Talks & Ideas

[bottom] [Cross-Straight] [APRIM] [Accretion Workshop]

17.12.01

Seminar: Shahram Abbassi vertical structure of ADAFs: Hot it changes in ansymmetic \/asymmetric magnetic field & Fourier analysis

  • ADAF: 2 temperature why the B field is more important in two temperature?
  • Inflow rate is not constant
    • Convection (CDAF)
      • Prof. Yuan: ADAF is convectively stable !!
    • Inflow/outflow (ADIOS)
  • Even / Odd symmetric B-field are they realistic?

17.11.27

Lunch Seminar: Lei Hao (SHAO) TMT

  • Grand Layer Adaptive Optics (GLAO) vs. star oriented MCAO
  • relic of AGN activities: Hanny's Voorwerp

17.11.23

Xu Kong (USTC) Star formation quenching and mass assembly of galaxies

  • The origin of the bimodality (Faber+07)
Faber07.png
  • SF Quenching
    • Stellar mass (or structure)
      • SNe feedback / AGN feedback
      • Morphology / Bar / Bulge / disk
    • External (or Environment)
      • Tidal/ram pressure (stripping of cold gas)
      • Strangulation (stripping of hot gas atmosphere)
      • Harassment (impulsive encounters with other satellites)
  • inside-out or outside-in quenching
    • inside-out: galaxies still made stars on their outskirt but no longer in their interiors (Wang+11, Lin+13)
    • Outside-in: the quenching of SF seems to start in the outer parts of the galaxies and then spread to the cores.
  • How galaxy mass assembly mode depends on stellar mass $M_{\star}$
    • Massive galaxies: AGN feedback
    • Low-mass galaxies: shallower potential wells
  • Less massive galaxies ($M_{\star} < 10^{10}\,M_{\odot}$) mainly grow "outside-in"
  • The inside-out mode becomes important for the massive galaxies ($M_{\star} > 10^{10.5}\,M_{\odot}$).
  • The cessation of star formation propagates from the center of a galaxy outward as it moves to the red sequence (inside-out mode) (Li+17).
  • Inside-out picture of galaxy formation is supported by the gradients in oxygen abundance of HII region (Lin+17).
  • Quenching of SF in ETGs or Massive galaxies
    • AGN fedback: remove the gas reservoir
    • MQ: galactic disks become stellar spheroid, disk becomes stable against fragmentation to bound star-forming clumps (don't need remove gas).
bh_bulge.jpg
  • The quenching time scale of ETGs is very shorter than that of LTGs.

17.10.27 Seminar

Alberto Sesana (Birmingham Univ.) An overview of massive black holes along the cosmic history: formation, dynamics and gravitational waves

  • Formation of Seed of Massive black hole ($10^{4-5}\, M_{\odot}$)
    • direct collapse of PopIII gas (need to overcome the angular momentum)
  • Hierarchy growth of Black hole (Lucia+06) -> co-evolution between black hole and its host galaxy
    • Binary SMBHs are inevitable
  • Massive Black hole binaries
    • double quasars (Komossa 03) <- 10kpc
    • double peaked NL (Comerford 13). <- 1 kpc
    • double radio cores (Rodriguez 06). <- 10pc
    • shifted BL (Tsalmatzsa 11) / accelerating BL
  • Gravitational Waves -> characteristic of quadrapole shape
GW_freq.png

17.10.19 Colloquium

L. Athanassoula (LAM) Dynamical and chemical modeling of Milky Way-type galaxies

  • Major mergers:
    • Spiral (star) + Spiral (star) -> Elliptical (Toomre & Toomre 72, Toomre 77)
    • Spiral (w/ gas) + Spiral (/w gas) -> ? (de Vauccoulus)
  • Merging in simulations couldn't reproduce the classical bulge (Hopkins+)
  • Major merger simulation
    • include - gas, SF, feedback & cooling, & chemical evolution
    • more realistic - hot gaseous halo / AGN-like feedback / improve gas physics (GIZMO) / better modeling of the progenitors
Oldest stars intermediate age stars Youngest stars
gas poor gas poor gas rich
classical bulge thick disk & its bar Thin disk, bar, spirals, rings, disky pseudo-bulge
Violent relaxation strong shuffling secular evolution
2 proto galaxies merging period disk formation
Merger driven secular
---——> Time
  • The thick disk forms earlier and in a considerably shorter time scale, and thin disk forms a quite later time.
  • Chemical evolution - single stellar population (SSP) from evolution of individual stars with given initial mass function.
  • Shape of the bar depends on the stellar velocity dispersion (i.e. toomre Q) (EA+1983)

