Year: 2026
Type: preprint
Abstract: We present a systematic spectroscopic study of hydrogen Brackett-alpha (Br-alpha) and carbon monoxide (CO) fundamental-band (4.3-5.2 micron) emission from a homogeneous sample of 0.2-1.5 Msun pre-main-sequence (PMS) stars in the Orion Nebula observed with JWST/NIRSpec-MOS as part of our Chandra-JWST project. Using 73 Br-alpha and 46 CO spectra, we investigate correlations between warm-gas emission, stellar properties, accretion, and environment with censored correlation and regression analyses accounting for multiple testing. Br-alpha luminosity correlates strongly with accretion luminosity (Lacc), even after excluding sources within 2' of Theta1 Ori C, the nebula's main ionizing O-type star, whose radiation may bias proplyd Lacc estimates. This supports Br-alpha as a robust empirical tracer of accretion in PMS stars. Br-alpha also correlates with visual extinction (Av) and more weakly with stellar bolometric luminosity and mass. CO fundamental-band luminosities likewise correlate positively with Lacc and Av, relationships that persist in a larger combined JWST/NIRSpec+MIRI sample spanning multiple star-forming regions. In contrast to Br-alpha, CO luminosity shows no significant dependence on basic stellar properties, suggesting that warm molecular gas is governed primarily by accretion and local disk conditions. The weaker correlations of the Spitzer/IRAC spectral slope with Lacc and Av suggest that warm inner-disk gas may evolve or disperse faster than optically thick dust. Overall, the CO results tentatively indicate declining warm-gas emission as disks evolve, modulated by accretion-powered thermal and ultraviolet excitation, although variations in emitting area inherited from natal core conditions may also contribute.
Source: arXiv (Cornell University)
Authors: Getman, Konstantin V., Ramirez-Tannus, Maria Claudia, Frediani, Jenny, Luhman, Kevin L., Feigelson, Eric D., Portilla-Revelo, Bayron, Rab, Christian, Brunn, Valentin, Forbrich, Jan, Haworth, Thomas J., Waters, Rens, Bik, Arjan, Law, Charles J., Winter, Andrew J., Airapetian, Vladimir S., Waggoner, Abygail R., Kuhn, Michael A., Cleeves, L. Ilsedore, Dzib, Sergio A., Padovani, Marco
Institutions: Pennsylvania State University, Max Planck Institute for Astronomy, Stockholm University, Max Planck Institute for Extraterrestrial Physics, Ludwig-Maximilians-Universität München, Arcetri Astrophysical Observatory, National Institute for Astrophysics, University of Hertfordshire, Queen Mary University of London, Radboud University Nijmegen, Space Research Organisation Netherlands, University of Minnesota, Goddard Space Flight Center, American University, National Aeronautics and Space Administration, University of Wisconsin–Madison, University of Virginia, Max Planck Institute for Radio Astronomy
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7222246366