The Cen A galaxy group: dynamical mass and missing baryons. (arXiv:2111.10306v2 [astro-ph.GA] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Muller_O/0/1/0/all/0/1">Oliver Müller</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lelli_F/0/1/0/all/0/1">Federico Lelli</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Famaey_B/0/1/0/all/0/1">Benoit Famaey</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pawlowski_M/0/1/0/all/0/1">Marcel S. Pawlowski</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Fahrion_K/0/1/0/all/0/1">Katja Fahrion</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rejkuba_M/0/1/0/all/0/1">Marina Rejkuba</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hilker_M/0/1/0/all/0/1">Michael Hilker</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Jerjen_H/0/1/0/all/0/1">Helmut Jerjen</a>
The nearby elliptical galaxy Cen A is surrounded by a flattened system of
dwarf satellite galaxies with coherent motions. Using a novel Bayesian
approach, we measure the mean rotation velocity $v_{rm rot}$ and velocity
dispersion $sigma_{rm int}$ of the satellite system. We find $v_{rm
rot}/sigma_{rm int} simeq 0.7$ indicating that the satellite system has
non-negligible rotational support. Using Jeans’ equations, we measure a
circular velocity of 258 km s$^{-1}$ and a dynamical mass of $1.2times
10^{13}$ M$_odot$ within 800 kpc. In a $Lambda$CDM cosmological context, we
find that the Cen A group has a baryon fraction $M_{rm b}/M_{200}simeq0.035$
and is missing $sim$77$%$ of the cosmologically available baryons.
Consequently, Cen A should have a hot intergalactic medium with a mass of
$sim$8$times$10$^{11}$ M$_odot$, which is more than $sim$20 times larger
than current X-ray estimates. Intriguingly, The whole Cen A group lies on the
baryonic Tully-Fisher relation defined by individual rotationally supported
galaxies, as expected in Milgromian dynamics (MOND) with no need of missing
baryons.
The nearby elliptical galaxy Cen A is surrounded by a flattened system of
dwarf satellite galaxies with coherent motions. Using a novel Bayesian
approach, we measure the mean rotation velocity $v_{rm rot}$ and velocity
dispersion $sigma_{rm int}$ of the satellite system. We find $v_{rm
rot}/sigma_{rm int} simeq 0.7$ indicating that the satellite system has
non-negligible rotational support. Using Jeans’ equations, we measure a
circular velocity of 258 km s$^{-1}$ and a dynamical mass of $1.2times
10^{13}$ M$_odot$ within 800 kpc. In a $Lambda$CDM cosmological context, we
find that the Cen A group has a baryon fraction $M_{rm b}/M_{200}simeq0.035$
and is missing $sim$77$%$ of the cosmologically available baryons.
Consequently, Cen A should have a hot intergalactic medium with a mass of
$sim$8$times$10$^{11}$ M$_odot$, which is more than $sim$20 times larger
than current X-ray estimates. Intriguingly, The whole Cen A group lies on the
baryonic Tully-Fisher relation defined by individual rotationally supported
galaxies, as expected in Milgromian dynamics (MOND) with no need of missing
baryons.
http://arxiv.org/icons/sfx.gif