Sandra Faber (UCSC) Candles: The evolution of Galaxies after z~3

  • Galaxy evolution within $\Lambda$CDM could be complicated:
    • Star-formation physics
    • Feedback physics
    • Mergers
  • if the major-model is true, all bright AGN should bein disturbed environment.
  • Mergers do not play a significant role in fueling the central SMBH in most x-ray selected active galaxies at z~2. (Kocevski+12).
  • mergers were not that frequent (Lotz+15; Rodriguez-Puebla+17)
  • Toy-model (SHAM) -> $M_{\star}$ vs. $M_{halo}$ (Rodriguez-Puebla+17)
  • UVJ diagram (L'Abbe+05, Williams+09)
    • a primary tool for understanding galaxy evolution
    • distinguish between redness by intrinsic reason and redness by obscuration
  • BH fundamental plane: $M_{BH}$ in fixed $M_{\star}$ is smaller in larger $R_{e}$.
    • $M_{BH} \sim M_{\star}^{1.94} \, R_{e}^{-1.76}$
  • Halos are easier to quench at late time.

High Energy Astrophysics Division (HEAD) meeting @ Sun Valley, Idaho, USA (17.08.20-24)

Johannes Buchner // The Compton-thick growth of supermassive black holes constrained//

  • buchner+15, Merloni 15

Jillian Bellovary The growth of supermassive black holes in cosmological simulations

Jone Miller @ U of Michigan

  • Jet vs. Wind (Ashley King+13)
  • AGN wind self-similar MHD models (Fukumura+17)
  • B-field limit at the disk (Miller+16)
    • MHD model: B pressure > gas pressure
    • MCF model: B poloidal field > ram pressure

AGN Workshop @ Harbin (17.07.21-24)

Luis Ho (KIAA)

  • Luminosity function may not be correct.
    • Normalization may not be good. (currently 25% is baryon, but if we integrate it carefully, it becomes a few %)
    • duty cycle of jet is 5-10% -> not enough to explain heating.
    • etc …
  • Need to share the idea of simulations in different scales (no single run can cover every scale).

idea raised by Prof. Yuan

  • There is a maximum black hole mass for every red-shift, which is $M_{\rm BH} < 10^{10}\,M_{\odot}$
    • Why they have a limit to grow?
    • -> Simulate with different initial density and/or other initial properties to see whether there is a limit or not.
  • SFR-$\dot{M}_{\rm BH}$ has been observed to positive relation mostly. But some people argued that it may be negative.
    • -> Check the correlation in our simulation result.
  • Check if there is a delay between black hole accretion and star formation

Accretion Workshop @ SJTU

17.07.12

Feng Yuan (SHAO) Numerical simulation of black hole accretion and outflow

  • Wind confirmed by observation: Sgr A* (Aitket+01, Bower+03, Yuan+03)
  • ADIOS (Begelman colleagues) or CDAF (Narayan colleagues)
  • CDAF is not correct (convective instability is stable; net inflow & outflow is not significant)
  • virtual trajectory particle for wind study (Yuan+15)
  • disk-jet (Yuan+14,15,16)
    • matter dominate
    • powered by the rotation of disk
    • powered by the magnetic tower mechanism, not by Blanford-payne mechanism
      • difficulty in BP model:
        hard to sustain global poloidal magnetic field due to turbulent motion near the disk
        But, for protostellar disk, the temperature would be low to make it more stable, maybe okay.

