Timothy Heckman

The geometry of the neutral gas in and around galaxies is a key regulator of the escape of ionizing photons. We present the first statistical study aimed at linking the neutral and ionized gas distributions to the Lyman continuum (LyC) escape fraction (fLyC esc) in a sample of 22 confirmed LyC leakers and non-leakers at z≈ 0.35 using the Keck Cosmic Web Imager (Keck/KCWI) and the Low Resolution Spectrograph 2 (HET/LRS2). Our integral field unit data enable the detection of neutral and low-ionization gas, as traced by Mg ii, and ionized gas, as traced by [O ii], extending beyond the stellar continuum for seven and ten objects, respectively. All but one object with extended Mg ii emission also show extended [O ii] emission; in this case, Mg ii emission is always more extended than [O ii] by a factor 1.2 on average. Most of the galaxies with extended emission are non or weak LyC leakers (fLyC esc< 5%), but we find …

We present rest-frame optical spectroscopy using JWST/NIRSpec IFU for the radio galaxy TN J1338-1942 at z=4.1, one of the most luminous galaxies in the early Universe with powerful extended radio jets. Previous observations showed evidence for strong, large-scale outflows on the basis of its large (~150 kpc) halo detected in Ly-alpha, and high velocity [O II] emission features detected in ground-based IFU data. Our NIRSpec/IFU observations spatially resolve the emission line properties across the host galaxy in great detail. We find at least five concentrations of line emission, coinciding with discrete continuum features previously detected in imaging from HST and JWST, over an extent of ~2'' (~15 kpc). The spectral diagnostics enabled by NIRSpec unambiguously trace the activity of the obscured AGN plus interaction between the interstellar medium and the radio jet as the dominant mechanisms for the ionization state and kinematics of the gas in the system. A secondary region of very high ionization lies at roughly 5 kpc distance from the nucleus, and within the context of an expanding cocoon enveloping the radio lobe, this may be explained by strong shock-ionization of the entrained gas. However, it could also signal the presence of a second obscured AGN, which may also offer an explanation for an intriguing outflow feature seen perpendicular to the radio axis. The presence of a dual SMBH system in this galaxy would support that large galaxies in the early Universe quickly accumulated their mass through the merging of smaller units (each with their own SMBH), at the centers of large overdensities. The inferred black hole mass to stellar …

In the current JWST era, rest-frame UV spectra play a crucial role in enhancing our understanding of the interstellar medium (ISM) and stellar properties of the first galaxies in the epoch of reionization (z> 6). Here, we compare well-known and reliable optical diagrams sensitive to the main ionization source (ie, star formation, SF; active galactic nuclei, AGN; and shocks) to UV counterparts proposed in the literature—the so-called" UV–BPT diagrams"—using the HST COS Legacy Archive Spectroscopic SurveY (CLASSY), which is the largest high-quality, high-resolution, and broad-wavelength range atlas of far-UV spectra for 45 local star-forming galaxies. In particular, we explore where CLASSY UV line ratios are located in the different UV diagnostic plots, taking into account state-of-the-art photoionization and shock models, and, for the first time, the measured ISM and stellar properties (eg, gas-phase metallicity …

We report observations of a powerful ionized gas outflow in a z = 4.1 luminous () radio galaxy TNJ1338-1942 hosting an obscured quasar using the Near Infrared Spectrograph (NIRSpec) on board JWST. We spatially resolve a large-scale (~15 kpc) outflow and measure resolved outflow rates. The outflowing gas shows velocities exceeding 900 and broad line profiles with line widths exceeding 1200 located at ~10 kpc projected distance from the central nucleus. The outflowing nebula spatially overlaps with the brightest radio lobe, indicating that the powerful radio jets are responsible for the extraordinary kinematics exhibited by the ionized gas. The ionized gas is possibly ionized by the central obscured quasar with a contribution from shocks. The spatially resolved mass outflow rate shows that the region with the broadest line profiles exhibits the strongest outflow rates, with an integrated mass outflow rate of ~500 . Our hypothesis is that an over-pressured shocked jet fluid expands laterally to create an expanding ellipsoidal "cocoon" that causes the surrounding gas to accelerate outwards. The total kinetic energy injected by the radio jet is about 3 orders of magnitude larger than the total kinetic energy measured in the outflowing ionized gas. This implies that kinetic energy must be transferred inefficiently from the jets to the gas. The bulk of the deposited energy possibly lies in the form of hot (~ K) X-ray-emitting gas.

