Dark Matter Halos are Capable of Stripping Galaxies of Gasby Tommy on 17/01/2017
This result clearly indicates the particulate nature of dark matter axions.
This doesn’t bode well for modified gravity theories of dark matter.
Cold gas stripping in satellite galaxies: from pairs to clusters, Toby Brown, Barbara Catinella, Luca Cortese, Claudia del P. Lagos, Romeel Dave, Virginia Kilborn, Martha P. Haynes, Riccardo Giovanelli and Mika Rafieferantsoa, MNRAS, 466, 2, 1275-1289 (16 January 2017) doi:10.1093/mnras/stw2991
In this paper we investigate environment driven gas depletion in satellite galaxies, taking full advantage of the atomic hydrogen (HI) spectral stacking technique to quantify the gas content for the entire gas-poor to -rich regime. We do so using a multi-wavelength sample of 10,600 satellite galaxies, selected according to stellar mass (log M⋆/M⊙ ≥ 9) and redshift (0.02 ≤ z ≤ 0.05) from the Sloan Digital Sky Survey, with HI data from the Arecibo Legacy Fast ALFA (ALFALFA) survey. Using key HI-to-stellar mass scaling relations, we present evidence that the gas content of satellite galaxies is, to a significant extent, dependent on the environment in which a galaxy resides. For the first time, we demonstrate that systematic environmental suppression of gas content at both fixed stellar mass and fixed specific star formation rate (sSFR) in satellite galaxies begins in halo masses typical of the group regime (log Mh/M⊙ < 13.5), well before galaxies reach the cluster environment. We also show that environment driven gas depletion is more closely associated to halo mass than local density. Our results are then compared with state-of-the-art semi-analytic models and hydrodynamical simulations and discussed within this framework, showing that more work is needed if models are to reproduce the observations. We conclude that the observed decrease of gas content in the group and cluster environments cannot be reproduced by starvation of the gas supply alone and invoke fast acting processes such as ram-pressure stripping of cold gas to explain this.
See also: https://arxiv.org/abs/1701.01754
xGASS: Gas-rich central galaxies in small groups and their connections to cosmic web gas feeding, Steven Janowiecki, Barbara Catinella, Luca Cortese, Amélie Saintonge, Toby Brown and Jing Wang, Accepted to MNRAS (6 January 2017)
We use deep HI observations obtained as part of the extended GALEX Arecibo SDSS survey (xGASS) to study the cold gas properties of central galaxies across environments. We find that, below stellar masses of 1010.2 M⊙, central galaxies in groups have an average atomic hydrogen gas fraction ~ 0.3 dex higher than those in isolation at the same stellar mass. At these stellar masses, group central galaxies are usually found in small groups of N = 2 members. The higher HI content in these low mass group central galaxies is mirrored by their higher average star formation activity and molecular hydrogen content. At larger stellar masses, this difference disappears and central galaxies in groups have similar (or even smaller) gas reservoirs and star formation activity compared to those in isolation. We discuss possible scenarios able to explain our findings and suggest that the higher gas content in low mass group central galaxies is likely due to contributions from the cosmic web or HI-rich minor mergers, which also fuel their enhanced star formation activity.
ICRAR Press Release: http://www.icrar.org/galaxy-murder-mystery/
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