Xinwu Cao Magnetically driven outflows from accretion disks in X-ray binaries and active galactic nuclei

  • Magnetic Prandtl number -> how turbulent in the accretion disk
  • Slim disk: optically thick, geometrically thick
  • Standard thin disk: optically thick, geometrically thin
  • ADAF: optically thin, hot, geometrically thick
  • accretion mode transition occurs while $\dot{m} \sim \dot{m} \sim 0.01$
  • large-scale magnetic fields dragging in thin accretion disks (Lubow+94)
  • The angular momentum of the disk is removed predominantly by the magnetically driven outflows. (Cao & Spruit 13)
  • state transition (Fender & Belloni 12)
Fender12.png
  • Why do only a small fraction of AGNs contain relativistic jets -> stronger magnetic field near the RL quasars than near the RQ quasars.
    • AGN will appear as RL one if rotation is lower than a critical value at the Bondi radius, otherwise it will appear as a RQ AGN
  • A clumpy disk region would be an obstacle for accumulation of external magnetic field
  • Why are jets switched off in the thermal state of XRBs, but still present in bright AGNs?

Yuexing Li (PSU) The Light and Sound From the Cosmic Dawn

  • What are the seeds of the first massive black holes?
  • How do the first black holes grow?
  • Did black holes and host galaxies co-evolve in the early universe?
  • Black hole models
    • Seed models (Rees78, Volonteri 10, Bromm & Loeb 03, Begelman+06, Li+07)
      • Stellar mass seed of 10-1000 $M_{\odot}$ from PopIII stars
      • Intermediate mass seeds of $10^{3} M_{\odot}$ from supermassive stars and stellar collisions
      • Massive seeds of $10^{4-5} M_{\odot}$ from direct collapse of hot, dense gas clumps
    • Accretion models (Bondi & Holye 44, Springel+05, Booth & Schaye 09, Li 11, Zhu+17)
      • Bondi accretion & Chaotic cold accretion
      • Eddington-limited accretion & super-critical accretion
    • Feedback
      • radiative feedback, thermal feedback …
  • super Eddington accretion doesn't make substantial mass growth of BH due to strong AGN feedback proportional to the accretion rate.
  • LISA detectability of GW from SMBH mergers (Li+17)

Qingjuan Yu (KIAA) evolution of massive binary black hole and GW radiation

  • Multi-wavelength GW astronomy (Colpi & Sesana 16)
Colpi16.png
  • Micro-lensing of lensed QSOs can probe the structure of disk accretion (Yan+14)
  • dual AGN frequency (Yu+11)
  • Observational appearance of a massive binary black hole depends on the evolutionary sage of the BBH and its environment both kpc-scale / sub-pc scale (accretion system)
  • stochastic GWB due to massive BBH mergers (galaxy merger rate + galaxy stellar mass function + BH-galaxy relation)
  • BH merger would be delayed after Galaxy merger.

Yi­Jung Yang (Sun Yat-sen Univ.) Cradle of seed black holes: two ULXs and a candidate nuclear IMBH in a blue compact dwarf galaxy

  • Ultra-luminous X-ray Sources (ULXs)
    • $L_{\rm edd} = 1.3 \times 10^{38} \left( \frac{M_{\rm bh}}{M_{\odot}} \right)$ erg/s
    • $10^{38} < L < 10^{41}$: relativistic beaming; thin/slim accretion disk radiation; pressure-dominated accretion disk
    • $L>10^{41}$: IMBHs $10^{2-6} M_{\odot}$ (Farrell+09)
    • Evolution of seed black holes (Greene 2012)
Greene12.png
  • Fundamental plane of BH activity (Merloni+03)
  • two ULXs in NGC 4861 are in "Very High" state, indicating super-Eddington accretion, meaning that the BH are accreting materials from their surroundings very efficiently and might grow heavier through time.
  • low-metallicity, star-forming BCDs are the ideal place to search for seed black holes /or massive stellar black holes.

