Galaxy sizes correlate closely with the sizes of their parent dark matter haloes, suggesting a link between halo formation and galaxy growth. However, the precise nature of this relation and its scatter remains to be understood fully, especially for low-mass galaxies. We analyse the galaxy–halo size relation (GHSR) for low-mass ($M_\star \sim 10^{7-9}\, {\rm M}_\odot$) central galaxies over the past 12.5 billion years with the help of cosmological volume simulations (FIREbox) from the Feedback in Realistic Environments (FIRE) project. We find a nearly linear relationship between the half-stellar mass galaxy size R1/2 and the parent dark matter halo virial radius Rvir. This relation evolves only weakly since redshift z = 5: $R_{1/2}\, [{\rm kpc}] = (0.053\pm 0.002)(R_{\rm vir}/35\, {\rm kpc})^{0.934\pm 0.054}$, with a nearly constant scatter $\langle \sigma \rangle = 0.084\, [{\rm dex}]$. While this ratio is similar to what is expected from models where galaxy disc sizes are set by halo angular momentum, the low-mass galaxies in our sample are not angular momentum supported, with stellar rotational to circular velocity ratios vrot/vcirc ∼ 0.15. Introducing redshift as another parameter to the GHSR does not decrease the scatter. Furthermore, this scatter does not correlate with any of the halo propertiesmore »
Inferring the concentration of dark matter subhaloes perturbing strongly lensed images
ABSTRACT We demonstrate that the perturbations of strongly lensed images by low-mass dark matter subhaloes are significantly impacted by the concentration of the perturbing subhalo. For subhalo concentrations expected in Lambda cold dark matter (ΛCDM), significant constraints on the concentration can be obtained at Hubble Space Telescope (HST) resolution for subhaloes with masses larger than about $10^{10}\, {\rm M}_\odot$. Constraints are also possible for lower mass subhaloes, if their concentrations are higher than the expected scatter in CDM. We also find that the concentration of lower mass perturbers down to $\sim 10^8\, {\rm M}_\odot$ can be well constrained with a resolution of ∼0.01 arcsec, which is achievable with long-baseline interferometry. Subhalo concentration also plays a critical role in the detectability of a perturbation, such that only high-concentration perturbers with mass $\lesssim 10^9\, {\rm M}_\odot$ are likely to be detected at HST resolution. If scatter in the ΛCDM mass–concentration relation is not accounted for during lens modelling, the inferred subhalo mass can be biased by up to a factor of 3 (6) for subhaloes of mass $10^9 \, {\rm M}_\odot \,(10^{10} \, {\rm M}_\odot$); this bias can be eliminated if one varies both mass and concentration during lens fitting. Alternatively, one more »
- Publication Date:
- NSF-PAR ID:
- 10334137
- Journal Name:
- Monthly Notices of the Royal Astronomical Society
- Volume:
- 507
- Issue:
- 1
- Page Range or eLocation-ID:
- 1202 to 1215
- ISSN:
- 0035-8711
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript1.0
- Publisher's Version of Record
- https://doi.org/10.1093/mnras/stab2209
