The HI content of isolated ultra-diffuse galaxies: A sign of multiple formation mechanisms?
Abstract
We report on the results of radio observations in the 21 cm emission line of atomic hydrogen (HI) of four relatively isolated ultra-diffuse galaxies (UDGs): DGSAT I, R-127-1, M-161-1, and SECCO-dI-2. Our Effelsberg observations resulted in non-detections for the first three UDGs, and a clear detection for the last. DGSAT I, R-127-1, and M-161-1 are quiescent galaxies with gas fractions that are much lower than those of typical field galaxies of the same stellar mass. On the other hand, SECCO-dI-2 is a star forming gas-rich dwarf, similar to two other field UDGs that have literature HI data: SECCO-dI-1 and UGC 2162. This group of three gas-rich UDGs have stellar and gaseous properties that are compatible with a recently proposed theoretical mechanism for the formation of UDGs, based on feedback-driven outflows. In contrast, the physical characteristics of R-127-1 and M-161-1 are puzzling, given their isolated nature. We interpret this dichotomy in the gaseous properties of field UDGs as a sign of the existence of multiple mechanisms for their formation, with the formation of the quiescent gas-poor UDGs remaining a mystery.
- Publication:
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Astronomy and Astrophysics
- Pub Date:
- May 2017
- DOI:
- 10.1051/0004-6361/201730795
- arXiv:
- arXiv:1703.05610
- Bibcode:
- 2017A&A...601L..10P
- Keywords:
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- galaxies: dwarf;
- galaxies: formation;
- galaxies: ISM;
- galaxies: fundamental parameters;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- Accepted by A&