Thick as thieves unveiling the most compact and obscured nuclei - - PowerPoint PPT Presentation

Thick as thieves — unveiling the most compact and obscured nuclei

Susanne Aalto Department of Space, Earth and Environment (SEE), Chalmers University of Technology Sweden +many collaborators

Outline

• Dusty nuclei

– Why do we care? – the torii – example NGC1068 – the Compact Obscured Nuclei (CONs) – example IC860 – ALMA CON-quest

• Related posters:

– CON-quest: Falstad, Onishi; – H2S: Sato

• Dusty Feedback

– AGN and starburst feedback – Collimated molecular outflows in dusty galaxies – example NGC1377

Dusty growth: U/LIRGs and obscured nuclei

• Luminous and Ultraluminous Infrared

Galaxies, (U)LIRGs (LIR>1011 Lsun), are dusty galaxies

– Often interacting - fundamental to our understanding of galaxy evolution (e.g. Elbaz & Cesarsky 2003; Sanders & Mirabel 1996). Some have even more embedded nuclei that harbour a very active evolutionary stage of AGNs and/or starbursts.

• Obscured AGNs

– Most AGNs in the universe are obscured (e.g. Brandt and Alexander) – Shape and structure of torus linked to feeding of SMBH and feedback – Starburst-AGN connection – How is the small scale (< 1 pc) obscuration linked to that at 10-100 pc – or on larger scales?

• The nuclear activity will often drive

mechanical feedback in the form of molecular winds, jets and outflows

The Antennae: 100 µm PACS

• n HST (Klaas +10)

Arp220

Winds and jets Garcia-Burillo+14

NASA, ESA, and C. Wilson

from Alexander 2011

Diaz-Santos+17

DUSTY NUCLEI

NGC1068: Imaging an AGN-obscuring dust torus with ALMA

• High resolution (0.”06) ALMA λ=450 µm
• bservations reveal:
• r=3.5 pc dusty turbulent torus with

Mgas=1x105 Msun (Garcia-Burillo+16, Gallimore+16).

• Diagnostic HCN/HCO+ line ratios change

with distance to nucleus (Garcia- Burillo+14, Viti+14, Imanishi+16,18).

For more ALMA studies of AGN torii see e.g. Combes+19 (survey) , Izumi+18 (Circinus), Espada+17 (Cen A) , Aalto+17,20 (NGC1377)

• Even higher resolution observations (0.”02)

reveal apparent counter-rotation. (Imanishi+18, Impellizzeri+19, Garcia- Burillo+19). Counter-rotation can be real, or an effect of inflow or ”outflowing torus”.

• Column density estimated to

N(H2)=1023 cm-2 on scales of a few pc

From Garcia- Burillo+19 (Garcia-Burillo+14,16)

OPAQUE NUCLEI – THE CONS

CONs – Compact Obscured Nuclei - N(H2)>1025 cm-2 Av>>1000

• Hidden growth in our time:

– AGN statistics and/or growth of nuclear stellar spheroid. – Starburst-AGN connection.

• Relation to distant DOGs? SMGs?
• Potential sources of cosmic neutrinos (e.g. Berezinskii & Ginzburg 1981;

Bahcall & Waxman 2001, Yoast-Hull+17).

• <0. “1 (<20 pc) nuclear

emission

• τ(860 μm) = 1 (i.e., NH>1025

cm−2). NGC4418

1 −1 −1 1 1 −1 R.A. offset [arcsec] −1 1

• Dec. offset [arcsec]

0.35" x 0.26" 50 pc (k) 860 µm 5 10 15

mm/submm continuum Example: NGC4418 (e.g Sakamoto+10,13, Costagliola+13 – see also Varenius+14 for VLBI imaging)

Some (U)LIRGs harbour CONs - Still unknown how common they are. Extremely important to understand

• bscured phase:

Buried nuclei can be traced by vibrationally excited molecules at long wavelengths– e.g. HCN

Vibrationally excited HCN (HCN-VIB) requires TB(14 µm) > 100 K.

