SDSS–IV MaNGA : The Inner Density Slopes of nearby galaxies. (arXiv:1903.09282v1 [astro-ph.GA])

SDSS–IV MaNGA : The Inner Density Slopes of nearby galaxies. (arXiv:1903.09282v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Li_R/0/1/0/all/0/1">Ran Li</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Li_H/0/1/0/all/0/1">Hongyu Li</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Shao_S/0/1/0/all/0/1">Shi Shao</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lu_S/0/1/0/all/0/1">Shengdong Lu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zhu_K/0/1/0/all/0/1">Kai Zhu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wang_C/0/1/0/all/0/1">Chunxiang Wang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gao_L/0/1/0/all/0/1">Liang Gao</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mao_S/0/1/0/all/0/1">Shude Mao</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dutton_A/0/1/0/all/0/1">Aaron A. Dutton</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ge_J/0/1/0/all/0/1">Junqiang Ge</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wang_Y/0/1/0/all/0/1">Yunchong Wang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Leauthaud_A/0/1/0/all/0/1">Alexie Leauthaud</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zheng_Z/0/1/0/all/0/1">Zheng Zheng</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bundy_K/0/1/0/all/0/1">Kevin Bundy</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Brownstein_J/0/1/0/all/0/1">Joel R. Brownstein</a>

We derive the mass weighted total density slopes within the effective
(half-light) radius, $gamma’$, for more than 2000 nearby galaxies from the
SDSS-IV MaNGA survey using Jeans-anisotropic-models applied to IFU
observations. Our galaxies span a wide range of the stellar mass ($10^9$
$M_{rm odot}< M_* < 10^{12}$ M$_{odot}$) and the velocity dispersion (30 km/s $< sigma_v <$ 300 km/s). We find that for galaxies with velocity dispersion $sigma_v>100$ km/s, the density slope has a mean value $langle
gamma^{prime} rangle = 2.24$ and a dispersion $sigma_{gamma}=0.22$, almost
independent of velocity dispersion. A clear turn over in the $gamma’-sigma_v$
relation is present at $sigmasim 100$ km/s, below which the density slope
decreases rapidly with $sigma_v$. Our analysis shows that a large fraction of
dwarf galaxies (below $M_* = 10^{10}$ M$_{odot}$) have total density slopes
shallower than 1, which implies that they may reside in cold dark matter halos
with shallow density slopes. We compare our results with that of galaxies in
hydrodynamical simulations of EAGLE, Illustris and IllustrisTNG projects, and
find all simulations predict shallower density slopes for massive galaxies with
high $sigma_v$. Finally, we explore the dependence of $gamma’$ on the
positions of galaxies in halos, namely centrals vs. satellites, and find that
for the same velocity dispersion, the amplitude of $gamma’$ is higher for
satellite galaxies by about 0.1.

We derive the mass weighted total density slopes within the effective
(half-light) radius, $gamma’$, for more than 2000 nearby galaxies from the
SDSS-IV MaNGA survey using Jeans-anisotropic-models applied to IFU
observations. Our galaxies span a wide range of the stellar mass ($10^9$
$M_{rm odot}< M_* < 10^{12}$ M$_{odot}$) and the velocity dispersion (30
km/s $< sigma_v <$ 300 km/s). We find that for galaxies with velocity
dispersion $sigma_v>100$ km/s, the density slope has a mean value $langle
gamma^{prime} rangle = 2.24$ and a dispersion $sigma_{gamma}=0.22$, almost
independent of velocity dispersion. A clear turn over in the $gamma’-sigma_v$
relation is present at $sigmasim 100$ km/s, below which the density slope
decreases rapidly with $sigma_v$. Our analysis shows that a large fraction of
dwarf galaxies (below $M_* = 10^{10}$ M$_{odot}$) have total density slopes
shallower than 1, which implies that they may reside in cold dark matter halos
with shallow density slopes. We compare our results with that of galaxies in
hydrodynamical simulations of EAGLE, Illustris and IllustrisTNG projects, and
find all simulations predict shallower density slopes for massive galaxies with
high $sigma_v$. Finally, we explore the dependence of $gamma’$ on the
positions of galaxies in halos, namely centrals vs. satellites, and find that
for the same velocity dispersion, the amplitude of $gamma’$ is higher for
satellite galaxies by about 0.1.

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