has also been associated with the cluster [DBS2003] 179. This work brings the total number of known Galactic WRs to 476, or ~7-8% of the total empirically estimated population. An examination of their Galactic distribution reveals a tracing of spiral arms and an enhanced WR surface density toward several massive-star formation sites (abridged).

Accepted to the Astronomical Journal on May 20, 2011. Document is 39 pages, including 20 figures and 8 tables

References in corpus (17)

• Physical Properties of Wolf-Rayet Stars
• A census of the Wolf-Rayet content in Westerlund 1 from near-infrared imaging and spectroscopy
• The most massive stars in the Arches cluster
• A massive cluster of Red Supergiants at the base of the Scutum-Crux arm
• Discovery of an Extraordinarily Massive Cluster of Red Supergiants
• A downward revision to the distance of the 1806-20 cluster and associated magnetar from Gemini near-Infrared spectroscopy
• A third red supergiant rich cluster in the Scutum-Crux Arm
• The Quintuplet Cluster I. A K-band spectral catalog of stellar sources
• Searching for hidden Wolf-Rayet stars in the Galactic Plane - 15 new Wolf-Rayet stars
• New Galactic Wolf-Rayet stars, and candidates. An annex to The VIIth Catalogue of Galactic Wolf-Rayet Stars
• Massive stars in the Cl 1813-178 Cluster. An episode of massive star formation in the W33 complex
• Obscured clusters.I. GLIMPSE30 - Young Milky Way Star Cluster Hosting Wolf-Rayet Stars
• Discovery of a young massive stellar cluster near HESS J1813-178
• The young Galactic star cluster [DBS2003]179
• The Discovery of a Massive Cluster of Red Supergiants with GLIMPSE
• Identification of the Infrared Counterpart to a Newly Discovered X-ray Source in the Galactic Center
• Discovery of two Galactic Wolf-Rayet stars in Circinus

Cited by in corpus (50)

• Grids of stellar models with rotation II. WR populations and supernovae/GRB progenitors at Z = 0.014
• Spatial distribution of Galactic Wolf-Rayet stars and implications for the global population
• Near-infrared proper motions and spectroscopy of infrared excess sources at the Galactic Center
• The G305 star-forming complex: the central star clusters Danks 1 and Danks 2
• The Efficiency of Stellar Reionization: Effects of Rotation, Metallicity, and Initial Mass Function
• New galactic star clusters discovered in the VVV survey. Candidates projected on the inner disk and bulge
• Massive open star clusters using the VVV survey I. Presentation of the data and description of the approach
• Identification of new Galactic symbiotic stars with SALT. I. Initial discoveries and other emission line objects
• Near- and Mid-Infrared colors of evolved stars in the Galactic plane. The Q1 and Q2 parameters
• Massive open star clusters using the VVV survey II. Discovery of six clusters with Wolf-Rayet stars
• A Near-Infrared Survey of the Inner Galactic Plane for Wolf-Rayet Stars II. Going Fainter: 71 More New WR Stars
• Extreme infrared variables from UKIDSS - II. an end-of-survey catalogue of eruptive YSOs and unusual stars
• Unlocking Galactic Wolf-Rayet stars with $\text{Gaia}$ DR2 II: Cluster and Association membership
• The Massive Star-Forming Regions Omnibus X-Ray Catalog, Second Installment
• Recurrent dust formation by WR 48a on a 30-year timescale
• The Massive Star-Forming Regions Omnibus X-Ray Catalog, Third Installment
• Supernova explosions of massive stars and cosmic rays
• Variable dust emission by WC type Wolf-Rayet stars observed in the NEOWISE-R survey
• The G305 star-forming complex: radio continuum and molecular line observations
• Palomar/TripleSpec observations of {\it Spitzer}/MIPSGAL~24\mic\ circumstellar shells: unveiling the nature of their central sources
• Massive Stars in the W33 Giant Molecular Complex
• A Near-Infrared Survey of the Inner Galactic Plane for Wolf-Rayet Stars III. New Methods: Faintest WR Stars
• Obscured clusters.IV. The most massive stars in [DBS2003]179
• Characterizing Wolf-Rayet Stars in the Near and Mid Infrared
• X-ray diagnostics of massive star winds
• Impact of main-sequence mass loss on the appearance, structure and evolution of Wolf-Rayet stars
• Massive stars in the giant molecular cloud G23.3-0.3 and W41
• High Resolution LAsMA ${}^{12}$CO and ${}^{13}$CO Observation of the G305 Giant Molecular Cloud Complex : I. Feedback on the Molecular Gas
• A Radio Characterization of Galactic compact Bubbles
• Chasing the Identification of ASCA Galactic Objects (ChIcAGO) - An X-ray Survey of Unidentified Sources in the Galactic Plane I: Source Sample and Initial Results
• Young Stellar Clusters Containing Massive Young Stellar Objects in the VVV Survey
• WR 120bb and WR 120bc: a pair of WN9h stars with possibly interacting circumstellar shells
• High resolution LAsMA ${}^{12}$CO and ${}^{13}$CO observation of the G305 giant molecular cloud complex : II. Effect of feedback on clump properties
• Spitzer/infrared spectrograph investigation of MIPSGAL 24 μm compact bubbles : Low resolution observations
• Massive open star clusters using the VVV survey IV. WR 62-2, a new very massive star in the core of the VVV CL041 cluster
• Applications of Machine-Learning Algorithms for Infrared Colour Selection of Galactic Wolf-Rayet Stars
• Probing the Dragonfish star-forming complex: the ionizing population of the young massive cluster Mercer 30
• Cluster formation induced by a cloud--cloud collision in [DBS2003]179
• Analysis of the WN star WR 102c, its WR nebula, and the associated cluster of massive stars in the Sickle Nebula
• A multi-wavelength analysis of the diffuse HII region G25.8700+0.1350
• A study of the interstellar medium towards the unidentified dark TeV $\gamma$-ray sources HESS J1614-518 and HESS J1616-508
• Discovery of a Wolf-Rayet Star Through Detection of its Photometric Variability
• The VVV Open Cluster Project II. Near-infrared sequences of 37 open clusters on eight-dimensional parameter space
• Search for new Galactic Wolf-Rayet stars using Gaia DR3. I. Candidate selection and the follow-up of the bright sample
• Multiwavelength and astrometric study of the DBS-89-90-91 embedded clusters region
• Constraints on the Minor Merging and Star Formation History of the Wolf-Rayet Galaxy NGC 5430 Through Observations
• Massive Stars in Molecular Clouds Rich in High-energy Sources: The Bridge of G332.809-0.132 and CS 78 in NGC 6334
• Clustered star formation towards Berkeley 87 / ON2. I. Multi-wavelength census and the population overlap problem
• Techniques for Observing Binaries in Other Galaxies
• LAMOST J040901.83+329355.6 -- a new Galactic star with Wolf--Rayet characteristics on a post-AGB to CSPN transitional stage