Rotational transitions in the mm/submm. (e.g. Sakamoto+10, Aalto+15a,b, Imanishi+13, Martin+16, Aalto+16, Imanishi+16); cm wavelengths (e.g. Salter+08); mid-IR HCN absorption line (Lahuis+07)

14 µm IR field Vibrationally excited HCN (HCN-VIB)

ν=0 ladder ν2=2 ladder

Cartoon by F. Costagliola

ALMA 345-100 GHz, 25-90 mas

• bservations of the early-type LIRG IC860 (Aalto+19)
• HCN-VIB probes inner region – but opacities. Tex -TB matching: diminishing

line-to-continuum ratio in inner r=4 pc.

• mm continuum optically thick: – N(H2) >1026 cm-2 - ”brick wall”. Average

gas densities n>107 cm-3 within r=9pc. (Assuming standard dust-gas ratio. Compare ULIRG core Arp220 (Scoville+17, Sakamoto+17, Barcos- Munos+18).(Beware of potential self-heating (Kaufman+98,Gonzalez- Alfonso+19).

• Rotating thick turbulent nuclear disk + inflow+outflow

Nature of buried source:

• Accreting SMBH – potentially undermassive
• A starburst consisting only of massive O-stars – i.e. extremely

skewed initial mass function (IMF).

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HCN-VIB 3-2

Major axis

• f rotation

14 pc

IC 860

Ground state HCN, HCO+, CS lines continuum- and self absorbed in central 50 pc.

Minor and major axis position-velociy diagrams

Massive inflow + onset of extremely dusty feedback?

Layered structure of non-circular motions:

• Assymmetric foreground absorption inflow:

Reversed P-Cygni in HCN, HCO+. Inflow on scales >50 pc down to nucleus. The time-scale of gas to reach the nucleus from r=50 pc is 1 Myr

• Compact, dense outflow: P-Cygni in CS 7-6, HC15N out to
• 300 km/s. Broad, minor axis HCN-VIB features may be

base of outflow. Vibrationally excited HC3N v7=2 also seen along minor axis. Extent of dense outflow: 20 pc Cartoons of two scenarios:

• A. near-face-on with out-of-plane inflow.
• B. Near-edge-on where obscuration consists of

torus and in-plane inflow

A. B.

Massive inflow supplies nuclear gas/dust column – what allows for the build-up of of N(H2)=1026 cm-2? Witnessing the onset of dense feedback? – Or a failed wind? Timescales? Ongoing radio studies (Merlin/VLA/VLBI) reveal compaxt collimated jet-like structures + SNRs

ALMA CON-quest survey

(see posters by Falstad and Onishi)

• CON-quest: Deep survey of 38 nearby

ULIRGs, LIRGs and low luminosity dusty

• galaxies. (PI: S.Aalto)

– HCN, HCO+, HOC+, HCN-VIB 3-2 – Dense outflow statistics – Resolved HCN/HCO+ ratio maps – Nuclear dynamics and SMBH masses – Deep 1mm continuum images – Prime data analysts: König, Falstad, Onishi, Nishimura

• What are CONs and what are their

timescales??

• How common are they? Is there a

luminosity dependence on their prevalence?

– Preliminary: The CON detection rates are 20 − 25% in FIR-selected (U)LIRGs with LFIR>1011 Lsun, and 0% in lower luminosity galaxies.’

• CON hosts?

– Preliminary: Major merger ULIRGs – minor merger LIRGs? Possible link to post- starburst signatures still needs investigation.

