Coral Wheeler

Please check it out and let me know what you think! Many thanks to my amazing co-authors: ‪@jorgitomoreno.bsky.social‬, ‪@astronomerc.bsky.social‬, @katycosmiq.bsky.social ‪@jbprime.bsky.social‬, ‪@mbkplus.bsky.social‬, @astrogandhi.bsky.social, ‪@sloebman.bsky.social‬, (/end)

Main takeaway: mass estimates of ultra-faint galaxies used to constrain dark-matter physics or to place constraints on the low-mass threshold of galaxy formation must take into account surface brightness limits or risk significant biases. (5/6)

Failing to detect the stellar halo (SB cut; solid symbols) also increases the [Fe/H] of the simulated ultra-faints, but not enough to solve the discrepancy in the MZR at the lowest masses. (4/6)

while biasing mass estimates too high. Left: Wolf+ 2010 mass estimates compared to NFW profiles. Right: mass estimates for the *same galaxies* if outer stars below a certain effective surface brightness are removed. The galaxies are incorrectly placed in more massive halos. (3/6)

Since then, more and more stars at large half-light radii have been detected around observed ultra-faint galaxies.

In this latest paper, we explore how removing stars at large radii (SB Cut; solid symbols) leads to predicted UFD sizes that are closer to observations, (2/6)

How invisible stellar halos bias our understanding of ultra-faint galaxies We explore how a realistic surface brightness detection limit of $μ_V \approx 32.5$ mag arcsec$^{-2}$ for stars at the edges of ultra-faint galaxies affects our ability to infer their underlying prope...

Paper Day! arxiv.org/abs/2506.15785; “How invisible stellar halos bias our understanding of ultra-faint galaxies”

In Wheeler+2019, we speculated that observed UFDs might be the bright central cores of more extended objects, and that they may have invisible stellar halos. (1/5)

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