Timothy Heckman

We present a spatially resolved analysis of stellar populations in the brightest z > 6 galaxy known to date (AB mag 23), the strongly lensed MACS0308−zD1 (dubbed the “Cosmic Spear”) at z _spec = 6.2. New JWST NIRCam imaging and high-resolution NIRSpec integral field unit (IFU) spectroscopy span the rest-frame ultraviolet to optical. The NIRCam imaging reveals bright star-forming clumps and a tail consisting of three distinct, extremely compact star clusters that are multiply imaged by gravitational lensing. The star clusters have delensed effective radii of R _eff ≲ 8 pc, stellar masses of M _* ∼ 10 ⁶ –10 ⁷ M _⊙ , and high stellar mass surface densities of Σ _* ≳ 2 × 10 ⁴ M _⊙ pc ⁻² . While their stellar populations are very young (∼6–11 Myr), their dynamical ages exceed unity, consistent with the clusters being gravitationally bound systems. Placing the star clusters in the size versus stellar mass density plane, we find they occupy a region similar to other high-redshift star clusters within galaxies observed recently with JWST, being significantly more massive and denser than local star clusters. Spatially resolved analysis of the brightest clump reveals a compact, intensely star-forming core. The ionizing photon production efficiency ( ξ _ion ) is slightly suppressed in this central region, potentially indicating a locally elevated Lyman continuum escape fraction facilitated by feedback-driven channels.

We present spatially resolved rest-optical spectroscopy of 38 star-forming galaxies at 0.5 < z < 1.5 from the JWST/NIRSpec Micro-Shutter Assembly (MSA)-3D survey, which employs a slit-stepping strategy to build integral field unit–like data cubes with a spatial sampling of ∼0 . ″ 1. We map emission-line morphology, excitation, and kinematics of the warm-ionized gas using [N II ]/H α , [S II ]/H α , and [O III ]/H β . Relative to z ∼ 0 galaxies at fixed stellar mass, our sources show systematically lower [N II ]/H α and [S II ]/H α and elevated [O III ]/H β , consistent with harder radiation fields and lower metallicities. Radially, [O III ]/H β profiles are typically flat or mildly positive, whereas [N II ]/H α also remains flat or declines outward, mirroring metallicity trends. On kiloparsec scales, we find a strong positive correlation between [N II ]/H α and velocity dispersion ( σ ), linking local excitation to turbulent or shock-driven kinematics. Six galaxies (∼16% of the sample) host spatially localized regions with elevated [N II ]/H α , high EW(H α ), and V rms ≡ V 2 + σ 2 > 250 km s − 1 , indicative of weak active galactic nucleus (AGN) activity, shocks, or outflows. For these candidates, we infer modest warm-ionized outflow rates of 1−4 M _⊙ yr ⁻¹ and kinetic powers ∼0.1%−1% of the AGN bolometric luminosity (from central [O III ] or H α ). These values place our sample at the low-energy tail of known AGN-driven outflows yet in continuity with M ̇ out – L _AGN scaling relations across 0 < z < 6. A completeness assessment shows MSA-3D is sensitive to AGN with L _AGN ≳ 10 ⁴³ erg s ⁻¹ , underscoring both the promise and current limitations of detecting weak AGN activity in distant galaxies with resolved spectroscopy.