Example of LIRG CON hosts: Dusty S0/galaxies – minor mergers: HST V-band Images HST GO-1: J. Gallagher, Sample CON-quest HCN, HCN/HCO+ ratio, spectra and continuum maps

Zw049.057 NGC4418

CON-quest members: S. Aalto; N. Falstad; S. König; K. Onishi; Y. Nishimura; G. Privon; ; J. Mangum; S. Martin; K. Sakamoto S. Muller; S. Garcia-Burillo; E. Gonzalez-Alfonso; G. Fuller; T. Greve; F. Combes; C. Henkel; A. Evans; S. Mühle; T. Diaz-Santos; C. Ricci; K. Kohno; N. Harada; T. Izumi; M. Imanishi; J. Gallagher III; S. Viti; P. van der Werf; L. Barcos- Munos; S. Linden

Hot and opaque cores – where are the

• utflows? (Hallqvist+17, Falstad+19)
• HCN-VIB luminous galaxies do not

show strong FIR OH λ=119 µm P- Cygni profiles. But they do show inflows.

• Why?
• Outflow collimation.
• Obscured, compact flows

CO outflow signatures now found for most CONs: I17208 (Garcia-Burillo+14); Zw049 (Falstad+18);NGC4418 (Fluetsch+18); Arp220 (e.g. Barcos-Munos+17); ESO320 (Pereirs-Santaella+16); IC860 (Aalto+19) Follow up studies on MUSE,HST, VLA, ALMA (CON-firm, PI: Falstad)

Plot from Falstad+19

Median OH outflow velocity as a function of the HCN-vib luminosity relative to the the total infrared luminosity. Velocities Vout (from Veilleux+13)

OH inflow signature

MOLECULAR OUTFLOWS

The nuclear activity will often drive mechanical feedback in the form of winds, jets and

• utflows. The feedback may:

– Regulate SMBH growth and link it to the host galaxy – Magorrian relation. – help partially explain ” dead” properties of local ellipticals. – reduce star formation efficiency

Outflows and winds from galaxies are multi-phase. There is mounting evidence that cold (10-100 K) molecular gas in

• utflows is common and that the cold gas

may in some cases dominate mass and momentum flux

AGN and starburst feedback

M82 NGC1377

Artists impression

NGC253

MOLECULAR ”JETS” IN DUSTY NUCLEI?

Collimated outflows in CONs?

400 km/s OH (4-6 GHz) VLA line wing seen with the VLA (Falstad+19 see also Baan+89). Weak radio continuum (5 GHz associated with collimated NIR dust feature or shadow.

HST image of Zw049 (Falstad+18, Gallagher et al in prep.)

CO 2-1, 6-5 tracing very dense nuclear

• utflow . Also the 690

GHz dust is partially tracing the nuclear

• uflow. (ALMA+SMA)

Arp220

• ALMA reveals very dense and

fast (850 km/s) outflow in ULIRG Arp220. TB(HCN) > TB(CO) (Barcos-Munos+17). Very opaque dust in core and

• utflow (Scoville+17,

Sakamoto+17) Zw049.057

The most extreme FIR-excess, radio-quiet galaxy NGC1377

Small, lenticular galaxy LFIR=5x109 Lsun Excess FIR emission with q>3.9 – off FIR-Radio correlation by factor >37 Deep silicate absorption (Spoon+07). No Pα, Br γ - Faint Hα, [N II] and [Ne II] lines, Faint PAH (Roussel+03,06). Roussel+06

Featureless morphology apart from southern minor axis dust structure Post- starburst/LINER

• ptical characteristics

What is powering the compact IR luminosity - Obscured AGN or nascent starburst? HST v-band

ALMA reveals a molecular jet - precessing?

Grey scale: Systemic velocities Red and blue: High velocity gas High velocity gas aligned along line-of- sight 100 pc

A molecular ”jet” swirling around an axis perpendicular to the line of sight may reproduce

• bservations. May signal obscured, accreting SMBH

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Compare to garden sprinkler

Molecular mass: jet: 1-6x107, (“wind”: 108 M⊙) - Extent: 400 pc Opening angle: jet:small, wind: 50◦– 70◦ Age: jet: 0.5-2 Myr? Outflow velocity: jet: 200 - 800 kms-1, wind: 30-100 kms-1 dM/dt: jet: 6–30 M⊙ yr−1 dP/dt: jet:10-40LIR/c

ALMA Band 9, 50 mas CO 6-5 observations show base of molecular jet

• Dense (n>104 cm-3), warm molecular gas (>100 K) in the jet +

narrow wind on scales 10-20 pc (Aalto+17)

• Strong excitation gradient along jet.
• Herschel shows very high CO excitation – originating in jet launch

region in nucleus?