Quasar-driven galactic outflows are a major driver of the evolution of massive galaxies. We report observations of a powerful galactic-scale outflow in a z= 3 extremely red and intrinsically luminous (L bol≃ 5× 10 47 erg s− 1) quasar SDSSJ1652+ 1728 with the Near-infrared Spectrograph on board JWST. We analyze the kinematics of rest-frame optical emission lines and identify the quasar-driven outflow extending out to∼ 10 kpc from the quasar with a velocity offset of (v r=±500 km s− 1) and high velocity dispersion (FWHM= 700–2400 km s− 1). Due to JWST's unprecedented surface brightness sensitivity in the near-infrared, we unambiguously show that the powerful high velocity outflow in an extremely red quasar encompasses a large swath of the host galaxy's interstellar medium. Using the kinematics and dynamics of optical emission lines, we estimate the mass outflow rate—in the warm ionized phase alone …

Galactic winds have long been identified to provide various feedback effects that impact the galaxy evolution. While galactic winds have been intensely studied in the low-z universe given abundant spectroscopic data, their properties at the highest redshifts (z>~ 6) are largely unknown. This is because the predominant diagnostics of outflows-blueshifted UV absorption lines-are not feasible for high spectral resolution observations due to the faint UV continuum. One solution is to search for highly magnified galaxies, where strong gravitational lensing can uncover early galaxies that are bright enough for detailed UV+ optical spectroscopic analyses. Toward this goal, we propose to observe the strongly lensed galaxy MACS0308-zD1. Given an AB magnitude of 23.4, a confirmed spectroscopic redshift of 6.2 from ALMA, and a magnification of 20 times, MACS0308-zD1 serves as the brightest known lensed galaxy at z> …

At z> 6, galaxies transformed the universe by releasing ionizing, Lyman continuum (LyC) photons and reionizing the intergalactic medium (IGM). However, which galaxies dominated reionization and how their LyC photons escaped remains unknown. Because of the high IGM opacity during the epoch of reionization, we can only study the physics of LyC escape at lower redshift. We propose the first analysis of the MIR spectral properties of LyC-emitting galaxies. Using full-coverage MIRI MRS spectra of 4 of the strongest LyC emitters at z= 0.3 and a matched control sample of 4 non-emitters, we will investigate the role of the ionizing spectrum and dust content in LyC escape. The full MIRI spectra will capture a suite of nebular lines from different ionization states, which span the energies of the predicted ionizing spectra. These lines will constrain the shape of the ionizing spectrum and show whether LyC-emitting …

The reionization of the intergalactic medium (IGM) at z> 6 is one of the major transformations in the universe's history, but we do not yet know which galaxies were responsible for this event. Unfortunately, IGM absorption prevents us from directly measuring escaping ionizing Lyman continuum (LyC) photons from z> 6 galaxies. Instead, we must identify the galaxy properties that correlate with LyC escape using lower-redshift samples. To address this issue, we have undertaken the Low-redshift Lyman Continuum Survey, the largest survey of LyC emission at low redshift to date. With HST UV observations of 66 galaxies at z~ 0.3, we have nearly tripled the number of low-redshift LyC detections. Although LyC emitters span a wide range of properties, strong LyC escape is associated with strong and narrow Ly-alpha emission, high nebular [O III]/[O II] ratios, compact star formation, low dust extinction, weak UV absorption …