arXiv subjects

Gavin Farley

Publications and source records attributed to Gavin Farley.

5 recordsLinked to original sources

arXiv2026

Revealing the Structure and Magnetization of GRB Jets with ALMA Polarization Observations

We present a systematic study of the currently available ALMA millimeter polarimetric sample of gamma-ray burst (GRB) afterglows. Our sample comprises 24 observations (20 new) of 11 long-duration GRBs spanning $\approx0.1$-87 days after the burst. We detect significant linear polarization in 8 observations across 6 events, with polarization degrees ranging from $\Pi_L\approx0.6\%$ to $2.4\%$. For the remaining observations, we place deep upper limits (median $\Pi_L\lesssim1\%$). Multi-epoch observations reveal diverse polarization evolution. GRB 190114C yields the best-sampled $\Pi_L$ for a radio afterglow to date, with early evolution favoring patchy magnetic fields in the reverse shock (RS) and later polarization broadly consistent with forward-shock (FS) models. GRB 220921A exhibits a rapid rise in polarization from $\Pi_L\lesssim0.4\%$ to $2.4\%$ over 1.9-6.8 days, inconsistent with toroidal RS magnetic-field models but broadly consistent with several FS random-field models. GRB 221009A yields the highest-significance polarization detections in the sample ($\Pi_L\approx1.4$-$1.6\%$), yet neither existing FS nor RS polarization models reproduce both the observed polarization evolution and the viewing geometry inferred from broadband afterglow modeling, with the exception of patchy fields in the RS. Deep upper limits for GRB 171205A rule out RS toroidal-field models for the published off-axis geometry, while a strong, single-epoch detection of GRB 190829A, if RS-dominated, requires a nearly on-axis geometry for toroidal-field configurations. Interpreting the observations within a patchy-field framework implies magnetic-field coherence scales of order $\theta_B\sim10^{-3}$-$10^{-2}$ rad. These observations demonstrate the diagnostic power of radio/mm polarimetry for probing the magnetic-field structure, emission region, and viewing geometry of relativistic GRB jets.

astro-ph.HE↗

arXiv2026

The Radio Properties of Extreme Coronal Line Emitters: Constraints on the Sub-parsec Environment

A tiny fraction ($\ll1\%$) of galaxies display luminous, high-ionization metal emission lines, which may be persistent or variable. These extreme coronal lines (ECLs) are produced when soft X-ray photons intercept dense gas ($n\gtrsim10^{6-7}~{\rm cm^{-3}}$). The high X-ray flux required implicates intense nuclear activity, likely originating from tidal disruption events (TDEs) and active galactic nuclei (AGN). As ECLs are rarely seen even within these classes, their production may also require specific environmental conditions, but the details remain unclear (e.g., the geometry and volume filling factor of the ECL-producing gas). Here, we present the radio properties of a population of $27$ low-redshift ($z<0.3$) ECL emitting galaxies (ECLEs), providing a unique and previously unexplored probe of the properties of the circumnuclear medium (CNM; $\lesssim1$ pc from the black hole) in these systems. We find that $\sim 50\%$ of ECLEs produce radio synchrotron emission with luminosity and evolution consistent with TDEs and/or AGN. Radio spectral modeling of four ECLEs reveals that the ECL-producing region is (1) clumpy with a low volume filling factor ($10^{-5}\lesssim f_{V}\lesssim10^{-2}$) and (2) likely distinct from the radio emitting region (implying, e.g., a clumpy toroidal geometry). For time-variable ECLEs, these are some of the first observational constraints on the CNM geometry in formerly quiescent galactic nuclei. The unique nature of ECLEs makes them an excellent high-energy laboratory to connect the physics of accretion, photoionization, and feedback in galactic nuclei, thus motivating continued multi-wavelength monitoring.

