Kavli Affiliate: David N. Spergel
| First 5 Authors: Jacob Nibauer, Jacob Nibauer, , ,
| Summary:
Stellar streams are sensitive tracers of low-mass dark matter subhalos and
provide a means to test the Cold Dark Matter (CDM) paradigm on small scales. In
this work, we connect the intrinsic velocity dispersion of the GD-1 stream to
the number density and internal structure of dark matter subhalos in the mass
range $10^5$-$10^9 M_odot$. We measure the radial velocity dispersion of GD-1
based on 160 identified member stars across four different spectroscopic
catalogs. We use repeat observations of the same stars to constrain binarity.
We find that the stream’s intrinsic radial velocity dispersion ranges from
approximately 2-5 km/s across its length. The region of GD-1 with the highest
velocity dispersion represents a $4sigma$ deviation from unperturbed stream
models formed in a smooth Milky Way potential, which are substantially colder.
We use perturbation theory to model the stream’s velocity dispersion as a
function of dark matter subhalo population parameters, including the number of
low-mass subhalos in the Milky Way, the dark matter half-mode mass, and the
mass-concentration relation of subhalos. We find that the observed velocity
dispersion can be explained by numerous impacts with low-mass dark matter
subhalos, or by a single impact with a very compact subhalo with $M gtrsim
10^8 M_odot$. Our constraint on the fraction of mass in subhalos is
$f_mathrmsub = 0.05^+0.08_-0.03$ (68% confidence). In both scenarios,
our model prefers subhalos that are more compact compared to CDM mass-size
expectations. These results suggest a possible deviation from CDM at low
subhalo masses, which may be accounted for by dark matter self-interactions
that predict higher concentrations in lower-mass subhalos.
| Search Query: ArXiv Query: search_query=au:”David N. Spergel”&id_list=&start=0&max_results=3