Jeffrey A. Rich

Context. The nearly edge-on starburst galaxy NGC 253 has been observed to exhibit extended halo emission in multiple bands, making it an ideal laboratory for studying the transfer of matter from the disk to the halo. Aims. We aim to determine how the cosmic-ray electrons (CREs) flow from the disk to the halo and understand what drives their propagation. Methods. By combining data from multiple observations, we generated improved total intensity images at 943 MHz with a resolution of 13″ from the Australian SKA Pathfinder (ASKAP), and at 216 MHz with a resolution of 45″ from the Murchison Widefield Array (MWA). The 1D advection and diffusion equations were solved, and the solutions were fitted to the observed synchrotron emission intensity and spectral-index profiles to constrain the propagation model and parameters. Results. The ASKAP total intensity map has an rms noise of 16 μJy beam ⁻¹ , reaching the classical confusion limit, and the MWA map has an rms noise of 1 mJy beam ⁻¹ . The sensitivities are significantly improved in comparison to previous observations at similar frequencies. In the ASKAP image, we identify a clear loop-like structure in the northwestern radio spur, extending vertically up to ∼9 kpc above the disk, while the southeastern spur reaches heights of ∼8 kpc. The synchrotron emission intensity profiles perpendicular to the disk can be fitted with exponential components in the central regions and with Gaussian components in the outer regions. This result implies that CREs in these two regions propagate differently. By jointly fitting the vertical synchrotron emission intensity profiles at 943 MHz and 216 MHz, together with the corresponding synchrotron spectral-index profiles, our results provide the clearest evidence to date that CREs are transported from the disk by advection in the central region and by diffusion elsewhere in NGC 253. The advection speed in the central region increases exponentially with height and reaches the escape speed to form a superwind of CREs at about 5.5 kpc. This superwind is associated with regions in the disk with active star formation and X-ray emission, indicating a bulk motion of baryons caused by the advection. The combined thermal, magnetic, cosmic-ray, and ram pressures exceed the gravitational pressure below | z | ≲ 5.5 kpc, and this overpressure condition accelerates the superwind. Conclusions. High-sensitivity low-frequency radio observations provide an important probe of the transport of CREs. With these observations, we have revealed a newly detailed view into the kinematic origin of the superwind from the center of NGC 253.

We present the morphological, photometric, and spectroscopic properties of a z ∼ 1 galaxy, “lil gal,” serendipitously detected in JWST Mid Infrared Instrument (MIRI) images of nearby galaxy VV 340. In the MIRI F560W and F770W images, we identify what appears to be a spiral galaxy with a central bulge. However, in the F1500W image, a second peak appears ∼ 0 . ″ 7 northwest (NW) from the central bulge, calling into question the nature of this source as a clumpy disk, a high-redshift interloper, or a galaxy merger. Multiband analyses of the three MIRI and four Hubble Space Telescope images suggest a photometric redshift of ∼0.92. Spectroscopic analyses of data from the Keck Near-Infrared Echellette Spectrometer (NIRES) reveal two sets of [N ii ] and H α emission lines corresponding to the two observed sources. A redshift of z = 0.9248 is identified for the NW companion. Fainter emission lines are identified from the underlying galaxy at z = 0.9225, suggesting a merging galaxy pair at a projected separation of ∼5 kpc. From the emission line ratios from Keck NIRES and Keck Cosmic Web Imager spectra, we classify the system as hosting regions of active star formation, likely attributed to merger-induced starburst activity. The results demonstrate the necessity of resolved, spectroscopic follow-up analyses of galaxies found in deep JWST images to disentangle the role of galaxy mergers from clumpy disk galaxies at z ∼ 1 to cosmic noon and beyond.

To reproduce observed galaxy properties, cosmological simulations require that massive galaxies experience feedback from active galactic nuclei, which regulates star formation within those galaxies. However, the energetics and timescales of these feedback processes are poorly constrained. We combined optical, infrared, submillimeter, and radio observations of the active galaxy VV 340a, which is hosting a low-power jet launched from a supermassive black hole at its center. We found that the jet undergoes precession, with a period of (8.2 ± 5.5) × 10 ⁵ years, and drives an outflow of gas at a rate of 19.4 ± 7.9 solar masses per year. The jet shocks the gas, producing highly ionized plasma that extends several kiloparsecs from the nucleus. The outflow ejects sufficient gas from the galaxy to influence its star-formation rate.

