Abundance of dwarf galaxies around low-mass spiral galaxies in the Local Volume

Abstract

The abundance of satellite dwarf galaxies has long been considered a crucial test for the current model of cosmology leading to the well-known missing satellite problem. Recent advances in simulations and observations have allowed the study of dwarf galaxies around host galaxies in more detail. Using the Dark Energy Camera we surveyed a 72 deg 2 area of the nearby Sculptor group, also encompassing the two low-mass Local Volume galaxies NGC 24 and NGC 45 residing behind the group, to search for as yet undetected dwarf galaxies. Apart from the previously known dwarf galaxies we found only two new candidates down to a 3σ surface brightness detection limit of 27.4 r mag arcsec −2. Both systems are in projection close to NGC 24. However, one of these candidates could be an ultra-diffuse galaxy associated with a background galaxy. We compared the number of known dwarf galaxy candidates around NGC 24, NGC 45, and five other well-studied low-mass spiral galaxies (NGC 1156, NGC 2403, NGC 5023, M 33, and the LMC) with predictions from cosmological simulations, and found that for the stellar-to-halo mass models considered, the observed satellite numbers tend to be on the lower end of the expected range. This could mean either that there is an overprediction of luminous subhalos in ΛCDM or that we are missing some of the satellite members due to observational biases.

A Search for Satellite Galaxies of Nearby Star-Forming Galaxies with Resolved Stars in LBT-SONG

“…The first results from the LBT-SONG survey identified two dwarf satellite candidates of NGC 628 (Davis et al 2021). Additionally, Müller et al (2018) and Müller & Jerjen (2020) assembled dwarf candidate catalogs for the diffuse Leo-I and Sculptor groups, which, if confirmed, will shed light on the SLF of dwarfs in group environments, and comparison to isolated systems may reveal environmental effects on the SLF. However, larger host samples are needed to constrain the SMF and SMHM relation.…”

Satellite mass functions and the faint end of the galaxy mass-halo mass relation in LCDM

“…Additionally, two dwarfs have been confirmed as satellites of the Magellanic analogs NGC 2403 and NGC 4214 with HST data for the Hyper Suprime Cam survey MADCASH. Müller & Jerjen (2020) report, in addition, two candidate faint dwarfs possibly associated to NGC 24 in the Sculptor group using the Dark Energy Camera. As data continues to accumulate around dwarf primaries, the census of their satellite population is starting to emerge as the most promising and effective way to constrain the galaxyhalo connection at the low mass end.…”

Non-minimally Coupled Ultra-light Axions as Cold Dark Matter

“…While CMB anisotropy and galaxy clustering data show the CDM to be a viable candidate of dark matter for large scales k < 0.1 Mpc −1 , there could be multiple issues with the model at smaller scales. N-body simulations based on the CDM model overpredict the number of satellite galaxies of the Milky way by over an order of magnitude [36][37][38][39][40][41]. Many other results also suggest that the WIMP picture of cold dark matter predicts more power at galactic scales than has been inferred from observations/N-body simulations [42], e.g.…”