HI rotation curves and mass-size relation for 568 galaxies from the Apertif Wide-area Extragalactic Survey

summary

Video file (mp4)

The gist

The gist The extended H i rotation curves of galaxies are one of the most powerful tools for studying galaxy evolution and for testing different dark matter and modified gravity models Data

In short

Researchers analyzed kinematic models from 568 galaxies detected in HI using AWES data, creating the largest homogeneous sample of HI rotation curves to date. The study found that these disks become flat at large radii and exhibit a very tight mass-size relation, suggesting H I disks have a constant average surface density.

Key concepts

HI Rotation Curves
These are graphs showing how the speed of gas clouds changes as you move away from the center of a galaxy. They are powerful tools for studying how galaxies evolve and test theories about dark matter or gravity by measuring the gravitational pull.
Mass-Size Relation
This describes the relationship between how much gas (HI mass) a galaxy has and its physical size. The study found this relation is extremely tight, meaning galaxies of similar sizes have very similar amounts of HI gas, implying a consistent average density.
Surface Density Profile
This profile maps how the density of neutral hydrogen gas changes across the face of a galaxy. By studying these profiles, researchers inferred that H I disks maintain an almost constant average surface density throughout their extent.
Kinematic Modeling (3DBAROLO)
This is the computational method used to create 3D models of galaxy rotation based on observed line data. The code accounts for instrumental effects like beam smearing, allowing researchers to recover true rotation velocities even in galaxies with limited resolution.

Terminology used across episodes

This episode discusses

The paper

HI rotation curves and mass-size relation for 568 galaxies from the Apertif Wide-area Extragalactic Survey · Read on arXiv

Konstantin Haubner, Federico Lelli, Enrico Di Teodoro, Kelley M. Hess, Francis Duey, Stacy McGaugh, James Schombert, Elizabeth A. K. Adams, W.J.G. de Blok, Danielle M. Lucero, Helga Dénes, Julián Garrido, Joeri van Leeuwen, Manuel Parra-Royón, Anastasia A. Ponomareva, Susana Sánchez Exposito

INAF – Arcetri Astrophysical Observatory · Dipartimento di Fisica e Astronomia, Università degli Studi di Firenze · Department of Space, Earth and Environment, Chalmers University of Technology · Netherlands Institute for Radio Astronomy (ASTRON) · Instituto de Astrofísica de Andalucía (CSIC) · Department of Astronomy, Case Western Reserve University · Department of Physics, University of Oregon · SKA Observatory SKA-Mid Science Operations Centre · Kapteyn Astronomical Institute, University of Groningen · Department of Astronomy, University of Cape Town · Department of Physics, Virginia Tech · College of Sciences and Engineering, Universidad San Francisco de Quito · Centre for Astrophysics Research, School of Physics, Astronomy and Mathematics, University of Hertfordshire

The extended HI rotation curves of galaxies are one of the most powerful tools for studying galaxy evolution and for testing different dark matter and modified gravity models. However, their sample sizes have historically been limited to a few hundred galaxies, mostly due to the survey speed of radio interferometers. Here, we present a first data release of HI kinematic models from the Apertif Wide-area Extragalactic Survey (AWES). Starting from 1924 galaxies detected in HI, we constructed 568 reliable kinematic models, which provide rotation curves, velocity dispersion profiles, surface density profiles, and HI disk geometries. This dataset constitutes the largest homogeneous HI rotation curve sample to date. The HI disks of the modeled galaxies span three orders of magnitude in HI mass, have outer rotation velocities between 20 and 300 km/s, and extend from 2 to more than 60 kpc. The number of data points of the rotation curves ranges from 3 to 23, with a peak value at 4 and a broad tail to larger values. The rotation curves display a variety of inner shapes, but in general, they tend to become flat at large radii. Based on the HI surface density profiles derived during the kinematic modeling, we studied the HI mass-size relation with a large homogeneous sample of 213 galaxies. The relation is very tight, with an observed scatter along the mass direction of 0.101 dex and an inferred intrinsic scatter along the same direction of only 0.067 +/- 0.007 dex. The best fitting slope is 1.96 +/- 0.03 when fitting for mass as a function of size, indicating that HI disks have a constant average surface density.