A primary question is how active galactic nuclei (AGN) feedback modifies the circumgalactic medium (CGM). We present a search for faint H α emission from the cool ionized CGM ( T ∼ 10 ⁴ K) around radio galaxies by stacking background-quasar spectra from Dark Energy Spectroscopic Instrument (DESI) sight lines. We take into account the projected distance and position angle of each quasar sight line relative to the radio-jet axis, and test whether jet–CGM coupling is anisotropic. We detect a strong H α excess at >5 σ along the collimated radio-jet axis ( θ < 20 ^∘ ) with a mean integrated flux of 1.19 × 10 ⁻¹⁷ erg cm ⁻² s ⁻¹ . In contrast, the azimuthally averaged stack over all 324 sight-line angles yields no detection (σ ), indicating that this excess emission is very localized along the radio jet. We also find that the jet-aligned H α signal is radially structured, where the strongest emission occurs near the host galaxy just outside the optical half-light radius, and rising again near the projected radio-lobe region. The jet-aligned stacks reveal H α signal that is roughly 100 times brighter than normal halos. In the same sight lines however, Mg ii absorption shows no difference in incidence between jet-aligned and off-axis directions, with broadly similar equivalent widths, column densities, and line widths. This striking contrast shows that while Mg ii traces the ambient, clumpy cool CGM reservoir, the H α emission directly captures localized, low-covering-fraction clouds whose density, pressure, or ionization level has been dramatically boosted by the propagating jet. These results deliver clear evidence of localized jet–CGM interaction in radio-jetted AGNs.

Small-scale multiphase structure plays a central role in galactic-wind evolution, yet the parsec-scale morphology and excitation of the warm ionized gas remain poorly constrained. We present deep Hubble Space Telescope (HST) narrow-band imaging of the southern wind of Messier 82 (M82) in H α , [O iii ], [S ii ], and [N ii ], designed to resolve the warm ionized phase on parsec scales. The H α emission is detected to ≈2.1 kpc above the disk, while the fainter emission lines are detected over smaller radial extents, with [O iii ] reaching ≈1.5 kpc. We develop a filament-finding pipeline for the H α image and construct a quantitative catalogue of the filamentary structures. The wind forms a highly connected network of strands and knots, dominated by compact filaments with typical projected widths of ≃5.3 pc and lengths of ≃9.5 pc. Both the projected covering fraction and the line-flux contribution of the filamentary component decline with height, showing that the outer wind becomes increasingly dominated by diffuse emission. Optical line-ratio diagnostics indicate that the warm ionized gas occupies an intermediate excitation regime: photoionization by the central starburst can energetically power the observed H α luminosity, while the systematic separation between filamentary and diffuse emission, together with the evolution of the line ratios with vertical distance, suggests an increasing contribution from shocks or other similar heating in the diffuse outer wind. These results show that separating filamentary and diffuse emission in high-resolution imaging provides a powerful way to connect the morphology, excitation, and multiphase structure of galactic winds.

Star-forming galaxies drive massive outflows that play an important role in galaxy evolution by regulating feedback and influencing the dynamics of surrounding media. Measuring galactic outflow rates is essential for quantifying feedback efficiency and the amount of mass, momentum, and energy deposited into the circumgalactic medium (CGM). In this paper, we examine 17 galactic outflows from the COS Legacy Archive Spectroscopy Survey (CLASSY) survey with radiative transfer modeling of UV absorption lines presented in M. Huberty et al. to study their spatial distributions and kinematic properties. We study the Si ii , Si iii , and Si iv ionization states that trace the cool and warm phases of the outflows and find that Si ii– traced winds generally behave differently than the warmer Si iii– and Si iv– traced winds. We derive the mass, momentum, and energy loading factors, which we find scale inversely proportional to stellar mass. We find that our measurements of the mass and momentum loading factors are in agreement with the hydrodynamic FIRE-2 simulations. We model the velocity profiles of the winds, with profiles reaching a maximum velocity of 620 km s ⁻¹ on average, in agreement with hydrodynamic simulations from the Cholla Galactic OutfLow Simulations (CGOLS). We also investigate the relationship between outflow properties and the age of the stellar population from spectral energy distribution (SED) fitting. We find that outflows associated with young (<5 Myr) star-forming regions are more likely to have a column density dominated by cooler gas and have mass outflow rates that decrease with radius.

