AGC 322753: a Dark Galaxy Candidate detected by ALFALFA and FASHI
Abstract
We report the possible detection of a Dark Galaxy Candidate (DGC; AGC 322753), via the cross-matching of the Arecibo Legacy Fast ALFA (ALFALFA) and the FAST All Sky HI (FASHI) HI blind surveys. It is detected by both surveys at the same recessional velocity, with a comparable HI mass of 2×109 M⊙, and with similar HI spectral features. The ALFALFA and FASHI spectra show a double-peaked profile, compatible with a disc-like ordered rotation, and an HI linewidth at 50 per cent of the peak (W50) of ∼85 km s−1. The common intersection of the two beams allows the source position to be constrained with much greater precision than in either survey individually. Being detected by both radio telescopes, a Radio Frequency Interference (RFI) origin is excluded. No evidence of an optical counterpart was found down to ∼27.5 mag arcsec−2 in the DESI Legacy Imaging Surveys, which leads to a stellar mass limit of M⋆ ≲ 5×107 M⊙. Given this stellar mass limit, AGC 322753 has MHI/M⋆ ≳ 40. The HI mass is higher than expected for totally starless haloes; this could imply that AGC 322753 is not completely 'dark' but could host a luminous counterpart below the current optical detection limit.
Related
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BibTeX
@misc{monaci2026322753,
title = {{AGC 322753: a Dark Galaxy Candidate detected by ALFALFA and FASHI}},
author = {Marco Monaci and Duncan A. Forbes and Warrick J. Couch and Jean P. Brodie},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.39152},
eprint = {2609.39152},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.39152},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - AGC 322753: a Dark Galaxy Candidate detected by ALFALFA and FASHI
AU - Marco Monaci
AU - Duncan A. Forbes
AU - Warrick J. Couch
AU - Jean P. Brodie
PY - 2026
DA - 2026/09/30
PB - arXiv
DO - 10.48550/arxiv.2609.39152
UR - https://arxiv.org/abs/2609.39152
AB - We report the possible detection of a Dark Galaxy Candidate (DGC; AGC 322753), via the cross-matching of the Arecibo Legacy Fast ALFA (ALFALFA) and the FAST All Sky HI (FASHI) HI blind surveys. It is detected by both surveys at the same recessional velocity, with a comparable HI mass of 2×10^9 M_⊙, and with similar HI spectral features. The ALFALFA and FASHI spectra show a double-peaked profile, compatible with a disc-like ordered rotation, and an HI linewidth at 50 per cent of the peak (W_50) of ∼85 km s^−1. The common intersection of the two beams allows the source position to be constrained with much greater precision than in either survey individually. Being detected by both radio telescopes, a Radio Frequency Interference (RFI) origin is excluded. No evidence of an optical counterpart was found down to ∼27.5 mag arcsec^−2 in the DESI Legacy Imaging Surveys, which leads to a stellar mass limit of M_⋆ ≲ 5×10^7 M_⊙. Given this stellar mass limit, AGC 322753 has M_HI/M_⋆ ≳ 40. The HI mass is higher than expected for totally starless haloes; this could imply that AGC 322753 is not completely 'dark' but could host a luminous counterpart below the current optical detection limit.
ER -