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Publication Date

2025-5

First Advisor

James Lowenthal

Second Advisor

Tucker Jones

Document Type

Honors Project

Degree Name

Bachelor of Arts

Department

Astronomy

Keywords

astronomy, astrophysics, galaxies, extragalactic, spectroscopy, observational astronomy, galaxy formation, galaxy evolution, supermassive black holes, active galactic nuclei, AGN

Abstract

Every massive galaxy hosts a central supermassive black hole (SMBH), yet their origins are unknown and their co-evolution with their host galaxies is poorly understood. We utilize pseudo-integral field spectroscopy from slitstepping observations with JWST’s NIRSpec MSA to investigate the incidence of active galactic nuclei (AGN) around the cosmic time associated with the peak of star formation and black hole accretion. Our sample consists of 42 galaxies within the Extended Groth Strip, selected for z ∼ 3 and to reside on the star-forming main sequence. For 36/42 galaxies with the requisite emission lines, we categorize their ionization as driven by star formation or AGN activity using the Baldwin, Phillips & Terlevich (BPT) and Hα equivalent width versus [N II]/Hα (WHAN) diagnostic diagrams. Moreover, the spatially resolved spectra provide excellent sensitivity to AGN by allowing us to isolate the emission lines from the central kpc. We find only one target that exhibits a clear AGN signature according to both diagnostics, with two additional AGN detections from the WHAN diagram alone. Our AGN detections fall within the most massive ∼ 10% of galaxies in our sample. This result is consistent with the trend established lower redshifts, where AGN detections appear mass-dependent. Additionally, for AGN detections, we determine SMBH masses and bolometric luminosities in order to characterize them by their Eddington ratios. For non-detections, we report upper limits on Eddington ratios. Future work will examine our result in the context of multi-wavelength censuses of AGN.

Rights

©2025 Gena Levin. Access limited to the Smith College community and other researchers while on campus. Smith College community members also may access from off-campus using a Smith College log-in. Other off-campus researchers may request a copy through Interlibrary Loan for personal use.

Comments

vii, 91 pages: color illustrations, charts. Includes bibliographical references (pages 82-91).

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