Warm dark matter chills out: constraints on the halo mass function and the free-streaming length of dark matter with 8 quadruple-image strong gravitational lenses. (arXiv:1908.06983v1 [astro-ph.CO])

Warm dark matter chills out: constraints on the halo mass function and the free-streaming length of dark matter with 8 quadruple-image strong gravitational lenses. (arXiv:1908.06983v1 [astro-ph.CO])
<a href="http://arxiv.org/find/astro-ph/1/au:+Gilman_D/0/1/0/all/0/1">Daniel Gilman</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Birrer_S/0/1/0/all/0/1">Simon Birrer</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Nierenberg_A/0/1/0/all/0/1">Anna Nierenberg</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Treu_T/0/1/0/all/0/1">Tommaso Treu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Du_X/0/1/0/all/0/1">Xiaolong Du</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Benson_A/0/1/0/all/0/1">Andrew Benson</a>

The free-streaming length of dark matter depends on fundamental dark matter
physics, and determines the abundance and central densities of dark matter
halos on sub-galactic scales. Using the image positions and flux-ratios from
eight quadruply-imaged quasars, we constrain the free-streaming length of dark
matter, the amplitude of the subhalo mass function (SHMF), and the logarithmic
slope of the SHMF. We model both main deflector subhalos and halos along the
line of sight, and account for warm dark matter (WDM) free-streaming effects on
both the mass function and the mass-concentration relation. By calibrating the
evolution of the SHMF with host halo mass and redshift using a suite of
simulated halos, we infer a global normalization for the SHMF. Our analysis
accounts for finite-size background sources, and marginalizes over the mass
profile of the main deflector. Parameterizing dark matter free-streaming
through the half-mode mass $m_{rm{hm}}$, we constrain dark matter warmth and
the corresponding thermal relic particle mass $m_{rm{DM}}$. At $2 sigma$:
$m_{rm{hm}} < 10^{7.8} M_{odot}$ ($m_{DM} > 5.2 rm{keV}$). Assuming CDM,
we simultaneously constrain the projected mass in substructure between $10^6 –
10^{9} M_{odot}$ near lensed images and the logarithmic slope of the SHMF. At
$2 sigma$, we infer $1.3 – 6.6 times 10^{7} M_{odot} rm{kpc^{-2}}$,
corresponding to mean projected mass fractions of $bar{f}_{rm{sub}} =
0.034_{-0.022}^{+0.024}$, respectively. At $1 sigma$, we constrain the
logarithmic slope of the SHMF $alpha = -1.896_{-0.014}^{+0.010}$. These
results are in excellent agreement with the predictions of cold dark matter.

The free-streaming length of dark matter depends on fundamental dark matter
physics, and determines the abundance and central densities of dark matter
halos on sub-galactic scales. Using the image positions and flux-ratios from
eight quadruply-imaged quasars, we constrain the free-streaming length of dark
matter, the amplitude of the subhalo mass function (SHMF), and the logarithmic
slope of the SHMF. We model both main deflector subhalos and halos along the
line of sight, and account for warm dark matter (WDM) free-streaming effects on
both the mass function and the mass-concentration relation. By calibrating the
evolution of the SHMF with host halo mass and redshift using a suite of
simulated halos, we infer a global normalization for the SHMF. Our analysis
accounts for finite-size background sources, and marginalizes over the mass
profile of the main deflector. Parameterizing dark matter free-streaming
through the half-mode mass $m_{rm{hm}}$, we constrain dark matter warmth and
the corresponding thermal relic particle mass $m_{rm{DM}}$. At $2 sigma$:
$m_{rm{hm}} < 10^{7.8} M_{odot}$ ($m_{DM} > 5.2 rm{keV}$). Assuming CDM,
we simultaneously constrain the projected mass in substructure between $10^6 –
10^{9} M_{odot}$ near lensed images and the logarithmic slope of the SHMF. At
$2 sigma$, we infer $1.3 – 6.6 times 10^{7} M_{odot} rm{kpc^{-2}}$,
corresponding to mean projected mass fractions of $bar{f}_{rm{sub}} =
0.034_{-0.022}^{+0.024}$, respectively. At $1 sigma$, we constrain the
logarithmic slope of the SHMF $alpha = -1.896_{-0.014}^{+0.010}$. These
results are in excellent agreement with the predictions of cold dark matter.

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