2 research outputs found
Inferred galaxy properties during Cosmic Dawn from early JWST photometry results
Early photometric results from JWST have revealed a number of galaxy
candidates above redshift 10. The initial estimates of inferred stellar masses
and the associated cosmic star formation rates are above most theoretical model
predictions up to a factor of 20 in the most extreme cases, while this has been
moderated after the recalibration of NIRCam and subsequent spectroscopic
detections. Using these recent JWST observations, we use galaxy scaling
relations from cosmological simulations to model the star formation history to
very high redshifts, back to a starting halo mass of 10^7 solar masses, to
infer the intrinsic properties of the JWST galaxies. Here we explore the
contribution of supermassive black holes, stellar binaries, and an excess of
massive stars to the overall luminosity of high-redshift galaxies. Despite the
addition of alternative components to the spectral energy distribution, we find
stellar masses equal to or slightly higher than previous stellar mass
estimates. Most galaxy spectra are dominated by the stellar component, and the
exact choice for the stellar population model does not appear to make a major
difference. We find that four of the 12 high-redshift galaxy candidates are
best fit with a non-negligible active galactic nuclei component, but the
evidence from the continuum alone is insufficient to confirm their existence.
Upcoming spectroscopic observations of z > 10 galaxies will confirm the
presence and nature of high-energy sources in the early universe and will
constrain their exact redshifts.Comment: 20 pages, 13 figures, 5 tables. Accepted by MNRAS. 12 figures, 13
tables in appendice
POWDERDAY: Dust Radiative Transfer for Galaxy Simulations
We present powderday (available at https://github.com/dnarayanan/powderday), a flexible, fast, open-source dust radiative transfer package designed to interface with both idealized and cosmological galaxy formation simulations. powderday builds on fsps stellar population synthesis models, and hyperion dust radiative transfer, and employs yt to interface between different software packages. We include our stellar population synthesis modeling on the fly, allowing significant flexibility in the assumed stellar physics and nebular line emission. The dust content follows either simple observationally motivated prescriptions (i.e., constant dust-to-metals ratios, or dust-to-gas ratios that vary with metallicity), direct modeling from galaxy formation simulations that include dust physics, as well as a novel approach that includes the dust content via learning-based algorithms from the simba cosmological galaxy formation simulation. Active galactic nuclei (AGNs) can additionally be included via a range of prescriptions. The output of these models are broadband (912 Å–1 mm) spectral energy distributions (SEDs), as well as filter-convolved monochromatic images. powderday is designed to eliminate last-mile efforts by researchers that employ different hydrodynamic galaxy formation models and seamlessly interfaces with gizmo, arepo, gasoline, changa, and enzo. We demonstrate the capabilities of the code via three applications: a model for the star formation rate–infrared luminosity relation in galaxies (including the impact of AGNs), the impact of circumstellar dust around AGB stars on the mid-infrared emission from galaxy SEDs, and the impact of galaxy inclination angle on dust attenuation laws