Day 1680

Thursday.

2003.11096
Dark matter haloes in the multicomponent model. III. From dwarfs to galaxy clusters
Todoroki, Medvedev

A possibility of DM being multicomponent has a strong implication on resolving decades-long known cosmological problems on small scale. In addition to elastic scattering, the model allows for inelastic interactions, which can be characterized by a 'velocity kick' parameter. The simplest 2cDM model with cross section $0.01\lesssim\sigma/m<1\textrm{ cm}^{2}{ \rm g}^{-1}$ and the kick velocity $V_{k}\simeq 100\textrm{ km s}^{-1}$ has been shown to robustly resolve the missing satellites, core-cusp, and too-big-to-fail problems in $N$-body cosmological simulations tested on MW-like haloes of a virial mass $\sim5 \times 10^{11}$ M$_{\odot}$ (Paper I $\&$ II). With the aim of further constraining the parameter space available for the 2cDM model, we extend our analysis to dwarf and galaxy cluster haloes with their virial mass of $\sim 10^7 - 10^8$ and $\sim 10^{13} - 10^{14}$ M$_{\odot}$, respectively. We find $\sigma_{0} / m \gtrsim 0.1 \textrm{ cm}^{2}{\rm g}^{-1}$ is preferentially disfavored for both dwarfs and galaxy cluster haloes in comparison with observations, while $\sigma_{0} / m = 0.001 \textrm{ cm}^{2}{\rm g}^{-1}$ causes little perceptible difference from that of the CDM counterpart for most of the cross section's velocity dependence studied in this work. Our main result is that within the reasonable set of parameters the 2cDM model can successfully explain the observational trends seen in dwarf galaxy and galaxy cluster haloes and the model leaves us an open window for other possible alternative DM models.

2003.11499

Giants eating giants: mass loss and giant planets modifying the luminosity of the Tip of the Giant Branch

Jiminiez, Jorgensen, Verde

During the red giant phase, stars loose mass at the highest rate since birth. The mass-loss rate is not fixed, but varies from star-to-star by up to 5%, resulting in variations of the star's luminosity at the tip of the red giant branch (TRGB). Also, most stars, during this phase, engulf part of their planetary system, including their gas giant planets. Gas giant planet masses range between 0.1 to 2% of the host star mass. The engulfing of their gas giants planets can modify their luminosity at the TRGB, i.e. the point at which the He-core degeneracy is removed. We show that the increase in mass of the star by the engulfing of the gas giant planets only modifies the luminosity of a star at the TRGB by less than 0.1%, while metallicity can modify the luminosity of a star at the TRGB by up to 0.5%. However, the increase in turbulence of the convective envelope of the star, i.e., modification of the mixing length, has a more dramatic effect, on the star's luminosity, which we estimate could be as large as 5%. The effect is always in the direction to increase the turbulence and thus the mixing length which turns into a systematic decrease of the luminosity of the star at the TRGB. We find that the star-to-star variation of the mass-loss rate will dominate the variations in the luminosity of the TRGB with a contribution at the 5% level. If the star-to-star variation is driven by environmental effects --as it is reasonable to assume--, the same effects can potentially create an environmentally-driven mean effect on the luminosity of the tip of the red giant branch of a galaxy. Finally, we touch upon how to infer the frequency, and identify the engulfment, of exoplanets in low-metallicity RGB stars through high resolution spectroscopy as well as how to quantify mass loss rate distributions from the morphology of the horizontal branch.