JWST Reveals a Likely Jellyfish Galaxy at z=1.156 (2506.14117v1)

Abstract: We report the discovery of COSMOS2020-635829 as a likely jellyfish galaxy undergoing to ram pressure stripping in a (proto)cluster at $z > 1$. High-resolution imaging from the James Webb Space Telescope reveals a symmetric stellar disk coupled to a unilateral tail of star-forming knots to the south. We show that these extra-planar continuum sources are embedded within an ionized gas tail that is kinematically connected to the disk of COSMOS2020-635829. Likely representing the highest-redshift discovery of a ram pressure stripped ionized gas tail. The tail sources are characterized by extremely young stellar populations ($\lesssim 100\,\mathrm{Myr}$), have stellar masses of ${\sim}10^8\,\mathrm{M_\odot}$, and star formation rates of $0.1\text{--}1\,\mathrm{M_\odot\,yr^{-1}}$. This work reinforces the notion that ram pressure stripping can perturb group and cluster galaxies at $z > 1$ and likely contributes to environmental quenching even near Cosmic Noon.

• The paper identifies COSMOS2020-635829 as a jellyfish galaxy with a one-sided star-forming tail indicative of ram pressure stripping.
• It uses high-resolution JWST imaging and [OII] spectral analysis to tie the galaxy's unusual morphology to its overdense, proto-cluster environment.
• The findings imply that environmental interactions trigger in situ star formation, shaping galaxy evolution even at high redshifts.

Analysis of "JWST Reveals a Likely Jellyfish Galaxy at z = 1.156"

The research paper, "JWST Reveals a Likely Jellyfish Galaxy at $z = 1.156$", discusses the identification and analysis of the galaxy COSMOS2020-635829, inferred as undergoing ram pressure stripping (RPS) within a (proto)cluster environment. Utilizing data procured from the James Webb Space Telescope (JWST), the paper focuses on the distinctive morphology of the galaxy, characterized by a one-sided trail of star-forming regions that gives rise to the 'jellyfish' classification.

Key Findings and Methodology

1. Discovery and Identification: The researchers identified COSMOS2020-635829 as a potential jellyfish galaxy using JWST high-resolution imaging. This imaging revealed a symmetric stellar disk paired with an asymmetrical tail comprising star-forming knots, suggesting interactions consistent with RPS.
2. Environmental Context: The galaxy resides in an overdense region at a redshift of $z = 1.156$. The association with a high-density environment supports the hypothesis of environmental factors, such as RPS, influencing its morphology and star formation.
3. Ionized Gas Tail: Spectral analyses, notably of the [OII] emission, indicated the presence of an ionized gas tail, which kinetically associates with the galaxy's disk. The tail's orientation and kinematic properties reinforce the interpretation of ongoing ram pressure stripping.
4. Star Formation in the Tail: Photometric and spectroscopic data suggest that the star-forming regions within the tail are comprised of young stellar populations. These regions show significantly increased star formation rates, indicative of recent or ongoing interactions with the intracluster medium (ICM).

Numerical Analysis and Implications

• The star-forming knots in the tail exhibit stellar masses on the order of $\sim 10^8\,M_\odot$ with star formation rates ranging between $0.1\text{--}1\,M_\odot\,\text{yr}^{-1}$. These metrics suggest that even at high redshift, galaxies undergoing RPS can contribute significantly to in situ star formation.
• The paper posits that RPS effectively triggers star formation by compressing the gas in galactic outskirts, leading to an observable increase in star formation along the galaxy’s wake.

Theoretical and Practical Implications

• Environmental Quenching: The findings strengthen the narrative that environmental processes such as RPS significantly influence galaxy evolution at redshifts greater than 1. This adds evidence to models suggesting that quenching mechanisms are active well before reaching the current epoch.
• Future Observations and Theories: The evidence for active RPS at such redshifts hints at the necessity to integrate these dynamics into theoretical models of galaxy evolution. As the JWST and other upcoming astronomical instruments continue to provide unprecedented data, models will need to incorporate more complex environmental interactions.
• Potential for Broader Surveys: The methodology and results advocate for expanded surveys targeting similar environments to better understand the frequency and impact of RPS in galaxy clusters across different epochs.

This research enhances understanding of high-redshift galaxy dynamics, particularly in cluster environments, showcasing the effectiveness of JWST in elucidating fine morphological and kinematic details. These insights obligate further exploration into the roles of external pressures and star formation in shaping the evolutionary pathways of galactic structures in the universe.