Pushing Variability Searches to Extreme Dwarf Galaxies with the Vera C. Rubin Observatory Data Preview 2

Abstract

Galaxies with stellar masses M_⋆<10⁸ M_⊙, hereafter referred to as extreme dwarf galaxies (EDGs), represent one of the least explored regimes in the search for accreting intermediate-mass black holes. Using the recent Vera C. Rubin Observatory Data Preview 2 (DP2; covering 2025-04-25 to 2026-01-06), we present the first systematic search for variability among EDGs in the ELAIS-S1 field, the most extensively observed LSST Deep-Drilling Field in DP2. Applying single-band and cross-band variability statistics to difference-imaging light curves for 6.2×10⁴ EDGs with archival multiwavelength characterizations, we identify seven variable EDG candidates, all brighter than i-band magnitude of 24 and located within z<0.3. The two brightest candidates are previously known AGNs, three have light curves more consistent with supernovae, and two do not have a clear nature. The sample corresponds to an apparent EDG variable fraction of 6.8_−2.1^+3.1×10⁻⁴ at i-band magnitudes brighter than 24 and is expected to consist primarily of AGNs and supernovae. Compared to a magnitude-matched massive-galaxy sample with the same variability selection applied, the EDG variable fraction is comparable or at most lower by up to a factor of three. This proof-of-concept study demonstrates that Rubin will identify a statistically meaningful sample of variable EDG candidates, opening a new regime for black-hole demographics. Spectroscopic follow-up will nevertheless be required to secure redshifts and confirm individual candidates.

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BibTeX RIS

BibTeX

@misc{zou2026pushing,
  title = {{Pushing Variability Searches to Extreme Dwarf Galaxies with the Vera C. Rubin Observatory Data Preview 2}},
  author = {Fan Zou and W. N. Brandt and Elena Gallo and Franz E. Bauer and Angela Bongiorno and Colin J. Burke and Alister W. Graham and Hengxiao Guo and Lorena Hernández-García and Marcin Marculewicz and Dieu D. Nguyen and Swayamtrupta Panda and Alessandro Peca and Bindu Rani and Claudio Ricci and Ohad Shemmer and Wei Leong Tee and Zhibo Yu},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2610.10755},
  eprint = {2610.10755},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2610.10755},
}

RIS

TY  - UNPB
TI  - Pushing Variability Searches to Extreme Dwarf Galaxies with the Vera C. Rubin Observatory Data Preview 2
AU  - Fan Zou
AU  - W. N. Brandt
AU  - Elena Gallo
AU  - Franz E. Bauer
AU  - Angela Bongiorno
AU  - Colin J. Burke
AU  - Alister W. Graham
AU  - Hengxiao Guo
AU  - Lorena Hernández-García
AU  - Marcin Marculewicz
AU  - Dieu D. Nguyen
AU  - Swayamtrupta Panda
AU  - Alessandro Peca
AU  - Bindu Rani
AU  - Claudio Ricci
AU  - Ohad Shemmer
AU  - Wei Leong Tee
AU  - Zhibo Yu
PY  - 2026
DA  - 2026/10/07
PB  - arXiv
DO  - 10.48550/arxiv.2610.10755
UR  - https://arxiv.org/abs/2610.10755
AB  - Galaxies with stellar masses M_⋆<10^8 M_⊙, hereafter referred to as extreme dwarf galaxies (EDGs), represent one of the least explored regimes in the search for accreting intermediate-mass black holes. Using the recent Vera C. Rubin Observatory Data Preview 2 (DP2; covering 2025-04-25 to 2026-01-06), we present the first systematic search for variability among EDGs in the ELAIS-S1 field, the most extensively observed LSST Deep-Drilling Field in DP2. Applying single-band and cross-band variability statistics to difference-imaging light curves for 6.2×10^4 EDGs with archival multiwavelength characterizations, we identify seven variable EDG candidates, all brighter than i-band magnitude of 24 and located within z<0.3. The two brightest candidates are previously known AGNs, three have light curves more consistent with supernovae, and two do not have a clear nature. The sample corresponds to an apparent EDG variable fraction of 6.8_−2.1^+3.1×10^−4 at i-band magnitudes brighter than 24 and is expected to consist primarily of AGNs and supernovae. Compared to a magnitude-matched massive-galaxy sample with the same variability selection applied, the EDG variable fraction is comparable or at most lower by up to a factor of three. This proof-of-concept study demonstrates that Rubin will identify a statistically meaningful sample of variable EDG candidates, opening a new regime for black-hole demographics. Spectroscopic follow-up will nevertheless be required to secure redshifts and confirm individual candidates.
ER  -

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