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/S1743921314007376 Circumstellar Environments of MYSOs Revealed by IFU Spectroscopy F. Navarete 1 , A. Damineli 1 , C. L. Barbosa 2 and R. D. Blum 3 1 IAG-USP, Rua do Mat˜ ao, 1226, 05508-900, S˜ ao Paulo, SP Brazil email: navarete@usp.br 2 UNIVAP, S˜ ao Jos´ e dos Campos, SP, Brazil 3 NOAO, 950 N Cherry Ave., Tuczon, AZ 85719 USA Abstract. Formation of massive stars (M> 8 M⊙) is still not well understood and lacks of observational constraints. We observed 7 MYSO candidates using the NIFS spectrometer at Gemini North Telescope to study the accretion process at high angular resolution (∼ 50 mas) and very closer to the central star. Preliminary results for 2 sources have revealed circumstellar structures traced by Brackett-Gamma, CO lines and extended H 2 emission. Both sources present kinematics in the CO absorption lines, suggesting rotating structures. The next step will derive the central mass of each source by applying a keplerian model for these CO features. Keywords. Stars: formation, Stars: early-type, Stars: pre-main sequence, Stars: circumstellar matter, Techniques: spectroscopic, Techniques: high angular resolution 1. Introduction The formation mechanisms of massive stars is one of the most important problems in stellar astrophysics and still poorly understood. While low mass young stellar objects (YSOs) reach the zero age main sequence (ZAMS) after the accretion period is finished, the massive ones (MYSOs) reach the main sequence while the accretion is still ongoing. Recently, Navarete et al. (2014) carried a survey of extended H 2 emission towards a well defined sample of MYSO candidates. They found that ∼ 20% of the sample is associated to jet-like structures, suggesting bipolar outflows. These observational evidences supports the accretion scenario (Krumholz et al. 2005) and also indicate that massive stars cannot be merely formed by merging of low mass stars (Bonnell et al. 2001). Although the scenario of an accretion disk may apply for all massive stars, the details are lacking. There are a few examples of well documented accretion disks around massive (10-20 M ⊙ ) forming stars (Davies et al. 2010; Murakawa et al. 2013). Disks have been also identified through profile fitting of emission features seen in high spectral resolution data (Bik & Thi 2004; Blum et al. 2004). In order to study the details of the circumstellar environment around MYSOs, we present K-band integral field spectroscopy of six MYSOs associated to large scale H 2 outflows, identified by Navarete et al. (2014); and one source selected from Varricatt et al. (2010). 2. Observations K-band (λ ≈ 2.2 μm, R ≈ 5200) spectra of 7 MYSO candidates were obtained with the Near-infrared Integral Field Spectrograph (NIFS) deployed at the 8-m Gemini North Telescope (Hawaii). 453 at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S1743921314007376 Downloaded from https://www.cambridge.org/core. IP address: 54.191.40.80, on 20 Aug 2017 at 03:09:33, subject to the Cambridge Core terms of use, available