---
title: "AGC 322753: A dark galaxy candidate detected by ALFALFA and FASHI"
description: "ABSTRACT We report the possible detection of a dark galaxy candidate (AGC 322753), via the cross-matching of the Arecibo Legacy Fast ALFA (ALFALFA) and the FAST All Sky H i (FASHI) H i blind surveys. It is detected by both surveys at the same recessional velocity, with a comparable H i mass of $2 \\times 10^{9} \\ {\\rm…"
datePublished: "2026-10-13"
lastmod: "2026-10-27T12:39:04+00:00"
authors:
  - "Marco Monaci"
  - "Duncan A Forbes"
  - "Warrick J Couch"
  - "Jean P Brodie"
journal: "Monthly Notices of the Royal Astronomical Society"
publisher: "Oxford University Press (OUP)"
doi: "10.1093/mnras/stag1874"
publicationType: "journal-article"
schemaType: "ScholarlyArticle"
volume: "552"
issue: "4"
license: "https://creativecommons.org/licenses/by/4.0/"
sponsor: "AGC; Australian Research Council; NASA; U.S. Department of Energy Office of Science; Chinese Academy of Sciences; Chinese National Natural Science Foundation"
language: "en-GB"
slug: "10.1093-mnras-stag1874"
---

# AGC 322753: A dark galaxy candidate detected by ALFALFA and FASHI

**Authors:** Marco Monaci, Duncan A Forbes, Warrick J Couch, Jean P Brodie  
**Journal:** Monthly Notices of the Royal Astronomical Society  
**Publisher:** Oxford University Press (OUP)  
**Published:** 2026-10-13  
**Volume:** 552  
**Issue:** 4  
**DOI:** [10.1093/mnras/stag1874](https://dx.doi.org/10.1093/mnras/stag1874)

## Abstract

ABSTRACT We report the possible detection of a dark galaxy candidate (AGC 322753), via the cross-matching of the Arecibo Legacy Fast ALFA (ALFALFA) and the FAST All Sky H i (FASHI) H i blind surveys. It is detected by both surveys at the same recessional velocity, with a comparable H i mass of $2 \times 10^{9} \ {\rm M}$1\odot$, and with similar H i spectral features. The ALFALFA and FASHI spectra show a double-peaked profile, compatible with a disc-like ordered rotation, and an H i linewidth at 50 per cent of the peak (W$$1{50}$) of $\sim 85$ 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 origin is excluded. No evidence of an optical counterpart was found down to $\sim$ 27.5 mag arcsec$^{-2}$ in the DESI Legacy Imaging Surveys, which leads to a stellar mass limit of $M$1\bigstar \lesssim 5 \times 10^7 \ {\rm M}$1\odot$. Given this stellar mass limit, AGC 322753 has $M$1{\rm H\,{\small I}}/M$1\bigstar \gtrsim 40$. The H i 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.

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