Michiel Cottaar

Michiel Cottaar
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Michiel Cottaar
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Solar and Stellar Astrophysics (8)
 
Astrophysics of Galaxies (4)

Publications Authored By Michiel Cottaar

2017Feb
Affiliations: 1Department of Astronomy, University of Florida, 2Department of Astronomy, University of Florida, 3Western Washington University, 4University of Oxford, 5Yale, 6Department of Astronomy, University of Florida, 7Leiden Observatory, 8Steward Observatory, 9University of Michigan, 10University of Michigan, 11Vanderbilt University, 12University of Virginia, 13Wesleyan University, 14University of Virginia, 15University of Virginia, 16University of Virginia

The kinematics and dynamics of young stellar populations tests theories of their formation. With this aim, we continue our analysis of the SDSS-III/APOGEE INfrared Spectra of Young Nebulous Clusters (IN-SYNC) survey, a high resolution near infrared spectroscopic survey of young clusters. We focus on the Orion A star-forming region, for which IN-SYNC obtained spectra of ~2700 stars. Read More

2015Nov
Affiliations: 1Department of Astronomy, University of Florida, 2Department of Astronomy, University of Florida, 3Western Washington University, 4University of Oxford, 5Yale, 6Department of Astronomy, University of Florida, 7Leiden Observatory, 8Steward Observatory, 9ETH Zurich, 10University of Michigan, 11Vanderbilt University, 12University of Virginia, 13Wesleyan University, 14University of Virginia, 15University of Virginia, 16University of Virginia, 17Apache Point Observatory and New Mexico State University

We present the results of the SDSS APOGEE INfrared Spectroscopy of Young Nebulous Clusters program (IN-SYNC) survey of the Orion A molecular cloud. This survey obtained high resolution near infrared (NIR) spectroscopy of about 2700 young pre-main sequence stars throughout the region, acquired across five distinct fields spanning 6deg field of view (FOV). With these spectra, we have measured accurate stellar parameters (T_eff, log g, v sin i) and extinctions, and placed the sources in the Hertzsprung-Russel Diagram (HRD). Read More

Most field stars will have encountered the highest stellar density and hence the largest number of interactions in their birth environment. Yet the stellar dynamics during this crucial phase are poorly understood. Here we analyze the radial velocities measured for 152 out of 380 observed stars in the 2-6 Myr old star cluster IC 348 as part of the SDSS-III APOGEE. Read More

Over two years 8,859 high-resolution H-band spectra of 3,493 young (1 - 10 Myr) stars were gathered by the multi-object spectrograph of the APOGEE project as part of the IN-SYNC ancillary program of that SDSS-III survey. Here we present the forward modeling approach used to derive effective temperatures, surface gravities, radial velocities, rotational velocities, and H-band veiling from these near-infrared spectra. We discuss in detail the statistical and systematic uncertainties in these stellar parameters. Read More

We have used Sloan Digital Sky Survey-III (SDSS-III) Apache Point Observatory Galactic Evolution Experiment (APOGEE) radial velocity observations in the near-infrared $H$-band to explore the membership of the nearby ($86.7 \pm 0.9$ pc) open cluster Coma Berenices (Melotte 111), concentrating on the poorly-populated low-mass end of the main sequence. Read More

Orbital motions from binary stars can broaden the observed line-of-sight velocity distribution of a stellar system, artificially inflating the measured line-of-sight velocity dispersion, which can in turn lead to erroneous conclusions about the dynamical state of the system. Cottaar et al. (2012b) proposed a maximum likelihood procedure to recover the intrinsic velocity dispersion of a resolved star cluster from a single epoch of radial velocity data of individual stars, which they achieved by simultaneously fitting the intrinsic velocity distribution of the single stars and the centres of mass of the binaries along with the velocity shifts caused by binary orbital motions. Read More

Radial velocity measurements can be used to constrain the dynamical state of a stellar cluster. However, for clusters with velocity dispersions smaller than a few km/s the observed radial velocity distribution tends to be dominated by the orbital motions of binaries rather than the stellar motions through the potential well of the cluster. Our goal is to characterize the intrinsic velocity distribution of a cluster from a single epoch of radial velocity data, even for a cluster with a velocity dispersion of a fraction of a km/s, using a maximum likelihood procedure. Read More

Context. Westerlund I is the richest young cluster currently known in our Galaxy, making it one of the most massive clusters for which we can resolve the individual stars even in the crowded centre. This makes it an ideal target to assess whether massive clusters formed currently will remain bound or will disperse and contribute significantly to the stellar field population. Read More