Galaxy formation and evolution

Abstract:

We present a spatially resolved analysis of four star-forming galaxies at using data from the JWST Public Release Imaging for Extragalactic Research (PRIMER) and ALMA-[C II] Resolved ISm in STar-forming galaxies with ALma (CRISTAL) surveys to probe the stellar and interstellar medium properties on the sub- scale. In the JWST NIRCam imaging we find that the galaxies are composed of multiple clumps (between 2 and ∼8) separated by , with comparable morphologies and sizes in the rest-frame ultraviolet (UV) and optical. Using BAGPIPES to perform pixel-by-pixel spectral energy distribution (SED) fitting to the JWST data, we show that the star formation rate (SFR) () and stellar mass ( ) derived from the resolved analysis are in close () agreement with those obtained by fitting the integrated photometry. In contrast to studies of lower mass sources, we thus find a reduced impact of outshining of the older (more massive) stellar populations in these normal galaxies. Our JWST analysis recovers bluer rest-frame UV slopes () and younger ages () than archival values. We find that the dust continuum from ALMA-CRISTAL seen in two of these galaxies correlates, as expected, with regions of redder rest-frame UV slopes and the SED-derived , as well as the peak in the stellar mass map. We compute the resolved –relation, showing that the IRX is consistent with the local starburst attenuation curve and further demonstrating the presence of an inhomogeneous dust distribution within the galaxies. A comparison of the CRISTAL sources to those from the FirstLight zoom-in simulation of galaxies with the same and SFR reveals similar age and colour gradients, suggesting that major mergers may be important in the formation of clumpy galaxies at this epoch.

Abstract:

Blast wave models are commonly used to model relativistic outflows from ultra-relativistic gamma-ray bursts (GRBs), but are also applied to lower Lorentz factor ejections from X-ray binaries (XRBs). Here, we revisit the physics of blast waves and reverse shocks in these systems and explore the similarities and differences between the ultra-relativistic () and moderately relativistic () regimes. We first demonstrate that the evolution of the blast wave radius as a function of the observer frame time is recovered in the on-axis ultra-relativistic limit from a general energy and radius blast wave evolution, emphasizing that XRB ejections are off-axis, moderately relativistic cousins of GRB afterglows. We show that, for fixed blast wave or ejecta energy, reverse shocks cross the ejecta much later (earlier) on in the evolution for less (more) relativistic systems, and find that reverse shocks are much longer lived in XRBs and off-axis GRBs compared to on-axis GRBs. Reverse shock crossing should thus typically finish after 10–100 of days (in the observer frame) in XRB ejections. This characteristic, together with their moderate Lorentz factors and resolvable core separations, makes XRB ejections unique laboratories for shock and particle acceleration physics. We discuss the impact of geometry and lateral spreading on our results, explore how to distinguish between different shock components, and comment on the implications for GRB and XRB environments. Additionally, we argue that identification of reverse shock signatures in XRBs could provide an independent constraint on the ejecta Lorentz factor.

Abstract:

The earliest stages of star and cluster formation are hidden within dense cocoons of gas and dust, limiting their detection at optical wavelengths. With the unprecedented infrared capabilities of JWST, we can now observe dust-enshrouded star formation with ∼10 pc resolution out to ∼20 Mpc. Early findings from PHANGS-JWST suggest that 3.3 μm polycyclic aromatic hydrocarbon (PAH) emission can identify star clusters in their dust-embedded phases. Here, we extend this analysis to 19 galaxies from the PHANGS-JWST Cycle 1 Treasury survey, providing the first characterization of compact sources exhibiting 3.3 μm PAH emission across a diverse sample of nearby star-forming galaxies. We establish a selection criteria based on a median color threshold of F300M − F335M = 0.67 at F335M = 20 and identify 1816 sources. These sources are predominantly located in dust lanes, spiral arms, rings, and galaxy centers, with ∼87% showing concentration indices (CIs) similar to optically detected star clusters. Comparison with the PHANGS-HST catalogs suggests that PAH emission fades within ∼3 Myr. The Hα equivalent width of PAH emitters is 1–2.8 times higher than that of young PHANGS-HST clusters, providing evidence that PAH emitters are on average younger. Analysis of the bright portions of luminosity functions (which should not suffer from incompleteness) shows that young dusty clusters may increase the number of optically visible ≤3 Myr old clusters in PHANGS-HST by a factor between ∼1.8× and 8.5×.

Abstract:

The impact of active galactic nuclei (AGNs) on the evolution of galaxies explains the steep decrease in the number density of the most massive galaxies in the Universe. However, the fuelling of the AGN and the efficiency of this feedback largely depend on their environment. We use data from the Low Frequency Array Two-metre Sky Survey Data Release 2 (DR2), the Dark Energy Spectroscopic Instrument Legacy Imaging Surveys, and the Sloan Digital Sky Survey DR12 to make the first study of the orientations of radio jets and their optical counterpart in relation to the cosmic web environment. We find that close to filaments (), galaxies tend to have their optical major axes aligned with the nearest filaments. On the other hand, radio jets, which are generally aligned perpendicularly to the optical major axis of the host galaxy, show more randomized orientations with respect to host galaxies within of filaments. These results support the scenario that massive galaxies in cosmic filaments grow by numerous mergers directed along the orientation of the filaments while experiencing chaotic accretion of gas on to the central black hole. The AGN-driven jets consequently have a strong impact preferentially along the minor axes of dark matter haloes within filaments. We discuss the implications of these results for large-scale radio jet alignments, intrinsic alignments between galaxies, and the azimuthal anisotropy of the distribution of circumgalactic medium and anisotropic quenching.