The formation and evolution of low-surface-brightness galaxies

Abstract

Our statistical understanding of galaxy evolution is fundamentally driven by objects that lie above the surface-brightness limits of current wide-area surveys (µ ∼ 23 mag arcsec −2 ). While both theory and small, deep surveys have hinted at a rich population of lowsurface-brightness galaxies (LSBGs) fainter than these limits, their formation remains poorly understood. We use Horizon-AGN, a cosmological hydrodynamical simulation to study how LSBGs, and in particular the population of ultra-diffuse galaxies (UDGs; µ > 24.5 mag arcsec −2 ), form and evolve over time. For M * >10 8 M , LSBGs contribute 47, 7 and 6 per cent of the local number, mass and luminosity densities respectively (∼85/11/10 per cent for M * >10 7 M ). Today's LSBGs have similar dark-matter fractions and angular momenta to high-surface-brightness galaxies (HSBGs; µ < 23 mag arcsec −2 ), but larger effective radii (×2.5 for UDGs) and lower fractions of dense, star-forming gas (more than ×6 less in UDGs than HSBGs). LSBGs originate from the same progenitors as HSBGs at z > 2. However, LSBG progenitors form stars more rapidly at early epochs. The higher resultant rate of supernova-energy injection flattens their gas-density profiles, which, in turn, creates shallower stellar profiles that are more susceptible to tidal processes. After z ∼ 1, tidal perturbations broaden LSBG stellar distributions and heat their cold gas, creating the diffuse, largely gas-poor LSBGs seen today. In clusters, ram-pressure stripping provides an additional mechanism that assists in gas removal in LSBG progenitors. Our results offer insights into the formation of a galaxy population that is central to a complete understanding of galaxy evolution, and which will be a key topic of research using new and forthcoming deep-wide surveys.

The Influence of the Void Environment on the Ratio of Dark Matter Halo Mass to Stellar Mass in SDSS MaNGA Galaxies

“…In addition, Torres-Flores et al (2011) find that low-mass galaxies in the GHASP survey are dominated by dark matter, while those with higher masses are dominated by baryonic matter. Recent simulations by Martin et al (2019) show that low surface brightness galaxies have a slightly higher fraction of dark matter compared to high surface brightness galaxies. Our results in Figure 7 align with the SHMR, where the relative fraction of dark matter increases with decreasing luminosity.…”

One Hundred SMUDGes in S-PLUS: Ultra-diffuse Galaxies Flourish in the Field

“…By placing a large sample of field UDGs in stellar population scaling relations, we were able to confirm that UDGs, as a population, are similar to dwarf and giant galaxies. There are still puzzles to solve, such as the large globular cluster abundances in the largest UDGs (van Dokkum et al 2017;Toloba et al 2018) and the offset from the baryonic Tully-Fisher relation (Mancera Piña et al 2019), but we conclude that these should arise naturally from considering a broader range of galaxies within the current picture of galaxy formation (Martin et al 2019) rather than any exotic processes (Bennet et al 2018). Of course, these statements apply to the general case and individual exceptions, where UDGs form in tidal tails, for example, are not excluded.…”

AGN in dwarf galaxies: frequency, triggering processes and the plausibility of AGN feedback

“…Finally, we note that our AGN show no systematic offset, either in their derived rest-frame photometry ( Figure 1) or in their SFRs (not shown), from non-AGN, indicating that AGN do not contaminate the optical SFR measurements. The expected evolution of this quantity with redshift, in the Horizon-AGN cosmological simulation for dwarfs and massive galaxies, from Martin et al (2019). This ratio is expected to increase with redshift -e.g.…”