UMBH galaxies in Hydrangea (C-EAGLE)
Mass density plots of stellar particles in the Hydrangea project are shown below. The coulors indicate the particles that belong to the same subgroup as the Outlier. We follow the galaxies through 29 snapshots, based on their central BH, stellar particles and dark matter compound. The axes are in Mpc and centerred on the central BH.
UMBH_40_ID10_im0.05_p4.aviA: Halo 40 ID 10
Stripped remnant
The central BH grows rapidly ( grows from log(MBH/Msun) = 6.3 to log(MBH/Msun) =7.5 ) between z = 2.6 and z = 2.25 after what looks like major merger. In general is is a relatively small/compact galaxy.
Interaction with larger galaxy (ID 4279 ~x10 more massive BH) at z ~0.5, leads to puffing up of stars. Subsequent interaction around z = 0.15 removes outer stars. Third interaction (with galaxy ID 4279 ) around z = 0.05 leads to new puff-up and substantial stripping/stretching.
Then there is a fourth interaction at z = 0.025. Unclear whether this one would likely merge, more likely dispersal candidate. At snapshot 27 its stellar mass was still 10.0 log(M*/Msun). It is pushed over the 'outlier barrier' at the last snapshot when log(M*/Msun) = 9.4
Note: host is a satellite itself, there is an even more massive galaxy within <~ 200 kpc with several > 8.0 BHs.
At z = 0 we see a clear stellar core with a trailing tail.
UMBH_7_ID2_im0.05_p4.aviB: Halo 7 ID 2
Stripped remnant
Rapid BH growth from z ~ 4.2 to 3.5 after major merger, second jump after major merger at z ~ 2.
First (close) passage to central galaxy at z = 1 - no visible impact on stars, but central steals smaller galaxy that was lingering around. After multiple further pericentre passages with this galaxy, disintegration begins around z = 0.17, then another major puff-up/stripping phase at z = 0.08. Object at z = 0 is essentially a ‘nugget’ flying out of the main host.
In the last few snapshot, the galaxy is being stripped by the combined effort of its group. This is seen as the halo being loosened, and long 'arms' of stellar density appearing. This results in very spectacular stripped tails around z = 0 when coloured at Mpeak.
At z = 0 there is a faint but clear stellar core with two tails either side.
UMBH_24_ID3_im0.05_p4.aviStellar density at +-30 kpc
D-2300_s0p03.mp4C: Halo 24 ID 3
"Red Nugget" Stripped remnant with old BH
This BH was part of galaxy ID 2300 and had its rapid growth phase between ~6.7 and 5.5 then another ~x10 jump during a major merger at z ~ 4.6.
Capture- interaction also grows its own BH to ~6.0.
Captures its main (very massive) BH (~9.0) at z ~ 2.6 when it is ejected from its original host during a merger (it might just merge with the original host).
It resides in a very dense environment. Merges with a 10^9 Msun BH at z>2. Gets stripped from snap 13 onwards by the large group around it.
Subsequent severe stripping due to nearby BCG.
At z = 0: clear ‘nugget' stellar core on outskirts of BCG.
Stellar density + BHs
UMBH_21_ID2_im0.05_p4.aviGas Density
GalF_Gas_0p25.mp4Here’s a larger gas image showing the blast wave from that UMBH:
D: Halo 21 ID 2
Relic
BH growth starts at z = 5 after major merger, M = 10^7 by z = 4. Its massive black hole particle comes out of a merger, but this time between two galaxies that each contribute a ~2x10^7 M_sun BH particle. Just after these merge, the mass of the BH shoots up to ~2x10^9 M_sun, within less than 125 Myr (z = 2.69 to z = 2.57).
For this one, we also show the gas density. You can clearly see two gas blobs merging in the centre, and then there is an enormous feedback blast wave that completely blows the gas filaments to pieces. Hence no more star formation
The galaxy sits on the outskirts of a cluster, and is flying through it around z = 0.6 but without losing appreciable stellar mass.
Galaxy relaxes by z = 2. No more interactions or BH growth. Clear ‘relic’ galaxy. Forms in dense region with several proto-galaxies at z ~6.
At z = 0: isolated massive galaxy.
Zoom in on Galaxy E (stellar density)
UMBH_24_ID5_im0.05_p4.aviGalH_StBH_0p15.mp4Interaction with proto-cluster (stellar density)
GalH_St_1p0.mp4Disconnected stellar Halo
DisconnectedStellarHalo_24_5.mp4E: Halo 24 ID 5
First merger/stellar growth phase between z = 6 and 3.5, but without BH growth. BH growth starts at z = 3.2, triggered by intermediate merger. Second (triple) merger triggers growth of BH mass to 10^9.45Msun by z = 2.7, while causing an AGN feedback blast. By z = 2.0 all the gas has been cleared from its immediate environment and it is qualified as a MBH(M*) 'outlier' from this point onwards.
It has a merger at z ~ 1, with most of the black hole mass coming in from the minor progenitor.
The final merger then happens around z = 1. 3. This galaxy (13881) flies in with also a Mbh of 7.7, causing subfind to make an extra galaxy between snap 9 and 14 (z = 1.3 to 0.7).
Interaction with two small galaxies from z ~ 0.8. From z = 0.725, halo starts sloshing around core+BH, and then disconnects from z = 0.615, leaves together with the two smaller galaxies. The BH takes away the core, and the halo forming its own galaxy (the colouring here is marking the star particles in the galaxy at z ~ 2).
When zooming out to a box size of 2 Mpc, it’s clear that the galaxy is interacting with a proto-cluster structure (without a clearly dominant central) at that point.
This event decreased its half mass radius by 90\% and causes UMBH-galaxy E to lose 64% of its stellar mass
BH+stellar core remains as compact, fairly isolated object. It moves to emptier region at z ~ 0.36 and is completely isolated thereafter. At z = 0: isolated compact galaxy.
At z = 0 the BH + associated stars have been flung out of the cluster and are therefore classed as a central.