Early Results from the Coma Legacy IFU Survey (CLIFS): Ram Pressure Induced Shocks and Ionization in Jellyfish Tails

Abstract

Jellyfish galaxies, which exhibit tails of gas opposite to their direction of motion, are a galaxy population showcasing the most extreme effects of ram pressure stripping (RPS). We present the emission line properties of a preliminary sample of five jellyfish galaxies in the Coma cluster, observed with the WEAVE Large-IFU as part of the Coma Legacy IFU Survey (CLIFS). When complete, CLIFS will form a sample of 29 jellyfish galaxies in Coma, selected based on the presence of one-sided tails in the radio continuum, enabling a comprehensive picture of the effects of ram pressure on galaxies in the Coma cluster. We extract emission line properties and confirm consistency between disk fluxes measured from WEAVE and MaNGA for galaxies with overlapping disk coverage between surveys. Comparing resolved radio and H$α$-based star formation rates, we find that, in contrast to the disk, the dominant source of tail emission is not star formation. We find evidence for diffuse ionized gas excited by RPS-driven shocks in the tails, as indicated by: (1) LINER-like tail emission with the [OI]/H$α$ BPT diagnostic; (2) enhanced [OII]/H$α$ ratios in the tails relative to the disks; and (3) similarly elevated emission line velocities and velocity dispersions in the tails with respect to the disks. These results demonstrate that ram-pressure-driven shocks dominate the ionized emission in jellyfish galaxy tails.

Figures (11)

• Figure 1: Left: SFR versus stellar mass from the GALEX-SDSS-WISE Legacy catalogue salim_2016salim_2018, derived using UV/optical/midIR SED fitting. Apertures used likely do not contain the full extent of the RPS tails. Undisturbed Coma cluster galaxies are shown with blue Xs, LOFAR-identified Coma jellyfish are shown with light purple triangles, and the 5 jellyfish described in this paper are shown with dark purple stars. Right: Projected phase space distribution of Coma cluster galaxies. The virial radius $r_{180}=1.85~\mathrm{Mpc}$ and velocity dispersion $\sigma=834~\mathrm{km/s}$ of the Coma cluster are calculated using equations (5) and (6) in yang_2007, adopting a halo mass of $10^{15}\mathrm{M}_\odot$.
• Figure 2: Left: Covariance calibration factor as a function of bin size (see text for details). Data points correspond to median values and the error bars span between the 16th and 84th percentile, with colours distinguishing the five galaxies in this work. Right: Residuals between the observed ($O_\lambda$) and best-fit model spectrum ($M_\lambda$), for each wavelength ($\lambda$) and spaxel ($k$) with $g$-band signal-to-noise greater than 3, with all 5 galaxies included. Residuals are normalized by the error spectrum ($\epsilon_\lambda$). The dashed line shows the best-fit Gaussian distribution.
• Figure 3: Example observed spectrum (black) and errors (grey regions) and best-fit model (purple) for the central spaxel of CLIFS 219. The top panel shows the full spectrum, with shaded regions marking empty areas in the spectrum from chip gaps. Key emission and absorption features are highlighted in the lower panels: [O2] in the centre left, H$\beta$ and [O3] in the centre right, [N2], H$\alpha$, and [S2] in the bottom left, and the Ca2 triplet in the bottom right.
• Figure 4: Ratio of disk flux measurements between WEAVE and MaNGA for BPT emission lines. Point shapes and colours distinguish the three galaxies with both CLIFS and MaNGA data. Errors on the ratios are included, but are smaller than the points in most cases. The dashed horizontal line at unity indicates where flux measurements are equivalent between the two surveys.
• Figure 5: Top row: RGB images of each galaxy in the CLIFS sample created using SDSS g, r, and i-band images and astropy.visualization.make_ lupton_ rgb. Middle row: WEAVE H$\alpha$ flux maps, obtained from the MaNGA DAP for the same fields of view. Overlaid are the MaNGA FOVs for the galaxies with both MaNGA and WEAVE coverage. Bottom row: LOFAR radio continuum flux maps for the same fields of view. Overlaid are the tail regions defined in Section \ref{['sec:methods:regions']}.