Projects
Understanding Lyα escape fraction in CRISTAL-o2 galaxy at z~5.3
August 2025 - December 2025
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. in prep).
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 central to unveiling the physical conditions governing galaxies in the early Universe.
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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 ALPHINE-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, Davies et al., in prep, Herrera-Campus et al. 2025). 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 findings make CRISTAL-02 a unique source for examining the interplay between AGN activity, outflows, and Lyα radiative transfer in a high-redshift system.
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Using MUSE/VLT Lyα IFU data together with JWST/NIRSpec IFU observations of Hα and Hβ and NIRCam UV imaging, we generated spatially matched Lyα and Hα maps and study the behaviour of gas along the [CII] outflow and the galactic disc. This work investigates whether the AGN candidates facilitate the escape of Lyα photons by clearing low-density channels through outflows, or conversely, whether their energetic environments enhance dust and turbulence that suppress Lyα emission.
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Our preliminary results suggest that, although both AGN candidates reside in the same galaxy, they show different influences on local Lya escape conditions and ionization properties. Clump A, with lower dust attenuation, shows enhanced Lyα/Hα ratios and higher escape fraction, whereas Clump B displays stronger Hα and UV emission but suppressed Lyα despite a higher ionization efficiency. These results suggest that AGN-driven outflows and anisotropic clearing of the interstellar medium critically regulate Lyα visibility in the early Universe.
NGC5972 jet feedback
August 2021 - February 2025
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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
September 2023 - June 2024
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.