A detailed star formation history of the distant Milky Way satellite Canes Venatici I: An old dwarf spheroidal forming most of its stars after reionisation
Abstract
Canes Venatici I (CVnI) is a distant Milky Way (MW) dwarf spheroidal (dSph) satellite. To date, there is no consensus on its evolution and the properties of its stellar population. This work is aimed at obtaining an accurate picture of the star formation history (SFH) and metallicity distribution of CVnI to reconstruct its evolution in detail, as well as to infer the possible effects of internal and external feedback. We used archival HST/ACS observations to obtain the deepest colour-magnitude diagram (CMD) to date, reaching ∼2 mag below the old main sequence turn-off. We derived the SFH and metallicity distribution of CVnI using a state-of-the-art CMD-fitting technique. We found that the SFH is dominated by a single star formation period, which peaked around 11.8 Gyr ago, well after the reionisation epoch, and remained active until ∼10.4 Gyr ago. The galaxy's global metallicity, [Z/H], ranges from -2.4 to -1.5 dex. Interestingly, while its star population is old and metal-poor, compared to other MW satellites of a similar size and luminosity that formed most of their stars in a single burst, CVnI experienced a delayed star formation period. We carried out an exhaustive set of tests with synthetic and real populations to ensure the reliability of these results. We suggest that the evolution of CVnI could have been regulated by its mass accretion history. The galaxy would have evolved above (but still close to) a theoretic redshift-dependent critical mass above which it is possible to maintain star formation. The combined effect of SN feedback would have made CVnI's halo mass subcritical at z≈2, definitively quenching its star formation. We cannot rule out the possible influence of gravitational interaction of CVnI with the MW at early ages, as hinted at by the most recent calculations of its orbit.
Versions
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BibTeX
@misc{perezgarcia2026detailed,
title = {{A detailed star formation history of the distant Milky Way satellite Canes Venatici I: An old dwarf spheroidal forming most of its stars after reionisation}},
author = {Pedro Pérez-García and Carme Gallart and Matteo Monelli and Santi Cassisi and Giuseppina Battaglia and Leticia Carigi and Emma Fernández-Alvar and Peter B. Stetson and Francisco Surot},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2611.05274},
eprint = {2611.05274},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2611.05274},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - UNPB
TI - A detailed star formation history of the distant Milky Way satellite Canes Venatici I: An old dwarf spheroidal forming most of its stars after reionisation
AU - Pedro Pérez-García
AU - Carme Gallart
AU - Matteo Monelli
AU - Santi Cassisi
AU - Giuseppina Battaglia
AU - Leticia Carigi
AU - Emma Fernández-Alvar
AU - Peter B. Stetson
AU - Francisco Surot
PY - 2026
DA - 2026/11/03
PB - arXiv
DO - 10.48550/arxiv.2611.05274
UR - https://arxiv.org/abs/2611.05274
AB - Canes Venatici I (CVnI) is a distant Milky Way (MW) dwarf spheroidal (dSph) satellite. To date, there is no consensus on its evolution and the properties of its stellar population. This work is aimed at obtaining an accurate picture of the star formation history (SFH) and metallicity distribution of CVnI to reconstruct its evolution in detail, as well as to infer the possible effects of internal and external feedback. We used archival HST/ACS observations to obtain the deepest colour-magnitude diagram (CMD) to date, reaching ∼2 mag below the old main sequence turn-off. We derived the SFH and metallicity distribution of CVnI using a state-of-the-art CMD-fitting technique. We found that the SFH is dominated by a single star formation period, which peaked around 11.8 Gyr ago, well after the reionisation epoch, and remained active until ∼10.4 Gyr ago. The galaxy's global metallicity, [Z/H], ranges from -2.4 to -1.5 dex. Interestingly, while its star population is old and metal-poor, compared to other MW satellites of a similar size and luminosity that formed most of their stars in a single burst, CVnI experienced a delayed star formation period. We carried out an exhaustive set of tests with synthetic and real populations to ensure the reliability of these results. We suggest that the evolution of CVnI could have been regulated by its mass accretion history. The galaxy would have evolved above (but still close to) a theoretic redshift-dependent critical mass above which it is possible to maintain star formation. The combined effect of SN feedback would have made CVnI's halo mass subcritical at z≈2, definitively quenching its star formation. We cannot rule out the possible influence of gravitational interaction of CVnI with the MW at early ages, as hinted at by the most recent calculations of its orbit.
ER -