Robust H i kinematics of gas-rich ultra-diffuse galaxies: hints of a weak-feedback formation scenario

Mancera Piña, Pavel E.; Fraternali, Filippo; Oman, Kyle A.; Adams, Elizabeth AK; Bacchini, Cecilia; Marasco, Antonino; Oosterloo, Tom; Pezzulli, Gabriele; Posti, Lorenzo; Leisman, Lukas; Cannon, John M.; di Teodoro, Enrico M.; Gault, Lexi; Haynes, Martha P.; Reiter, Kameron; Rhode, Katherine L.; Salzer, John J.; Smith, Nicholas J.

Abstract

We study the gas kinematics of a sample of six isolated gas-rich low surface brightness galaxies, of the class called ultra-diffuse galaxies (UDGs). These galaxies have recently been shown to be outliers from the baryonic Tully–Fisher relation (BTFR), as they rotate much slower than expected given their baryonic mass, and to have a baryon fraction similar to the cosmological mean. By means of a 3D kinematic modelling fitting technique, we show that the H I in our UDGs is distributed in ‘thin’ regularly rotating discs and we determine their rotation velocity and gas velocity dispersion. We revisit the BTFR adding galaxies from other studies. We find a previously unknown trend between the deviation from the BTFR and the exponential disc scale length valid for dwarf galaxies with circular speeds ≲ 45 km s−1, with our UDGs being at the extreme end. Based on our findings, we suggest that the high baryon fractions of our UDGs may originate due to the fact that they have experienced weak stellar feedback, likely due to their low star formation rate surface densities, and as a result they did not eject significant amounts of gas out of their discs. At the same time, we find indications that our UDGs may have higher-than-average stellar specific angular momentum, which can explain their large optical scale lengths.

Citation

Mancera Piña, P. E., Fraternali, F., Oman, K. A., Adams, E. A., Bacchini, C., Marasco, A., Oosterloo, T., Pezzulli, G., Posti, L., Leisman, L., Cannon, J. M., di Teodoro, E. M., Gault, L., Haynes, M. P., Reiter, K., Rhode, K. L., Salzer, J. J., & Smith, N. J. (2020). Robust H i kinematics of gas-rich ultra-diffuse galaxies: hints of a weak-feedback formation scenario. Monthly Notices of the Royal Astronomical Society, 495(4), 3636-3655. https://doi.org/10.1093/mnras/staa1256

• Journal Article Type: Article
• Acceptance Date: Apr 29, 2020
• Online Publication Date: May 7, 2020
• Publication Date: 2020-07
• Deposit Date: Jul 31, 2020
• Publicly Available Date: Jul 31, 2020
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Publisher: Royal Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 495
• Issue: 4
• Pages: 3636-3655
• DOI: https://doi.org/10.1093/mnras/staa1256
• Public URL: https://durham-repository.worktribe.com/output/1265096