We detail the spectral analysis of a 170 ks XRISM Resolve observation of the core of Cygnus A. The high spectral resolution of Resolve has enabled us to probe the inner accretion region of Cygnus A by analyzing the 6.4 keV Fe K α line complex. We find that it consists of two Keplerian broadened components: a broad component with a velocity dispersion of 340 0 − 600 + 800 km s ⁻¹ and a narrow component of 44 0 − 50 + 60 km s ⁻¹ . For an inclination of 50°–85°, constrained by very long baseline interferometry, we find that the broad component arises from a distance of ∼0.1–0.17 pc (800–1400 gravitational radii) and the narrow component from ∼6 to 10 pc (50,000–80,000 gravitational radii) from the central black hole depending on the inclination angle. Our result suggests that the origin of the broad component is consistent with the broad line region and the narrow component from the torus of Cygnus A. We also find a potential emission line possibly from intermediate ionized Fe XVII with a very low dispersion (−1 ) that originates from either the outer edge of the torus or the narrow line region. Finally, we find that the Fe K edge is redshifted compared to the Fe K α line components, suggesting a line-of-sight bulk velocity of 470 ± 100 km s ⁻¹ . Such a shift may be due to an inflowing wind or relative motion between the two components originating from the near and far side of an inflowing torus, respectively.

We present a radio continuum study of photometrically selected post-starburst galaxies (PSBs) at cosmic noon (0.5 < z < 3) in the UKIRT Infrared Deep Sky Survey (or UKIDSS) Ultra Deep Survey field to assess if radio-mode active galactic nuclei (AGN) are linked to the quenching of star formation at cosmic noon. Cross-matching with deep Very Large Array imaging at 1.4 GHz results in a mean radio detection fraction ( f det ) of only 0.8% for PSBs above a radio luminosity threshold of L _1.4GHz ≥10 ²⁴ W Hz ⁻¹ , increasing to 5% ± 2% for massive PSBs with stellar masses M _* > 10 ¹¹ M _⊙ . Massive PSBs exhibit a detection fraction comparable to that of massive quiescent galaxies ( f _det = 8% ± 1%), though both classes have lower fractions than massive star-forming galaxies ( f _det = 13% ± 1%) in the same field. The radio luminosities of detected PSBs, L _{1.4 GHz} ∼ 10 ^22.8 –10 ^24.9 W Hz ⁻¹ , exceed those expected from star formation by a median factor of 37, indicative of a possible AGN origin. Their compact morphologies (≲15 kpc at z _med = 1.5) suggest low-luminosity AGN hosting less powerful jets. Stacking the undetected PSBs reveals a weak radio detection (3.9 σ ) in the highest-mass bin ( M _* > 10 ¹¹ M _⊙ ). In contrast, 1.4 GHz-detected quiescent galaxies exhibit luminosities reaching the radio-loud regime and show a higher prevalence of extended morphologies indicative of large-scale jetted AGN. An AGN contribution is also detected in stacked measurements of quiescent galaxies. Overall, our results support a short radio AGN duty cycle in PSBs, characterized by weak radio jets, suggesting that radio-driven maintenance-mode feedback may become important at later evolutionary stages.

Galactic winds shape galaxy evolution; however, the outflowing gas is complex: it consists of multiple ionization phases, and its properties vary spatially. Therefore, methods that combine high-fidelity observations with state-of-the-art galactic-wind models are limited. Here we investigate methods for fitting the column density profiles derived from high-quality outflow observations with the multiphase, multiscale wind model from D. B. Fielding & G. L. Bryan. We identify three key outflow parameters: the initial hot-phase mass-loading factor ( η _M,hot,0 ), the initial cool-phase mass-loading factor ( η _M,cool,0 ), and the initial cool-cloud mass ( M _cl,0 ). We obtain good fits (reduced χ ² < 1.5) for most galaxies, with tight constraints on η _M,cool,0 and moderate constraints on the other two parameters. We find the inferred η _M,cool,0 and η _M,hot,0 are mostly of order unity, with significant scatter. The constraints on η _M,hot,0 suggest that the interaction between the cool and hot phases allow us to indirectly constrain the properties of the hot wind from cool-outflow observations. The model also predicts various radial trends. First, for all galaxies, the cool-phase outflow velocity increases rapidly between 1 and 2 r ₅₀ , then reaches a plateau, where r ₅₀ is the half-light radius of the galaxy. Second, most galaxies exhibit increasing η _M,cool and decreasing η _M,hot with radius, with a few showing the reverse trends. These results should be interpreted as effective, model-conditional constraints but are consistent with other recent multiphase simulations and observations. This highlights that the velocity–radius mapping encoded in UV absorption profiles enables recovery of outflow spatial structures from spatially integrated spectra. Our method paves the way for future broad parameter studies and guides updates of outflow simulations in future work.