We present high-resolution Keck Cosmic Web Imager and MUSE integral field unit spectroscopy of VV 114, a local IR-luminous merger undergoing a vigorous starburst and showing evidence of galactic-scale feedback. The high-resolution data allow for spectral deblending of the optical emission lines and reveal a broad emission line component (σ _broad ∼ 100–300 km s⁻¹) with line ratios and kinematics consistent with a mixture of ionization by stars and radiative shocks. The shock fraction (percentage of ionization due to shocks) in the high-velocity gas is anticorrelated with the projected surface number density of resolved star clusters, and we find that the radial density profiles around clusters are fit well by models of adiabatically expanding cluster winds driven by massive stellar winds and supernovae (SNe). The total kinetic power estimated from the cluster wind models matches the wind + SN mechanical energy deposition rate estimated from the soft-band X-ray luminosity, indicating that at least 70% of the shock luminosity in the galaxy is driven by the star clusters. Hubble Space Telescope narrowband near-IR imaging reveals embedded shocks in the dust-buried IR nucleus of VV 114E. Most of the shocked gas is blueshifted with respect to the quiescent medium, and there is a close spatial correspondence between the shock map and the Chandra soft-band X-ray image, implying the presence of a galactic superwind. The energy budget of the superwind is in close agreement with the total kinetic power of the cluster winds, confirming the superwind is driven by the starburst.

We apply population synthesis techniques to analyze TYPHOON long slit spectra of the starburst barred spiral galaxy M83. The analysis covers a central square of 5′ side length. We determine the spatial distribution of dust through the analysis of reddening and extinction, together with star formation rates, ages, and metallicities of young and old stellar populations. For the first time, a spatial one-to-one comparison of metallicities derived from full spectral fitting techniques with those obtained from individual young stellar probes has been carried out. The comparison with blue supergiant stars, young massive star clusters, and super star clusters shows a high degree of concordance when wavelength coverage in the B band is available. The metallicity of the young population is supersolar and does not show a radial metallicity gradient along the investigated part of the disk, in agreement with our chemical evolution model. However, a notable decrease in metallicity is observed in a tightly confined region at the galaxy center, coinciding with circumnuclear orbits. We attribute this to matter infall either from the circumgalactic medium, a dwarf galaxy interloper, or, alternatively, to active-galactic-nucleus-interrupted chemical evolution. We confirm the presence of a dust cavity with a diameter of 260 pc close to the galaxy center. Dust absorption and molecular CO emission are spatially well correlated. We find an anticorrelation between R _V , the ratio of dust attenuation to reddening, and the emission strength of molecular species present in photodissociation regions. We confirm our results by using alternative fitting algorithms and stellar libraries.

We present high-resolution Keck Cosmic Web Imager (KCWI) and MUSE IFU spectroscopy of VV 114, a local infrared-luminous merger undergoing a vigorous starburst and showing evidence of galactic-scale feedback. The high-resolution data allow for spectral deblending of the optical emission lines and reveal a broad emission line component ($σ_{\rm{broad}} \sim$~100--300 km s$^{-1}$) with line ratios and kinematics consistent with a mixture of ionization by stars and radiative shocks. The shock fraction (percent ionization due to shocks) in the high velocity gas is anticorrelated with projected surface number density of resolved star clusters, and we find radial density profiles around clusters are well fit by models of adiabatically expanding cluster winds driven by massive stellar winds and supernovae (SNe). The total kinetic power estimated from the cluster wind models matches the wind+SNe mechanical energy deposition rate estimated from the soft band X-ray luminosity, indicating that at least 70\% of the shock luminosity in the galaxy is driven by the star clusters. \emph{Hubble Space Telescope} narrow band near-infrared imaging reveals embedded shocks in the dust-buried infrared nucleus of VV 114E. Most of the shocked gas is blueshifted with respect to the quiescent medium, and there is a close spatial correspondence between the shock map and the \emph{Chandra} soft band X-ray image, implying the presence of a galactic superwind. The energy budget of the superwind is in close agreement with the total kinetic power of the cluster winds, confirming the superwind is driven by the starburst.

We present the spatially resolved relationship between the dust-to-gas mass ratio (DGR) and gas-phase metallicity (Zgas or 12+log(O/H)) (i.e., DGR-Zgas relation) of 11 nearby galaxies with a large metallicity range (1.5 dex of 12+log(O/H)) at (sub-)kpc scales. We used the large field-of-view (> 3') optical pseudo-Integral Field Spectroscopy data taken by the TYPHOON/PrISM survey, covering the optical size of galaxies, combining them with multi-wavelength data (far-UV to far-IR, CO, and HI 21 cm radio). A large scatter of DGR in the intermediate metallicity galaxies (8.0 < 12+log(O/H) < 8.3) is found, which is in line with dust evolution models, where grain growth begins to dominate the mechanism of dust mass accumulation. In the lowest metallicity galaxy of our sample, Sextans A (12+log(O/H) < 7.6), the star-forming regions have significantly higher DGR values (by 0.5-2 dex) than the global estimates from literature at the same metallicity but aligns with the DGR values from metal depletion method from Damped Lyman Alpha systems and high hydrogen gas density regions of Sextans A. Using dust evolution models with a Bayesian MCMC approach suggests: 1) a high SN dust yield and 2) a negligible amount of photofragmentation by UV radiation, although we note that our sample in the low-metallicity regime is limited to Sextans A. On the other hand, it is also possible that while metallicity influences DGR, gas density also plays a role, indicating an early onset of dust grain growth in the dust mass build-up process despite its low metallicity.