Speaker
Description
We present a morphological analysis of dwarf galaxies in the Perseus cluster using Euclid Early Release Observations (ERO), exploiting the VIS instrument's diffraction-limited resolution and exceptional surface brightness sensitivity. Working from the ~1100-dwarf ERO catalog of Marleau et al. (2025), we develop a novel cumulative light fraction approach for measuring isophotal shapes in low surface brightness systems. Rather than tracing contours at fixed surface brightness levels — which is unreliable in noisy regimes — we extract isophotes at fixed fractions of the total galaxy flux and quantify the $c_4$ Fourier coefficient, validated to $r > 0.98$ accuracy across SNR 5–100.
Applying this method to 804 early-type Perseus dwarfs, we identify 13 galaxies with significantly boxy isophotes ($c_4 < -0.0175$). These systems are red, fully quenched, and show no disk or spiral features despite Euclid's resolution. We find a strong anticorrelation between $c_4$ and effective radius ($r = -0.75$, $p = 0.003$): the physically largest dwarfs are the boxiest.
To interpret this, we generate synthetic Euclid observations of tidally transformed dwarf simulations (Smith et al. 2021) across 240 viewing angles. The size–shape correlation arises naturally from projection effects: face-on orientations simultaneously maximize apparent size and reveal the full rectangular profile of a tidally induced peanut structure, while edge-on views yield rounder, more compact morphologies. Dry mergers are disfavored by the elongated axis ratios of the sample and the high velocity dispersion of Perseus. Correcting for viewing geometry, we estimate a parent population of ~30 such tidally transformed, peanutty remnants in Perseus.
| Talk category | NOVA Network 1 |
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