Daniel Siegel (Columbia Univ.) Remnant accretion disks from neutron star mergers

  • GRhyro code for accretion physics: Einstein Toolkit
  • r-process nucleosynthesis enhances outflow (Siegel & Metger 16)
  • neutron rich ejecta from NS-NS or NS-BH mergers (decompression / rapid neutron capture (r-process)) -> heavy radioactive elements (alpha, beta decay, nuclear fission further expansion) -> thermal emission (kilonova; quasi isotropic, long lasting, high fraction of events)
  • first identification of self-regulation in neutrino-cooled accretion disks.

Xiangdong Li Failed supernovae and the formation of black hole low­mass X­ray binaries

  • Core-collapse SN (progenitor mass < 40 $M_{\odot}$) / Failed SN (progenitor mass > 40 $M_{\odot}$) (Fryer 1999)

Shuang­Nan Zhang (Institute of High Energy physics) On the problems of matter fall onto/into BH and EM radiation from BH merger

  • Oppenheimer Solution 1939: Singularity (co-moving observer) vs. Frozen Star (rest frame)
  • "Frozen star"-BH paradox: Gravitation (Minser, Thorne; Book)
    • distinguish between "frozen star" and "real" BH
      • merging two "frozen star" -> GW + EM
      • merging two "real" BH -> GW
  • Conclusion: "Frozen star" is wrong
    • matter is not accumulated outside of event horizon even in rest-frame point of view
  • What is BH?
    • mathematical BH: singularity or point mass
    • physical BH: all mass inside its event horizon
      • all mass outside event horizon
      • Not necessarily a singularity
    • astrophysical BH: physical BH formed in physical universe and clocked by outside observer
      • all mass inside event horizon but not a singularity
      • formed by gravitational collapse
  • Time-scale of BH merging via GW » EM

17.07.13

Gordon Ogilvie (Cambridge) Dynamics of eccentric and warped accretion discs

  • Warped discs around black hole (Nealon, Price, Nixson 15)
Nealon15.png
  • Prograde precession due to pressure in 3D eccentric discs (not shown in 2D models)
  • Kozai-Lidov instability is possible in interior discs inclined at less than $39^{\circ}$ (Zanazzi & Lai 17; Lubow & Ogilvie 17)
  • A net poloidal magnetic flux breaks the resonance in Keplerian warped discs and impedes warp propagation (Paris & Ogilvie 17)

Rebecca Martin (Univ. of Nevada) Polar alignment of circumbinary disks around eccentric binaries

  • disc misalignments are common - Binary protostar IRS 43 (Brinch+16)
    • due to turbulence in the gas
  • Precession is communicated through the disc by waves that propagates at the sound speed Cs/2.
  • SPH simulations w/ PANTHOM code (Price 12)

Rebecca Nealon Misaligned accretion discs

  • Lense-Thirring torque and viscosity produces the Bardeen-Petterson effect (1975)
  • Angular momentum kick during formation ? (Jonker & Nelema …)
  • Disk breaks in moderately inclined discs: inner torque vs. outer torque (at precession time scale is shorter than crossing time scale)
  • Truncated disc model (Ingram+16)
    • Precession of an inner accretion disc truncated at a specific radius $R_{t}$ (Ingram+09)
Ingram16.png
  • Precessing discs may be applied to QPOs
BHaccretionRings.gif

David Liptai General relativistic smoothed particle hydrodynamics (GR-SPH)

  • 3D-GRSPH into PHANTOM

Xing Wei (SJTU) Numerical Simulations and Experiment of Magnetorotational Instability

  • Keplerian disk is hydrodynamically stable -> MRI
  • MRI regime where centrifugal instability does not occur ($\Omega_{1} > \Omega_{2}\,{\rm but}\, r_{1}^{2}\Omega_{1} < r_{2}^{2}\Omega_{2}$)

