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A Unified H i Rotation Curve Database for 129 Local Volume Dwarf and Irregular Galaxies

This paper presents a unified, machine-readable database of standardized H i rotation curve data and kinematic parameters for 129 dwarf and irregular galaxies from four Local Volume surveys, designed to facilitate cross-survey analysis and retrieval-augmented generation applications.

Original authors: David C. Flynn

Published 2026-05-22

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CC BY 4.0

Original authors: David C. Flynn

Original paper licensed under CC BY 4.0 (http://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

Imagine you have four different libraries, each filled with books about the same neighborhood of small, quirky houses (dwarf and irregular galaxies). However, each library uses a completely different filing system, different handwriting styles, and different ways of measuring the houses. One library measures the height in feet, another in meters; one lists the owner's name, another just a code. If you wanted to compare all the houses at once, it would be a nightmare.

This paper is the author's solution to that mess. They have built a universal translator and a single, giant filing cabinet for 129 of these small galaxies.

Here is the breakdown of what they did, using simple analogies:

1. The Big Cleanup (The Database)

The author gathered data from four major astronomical surveys (LVHIS, VLA-ANGST, LITTLE THINGS, and WALLABY). Instead of leaving them as separate, messy piles of data, they standardized everything into a single, clean format (like converting all the books into the same font and layout).

The Result: A "Unified H i Rotation Curve Database." Think of this as a master spreadsheet where every galaxy has the same 27 fields of information, from its name and location to how fast it spins.
The Formats: They made this data available in formats that computers can easily read and talk to (JSON, CSV), which is like giving the library a digital robot that can instantly find any fact you ask for.

2. The Quality Control (The "Tier" System)

Not all the data in the library is equally good. Some entries are like a full, detailed biography of a galaxy, while others are just a single sentence summary. The author created two "Quality Tiers" to help users know what they are getting:

Tier 1 (The VIPs): 26 galaxies with "full multi-point" data. Imagine these are galaxies where we have a high-definition video of their spin, showing every twist and turn.
Tier 2 (The Summaries): 103 galaxies with "single-point" estimates. These are like a snapshot or a quick guess based on the width of the galaxy's gas cloud. It's useful, but less detailed.

3. The "Omega" Test (The Special Filter)

The author is interested in a specific mathematical idea called the $\omega$ (omega) correction.

The Analogy: Imagine you are watching a carousel. Usually, you expect the horses on the outside to move faster than the ones on the inside. But in some galaxies, the math gets weird. The author has a special "filter" (the $\omega$ correction) that checks if the galaxy spins in a way that matches a specific pattern they've seen in bigger galaxies before.
The "Omega-Ready" List: They filtered their database to find 24 galaxies that are "ready" for this test. These are the ones with enough detailed data (Tier 1) to see if the pattern holds true even for these tiny, dark-matter-heavy dwarfs.

4. Three Quick Examples

To show how useful this new database is, the author ran three simple tests:

The Lookup: They asked, "Tell me everything about galaxy IC 5152," and the database instantly gave the answer (it's a dwarf galaxy spinning at a specific speed).
The Group Filter: They asked, "Show me all the slow-spinning galaxies in the Centaurus A group," and the database found 11 of them.
The Math Test: They applied their special "omega" math to a galaxy called DDO 154. The result matched what they expected from bigger galaxies, suggesting the same rules might apply to both big and small galaxies.

5. What This Paper Is (and Isn't)

What it IS: It is a tool. It is a massive, organized collection of data designed to help other scientists do their own research. It's like handing a researcher a perfectly organized toolbox instead of a pile of loose screws.
What it ISN'T: The author is clear that they are not proposing a new theory of gravity or a new model of how the universe works. They are just organizing the data so others can test those theories. They are the librarians, not the authors of the new story.

The Bottom Line

This paper is a "data resource." It takes 129 messy, scattered galaxy datasets, cleans them up, organizes them into a single, easy-to-use format, and flags the best ones for a specific type of math test. It's a foundation for future discoveries, but the discovery itself belongs to whoever uses this new database next.

Where to find it: The author has put the entire database and the computer code used to build it on a public website called Zenodo, so anyone can download and use it.

