The cluster-central compact steep-spectrum radio galaxy 1321+045. (arXiv:2104.04548v2 [astro-ph.CO] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+OSullivan_E/0/1/0/all/0/1">Ewan O'Sullivan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kunert_Bajraszewska_M/0/1/0/all/0/1">Magdalena Kunert-Bajraszewska</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Siemiginowska_A/0/1/0/all/0/1">Aneta Siemiginowska</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Burke_D/0/1/0/all/0/1">D. J. Burke</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Combes_F/0/1/0/all/0/1">Françoise Combes</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Salome_P/0/1/0/all/0/1">Philippe Salomé</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Giacintucci_S/0/1/0/all/0/1">Simona Giacintucci</a>
The radio galaxy 1321+045 is a rare example of a young, compact steep
spectrum source located in the center of a z=0.263 galaxy cluster. Using a
combination of Chandra, VLBA, VLA, MERLIN and IRAM 30m observations, we
investigate the conditions which have triggered this outburst. We find that the
previously identified 5 kpc scale radio lobes are probably no longer powered by
the AGN, which seems to have launched a new ~20 pc jet on a different axis,
likely within the last few hundred years. We estimate the enthalpy of the lobes
to be 8.48 [+6.04,-3.56] x10^57 erg, only sufficient to balance cooling in the
surrounding 16 kpc for ~9 Myr. The cluster ICM properties are similar to those
of rapidly cooling nearby clusters, with a low central entropy (8.6 [+2.2,-1.4]
kev cm^2 within 8 kpc), short central cooling time (390 [+170,-150] Myr), and
t_cool/t_ff and t_cool/t_eddy ratios indicative of thermal instability out to
~45 kpc. Despite previous detection of Halpha emission from the BCG, our IRAM
30m observations do not detect CO emission in either the (1-0) or (3-2)
transitions. We place 3sigma limits on the molecular gas mass of M_mol
<=7.7×10^9 Msol and <=5.6×10^9 Msol from the two lines respectively. We find
indications of a recent minor cluster merger which has left a ~200 kpc tail of
stripped gas in the ICM, and probably induced sloshing motions.
The radio galaxy 1321+045 is a rare example of a young, compact steep
spectrum source located in the center of a z=0.263 galaxy cluster. Using a
combination of Chandra, VLBA, VLA, MERLIN and IRAM 30m observations, we
investigate the conditions which have triggered this outburst. We find that the
previously identified 5 kpc scale radio lobes are probably no longer powered by
the AGN, which seems to have launched a new ~20 pc jet on a different axis,
likely within the last few hundred years. We estimate the enthalpy of the lobes
to be 8.48 [+6.04,-3.56] x10^57 erg, only sufficient to balance cooling in the
surrounding 16 kpc for ~9 Myr. The cluster ICM properties are similar to those
of rapidly cooling nearby clusters, with a low central entropy (8.6 [+2.2,-1.4]
kev cm^2 within 8 kpc), short central cooling time (390 [+170,-150] Myr), and
t_cool/t_ff and t_cool/t_eddy ratios indicative of thermal instability out to
~45 kpc. Despite previous detection of Halpha emission from the BCG, our IRAM
30m observations do not detect CO emission in either the (1-0) or (3-2)
transitions. We place 3sigma limits on the molecular gas mass of M_mol
<=7.7×10^9 Msol and <=5.6×10^9 Msol from the two lines respectively. We find
indications of a recent minor cluster merger which has left a ~200 kpc tail of
stripped gas in the ICM, and probably induced sloshing motions.
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