Massive pre-main sequence stars in M17

Abstract

The formation process of massive stars is still poorly understood. Massive young stellar objects (mYSOs) are deeply embedded in their parental clouds, they are rare and thus typically distant, and their reddened spectra usually preclude the determination of their photospheric parameters. M17 is one of the best studied HII regions in the sky, is relatively nearby, and hosts a young stellar population. With X-shooter on the ESO Very Large Telescope we have obtained optical to near-infrared spectra of candidate mYSOs, identified by Hanson et al. (1997), and a few OB stars in this region. The large wavelength coverage enables a detailed spectroscopic analysis of their photospheres and circumstellar disks. We confirm the pre-main sequence (PMS) nature of six of the stars and characterise the O stars. The PMS stars have radii consistent with being contracting towards the main sequence and are surrounded by a remnant accretion disk. The observed infrared excess and the (double-peaked) emission lines provide the opportunity to measure structured velocity profiles in the disks. We compare the observed properties of this unique sample of young massive stars with evolutionary tracks of massive protostars by Hosokawa & Omukai (2009), and propose that these mYSOs near the western edge of the HII region are on their way to become main-sequence stars ($\sim 6-20$ $M_{\odot }$) after having undergone high mass-accretion rates (${\dot{M}}_{\mathrm{acc}}\sim 10^{-4}-10^{-3}$ $M_{\odot }$ $\mathrm{y}{\mathrm{r}}^{-1}$). Their spin distribution upon arrival at the zero age main sequence (ZAMS) is consistent with that observed for young B stars, assuming conservation of angular momentum and homologous contraction.

Accepted for publication in A&A. Appendixes A and B have been truncated due to size limitations, the full version will be available on A&A

References in corpus (18)

• Binary interaction dominates the evolution of massive stars
• Molecfit: A general tool for telluric absorption correction. I. Method and application to ESO instruments
• Molecfit: A general tool for telluric absorption correction II. Quantitative evaluation on ESO-VLT X-Shooter spectra
• UBVJHK synthetic photometry of Galactic O stars
• BONNSAI: a Bayesian tool for comparing stars with stellar evolution models
• The young stellar population in M17 revealed by Chandra
• VLT K-band spectroscopy of massive young stellar objects in (ultra-)compact HII regions
• The VLT-FLAMES Tarantula Survey XXIV. Stellar properties of the O-type giants and supergiants in 30 Doradus
• A FUSE Survey of the Rotation Rates of Very Massive Stars in the Small and Large Magellanic Clouds
• Interstellar Weather Vanes: GLIMPSE Mid-Infrared Stellar-Wind Bowshocks in M17 and RCW49
• Optical spectroscopic variability of Herbig Ae/Be stars
• The Structure of Protoplanetary Disks Surrounding Three Young Intermediate Mass Stars. I. Resolving the disk rotation in the [OI] 6300 Åline
• The properties of ten O-type stars in the low-metallicity galaxies IC 1613, WLM and NGC 3109
• A dearth of short-period massive binaries in the young massive star forming region M17: Evidence for a large orbital separation at birth?
• The Intermediate-mass Young Stellar Object 08576nr292: Discovery of a disk-jet system
• The Morphology of M17-UC1 - A Disk Candidate Surrounding a Hypercompact HII Region
• The location, clustering, and propagation of massive star formation in giant molecular clouds
• VLT near- to mid-IR imaging and spectroscopy of the M17 UC1-IRS5 region

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• A relation between the radial velocity dispersion of young clusters and their age: Evidence for hardening as the formation scenario of massive close binaries
• Observing substructure in circumstellar discs around massive young stellar objects
• Surveying the Giant HII Regions of the Milky Way with SOFIA: II. M17
• Massive star cluster formation II. Runaway stars as fossils of sub-cluster mergers
• On the origin of close massive binaries in the M17 star-forming region
• Diffuse interstellar bands in the HII region M17: Insights into their relation with the total-to-selective visual extinction $R_V$
• Gamma-ray observation towards the young massive star cluster NGC 6618 in the M17 region
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• Probing the Missing Link between the Diffuse Interstellar Bands and the Total-to-Selective Extinction Ratio $R_V$ $-$ I. Extinction versus Reddening
• Massive pre-main-sequence stars in M17 -- Modelling hydrogen and dust in MYSO disks
• Massive pre-main-sequence stars in M17: $1^{\mathrm{st}}$ and $2^{\mathrm{nd}}$ overtone CO bandhead emission and the thermal infrared
• The spectroscopic binary fraction of the young stellar cluster M17
• New Massive Contact Twin Binary in a Radio-quiet HII Region Associated with the M17 Complex
• ALMA detections of circumstellar disks in the giant Hii region M17. Probing the intermediate- to high-mass pre-main-sequence population
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