New windows on massive stars: asteroseismology, interferometry, and spectropolarimetry Proceedings IAU Symposium No. 307, 2014 G. Meynet, C. Georgy, J. H. Groh & Ph. Stee, eds. c  International Astronomical Union 2015 doi:10.1017/S1743921314007315 The Massive Star Population at the Center of the Milky Way Francisco Najarro 1 , Diego de la Fuente 1 , Tom R. Geballe 2 , Don F. Figer 3 and D. John Hillier 4 1 Centro de Astrobiolog´ ıa (CSIC/INTA), ctra. de Ajalvir km. 4, 28850 Torrej´ on de Ardoz, Madrid, Spain 2 Gemini Observatory, 670 N. A’ohoku Place, Hilo, HI 96720, USA 3 Center for Detectors, Rochester Institute of Technology, 54 Lomb Memorial Drive, Rochester, NY 14623, USA 4 Department of Physics and Astronomy, University of Pittsburgh, 3941 O’Hara Street, Pittsburgh, PA 15260 Abstract. Recent detection of a large number of apparently isolated massive stars within the inner 80 pc of the Galactic Center has raised fundamental questions regarding massive star formation in a such a dense and harsh environment. Are these isolated stars the results of tidal interactions between clusters, are they escapees from a disrupted cluster, or do they represent a new mode of massive star formation in isolation? Noting that most of the isolated massive stars have spectral analogs in the Quintuplet Cluster, we have undertaken a combined analysis of the infrared spectra of both selected Quintuplet stars and the isolated objects using Gemini North spectroscopy. We present preliminary results, aiming at α-elements vs iron abundances, stellar properties, ages and radial velocities which will differentiate the top-heavy and star-formation scenarios. Keywords. stars: early-type –stars: mass loss – stars: winds – stars: abundances – Galaxy: center – infrared: stars 1. Massive stars in clusters and isolation at the Galactic Center. Star formation scenario The Galactic Center (GC), hosting three of the most massive young clusters in the Local Group (Central, Arches and Quintuplet), is a unique laboratory to investigate massive stars and massive star formation. Given the intense radiation fields and extreme stellar densities present in the GC, one may question if star formation occurs in the same manner as seen in the giant molecular clouds elsewhere in the Galaxy. Recent results have revealed the presence of a large number of isolated massive stars (Mauerhan et al. 2010a,b) at the GC which is comparable to the massive star population of each of the clusters (Figer et al. 1999, 2002). Such detection of apparently isolated massive stars in this region has raised a further fundamental issue - whether these massive field stars are results of tidal interactions among clusters, are escapees from a disrupted cluster, or represent a new mode of massive star formation in isolation (Dong et al. 2014). The first option has been investigated (Habibi et al. 2014) based on the spectral analogy of these “field” stars with those in the Quintuplet and Arches clusters suggesting that they could have been physically associated with the clusters. Indeed, following the numeri- cal dynamical simulations from Harfst et al. (2010), and including the effects of stellar evolution and the orbit of the Arches cluster in the Galactic Center potential, Habibi et al. (2014) models were able to account for ∼ 60% of the isolated sources within the 426 at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S1743921314007315 Downloaded from https://www.cambridge.org/core. IP address: 181.214.251.121, on 24 Apr 2020 at 15:59:03, subject to the Cambridge Core terms of use, available