astro-ph.HE↗

arXiv2026

A Self-Consistent Framework for Synchrotron Equipartition Analysis

Determining the energy, size, and velocity of synchrotron-emitting outflows is essential for testing models of their formation and evolution, but these quantities are often poorly constrained by observations alone. Equipartition analysis, therefore, provides a widely used framework for estimating these properties. Prior works have developed refinements to account for additional physical effects and other sources of energy (e.g., self-absorption, hot protons, and deviations from strict equipartition); however, these corrections are typically applied independently of one another, resulting in internal inconsistencies. In this work, we derive a self-consistent equipartition framework that accounts for the interdependence of various correction factors for Newtonian outflows and on- and off-axis relativistic jets. We implement our framework in an easy-to-use, publicly available code and apply it to study the tidal disruption events ASASSN-19bt and AT2019dsg, fast X-ray transient EP240414a, and active galactic nucleus J0231-0433. The interdependence of the corrections can increase energy estimates by a factor of ~5, suggesting that the energies of other synchrotron sources may be similarly underestimated in the literature. These results indicate that simultaneously incorporating these correction factors is essential for determining accurate outflow properties and constraining launch mechanisms.

astro-ph.HE↗

arXiv2026

Radio Observations of the Unusual Tidal Disruption Event AT 2022wtn: a Fast and Highly Energetic Outflow

We present multi-epoch, multi-frequency radio observations of the tidal disruption event (TDE) AT 2022wtn, obtained with the Karl G. Jansky Very Large Array (VLA) and Giant Metrewave Radio Telescope (GMRT), spanning 97-866 days after optical detection. The peak radio flux density increases until 300 days post optical discovery, flattens out for several hundred days, then begins to decrease at 534 days. Utilizing an updated equipartition analysis framework, we estimate several physical parameters of the event and the surrounding medium. We model AT 2022wtn with two different geometries: a spherical and a conical emitting region. The spherical outflow model gives an expansion velocity of $v\approx0.21c$ and a kinetic energy of $\sim3.8\times10^{49}$ erg, and the conical outflow model yields a higher energy ($\sim1.8\times10^{50}$) and velocity ($v\approx0.41c$) than the spherical case. After ruling out the possibility of a relativistic jet, we consider several potential origins for sub-relativistic outflow regions in TDEs including unbound debris streams, collisionally-induced outflows, an accretion-driven wind, and an outflow from an accretion disk state transition, and find only an accretion disk state transition outflow to be consistent with the high energy and velocity found in our equipartition results. AT 2022wtn is a uniquely powerful non-relativistic radio-emitting TDE, and joins a growing population that display a diverse range of outflow properties.

astro-ph.HE↗

arXiv2025

VENUS: A Strongly Lensed Clumpy Galaxy at $z\sim11-12$ behind the Galaxy Cluster MACS J0257.1-2325

We present the discovery of a strongly lensed galaxy at $z\sim11-12$, dubbed the ``Misty Moons'', identified in the JWST Treasury Survey, Vast Exploration for Nascent, Unexplored Sources (VENUS). The Misty Moons is gravitationally lensed by the galaxy cluster MACS J0257.1-2325 at $z=0.505$, and has five multiple images suggested by two independent lensing models. Two of the five images, ID1 and ID2 ($\mu\sim 20-30$), are very bright (F200W$\sim26$ AB mag) and exhibit blue SEDs with prominent Ly$\alpha$ breaks. In the source plane, the Misty Moons is a sub-$L^*$ galaxy ($M_{\rm UV}\sim-18.0$ mag) resolved into multiple stellar clumps, each of which has an effective radius of $r_\mathrm{eff}\sim 10-70$ pc and a stellar mass of $\sim10^7\ M_\odot$. These clumps dominate the stellar mass budget of the Misty Moons ($\gtrsim80\%$), similar to other high-$z$ clumps, which suggests a highly clustered mode of star formation in the early Universe, unlike seen in local dwarf galaxies. We convolve the source-plane image with the JWST/NIRCam point-spread function to produce a mock NIRCam image of the Misty Moons without lensing magnification, and find that the intrinsic galaxy has a radial surface-brightness profile comparable to those of $z\gtrsim10$ faint galaxies, such as JADES-GS-z13-0 and JADES-GS-z14-1, indicating that the Misty Moons represents a typical $z\gtrsim10$ faint galaxy. The Misty Moons, a lensed galaxy with resolved internal structures, provides an ideal laboratory for exploring the early stages of galaxy formation at $z\gtrsim10$.

astro-ph.GA↗