ram-pressure feeding of supermassive black holes

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Ram-pressure feeding of supermassive black holesRam-pressure feeding of supermassive black holes
Poggianti, B. M., et al. 2017, Nature, 548, 304
November 15, 2017
Supermassive black hole (SMBH)
• Most galaxies host SMBHs with MBH ∼ 106 − 1010 M at their center (Kormendy & Ho, 2013).
• In Milky Way, MSMBH ≈ 4.1× 106 M (Meyer et al. 2012).
• SMBH accrete matter−−−−−−−−−→ Active
AGN and Gas
• major mergers
• fast tidal encounters between galaxies
Ram-pressure stripping:
• due to the pressure exerted by the intergalactic medium (IGM) on the galaxy interstellar medium
• the most efficient of processes that remove gas from galaxies
• an enhancement of the SFR at first, thermal instabilities and turbulent motions lead to the collapse of molecular clouds
• quench the star formation when gas is removed
• galaxies undergoing gas stripping: “jellyfish” galaxies
Introduction Data and Methods Results
Jellyfish galaxies
HST + Chandra (Credit: NASA, ESA, CXC)
“Tentacles” are formed of stripped gas and newly born stars, extend for dozens of kpc beyond the galactic disks.
Introduction Data and Methods Results
GASP
GASP (GAs Stripping Phenomena in galaxies with MUSE, Poggianti et al. 2017, GASP I)
• Aim: study gas removal processes in galaxies
• Sample selection: visually inspected B-band WINGS, OMEGAWINGS, and PM2GC images searching for galaxies with optical signatures of gas-only removal mechanisms (Poggianti et al. 2016)
• Targets: 114 galaxies at z = 0.04− 0.07 with M∗ ∼ 109.2 − 1011.5 M in clusters, groups and the field
• Primary targets: 94 stripping candidates (“jellyfish galaxies”), 64 in cluster and 30 in the field
• Control sample: 20 disk galaxies with no morphological anomalies
Introduction Data and Methods Results
Observations
• Instrument: the MUSE spectrograph on the Very Large Telescope (VLT)
• a 1′ × 1′ field of view with 0.2′′ × 0.2′′ pixels, each data cube yields approximately 90,000 spectra
• Spectra: λ ∼ 4800− 9300 A with a resolution of ∼ 2.6 A and a sampling of 1.25 A pixel−1
• Exposures: at least 2700 s per galaxy
Data of the present work (7 galaxies): All the cluster jellyfish galaxies observed so far that have significant tentacles of ionized gas traced by Hα.
Introduction Data and Methods Results
Analysis methods
• Before analysis: datacube is average-filtered in the spatial dimension with a 5× 5 pixel bin (1′′, ∼ 0.8− 1.1 kpc).
• Emission lines: KUBEVIZ (Fossati et al., 2016), try a single and a double Gaussian profile fit, use double-component fits when both of components are detected to > 3σ, otherwise a single component is used.
• Stellar component subtraction: SINOPSIS (Fritz et al., 2017, GASP III), single stellar population (SSP) models from Charlot & Bruzual (in preparation) + nebular emission from CLOUDY.
• Stellar kinematics: the Penalized Pixel-Fitting (PPXF)
Introduction Data and Methods Results
Stellar and Hα velocity map
−60 −40 −20 0 20
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JO201a
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JO201b
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Introduction Data and Methods Results
Stellar and Hα velocity map
• The long ionized gas tentacles extend out to about 20–100 kpc.
• The stellar velocity field is regular, the stellar disk are undisturbed by the force acting on the gas.
• These galaxies are undergoing a gas-only removal mechanism, i.e., ram-pressure stripping.
Ionization sources of Hα:
• the central AGN
• low ionization nuclear emission-line regions (LINERs): a low-luminosity AGN or other mechanisms such as shocks or old stars
Introduction Data and Methods Results
Diagnostic diagrams and maps
log [NII]/Hα
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JO175
b)
• The two compenents of JO201 and JO204 are both powered by the AGN in the central region.
• JO204a has an AGN-powered extraplanar region, extending up to 15 kpc away from the disk (AGN ionization cone).
