Abstract We present James Webb Space Telescope (JWST) imaging of NGC 7469 with the Near-Infrared Camera and the Mid-InfraRed Instrument. NGC 7469 is a nearby, z = 0.01627, luminous infrared galaxy that hosts both a Seyfert Type-1.5 nucleus and a circumnuclear starburst ring with a radius of ∼0.5 kpc. The new near-infrared (NIR) JWST imaging reveals 66 star-forming regions, 37 of which were not detected by Hubble Space Telescope (HST) observations. Twenty-eight of the 37 sources have very red NIR colors that indicate obscurations up to A v ∼ 7 and a contribution of at least 25% from hot dust emission to the 4.4 μ m band. Their NIR colors are also consistent with young (<5 Myr) stellar populations and more than half of them are coincident with the mid-infrared (MIR) emission peaks. These younger, dusty star-forming regions account for ∼6% and ∼17% of the total 1.5 and 4.4 μ m luminosity of the starburst ring, respectively. Thanks to JWST, we find a significant number of young dusty sources that were previously unseen due to dust extinction. The newly identified 28 young sources are a significant increase compared to the number of HST-detected young sources (4–5). This makes the total percentage of the young population rise from ∼15% to 48%. These results illustrate the effectiveness of JWST in identifying and characterizing previously hidden star formation in the densest star-forming environments around active galactic nuclei (AGN).
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Dust Eddington ratios for star-forming galaxy subregions
Radiation pressure on dust is an important feedback process around star clusters and may eject gas from bright subregions in star-forming galaxies. The Eddington ratio has previously been constructed for galaxy-averaged observations, individual star clusters, and Galactic H ii regions. Here we assess the role of radiation pressure in thousands of subregions across two local star-forming galaxies, NGC 6946 and NGC 5194. Using a model for the spectral energy distribution from stellar population synthesis and realistic dust grain scattering and absorption, we compute flux and radiation pressure-mean opacities and population-averaged optical depth 〈τRP〉. Using Monte-Carlo calculations, we assess the momentum coupling through a dusty column to the stellar continuum. Optically-thin regions around young stellar populations are 30–50 times super-Eddington. We calculate the Eddington ratio for the subregions including the local mass of young and old stars and cool atomic and molecular gas. We compute the fraction of the total star formation that is currently super-Eddington, and provide an assessment of the role of radiation pressure in the dusty gas dynamics. Depending on the assumed height of the dusty gas and the age of the stellar population, we find that ∼0–10 per cent of the sightlines are super-Eddington. These regions may be accelerated to ∼5–15 km s−1 by radiation pressure alone. Additionally, our results show that for beamed radiation, the function 1 − exp (−〈τRP〉) is an excellent approximation to the momentum transfer. Opacities and optical depths are tabulated for SEDs of different stellar ages and for continuous star formation.
more » « less- NSF-PAR ID:
- 10423793
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- Monthly Notices of the Royal Astronomical Society
- Volume:
- 523
- Issue:
- 3
- ISSN:
- 0035-8711
- Page Range / eLocation ID:
- p. 4309-4325
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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