{
  "abstract": "We revisit the $M_{BH}-M_{bulge}$ relation for early-type galaxies by introducing a uniform bulge defined by dynamical decomposition. From the set of nearby galaxies with accurately measured black hole masses, we select 30 early-type galaxies that have been observed with wide-field integral-field unit instruments (MUSE, ATLAS3D, or PPAK). For each galaxy, we construct an orbit-superposition Schwarzschild model and obtain its stellar orbit distribution. In this framework, we define the bulge uniformly as comprising stellar orbits with circularity $λ_z < 0.7$ (or, in an alternative definition, $λ_z < 0.2$) and lying within $r < 3$ kpc. From these orbits, we reconstruct the spatial density distribution of the bulge and measure its mass ($M_{bulge}$), size ($R_{bulge}$) and surface density slope ($γ_{bulge}$). We find that the dynamical bulge defined by $λ_z < 0.7$ yields masses that are systematically consistent with the photometric bulge masses. Comparing to the bulge from photometric decomposition, using this dynamical bulge definition slightly decreases the scatter around the best-fitting from 0.56 to 0.47. More interestingly, we identify a clear trend: at a given bulge mass, galaxies hosting more compact bulges (i.e. smaller bulge sizes or steeper bulge density slopes) systematically contain more massive black holes; eight outliers show overmassive BHs together with ultra-compact bulges. We interpret this as direct observational evidence that the $M_{BH}-M_{bulge}$ relation evolves over a galaxy's merger history, with that history imprinted in bulge compactness. Incorporating compactness via an $M_{BH}-M_{bulge}-R_{e, bulge}$ (or $γ_{bulge}$) relation brings the outliers into agreement and reduces the overall scatter of the sample to $\\sim 0.3$.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2611.01469",
  "author_total": 7,
  "authors": [
    {
      "name": "Hanjing Shi"
    },
    {
      "name": "Ling Zhu"
    },
    {
      "name": "Sabine Thater"
    },
    {
      "name": "Yong Shi"
    },
    {
      "name": "Ana L. Chies-Santos"
    },
    {
      "name": "Luis Gabriel Dahmer Hahn"
    },
    {
      "name": "Zhengya Zheng"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/6q5n546ersc91.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2611.01469",
  "fulltext_url": null,
  "id": "6q5n546ersc91",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2611.01469",
  "language": null,
  "licence": "CC-BY-4.0",
  "licence_label": "CC BY 4.0",
  "licence_source": "article",
  "licence_url": "http://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "astro-ph.GA"
    ]
  ],
  "openalex": null,
  "pdf_url": "https://arxiv.org/pdf/2611.01469",
  "pmcid": null,
  "pmid": null,
  "published": "2026-11-01",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/6q5n546ersc91.ris",
  "sources": [
    {
      "first_seen": "2026-11-03T12:20:59Z",
      "native_id": "2611.01469",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2611.01469"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.GA",
      "subfield": "galaxies"
    }
  ],
  "title": "Dynamically defined bulges reveal that early-type galaxies with compact bulges host more massive black holes",
  "title_text": "Dynamically defined bulges reveal that early-type galaxies with compact bulges host more massive black holes",
  "type": "preprint",
  "updated_at": "2026-11-05T15:20:18Z",
  "url": "https://research.draconitic.com/paper/6q5n546ersc91",
  "venue": "arXiv",
  "versions": []
}