DOI: 10.1051/0004-6361/202661305

Transcript

Introduction to the show: ident: Astrophysics Radio. Generated commentary on the latest astrophysics papers.

Vera: I'm Vera.

Jocelyn: And I'm Jocelyn, here with Subrahmanyan.

Vera: We're looking at the paper: "HI rotation curves and mass-size relation for 568 galaxies from the Apertif Wide-area Extragalactic Survey".

Jocelyn: The gist The extended H i rotation curves of galaxies are one of the most powerful tools for studying galaxy evolution and for testing different dark matter and modified gravity…

Vera: First, who's behind it and why it matters.

Paper summary: Vera: We started by looking at the title, "HI rotation curves and mass-size relation for five hundred sixty-eight galaxies from the Apertif Wide-area Extragalactic Survey," and it’s clear this work is focused on building a robust database of these key galaxy properties using this survey <ref:2610.20718#pg1>.

Vera: What this means in simple terms is that when you look at a galaxy's size, you can predict its HI mass with very little error, and this consistency across so many galaxies tells us something fundamental about how these gas disks are organized <ref:2610.20718#pg2>.

Jocelyn: It reinforces the idea that H i disks have an almost constant average surface density across a huge range of masses and sizes, which they describe in the context of the paper <ref:2610.20718#pg2>.

Subrahmanyan: That constancy in surface density is what makes this dataset so useful for testing different theoretical explanations for why galaxies look the way they do, especially concerning stellar feedback and how gas settles <ref:2610.20718#pg2>.

Jocelyn: This paper lays down a very strong foundation with this large sample, and it points us toward needing higher resolution data later on for truly detailed inner structure studies <ref:2610.20718#pg3>.

Conclusion: Vera: So we've seen how they built this big database of rotation curves from the Apertif survey, and it’s clear the focus is on building this robust dataset <ref:2610.20718#pg1>.

Jocelyn: It’s interesting how they managed to get five hundred sixty-eight reliable models from that data set, which is a lot more than what we've seen for homogeneous HI rotation curve samples before <ref:2610.20718#pg1>.

Subrahmanyan: That sample size is substantial when you’re trying to test structure formation models because it allows for tighter constraints on the mass-size relation <ref:2610.20718#pg3>.

Vera: Yeah, they've put together a very tight relationship between the HI mass and the physical size of these galaxies, showing that the average surface density of the HI disk stays pretty constant regardless of whether you're looking at a small or a large galaxy <ref:2610.20718#pg2>.

Jocelyn: And they found that this mass-size relationship has very little scatter when you look at it, with an intrinsic error of only zero point zero six seven plus or minus zero point zero three four dex along the mass direction <ref:2610.20718#pg2>.

Subrahmanyan: That tight scatter, with that intrinsic error of zero point zero six seven plus or minus zero point zero three four dex, really constrains the physics driving that gas distribution and helps us see if our theories about dark matter halos match up <ref:2610.20718#pg2>.

Vera: It suggests a fairly universal way these disks settle into their final shape as they grow over cosmic time, based on the findings in "HI rotation curves and mass-size relation for five hundred sixty-eight galaxies from the Apertif Wide-area Extragalactic Survey" <ref:2610.20718#pg2>.

Jocelyn: The authors are pointing toward using this kind of tight constraint to test models that predict different density profiles for these galaxies, which is why they need higher resolution data later on <ref:2610.20718#pg3>.

Subrahmanyan: If the theory predicts a shallower slope for that mass-size relation than what they observed here, it won't match what they found in this paper <ref:2610.20718#pg2>.

Vera: The data itself is robust because they’ve done a lot of work on modeling and checking those kinematic pipelines to make sure the results are clean for these five hundred sixty-eight galaxies <ref:2610.20718#pg3>.

Jocelyn: This sets a good benchmark for what we might expect from higher resolution observations in the future, like what the WEAVE-Apertif project aims to do <ref:2610.20718#pg3>.

Subrahmanyan: We need that high resolution data to confirm these density profiles because current models struggle with those inner regions of galaxies <ref:2610.20718#pg3>.

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