Red geysers are a population of massive ( log M / M ⊙ ∼ 10.5 ), quiescent galaxies with large-scale but weak, bisymmetric ionized gas outflows, interpreted as signatures of ongoing, low-level active galactic nucleus (AGN) feedback. We investigate the kinematics and prevalence of cool ( T ∼ 100–1000 K) neutral gas traced by Na i D absorption, and its connection to galaxy environment and AGN activity. Using 140 red geyser galaxies from the Sloan Digital Sky Survey-IV Mapping Nearby Galaxies at Apache Point Observatory (or MaNGA), we measure spatially resolved velocities and dispersions via double-Gaussian fits to the Na i D doublet. We find that ∼70% of the cool gas is inflowing, with a median velocity of ∼47 km s ⁻¹ (∼10% of the expected freefall velocity), and that it also exhibits kinematically ordered motions with σ _NaD / σ _* ∼ 0.4. Additionally, the Na i D absorption is more prevalent in red geysers than in a matched control sample, with a higher detection fraction (63% versus 40%) and reservoir areas ∼1.6 times larger. Acceleration (∼1 Myr) and accretion (∼20 Myr) timescales indicate that the Na I D-absorbing clouds are likely young and short-lived. Another intriguing result is that radio-detected red geysers (30% of the sample) show inflowing gas reservoirs ∼7 times larger than in non-radio systems. Similarly, galaxies subject to environmental effects host inflowing gas reservoirs ∼2.7 times larger than isolated red geysers. We take this as evidence that galaxy environments play a key role in replenishing the cool gas reservoirs of red geysers, fueling central AGN activity, sustaining radio emission, and regulating long-term quiescence. These findings reveal that quiescent systems are governed by cycles of inflow, feedback, and regulation.

We present spatially resolved maps of morphology, kinematics, and energetics of warm ionized gas in six powerful radio galaxies at z ∼ 3.5-4, using JWST/NIRSpec integral field unit to quantify jet-driven feedback in the early Universe. All sources exhibit broad [O III ] emission-line profiles with W ₈₀ (line width) values of 950–2500 km s ⁻¹ across approximately tens of kiloparsecs, signifying large-scale outflows. The outflowing nebulae are preferentially aligned with the radio jet axis, suggesting a jet-driven origin. On average, the regions with the broadest lines and highest velocities are co-spatial with radio lobes or cores, and exhibit the strongest kinetic power. Ionized gas masses associated with the outflows span from ∼1 to 8 × 10 ⁹ M _⊙ , with total mass outflow rates of 80–950 M _⊙ yr ⁻¹ and kinetic powers between 10 ^43.2 and 10 ^45.0 erg s ⁻¹ . The outflow kinetic power corresponds to 0.15%–2% of the AGN bolometric luminosity, sufficient to impact galaxy evolution. However, only ≲1% of the jet's mechanical energy couples to the warm ionized gas via outflows, consistent with predictions from hydrodynamic simulations. A large fraction of the jet energy may instead reside in shock-heated hot gas, supported by X-ray detection, or used to thermalize the gas and produce the observed emission-line nebulae. Our results demonstrate that radio jets in massive, gas-rich systems at high redshift can inject significant kinetic and thermal energy into the surroundings, providing direct evidence for jet-driven feedback operating during the peak epoch of galaxy formation.