Young, Massive Star Candidates Detected throughout the Nuclear Star Cluster of the Milky Way

Abstract

Aims. Young, massive stars have been found at projected distances R < 0.5 pc from supermassive black hole, Sgr A* at the center of our Galay. In recent years, increasing evidence has been found for the presence of young, massive stars also at R > 0.5 pc. Our goal in this work is a systematic search for young, massive star candidates throughout the entire region within R ~ 2.5 pc of the black hole. Methods. The main criterion for the photometric identification of young, massive early-type stars is the lack of CO-absorption in the spectra. We used narrow-band imaging with VLT/ISAAC to search for young, massive stars within ~2.5 pc of Sgr A*. Results. We have found 63 early-type star candidates at R < 2.5 pc, with an estimated erroneous identification rate of only about 20%. Considering their K-band magnitudes and interstellar extinction, they are candidates for Wolf-Rayet stars, supergiants, or early O-type stars. Of these, 31 stars are so far unknown young, massive star candidates, all of which lie at R>0.5pc. The surface number density profile of the young, massive star candidates can be well fit by a single power-law, with Gamma = 1.6 +- 0.17 at R < 2.5 pc, which is significantly steeper than that of the late-type giants that make up the bulk of the observable stars in the NSC. Intriguingly, this power-law is consistent with the power-law that describes the surface density of young, massive stars in the same brightness range at R < 0.5 pc. Conclusions. The finding of a significant number of newly identified early-type star candidates at the Galactic center suggests that young, massive stars can be found throughout the entire cluster which may require us to modify existing theories for star formation at the Galactic center. Follow-up studies are needed to improve the existing data and lay the foundations for a unified theory of star formation in the Milky Way's NSC.

20 pages, 11 figures, Accepted for publication in Astronomy and Astrophysics

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Cited by in corpus (25)

• Large scale kinematics and dynamical modelling of the Milky Way nuclear star cluster
• The nuclear cluster of the Milky Way: Our primary testbed for the interaction of a dense star cluster with a massive black hole
• The Nuclear Cluster of the Milky Way: Total Mass and Luminosity (long version)
• KMOS view of the Galactic Centre I. Young stars are centrally concentrated
• Magnetically Confined Interstellar Hot Plasma in the Nuclear Bulge of our Galaxy
• Far-Infrared Spectroscopy of the Galactic Center. Hot Molecular Gas: Shocks versus Radiation near SgrA*
• The distribution of stars around the Milky Way's central black hole II: Diffuse light from sub-giants and dwarfs
• Numerical simulations of the possible origin of the two sub-parsec scale and counter-rotating stellar disks around SgrA*
• Mapping the Outer Edge of the Young Stellar Cluster in the Galactic Center
• Spectroscopic Detection of a Cusp of Late-type Stars around the Central Black Hole in the Milky Way
• ALMA Observations of the Galactic Center: SiO Outflows and High Mass Star Formation near Sgr A*
• On the origin of the B-stars in the Galactic center
• Observational Support for Massive Black Hole Formation Driven by Runaway Stellar Collisions in Galactic Nuclei
• Signatures of Young Star Formation Activity Within Two Parsecs of Sgr A*
• Random Forest Classification of Stars in the Galactic Centre
• Spectroscopically Identified Intermediate Age Stars at 0.5 - 3 pc Distance from Sgr A*
• Effects of turbulence in the Circumnuclear Disk
• Photometric Classification of Stars Around the Milky Way's Central Black Hole: I. Central Parsec
• The X-ray footprint of the CircumNuclear Disk
• A spectroscopic map of the Galactic centre -- Observations and resolved stars
• A Wide Metallicity Range for Gyr-old Stars in the Nuclear Star Cluster
• Detecting hot stars in the Galactic centre with combined near- and mid-infrared photometry
• Ices in the Galactic Centre : solid ice and gaseous CO in the central parsec
• Age and metallicity of the Milky Way's nuclear star cluster studied at 3 pc from Sagittarius A*
• 3D CMZ V: A new orbital model of our Galaxy's Center, informed by data across the electromagnetic spectrum