Introduction Data and Methods Results
Diagnostic diagrams and maps
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JO175
b)• JW100, JO206, and JO135 also exhibit signatures of AGN emission.
• An AGN ionization cone can be found in JO135.
Introduction Data and Methods Results
Diagnostic diagrams and maps
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• In JO194, the central emission is LINER-like.
• The spatial distribution of the LINER-like emission favours an AGN origin.
• Chandra (0.3–8 keV) X-ray luminosities of JO194 also support an AGN origin.
• For JO175, line ratios are consistent with photoionization by star formation.
Introduction Data and Methods Results
Properties of integrated spectra of the AGN regions
Figure 1. Extended Data Figure 1 - Summary diagnostic diagrams.
Table 1. Properties of GASP strongest jellyfishes
IDP16 IDWINGS cluster σcl RA DEC z M∗ LX L[OIII] EW(Hα) EW([OIII])
(km s−1) (M) (erg s−1, 0.3-8keV) erg s−1 A r.f. A r.f.
JO201 WINGSJ004130.30-091546.1 A85 982 ± 55 00 41 30.30 -09 15 45.98 0.04464 6.7 × 1010 7.3 × 1041 1.37±0.03 × 1042 46.0/14.4±1.0/0.9 141.8/44.2±6.1/2.6
JO204 WINGSJ101346.82-005450.9 A957 640 ± 47 10 13 46.84 -00 54 51.27 0.04243 4.4 × 1010 – 4.94±0.3 × 1040 12.8/10.6±0.5/0.4 23.5/19.2± 1.2/1.1
JW100 WINGSJ233625.05+210902.5 A2626 679 ± 60 23 36 25.05 +21 09 02.64 0.06019 3.2 × 1011 2.0 × 1041 2.16±0.06 × 1040 5.6/2.6±0.2/0.3 4.1/4.0± 0.1/0.1
JO206 WINGSJ211347.41+022834.9 IIZW108 611 ± 38 21 13 47.41 +02 28 35.50 0.05133 1.1 × 1011 7.7 × 1042 1.11±0.04 × 1041 33.5±1.0 50.1±2.2
JO135 WINGSJ125704.29-302230.6 A3532 805 ± 61 12 57 04.32 -30 22 30.19 0.05421 1.0 × 1011 3.2 × 1041 1.29±0.06 × 1041 26.3±1.0 39.4±1.8
JO194 WINGSJ235700.68-344050.1 A4059 752 ± 38 23 57 00.74 -34 40 49.94 0.04100 1.6 × 1011 1.4 × 1041 2.94±0.07 × 1039 3.2±0.07 0.9±0.02
JO175 WINGSJ205117.58-524921.5 A3716 848 ± 26 20 51 17.59 -52.49 22.34 0.04678 3.9 × 1010 – – 43.9±0.9 1.4±0.08
Introduction Data and Methods Results
Diagnostic diagrams and maps
• The great majority (6/7) of the jellyfish galaxies host an AGN.
• Only 3% of emission-line galaxies with a spectroscopic classification in low-redshift clusters show evidence for AGN activity.
• The high incidence of AGN among the most significant jellyfish galaxies uncovers a link between nuclear activity and strong ram-pressure stripping.
• Ram pressure drive gas towards the center−−−−−−−−−−−−−−−−−−→ AGN
• AGN inject energy into ISM−−−−−−−−−−−−−−→
directly eject gas Ram pressure stripping
(AGN can inject a large amount of energy into ISM, thus decrease its binding energy and make it more easily stripped.)
Introduction Data and Methods Results
Differential velocity vs. cluster-centric distance
0.0 0.5 1.0 1.5 2.0
rcl / R200
• σcl: cluster velocity dispersion
• The most favourable conditions for ram pressure are at high ICM density (i.e., low radii) and high vcl.
• The phase-space diagram strongly supports the hypothesis that it is ram pressure that triggers the AGN.
Introduction Data and Methods Results
Summary
• There is a close link between strong ram pressure and AGN activity in jellyfish galaxies, establishing for the first time a probable causal connection between the two phenomena.
• Ram pressure can be another possible mechanism for feeding the central SMBH with gas.
Introduction