The Smallest Scale of Hierarchy Survey (SSH)

We present new deep, wide-field imaging data from the Large Binocular Telescope (LBT) in g and r bands from the Smallest Scale of Hierarchy Survey (SSH) that reveal previously undetected tidal features and stellar streams in the outskirts of six dwarf irregular galaxies (NGC 5238, UGC 6456, UGC 6541, UGC 7605, UGC 8638, and UGC 8760) with stellar masses in the range 1.2 × 10 7 M ⊙ to 1.4 × 10 8 M ⊙ . The six dwarfs are located 1-2 Mpc away from large galaxies, which implies that the observed distortions are unlikely to be due to tidal effects from a nearby, massive companion. At the distances of ~3-4 Mpc at which the dwarfs lie, the identified tidal features are all resolved into individual stars in the LBT images and appear to consist of a population older than 1–2 Gyr. This excludes the possibility that they result from irregular and asymmetric star formation episodes that are common in gas-rich dwarf galaxies. The most plausible explanation is that we witness the hierarchical merging assembly of these dwarfs with their satellite populations. This scenario is also supported by the peculiar morphology and disturbed velocity field of their HI component. From the SSH sample, we estimate that a fraction of ~13% of the late-type dwarfs show signs of merging with satellites. This is in agreement with other recent independent studies and theoretical predictions within the ΛCDM cosmological framework.

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Publication Details

Journal
Astronomy and Astrophysics
Published
2024-09-23
DOI
https://doi.org/10.1051/0004-6361/202450106
Citations
4
Primary Topic
Astronomy and Astrophysical Research
Type
article
Field-Weighted Citation Impact
2.03
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The Smallest Scale of Hierarchy Survey (SSH)

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The Smallest Scale of Hierarchy Survey (SSH)

L. K. Hunt, Liese van Zee, John M. Cannon, M. Cignoni, D. Paris, M. Bellazzini, M. Tosi, Elena Sacchi, G. Beccari, R. Pascale, Sambit Roychowdhury, F. Annibali, F. Cusano, Lila Schisgal, Roelof S. de Jong, Laura E. Hunter
article en
4 citations

Abstract

We present new deep, wide-field imaging data from the Large Binocular Telescope (LBT) in g and r bands from the Smallest Scale of Hierarchy Survey (SSH) that reveal previously undetected tidal features and stellar streams in the outskirts of six dwarf irregular galaxies (NGC 5238, UGC 6456, UGC 6541, UGC 7605, UGC 8638, and UGC 8760) with stellar masses in the range 1.2 × 10 7 M ⊙ to 1.4 × 10 8 M ⊙ . The six dwarfs are located 1-2 Mpc away from large galaxies, which implies that the observed distortions are unlikely to be due to tidal effects from a nearby, massive companion. At the distances of ~3-4 Mpc at which the dwarfs lie, the identified tidal features are all resolved into individual stars in the LBT images and appear to consist of a population older than 1–2 Gyr. This excludes the possibility that they result from irregular and asymmetric star formation episodes that are common in gas-rich dwarf galaxies. The most plausible explanation is that we witness the hierarchical merging assembly of these dwarfs with their satellite populations. This scenario is also supported by the peculiar morphology and disturbed velocity field of their HI component. From the SSH sample, we estimate that a fraction of ~13% of the late-type dwarfs show signs of merging with satellites. This is in agreement with other recent independent studies and theoretical predictions within the ΛCDM cosmological framework.

Astronomy and AstrophysicsVol. 691
Dartmouth College (US), University of Pisa (IT), European Southern Observatory (DE), Istituto Nazionale di Fisica Nucleare (IT), Leibniz Institute for Astrophysics Potsdam (DE), Arcetri Astrophysical Observatory (IT), Astronomical Observatory of Rome (IT), Indiana University Bloomington (US), Istituto Nazionale di Fisica Nucleare, Sezione di Pisa (IT), Osservatorio di Astrofisica e Scienza dello Spazio, Macalester College (US), Ludwig-Maximilians-Universität München (DE), National Institute for Astrophysics (IT)
Openalex Percentile: Top 12%
Astronomy and Astrophysical Research
2.03
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