Star Formation and Nebular Attenuation from Pa$α$, Br$α$, and Br$β$ in Massive Dust-obscured Galaxies at Cosmic Noon using JWST
Year: 2026
Type: preprint
Abstract: Near-infrared hydrogen recombination lines can provide robust star-formation rates if the effects of dust attenuation continue to diminish towards longer wavelengths. To quantify near-infrared attenuation and ultimately measure accurate star-formation rates (SFRs) at the height of cosmic star-formation, we present Pa$α$, Br$α$, and Br$β$ detections in $27$ luminous infrared galaxies at $z\sim 1-2$, including pure star-forming galaxies as well as dust-obscure Active Galactic Nuclei (AGN). Using combined spectra from the JWST MIRI (Mid-Infrared Instrument) LRS (Low Resolution Spectrometer) and the Spitzer Space Telescope IRS we quantify the star formation rates of our sample using a sub-sample of 13 galaxies detected in Pa$α$ emission ($1.87\, μ$m), 14 galaxies detected in Br$α$ ($4.05\, μ$m), and 12 galaxies detected in Br$β$ ($2.63\, μ$m). By combining multiple near-infrared recombination lines in individual galaxies we calculate nebular attenuation, finding $A_λ\sim3$ mag at $\sim2\,μ$m and $A_λ\sim1$ mag at $\sim4\,μ$m. Nebular lines trace the SFR on $\sim 10$ Myr timescales, which we compare to the total infrared luminosity ($L_{\rm IR}$) which probes the star formation over the last $\sim 100$ Myr. SFRs measured from $L_{\rm IR}$ using common conversions are systematically higher than the SFRs derived from attenuation-corrected nebular line measurements by a factor of $\sim2.5$. This could be indicative of a declining or static star formation history with a past burst or systematic effects on $\rm SFR_{\rm IR}$ such as dust heating from evolved stellar populations, and/or an active galactic nucleus.
Source: arXiv (Cornell University)
Authors: Vanicek, Virginia, McKinney, Jed, Pope, Alexandra, Sajina, Anna, Alberts, Stacey, Stone, Meredith, Armus, Lee, Manning, Sinclaire M., Cooper, Olivia, DÍaz-Santos, Tanio, Eleazer, Miriam, Casey, Caitlin, Lai, Thomas S. -Y., Finkelstein, Steven, Sajkov, Leonid, Kirkpatrick, Allison, Taylor, Anthony
Institutions: Tufts University, Space Telescope Science Institute, European Space Agency, University of Arizona, University of Massachusetts Amherst, University of California, Santa Barbara, Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, University of Kansas, The University of Texas at Austin
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7214058030