Kavli Affiliate: Alexander P. Ji
| First 5 Authors: Quinn O. Casey, Burçin Mutlu-Pakdil, David J. Sand, Andrew B. Pace, Denija Crnojevic
| Summary:
We present deep Magellan$+$Megacam imaging of Centaurus I (Cen I) and
Eridanus IV (Eri IV), two recently discovered Milky Way ultra-faint satellites.
Our data reach $sim2-3$ magnitudes deeper than the discovery data from the
DECam Local Volume Exploration (DELVE) Survey. We use these data to constrain
their distances, structural properties (e.g., half-light radii, ellipticity,
and position angle), and luminosities. We investigate whether these systems
show signs of tidal disturbance, and identify new potential member stars using
Gaia EDR3. Our deep color-magnitude diagrams show that Cen I and Eri IV are
consistent with an old ($tausim 13.0$ Gyr) and metal-poor
($text{[Fe/H]}le-2.2$) stellar population. We find Cen I to have a half-light
radius of $r_{h}=2.60pm0.30’$ ($90.6pm11$ pc), an ellipticity of
$epsilon=0.36pm0.05$, a distance of $D=119.8pm4.1$ kpc ($m-M=20.39pm0.08$
mag), and an absolute magnitude of $M_{V}=-5.39pm0.19$. Similarly, Eri IV has
$r_{h}=3.24pm0.48’$ ($65.9pm10$ pc), $epsilon=0.26pm0.09$, $D=69.9pm3.6$
kpc ($m-M=19.22pm0.11$ mag), and $M_{V}=-3.55pm0.24$. These systems occupy a
space on the size-luminosity plane consistent with other known Milky Way dwarf
galaxies which supports the findings from our previous spectroscopic follow-up.
Cen I has a well-defined morphology which lacks any clear evidence of tidal
disruption, whereas Eri IV hosts a significant extended feature with multiple
possible interpretations.
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