Projects

Understanding Lyα escape fraction in CRISTAL-o2 galaxy at z~5.3

Left: COSMOS field showing region around the protocluster core (green circle, 2x2'), along with the enlarged image of the protocluster core. The area corresponds to 22.5" x 22.5" on the sky, 0.865Mpc co-moving, or 0.137 Mpc proper distance at z=5.298 (Capak et al. 2011). Right: JWST and ALMA observations of CRISTAL-02. 4 × 3” JWST/NIRCam 3-color composite image with the star-forming clumps (a-d) and faint companion (e) marked. Contours show the [C ii] λ158μm (Davies et al. 2026).

Lyα emission serves as a fundamental probe of the interstellar and circumgalactic media in early galaxies, yet its resonant scattering and sensitivity to dust and geometry complicate its interpretation. Understanding how Lyα photons escape is therefore crucial to study the physical conditions governing galaxies in the early Universe.

For this project, I am working with Dr. Lucia Guaita at UNAB, trying to do a spatially resolved study of a star-forming galaxy CRISTAL-02/ LBG-1 (Guaita et al. 2022) at redshiftz~5.3, located in the Cosmic Evolution Survey (COSMOS) field (Capak et al. 2011, Reichers et al. 2014) and identified as part of the ALPINE-CRISTAL-JWST program. Previous studies of this source revealed a diffused and extended Lyα emitting gas of radius~17.4 kpc (Guaita et al. 2022) and a [CII] outflow (Guaita et al. 2022, Herrera-Campus et al. 2025, Davies et al. 2026). The galaxy has been identified with five distinct clumps, two of which have been suggested as potential AGN candidates (hereafter, Clump A and B) (Ren et al. 2025). These properties make CRISTAL-02 a unique system to study the interplay between AGN/ star formation activity, outflows, and Lyα radiative transfer in a high-redshift environment.

Using integral field spectroscopy from MUSE/VLT and JWST/NIRSpec IFU, complemented by NIRCam UV imaging, we generated spatially matched Lyα, Hα and UV maps and studied the behavior of gas along the [CII] outflow and the galactic disc. We find that the Lyα emission is preferentially extended along the [CII] outflow direction, while Hα and UV emission trace the galactic disc. Clumps A and B show contrasting behavior: Clump A, with lower dust attenuation, exhibits enhanced Lyα/Hα ratios and higher Lyα escape fraction; Clump B shows stronger Hα and UV emission but suppressed Lyα, despite higher ionizing photon production efficiency. The results suggest that Lyα escape is governed by a combination of outflows, dust attenuation, and local gas conditions, laying the groundwork for future studies of similar high-redshift systems. This study provides among the first spatially resolved measurements of the Lyα escape fraction and ionizing photon production efficiency in distant systems and highlights the role of feedback-driven gas clearing and anisotropic outflows in shaping the observed Lyα properties.

What Powers the Gas in a "Transitioning" SO Galaxy? A Case Study of 2PBC J1332.1−7751

SO (lenticular) galaxies occupy an intriguing position between spiral and elliptical galaxies. They retain a disk-like structure but exhibit little ongoing star formation, making them important laboratories for understanding how galaxies transition from actively star-forming systems into quiescent galaxies. The physical pathways responsible for this transformation remain debated, with possible mechanisms including environmental effects, galaxy interactions and mergers, as well as secular internal evolution.

We investigate the nearby SO galaxy 2PBC J1332.1−7751 (z=0.00984), a transitioning system evolving from a blue, star-forming disk toward a quiescent red galaxy and exhibiting prominent LINER-like emission. 2PBC J1332.1−7751 is a particularly interesting case study in this context. As an isolated SO galaxy with a very low star-formation rate and strong LINER-like emission, it provides an opportunity to investigate the physical processes operating in a galaxy transitioning toward quiescence. In particular, its LINER-like ionization raises the question of what powers the remaining ionized gas after massive-star formation has largely declined. The system therefore allows us to explore the interplay between evolved stellar populations, a low-accretion AGN, and the surrounding interstellar medium, and to assess whether the observed gas excitation and kinematics provide evidence for ongoing AGN feedback or are primarily associated with the passive evolution of the stellar population.

Using spatially resolved MUSE spectroscopy, we combine emission-line diagnostics, gas kinematics, energetics, and an ionizing photon budget to investigate the origin of the ionized gas in 2PBC J1332.1−7751. By examining the spatial variation of the excitation mechanisms, we aim to determine how different ionization sources contribute across the galaxy and what this reveals about the evolution of an isolated SO system.

Jet feedback in a "Voorwerp Galaxy," NGC5972

Ali et al. 2025

Cartoon schematic diagram showing various mechanisms at play in NGC5972. The green helix represents the [O III] emission as observed from the HST image. The jet axis is indicated by the red line, and the radio emission is depicted by the dotted red lobes. The black clouds denote the shock regions perpendicular to the jet, as determined by BPT analysis. The red and blue structures represent the outflow region in the galaxy. The shocked cocoon is shown in yellow.

It is widely accepted that active galactic nuclei (AGN) feedback in the form of radio jets, radiation, and/or winds has a significant impact on the surrounding interstellar medium. However, the role of photoionization (by the accretion disk) vs that of shock ionization (by jets/winds) has not yet been unambiguously disentangled. Previous studies have shown that the spatial coincidence between optical and radio emission could indicate AGN jet/wind induced shock. However, there is a still lack of comprehensive understanding of the effects of highly energetic jets on the host and its immediate surroundings.

We intend to study the relationship between radio jets and the distribution and kinematics of the ionized gas in NGC5972, a "Voorwerp" galaxy. Our primary objective is to quantify the contribution of the jet to the feedback mechanism by analyzing the correlations between radio emission and optical [OIII] emission in extended emission line regions spanning several kiloparsecs. To achieve this, we are utilizing EVLA, GMRT polarization data and MUSE IFU spectroscopic data.

Probing Cosmology: Gravitational Lensing and Precision with GW+EM Lensed Signal

Detecting gravitational waves (GW) in combination with electromagnetic (EM) counterpart signals holds the potential to serve as an excellent cosmological probe (Liao et al. 2017). Thus, this project is focused on stimulating systems having compact binary coalescence (CBC) to study the GW+EM signals. We aim to use the gravitational lensing method to constrain the value of cosmological parameters to contribute a deeper understanding of the fundamental properties of the universe.

Our research methodology involves the creation of realistic Hubble Space Telescope (HST) image simulations tailored to various lens system configurations using the software "Glafic (Oguri 2010)." These simulations employ various mass and light profile for data generation. A central aspect of our project is to test the accuracy of lens modeling in terms of uncertainties in the Fermat potential δ(Δψ) from lensed GW+EM system. We created mock datasets for multiple lensing configurations, optimized best-fit lens models using chi-square analysis, and calculated differences in the lensing potential that could arise if model assumptions deviate from the true system. In particular, we investigated how uncertainties in the inferred Fermat potential could stem from mismatches between the mock and model configurations — specifically by varying the noise profiles, as well as the underlying mass density and light distribution models. This allowed us to quantify the sensitivity of lens modeling accuracy to different systematic factors.