[Paper Review] Hydrogen tails, plumes, clouds and filaments

B. Koribalski|arXiv (Cornell University)|Feb 18, 2020

Galaxies: Formation, Evolution, Phenomena4 citations

TL;DR

This paper reviews extended low-surface-brightness (LSB) neutral hydrogen (H i) structures—such as tidal tails, plumes, clouds, and filaments—in interacting galaxy systems, emphasizing their role in tracing gravitational interactions and ram pressure in galaxy groups and clusters. Using deep H i surveys and simulations, the study identifies massive H i features spanning hundreds of kiloparsecs, with key discoveries including the Magellanic Stream (180 kpc, 2.7×10⁸ M⊙) and large H i clouds like HIPASS J0731–69 (10⁹ M⊙), and highlights upcoming surveys like WALLABY and MeerKAT for detecting dark H i structures without stellar counterparts.

ABSTRACT

Here I present a brief review of interacting galaxy systems with extended low surface brightness (LSB) hydrogen tails and similar structures. Typically found in merging pairs, galaxy groups and clusters, HI features in galaxy surroundings can span many hundreds of kpc, tracing gravitational interactions between galaxies and ram pressure forces moving through the intra-group/cluster medium. Upcoming large HI surveys, e.g., with the wide-field (FOV = 30 square degrees) Phased Array Feeds on the Australian SKA Pathfinder (ASKAP), will provide a census of LSB structures in the Local Universe. By recording and comparing the properties (length, shape, HI mass, etc.) of these observed structures and their associated galaxies, we can - using numerical simulations - try to establish their origin and evolutionary path.

Motivation & Objective

• To compile and analyze a comprehensive catalog of extended low-surface-brightness H i structures in the Local Universe, including tidal tails, plumes, clouds, and filaments.
• To quantify the H i mass, length, and kinematics of these features to understand their origin and evolutionary pathways in galaxy interactions.
• To bridge optical and radio observations by correlating H i structures with stellar streams and tidal dwarf galaxies, especially where no stellar counterparts are detected.
• To prepare for upcoming wide-field H i surveys (e.g., WALLABY on ASKAP) by developing tools for detecting and classifying diffuse H i features in large 3D data volumes.
• To assess the detectability of H i tails and debris at cosmological distances using simulated H i images of merging systems.

Proposed method

• Compilation of observed H i structures from wide-field surveys (e.g., HIPASS, ASKAP, MeerKAT) and deep interferometric observations, with morphological classification and kinematic analysis.
• Use of 3D H i data cubes to measure H i mass, size, and velocity structure, accounting for projection effects and diffuse emission.
• Application of the modular Source Finding Application (SoFiA) to detect and classify extended H i features in large survey data volumes.
• Integration of single-dish and interferometric data to recover both dense clumps and diffuse H i emission, particularly in extended structures.
• Use of numerical simulations (e.g., of tidal interactions and ram pressure) to model and interpret observed H i morphologies and kinematics.
• Comparison of observed H i features with simulated H i images of merging systems (e.g., Arp 299 at z=0.1–0.6) to assess detectability at high redshift.

Experimental results

Research questions

• RQ1 What is the origin and evolutionary path of extended H i structures such as tidal tails, plumes, and detached clouds in galaxy groups and clusters?
• RQ2 How do the kinematics and morphology of H i features correlate with stellar tidal tails and star formation in interacting systems?
• RQ3 To what extent do H i structures trace gravitational interactions and ram pressure stripping in galaxy clusters?
• RQ4 What fraction of H i mass in galaxy systems is found in diffuse, low-surface-brightness structures without associated stars?
• RQ5 How will upcoming wide-field H i surveys like WALLABY and MeerKAT improve the detection and characterization of dark H i clouds and tidal debris?

Key findings

• The Magellanic Stream spans at least 180 kpc and contains 2.7×10⁸ M⊙ of H i, tracing interactions between the Milky Way and the Magellanic Clouds.
• HIPASS J0731–69 is a massive H i cloud with 10⁹ M⊙, located 200 kpc from NGC 2442, composed of clumps along a partial loop.
• Four large H i clouds, spanning ~500 kpc, were discovered around the elliptical galaxy NGC 1490, indicating widespread H i debris in group environments.
• H i rings of ~200 kpc diameter were detected around E/S0 galaxies M 105, NGC 5291, and NGC 1533, likely formed via tidal interactions.
• The NGC 2782 system hosts a 54 kpc western H i plume with 1.4×10⁹ M⊙, accounting for ~40% of the system’s total H i mass, consistent with a recent off-center collision.
• In Arp 299, a 180 kpc northern H i tail is present but barely visible in optical, accompanied by a faint LSB stellar tail offset by ~20 kpc, indicating H i dominance in tidal debris.