APRIM @ Taiwan


Cross-Strait Symposium @ ASIAA Taiwan


17.06.21

Junxian Wang: The UV/optical variation of AGNs

accbb1.png
accbb2.png
  • Bluer when brighter (BWB)
    • contamination from the host galaxy. other none variable redder component (<- No)
    • disk thermal fluctuation (instability) <- likely
      • BWB pattern depends on time scale of the variability
      • larger disk has naturally longer variation
      • variation at different timescales probes disk emission at different radii
  • Difference of accretion disk nature between radio-loud and radio-quiet quasars
    • inner disc in RL quasars is less variable
    • Inner disk in RL quasars is variable more slowly
      • Inner disk in RL quasars is more stable
        stronger magnetic field in the disk in RL stabilize the inner disk
    • not likely Inner disc in RL quasars truncated
  • variation of long wavelength delayed to that of short wavelength (Czerny+15)
  • X-ray loudness is an additional factor which controls the variation amplitude.
    • disc turbulence is linked to the process that heats the corona

17.06.19

Sourabh Nampalliwar

  1. eLISA
  2. Novikov Thorne disk model
  3. spin of black hole
  4. non-Kerr nature?

17.06.13

Book: Beckmann & Schrader Active Galactic Nuclei

  • Chapter 1
    • "reverberation mapping" -> constraints on the broad-line emission region size and on the mass of the central black hole (Peterson & Horne 04; Bentz+09)
    • "Big blue bump" -> a positive flux excess relative to an underlying power-law continuum. (evidence for the presence for an accretion disk) (Richstone & Schmidt 80)
  • Chapter 3
    • Masers are generally believed to be associated with star-forming regions but they can also be associated with evolved stars (Elitzur 92; Reid & Moran 88)
  • Chapter 4
    • Genzel+01 pointed out that although ULIRGs might become giant elliptical galaxies in the future, they generally invoke a more dynamic host galaxy with moderate rotation, with decoupled gas dynamics and stellar dynamics.

17.06.07

Journal: Igumenshchev 07 - Magnetically Arrested Disks and Origin of Poynting Jets: Numerical Study (by Fuguo)

  • Prof. Yuan: BP mechanism has never been confrimed because no poloidal magnetic field has not been found except for very close to the rotating axis.
MAD.png

17.05.24

seminar: multi-wavelength observations for CGM (by TaoTao Fang @ Ximen Univ.)

  • Prochaska (2016) -> definition of media (IGM, CGM, ISM …)
  • sembach+03 -> sketch of infalling clouds light up and hot galactic corona
  • HVC (High velocity cloud) -> key issue is distance. (Mostly likely inside Milky Way, but hard to measure).
  • X-ray background: Cosmic; Local Hot Bubble; Galactic Halo
  • baryonic distribution profile (Extended Hot Halo model; Fang, Bullock, Boylan- Kolchin 2013) - rule out NFW; baryonic profile follows dark matter
  • Extended Hot halo model (Maller & Bullock 2004): Hot gas in galactic halos is thermally unstable and prone to fragmentation, forming high-density, cold clouds.
  • How halo is kept being hot for hubble time is problem:Initially makes hot by shock waves, gravitational contract …
    • cooling time scale is quite short (shorter than hubble time scale), so it must cool down quickly which is not consistent with observation.
    • cosmic rays from shocks during stellar feedback can be a heating source.
  • Highly ionized OVI are associated w/ star-forming galaxies (Tumlinson+13)
  • Yoshida+16: Halpha gas can be extended to 90 kpc.
  • Li+15: EAGLE is not always match the observation.
  • AGN and SF in dwarf galaxy (Reines+14)

17.05.22

seminar: Blazar (By Alok Gupta @ AIRES)

  • Radio-loud: $F_{\rm 5GHz} / F_{\rm B} \gtrsim 10$ only 10-15% AGN are radio-loud.
  • Blazar
    • BL Lacs (Featureless optical spectra) + FSRQs ( Prominent emission lines) in optical spectra
    • non-thermal radiation
    • Jet axis angle < $10^{\circ}$
    • multi-wavelength & multi-timescale phenomena
  • HESS (High Energy Stereoscopic System) - [MAGIC(Europe); VERITAS(USA); CANGAROO(Austraila,Japan), MACE(India)]
  • Variability
    • shock fronts in the jets
    • Instabilities or hot spots on the accretion disk
    • Binary Black hole model
    • Helical Jet Structure model (Blandford & Marscher)
    • No time lag between different wavelength -> same source
  • Big Blue Bump -> strong evidence of accretion disk emission
  • Presence of QPOs are fairly common in XRBs, but are rare in AGNs. (Graham+15, Nature; Gierlinski+08, Nature)
  • Periodic frequency -> estimate of BH mass (Paul Wiita formula)