THE DUAL MOLECULAR ”JETS” OF THE LIRG MERGER NGC3256

Extreme jet collimation. Molecular gas along spine

• f jet

Narrow wind

A rotating disk wind

• Jet is surrounded by a

narrow rotating disk-wind

• Wind may be magneto-

centrifugally driven

• Energetics also allow jet

to be a gravitationally powered magneto- centrifugal wind

• Jet is changing direction –

jet/wind interactions

Projected 60-80 kms-1

High dispersion and gas inflow

• Velocity widths in jet ΔV>80 km/s on 2 pc scales – for r>30

pc.

• Jet may inject turbulence in jet-wind interactions
• ΔV>30 km/s in r=50 pc gas structure in ”disk”, but rotation
• f molecular disk is extremely slow suggesting a structure

with σ/vrot >1

• Redshifted CO and HCO+ self-absorption 20-30 km/s.

Foreground cool shell of infalling gas?

• Non-circular motion in nuclear disk matching

Keplerian rotation – inflow or projected outflow? Evidence for 10-15 degree warping out to r=20 pc - created by inflow?

NGC1377 – a post-CON?

• Compact 0.8 mm dust continuum suggest

an asymmetric dusty torus of radius r=2 pc.

• Column densities N(H2) > 1024 cm-2

for r<1-2 pc

• Nuclear dynamics is complex – launch

site of rotating wind, possible inflow. Cannot exclude binary SMBH. NGC1377 similar to CON host galaxies. But

• bscuration appears to occur on smaller scales

than in CONs. Disk gas may have been ejected by the molecular jet and wind. Feeding-cycle where ejected material return to fuel further growth? Would explain

• rigin of nuclear gas

0.8 mm continuum 5 pc

Nuclear high-velocity gas

2 pc

Compare to gas entrained/pushed by radio jets

• Molecular gas found lining radio jets – gas is pushed and heated – e.g. M51, NGC1068, IC5063 (e.g.

Matsushita+06,14; Garcia-Burillo+14,+17, Morganti+15, Dasyra+16, Oosterloo+17). In ESO 420-G13 a previously unknown jet is revealed through its interaction with the ISM.

• In NGC1377- no radio jet detected so far and the molecular gas appears to be on the jet axis:

Entrainment vs disk-wind? Is the jet powered by accretion onto the CND – not the accretion disk? The angular momentum loss may help the remaining gas reach the nucleus.

M51 NGC1068 (Garcia-Burillo+17)

(Matsushita+14)

colour: C2H (N=1-0) emission contours: jet emission @87GHz

Red: HCN(1-0)/CO(1-0) ratio

• map. Blue: 6 cm continuum

ESO 420-G13 (Fernández-Ontiveros+19)

Colour: ALMA CO 2-1 Contour: Ne II

Conclusions

• Compact Obscured Nuclei – CONS (N(H2)>1025 cm-2) are found in

some U/LIRGs. Rich in molecules.

– Can be probed by e.g. mid-IR pumped HCN. ALMA CON-quest survey. – IC860: massive inflow + nuclear column N(H2)>1026 cm-2. Evidence of very dense outflow.

• Accreting SMBH or top-heavy IMF SB?

– CONs appear at first not to have outflows – but mm/cm observations reveal fast outflows – collimated and obscured. – There is some evidence that CONs may have recurrent, cyclic nuclear activity.

• Extremely collimated and radio-quiet molecular jet in NGC1377.

MHD disk-wind?

– Jet appears to be precessing inside a rotating molecular wind. – Different from radio-jet driven molecular gas (or so it seems…) – New form of feedback: Outflow helped nuclear growth rather than negative feedback?

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HCN 3−2

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HCO+ 3−2 HCO+ 3−2 HCN 3−2

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Complex ground state HCN/HCO+ emission/absorption profiles