Galaxy formation and evolution

Abstract:

Recent observations by James Webb Space Telescope reveal an unexpectedly abundant population of rapidly growing supermassive black holes (SMBHs) in the early Universe, underscoring the need for improved models for their origin and growth. Employing new full radiative transfer hydrodynamical simulations of galaxy formation, we investigate the local and intergalactic feedback of SMBH progenitors for the Population III.1 (Pop III.1) scenario, i.e. efficient formation of supermassive stars from pristine, undisturbed dark matter minihaloes. Our cosmological simulations capture the R-type expansion phase of these Pop III.1 stars, with their H-ionizing photon luminosities of generating H ii regions that extend deep into the intergalactic medium, reaching comoving radii of . We vary both the Pop III.1 ionization flux and cosmological formation environments, finding the former regulates their final , whereas the latter is more important in setting their formation redshift. We use the results from our radiation-hydrodynamics simulations to estimate the cosmic number density of SMBHs, , expected from Pop III.1 progenitors. We find , consistent with the results inferred from recent observations of the local and high-redshift universe. Overall, this establishes Pop III.1 progenitors as viable candidates for the formation of the first SMBH, and emphasizes the importance of exploring heavy mass seed scenarios.

Abstract:

We present the first spatially resolved infrared images of supernova remnants (SNRs) in M33 with the unprecedented sensitivity and resolution of JWST. We analyze 40 SNRs in four JWST fields: two covering central and southern M33 with separate NIRCam (F335M, F444W) and MIRI (F560W, F2100W) observations, one ∼5 kpc-long radial strip observed with MIRI F770W, and one covering the giant H II region NGC 604 with multiple NIRCam and MIRI broad/narrowband filters. Of the 21 SNRs in the MIRI (F560W+F2100W) field, we found three clear detections (i.e., identical infrared and Hα morphologies), and six partial-detections, implying a detection fraction of 43% in these bands. One of the SNRs in this field, L10-080, is a potential candidate for having freshly formed ejecta dust, based on its size and centrally concentrated 21 μm emission. In contrast, only one SNR (out of 16) is detectable in the NIRCam F335M+F444W field. Two SNRs near NGC 604 have strong evidence of molecular (H2) emission at 4.7 μm, making them the farthest known SNRs with visible molecular shocks. Five SNRs have F770W observations, with the smaller younger objects showing tentative signs of emission, while the older, larger ones have voids. Multiwavelength data indicate that the clearly detected SNRs are also among the smallest, brightest at other wavelengths (Hα, radio, and X-ray), have the broadest line widths (Hα FWHM ∼ 250–350 km s−1), and the densest environments. No correlation between the JWST-detectability and local star formation history of the SNRs is apparent.

Abstract:

This paper is the second in a series presenting the catalogs and properties of the largest sample to date of ∼100,000 star clusters and compact associations, in 38 spiral galaxies observed by the PHANGS-HST Treasury survey. Here, we present spectral energy distribution (SED) fitting techniques used to compute the age, mass, and reddening for each object. Our decision-tree-based strategy incorporates categorical priors on model age, reddening, and metallicity determined from additional observed parameters: localized Hα emission, source morphology, and demographic-specific locations in the UBVI color–color diagram. This approach is implemented to mitigate model degeneracies, particularly between young dusty clusters and old clusters with minimal dust, which can have identical optical colors. Results based on Hα narrowband imaging from the ground and from Hubble Space Telescope are intercompared, and contrasted with previous SED-fitting efforts. The fraction of the population that is subject to such priors is ∼14%, and of this subset, ∼63% of old globular clusters (GCs) have ages that change by a factor of 10 or more relative to unconstrained fits with single metallicity (Z⊙) simple stellar population models. The demographics of the population are examined through age–mass and age–reddening diagrams (for individual galaxies as well as aggregated over the sample), and the GC mass function. We demonstrate relationships between cluster age–mass diagrams and properties of parent galaxies (galaxy morphology and location relative to the galaxy main sequence). We outline continuing efforts to improve the inference of physical properties, including the incorporation of JWST infrared photometry and updated synthesis models.