2025/04/07 by Bruce G. Elmegreen, Daniela Calzetti, Elmegreen, Bruce G. +57 · 1 citation
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics and Star Formation Studies #Azimuth #Galaxy #Hubble space telescope #Intensity (physics) #Measure (data warehouse) #Scale (ratio) #Space (punctuation) #Spectral line #Stellar, planetary, and galactic studies
paper · pdf · doi:10.48550/arxiv.2504.05430
published in arXiv (Cornell University) (Cornell University)
openalex publication_date 2025/04/07 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Power spectra (PS) of high-resolution images of M51 (NGC 5194) taken with the Hubble Space Telescope and the James Webb Space Telescope have been examined for evidence of disk thickness in the form of a change in slope between large scales, which map two-dimensional correlated structures, and small scales, which map three-dimensional correlated structures. Such a slope change is observed here in H-alpha, and possibly Pa-alpha, using average PS of azimuthal intensity scans that avoid bright peaks. The physical scale of the slope change occurs at ~120 pc and ~170 pc for these two transitions, respectively. A radial dependence in the shape of the H-alpha PS also suggests that the length scale drops from ~180 pc at 5 kpc, to ~90 pc at 2 kpc, to ~25 pc in the central ~kpc. We interpret these lengths as comparable to the thicknesses of the star-forming disk traced by HII regions. The corresponding emission measure is ~100 times larger than what is expected from the diffuse ionized gas. PS of JWST Mid-IR Instrument (MIRI) images in 8 passbands have more gradual changes in slope, making it difficult to determine a specific value of the thickness for this emission.