17.05.17

group: Comparison of Hydro simulations w/ SA models (By Quan Guo)

17.05.10

Journal: Jones+17 Using Collisions of AGN Outflows with ICM Shocks as Dynamical Probes (by Zhaoming)

Jones+17.png

17.05.08

Seminar: Microvariability in BLAZAR (by Prof. Paul Wiita)

  • ~10% of Quasars are also radio-loud galaxies
  • Interaction of Jets with ICM (bending doubles)
  • Optical polarization "high" -> synchrotron domination
  • Flat Spectrum Radio Quasars/ HPQs (High polarization) /OVVs (Optical violently variable) -> Blazar
  • Doppler boosting (Kellerman+08)
  • 0.08 mag variation over 1 hour in BL Lac (Miller, Carini & Goodrich 1989)
  • Radio Loud: R = (5 GHz radio/flux)/(500 nm optical) > 10 or 100; Radio Quiet: R < 1 or 10
  • Relativistic jet w/ turbulent plasma crossing a standing shock near bulk acceleration zone is supported by VLBI measurements for BL Lac (Marscher+08, Nature).
  • Jet-in-Jet model: Designed to explain TeV blazars, where Lorentz factor>100 are needed to allow those photons to escape interactions. Current-driven instabilities or magnetic reconnection in Poynting dominated jet w/ $\Gamma \sim 10$

17.05.05

Seminar:The inner structure of early-type galaxies since z=1 from a simulation perspective (by Dandan Xu @ Heidelberg)

  • SDSS, ATLAS3D, CALIFA, GAIA, LAMOST, MaNGA, MUSE -> Campaign for stellar kinematics
  • radial mass density profile almost isothermal: $\rho \sim r^{-2}$ (Koopmans+06; Auger+10; Sonnenfeld+13)
  • isothermal form kpc to 100 kpc (Gavazzi+07)
  • More massive systems- Salpeter IMF; lower-mass systems- Chabrier IMF (Sonnenfeld+15, Shu+15)
  • Anisotropic stellar orbit (Binney & Tremaine 08)
    • Anisotropy parameter $\beta$ in the book Galactic Dynamics , p294
  • Central dark matter fraction ~ 40%-50% for Illustris ETGs, noticeably higher than those from the SLACS
  • dark matter fraction is increasing (Illustris) or decreasing (Prof. Guo) toward outward?)
  • DM- NFW: slop: -1 (dwarf: slop > -1; ETGs: slop < -1).

17.05.04

Colloq.:Probing missing baryons with X-ray Spectroscopy (Wei Cui @ Tsinghua & Purdue Univ.)

  • Cosmology Guide Page
  • Missing baryon: Only 60 % of baryons is accounted by UV & Optical.
    • -> Significant amount of hot gas is present
  • Local missing baryons: Dai+2010
    • -> hot halo extended beyond galaxy
  • Missing Metals
    • SF history predicts 0.16 solar
    • but observed cosmic metallicity is about 0.015 solar.
    • -> hot gas has an average metallicity of 0.2-0.3 solar.
  • How to detect the hot gas? -> High-resolution X-ray spectroscopy !!
  • STS (US) -> Chandra
  • STI (US): dropped due to lack of funding -> Astro-E (Japan): failed -> Astro-E2: failed -> Hitomi: failed -> Charm: planned

17.05.03

Seminar:Measuring and Modeling Variability in Quasars and Blazars (by Prof. Paul Wiita @ TCNJ)

