JWST Reveals a Candidate Jellyfish Galaxy at z=1.156

TL;DR

This study reports COSMOS2020-635829 as a candidate jellyfish galaxy at $z = 1.156$ undergoing ram pressure stripping in a dense environment. It combines JWST COSMOS-Web imaging with Gemini GMOS-IFU spectroscopy to reveal a symmetric disk and a unilateral tail of blue knots co-spatial with an ionized gas tail, and maps the [OII] emission to trace the stripping. Kinematic analysis shows an ordered rotation in the disk and a coherent velocity gradient along the tail with a ~50 km s^-1 offset, and [OII] emission extends the ionized tail by ~20 kpc. Tail knots are very young (≤100 Myr) with masses around 100 million solar masses and SFRs of 0.1–1 solar masses per year, indicating in situ star formation in stripped gas and demonstrating that ram pressure stripping can operate in group and cluster environments at $z>1$ and contribute to environmental quenching near Cosmic Noon.

Abstract

We report the discovery of COSMOS2020-635829 as a candidate jellyfish galaxy undergoing 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. Using Gemini GMOS IFU observations, 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. If confirmed, this represents 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 shows that ram pressure stripping can potentially perturb group and cluster galaxies at $z > 1$ and may contribute to environmental quenching even near Cosmic Noon.

Figures (10)

• Figure 1: Thumbnail images of COSMOS2020-635829 for the 4 JWST filters used in this work. The RGB image on the right is a combination of the JWST F444W (red channel), the F277W (green channel), and F115W+F150W (blue channel). The dashed circles mark the four extra-planar sources that are identified in the tail of COSMOS2020-635829.
• Figure 2: Large scale structure around COSMOS2020-635829. The large star marks the position of COSMOS2020-635829. The colormap shows a 2D kernel density estimate of all galaxies from the COSMOS2020 catalog within 10 arcminutes of COSMOS2020-635829 and with $1.0 < z_\mathrm{phot} < 1.3$. Open circles correspond to groups/clusters from AMICO-COSMOS catalog within 10 arcminutes of COSMOS2020-635829 and with $1.0 < z_\mathrm{phot} < 1.3$.
• Figure 3: Color profile for the main disk of COSMOS2020-635829 measured in circular annuli from the galaxy center to the edge of the disk. Vertical error bars show the $1\sigma$ statistical uncertainties on the measured color, horizontal error bars show the annuli widths. The far right of the figure shows the color in the tail region, both integrated over the full tail (dashed line) as well as measured individually for the tail sources highlighted in Fig. \ref{['fig:panels']}.
• Figure 4: Overlay of the GMOS IFU-1 field-of-view (solid box) on top of the JWST F277W image of COSMOS2020-635829. In the dashed boxes we show the apertures along the proposed tail direction that are used for extracting spectra around the [Oii]$\mathrm{\lambda \lambda 3726-3729}$ doublet.
• Figure 5: Extracted spectra around the [Oii] line for various slices along the tail axis. The labels in each panel correspond to the aperture labels in Fig. \ref{['fig:ifu_overlay']}. The black line and shading show the observed spectrum and uncertainty and the red lines show 500 random samples from the posterior distribution for the best-fit double-Gaussian model. These spectra are shown post continuum subtraction with a first-order polynomial. For each spectrum we list the signal-to-noise ratio for the detection of the [Oii] doublet. The yellow bands mark regions of the spectrum where significant sky-line residuals are seen, these regions of the spectrum are masked during fitting.