Discovery, Characterization, and Potential Origins of a Stream in the Stellar Halo of Nearby LMC-Mass Galaxy NGC 55
Abstract
We present a previously undetected stellar stream in the halo of the LMC-mass dwarf galaxy NGC 55 (2 Mpc), as part of an ongoing effort to characterize the stellar halos of LMC/SMC-mass dwarfs in the DEEP component of the DECam Local Volume Exploration (DELVE) survey. This structure is aligned with an outflow traced by Hα emission, a spur and cloud of neutral hydrogen, and the ultra-diffuse and possibly disrupting satellite galaxy NGC 55-dw1. We investigate possible ex-situ progenitor scenarios for this stream through the local luminosity-metallicity relation and a set of toy dynamical models that include gaseous, stellar, and dark matter components. If the stream is a product of a previous merger, the progenitor galaxy had an absolute magnitude MV ≤ −7.2 and a stellar mass M* ≥ 105 M⊙ based on extrapolations of the detected stellar populations. If it is disrupted material from the ultra-diffuse satellite, their shared progenitor had an absolute magnitude MV ≤ −8.3 and a stellar mass M* ≥ 105.2 M⊙. We compare our stream and progenitor scenarios to those for NGC 300, a galaxy with a stellar mass similar to that of NGC~55 and known to host multiple structures in its halo. Our results demonstrate that even relatively isolated LMC-mass galaxies can have complex accretion histories, providing new tests of hierarchical galaxy formation at low masses.
Related
- Diversity of planetary origins and compositions traced by stellar abundance differences among co-natal star systems
- When Streams Curve Away: a Test of Dark Matter from Extragalactic Stellar Stream Populations
- The multiple origins of spurs in stellar streams: a challenge for dark matter diagnostics
- Potamides: Mapping Dark Matter Halo Shapes from Stellar Stream Tracks in the Local Universe
- The Pristine survey XXXI. A stream offset from the Stream: very metal-poor stellar debris trailing 100∘ from the LMC-SMC system
BibTeX
@misc{velguth2026discovery,
title = {{Discovery, Characterization, and Potential Origins of a Stream in the Stellar Halo of Nearby LMC-Mass Galaxy NGC 55}},
author = {Benjamin N. Velguth and Burçin Mutlu-Pakdil and Erik Tollerud and Sarah Pearson and Kristine Spekkens and Amandine Doliva-Dolinsky and Michael G. Jones and Denija Crnojević and Jeffrey L. Carlin and David J. Sand and Paul Bennet and Guy Stringfellow and William Cerny and Alex Drlica-Wagner and Joanna D. Sakowska and Jaclyn Jensen and Laura C. Hunter and Eric F. Bell and David Martínez-Delgado and Anirudh Chiti and Adam Smercina and Nitya Kallivayalil and Deepthi S. Prabhu and Alexander H. Riley and Yumi Choi and Noelia E. D. Noël and Sasha N. Campana and Guinevere Herron and Alistair R. Walker and Andrew B. Pace and Clara E. Martínez-Vázquez and Clecio R. Bom and Julio A. Carballo-Bello and Pol Massana and Gustavo E. Medina},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.22071},
eprint = {2609.22071},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.22071},
}
RIS
TY - UNPB
TI - Discovery, Characterization, and Potential Origins of a Stream in the Stellar Halo of Nearby LMC-Mass Galaxy NGC 55
AU - Benjamin N. Velguth
AU - Burçin Mutlu-Pakdil
AU - Erik Tollerud
AU - Sarah Pearson
AU - Kristine Spekkens
AU - Amandine Doliva-Dolinsky
AU - Michael G. Jones
AU - Denija Crnojević
AU - Jeffrey L. Carlin
AU - David J. Sand
AU - Paul Bennet
AU - Guy Stringfellow
AU - William Cerny
AU - Alex Drlica-Wagner
AU - Joanna D. Sakowska
AU - Jaclyn Jensen
AU - Laura C. Hunter
AU - Eric F. Bell
AU - David Martínez-Delgado
AU - Anirudh Chiti
AU - Adam Smercina
AU - Nitya Kallivayalil
AU - Deepthi S. Prabhu
AU - Alexander H. Riley
AU - Yumi Choi
AU - Noelia E. D. Noël
AU - Sasha N. Campana
AU - Guinevere Herron
AU - Alistair R. Walker
AU - Andrew B. Pace
AU - Clara E. Martínez-Vázquez
AU - Clecio R. Bom
AU - Julio A. Carballo-Bello
AU - Pol Massana
AU - Gustavo E. Medina
PY - 2026
DA - 2026/09/18
PB - arXiv
DO - 10.48550/arxiv.2609.22071
UR - https://arxiv.org/abs/2609.22071
AB - We present a previously undetected stellar stream in the halo of the LMC-mass dwarf galaxy NGC 55 (2 Mpc), as part of an ongoing effort to characterize the stellar halos of LMC/SMC-mass dwarfs in the DEEP component of the DECam Local Volume Exploration (DELVE) survey. This structure is aligned with an outflow traced by Hα emission, a spur and cloud of neutral hydrogen, and the ultra-diffuse and possibly disrupting satellite galaxy NGC 55-dw1. We investigate possible ex-situ progenitor scenarios for this stream through the local luminosity-metallicity relation and a set of toy dynamical models that include gaseous, stellar, and dark matter components. If the stream is a product of a previous merger, the progenitor galaxy had an absolute magnitude M_V ≤ −7.2 and a stellar mass M_* ≥ 10^5 M_⊙ based on extrapolations of the detected stellar populations. If it is disrupted material from the ultra-diffuse satellite, their shared progenitor had an absolute magnitude M_V ≤ −8.3 and a stellar mass M_* ≥ 10^5.2 M_⊙. We compare our stream and progenitor scenarios to those for NGC 300, a galaxy with a stellar mass similar to that of NGC~55 and known to host multiple structures in its halo. Our results demonstrate that even relatively isolated LMC-mass galaxies can have complex accretion histories, providing new tests of hierarchical galaxy formation at low masses.
ER -