Technical Summary: A Unified H i Rotation Curve Database for 129 Local Volume Dwarf and Irregular Galaxies

Problem Statement
Despite the scientific importance of dwarf and irregular galaxies as probes of baryonic mass, dark matter fractions, and kinematic relationships, no unified kinematic corpus exists that aggregates data from the four major Local Volume H i surveys (LVHIS, VLA-ANGST, LITTLE THINGS, and WALLABY DR2) in a machine-readable, schema-consistent format. Existing catalogs utilize disparate column conventions, distance estimation methods, and quality flags, which hinders cross-survey comparison and limits the utility of these datasets for retrieval-augmented generation (RAG) applications.

Methodology
The authors assembled and standardized rotation curve data from 129 dwarf and irregular galaxies drawn from four specific surveys:

LVHIS (33 galaxies): Ingested from Koribalski et al. (2019), excluding massive spirals and ellipticals. Data consists of single best-fit rotation velocities from published tilted-ring models.
VLA-ANGST (29 galaxies): Ingested from Ott et al. (2012), utilizing single-point profile-width estimates ( $V_{rot}$ derived from $W_{20}/2 \sin i$ ).
LITTLE THINGS (26 galaxies): Transferred from the Flynn (2026b) v7.0 corpus, retaining full multi-point tilted-ring rotation curves for galaxies with Q=1 quality flags.
WALLABY DR2 (41 galaxies): Filtered from the Flynn (2026b) v7.0 component based on morphology and peak rotation velocity, including Barolo tilted-ring models where available.

Data Construction and Schema
The resulting database is a unified JSON/CSV/JSONL corpus containing 27 standardized fields per galaxy. Key fields include identification, coordinates, morphology, distance (with method), kinematic parameters (inclination, position angle, peak rotation velocity), HI properties, and rotation curve data arrays.

Quality Tiers: The database distinguishes between two tiers:
- Tier 1 (26 galaxies): Full multi-point tilted-ring rotation curves (all LITTLE THINGS and multi-point WALLABY entries).
- Tier 2 (103 galaxies): Single-ring or profile-width velocity estimates (all LVHIS and VLA-ANGST entries).
Omega-Readiness: A specific flag (omega_ready) identifies galaxies suitable for the $\omega$ kinematic correction. This requires a quality tier of 1, at least 5 data points, and a kinematically regular rotation field. This criteria yielded 24 galaxies, all from the LITTLE THINGS survey. Two LITTLE THINGS galaxies (IC 10 and NGC 3738) were excluded due to high observational uncertainty relative to signal or anomalous inclination and velocity parameters.

Key Results and Worked Examples
The paper presents the database as a resource rather than a new dynamical model, demonstrating its utility through three query examples:

Single-Galaxy Query: Retrieval of kinematic parameters for IC 5152 (LVHIS), confirming its status as a Sculptor group member with specific inclination and rotation velocity.
Population Filter: Identification of 11 Centaurus A group members with peak rotation velocities below 80 km s $^{-1}$ .
Kinematic Correction Application: Application of the Flynn & Cannaliato (2025) two-boundary kinematic correction to DDO 154 (LITTLE THINGS). Using inner and outer boundary points, the calculated angular velocity offset ( $\omega$ ) was $6.162$ rad Gyr $^{-1}$ . This value is consistent with the mean of the SPARC spiral population ( $7.06 \pm 3.26$ rad Gyr $^{-1}$ ) and yields a negative outer gap ( $V_{adj} - V_{obs}$ ), aligning with previous findings on SPARC Q=1 spirals.

Significance and Claims
The primary significance of this work is the provision of a standardized, machine-readable corpus that enables retrieval-augmented generation (RAG) and systematic cross-survey kinematic analysis.

Descriptive Utility: The corpus allows for the testing of whether the kinematic regularity identified in massive spirals (via the $\omega$ correction) persists in genuinely dark-matter-dominated dwarfs where baryonic disk physics differs fundamentally.
Limitations: The authors explicitly note that the current corpus lacks full baryonic decomposition for the LITTLE THINGS sample, preventing a complete RMSE comparison between adjusted and baryonic velocities for the $\omega$ correction. Additionally, systemic velocities are missing for LVHIS entries, and five WALLABY galaxies exceed the strict Local Volume distance definition.
Scope: The paper clarifies that the $\omega$ correction is treated strictly as an empirical kinematic descriptor; no modification to Newtonian or relativistic gravity is proposed. The work serves as a data foundation for future cross-matching with HI mass models and cosmological simulations.

All numerical results and data processing were performed by the author using Python-based tools on a local HPC cluster, with AI assistance limited to manuscript review and formatting.