  • BL Lacertae Objects
    • non-thermal spectrum: radio through X-ray and gamma-ray
    • Radiation strongly polarized
    • highly variable in all bands
    • greatly enhanced emission from the AGN due to relativistic boosting of a jet pointing very close to us.
AGN_unif.jpg
  • double hump SED in blazar (Boettcher & Reimer 04)
  • Superluminal motion (Wehrle+96)

17.04.26

Journal: lightcurve fast-rise-exponential-decay in a LLAGN 7213 (by Fuguo)

  • Thermal-viscous disk instability model (Lasota 2001,2016)
    • The sharp rise is due to hydrogen instability; the exponential decline due to the accretion of gas within the hot branch.
  • Tidal-Disruption-Event
  • Radiation-Pressure instability
    • slow-rise-fast-decay
  • Darwin Draft
  • Boussineq approximation: Variation of Entropy
  • Ozmidov length
    • maximum size of turbulent eddies in a stratified fluid
    • vertical disturbances on scales larger than the length of Ozmidov, the turbulent eddies cannot dissipate the kinetic energy/

17.04.24

Seminar: KROSS redshift one (Martin Bureau @ Oxford Univ.)

  • kinematics at $z \sim 1$ (Stott+16)
  • galaxies disk-like but dynamically hotter, turbulent ($<\sigma>=60 {\rm \, km\, v^{-1}} <V/\sigma>=2.2$)
  • Schmit-Kennicut relation: $\Sigma_{\rm SFR} \propto \Sigma_{\rm gas}^{n}$, where n=1-1.5
    • Measure $\Sigma_{\rm SFR}$ and then calculate the $\Sigma_{\rm gas}$ through the SK relation by assuming gas-to-dust index same as that in z=0.

17.04.20

Colloq.:Supernova Zoo: Observation and Theory (Xiaofeng Wang @ Tsinghua Univ.)

  • why SN Ia is most luminous compared to other types? :
  • Which type of SNe becomes GRBs and why??
  • Ultranovae: 100-1000 times brighter than normal Core-collapse SNe, but much lower birth rate, 1 among every 1000 normal core-collapse SNe.
  • Formation of SN Ia
    • Accretion Explosion (Single Degenerate): delayed-detonation model
    • Merged Explosion (Double Degenerate): Violet Merger model
    • We don't know the progenitors of some of the explosions !! -> how they can be used as distance ladder?!! (Nobel prize 2011)
    • Which one is brighter?? If SD origin is way brighter, it can be marginally okay to connect to the distance ladder.
    • two populations of SNe Ia: Normal & Fast-Expanding
      • fast-expanding : fast because of the presence of high dense region on the orbital plane. (high density -> easy to detect the velocity close to the center at which the velocity is faster). For Double Degenerate progenitor, the progenitors already clear the circum-stellar dense region.
        • have higher metallicity (red color): located at galactic nuclei (likely young and metal-rich)
        • Single-Degenerate progenitor: evidence is sodium absorption lines (effects of circum-stellar medium)
Gal-Yam13.png
  • Peculiar SN Ia: Super-Chandrasekhar-mass SNe Ia
    • low expanding velocity: the progenitor's mass can be very large (—> 2.3 $M_{\odot}$ : it can be maintained as white dwarf by fast rotation): why massive progenitor lead to the slower expansion velocity?
  • Bottom Line: Even for Single Degenerated progenitor, they would be very difficult to be considered it as a standard candle because of the large scatter by the contamination of circum-stellar materials.
sn_zoo-1.png

17.04.16

Lunch Seminar:ULXs and IMBSs (Li-Jung Yang @ Sun-Ye-Sen Univ.)

