{
  "abstract": "We aim to provide a cookbook for purely astrometric selection of quasars with Gaia DR3 and to provide an example of its use for the identification of very luminous $z>2$ quasars. We analyse the Gaia DR3 astrometry of confirmed quasars and stationary sources. We show that the proper motion signal to noise $μ/σ_μ$ follows a Rayleigh-like distribution. We also show the importance of properly taking into account the correlation between proper motions in right ascension and declination, as well as the non-linear error propagation. We adopt the Mahalanobis distance to the null proper-motion hypothesis. A scaled $χ^2$ distribution with $k=2$ and scale $s=1.1485$ is fitted to Gaia-CRF3; the corresponding $\\pm2σ$ Gaussian-equivalent threshold is $D^2_{M(μ)}<7.097$. The final criteria combine this with the parallax condition and $\\mathrm{ruwe}<1.4$. Applying the new criteria to the SDSS DR16Q confirmed quasars, the recovery rate is $90.25\\%$. The suggested purely astrometric selection significantly improves both completeness and purity compared to other strategies used in the literature, reaching a quasar purity of approximately $95\\%$ ($\\sim2σ$ Gaussian-equivalent). It can be used to improve the selection purity and completeness for future quasar surveys. As an example, we use the suggested strategi to locate 24 very bright $z>2$ quasars without redshifts in the literature. Our proposed astrometric selection strategy recovers 95\\% of known quasars. Its potential use for new discoveries is demonstrated by the identification of 24 very luminous $z>2$ quasars. Ten of these are new discoveries and for an additional seven we correct the redshifts determined by other methods.}",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2610.13742",
  "author_total": 2,
  "authors": [
    {
      "name": "J. Li"
    },
    {
      "name": "J. P. U. Fynbo"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/5k81tjxnrmnw4.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2610.13742",
  "fulltext_url": null,
  "id": "5k81tjxnrmnw4",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2610.13742",
  "language": null,
  "licence": "LicenseRef-arXiv-nonexclusive-1.0",
  "licence_label": "arXiv licence",
  "licence_source": "article",
  "licence_url": "http://arxiv.org/licenses/nonexclusive-distrib/1.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "astro-ph.GA"
    ],
    [
      "openalex",
      "3103|Galaxies: Formation, Evolution, Phenomena"
    ]
  ],
  "openalex": "W7221560345",
  "pdf_url": "https://arxiv.org/pdf/2610.13742",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-09",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/5k81tjxnrmnw4.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:28:36Z",
      "native_id": "2610.13742",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2610.13742"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.GA",
      "subfield": "galaxies"
    }
  ],
  "title": "A strategy for astrometric quasar selection with Gaia DR3 and its application to discover new luminous $z>2$ quasars",
  "title_text": "A strategy for astrometric quasar selection with Gaia DR3 and its application to discover new luminous z>2 quasars",
  "type": "preprint",
  "updated_at": "2026-11-09T00:20:37Z",
  "url": "https://research.draconitic.com/paper/5k81tjxnrmnw4",
  "venue": "arXiv",
  "versions": []
}