  • Intermediate-Mass Black Holes (IMBHs; $10^2 - 10^6 M_{\odot}$)
    • SMBHs are thought to be grown from the seed black holes which are in the intermediate mass range.
    • Great potential targets for future gravitational wave search
    • Formation
      • via mergers of steller-mass black holes
      • remnants of POP III stars (formed in the early Universe)
      • direct collapse of pre-galactic gas disc
    • Dominant radiation of the accretion disk?
    • $M-\sigma_{\star}$ relation can be applied to IMBHs?
  • Fundamental Plane of BH activity (Merloni+03)
  • $\log{L_{\rm R}} = 4.8 + 0.78 \log{M_{\rm BH}} + 0.67 \log{L_{\rm X}}$ (Gultekin+14)
  • $R_{\rm X} = L_{\rm R}/L{\rm X} = \nu L_{\nu} {\rm (5 GHz)}/L_{\rm X} {\rm (2-10 keV)}$

17.04.13

Colloq: Molecular Gas in 3D: From Global Dynamics to SMBHs (Martin Bureau @ Oxford)

  • figures in CDM model prediction and role of stellar FB (lower mass end) and AGN FB (higher mass end)
volonteri%2B12.png
  • targeting the ETGs with respect of molecular gas (—> young stars !!)
    • No gas ? or Much gas but less effective to turn from gas to star ?
    • ATLAS3D (CARMA)
    • Kinematics tracer: Even ETGs are rotating !!! (Davis+13)
  • JAM model (Jeans model with random motion)
  • Tully-Fisher is meaningful because it explains the relation between baryon (luminosity) and total mass including dark matter (rotation velocity). (Bureau+96)
    • also can be applied to ETGs with CO moleculars
    • Then, velocity dispersion / systemic rotation is constant? Because, in ETGs Faber-Jackson relation shows similar form to Tully-fisher relation
  • CO can be measured up to z~7 while HI only can be measured within z~0.01.
  • mass to light ratio (M/L):
    • stellar populations: age, metallicity, non-solar abundance, star formation history, initial mass function, …
  • $M_{\rm BH}-\sigma_{\star}$ (McConnell&Ma+13)
    • Masers only captured in Syfert.
    • Each observational work done has weakness. —> Observing the molecular may could give more useful tool study the BH properties
    • Resolved molecular close to black hole with CARMA high-resolution 0.25" = 20 pc), size of the molecular disk ~ 1 kpc (Davis+13)
(1)
\begin{align} \frac{G M}{r^{2}} &= \frac{v^{2}}{r} \\ M &\propto v^{2} r \\ {\rm define}~~ & M/L \\ \Sigma &= \frac{M}{\pi r^{2}} \\ L &= \frac{v^{4}}{\pi G^2 (M/L) \Sigma} \\ L &\propto v^{4} (M/L)^{-1} \Sigma^{-1} \end{align}

17.04.11

Colloq: How did our Galaxy Form? (James Binney @ Oxford)

  • less DM particles —> thicker disk (why?? less mass DM may contributes smaller heating ? why heating more?)
  • where GMC is set to form in the simulation?
  • GMC heat the disk (stars interact w/ GMCs and their orbits transit from circular orbit to eccentric, then gravitational dynamical friction comes into play. —> later on spiral wave manage the heating) and blur the spiral structures at early time.
    In other word, GMCs stabilize the disk.
  • migrated can be identified for their mass or type??
  • HOT TO GET THICK DISC?
    • Add the star with initial high distance from the midplane.
      are the thick disk in pressure equillibrium and steady ?

17.04.05

Journal: Meece, Voit, & O'Shea Triggering and Delivery Algorithms for AGN Feedback (by Fulai)

  • AGN Triggering Mechanism
    • Cold-gas triggered Feedback
    • Boosted Bondi-like Triggering
    • Booth & Schaye 09
  • AGN Feedback from Jet
    • Thermal feedback
    • Kinetic feedback

17.03.27

Lunch:Kohei

  • dSphs are ideal for study dark matter
    • DM rich: D/L ~ 10 to 1000
    • proximity
    • clean (no $\gamma$ ray)
  • Problem in small scale $\Lambda$CDM
    • Core-cups problem (Oh+11)
    • missing satellites problem (Moore+99)
    • too-big-to-fail problem (Boylan-Kolchin+12)
    • Satellite plane problem

17.03.23

Journal: X-ray Multi-epoch and Multi-instrument Study of Galaxy (measuring BH spin) (Yu Wang @ Fudan Univ.)

  • X-ray reflection (broad iron line) - BH spin measurement
  • "disk reflection method" (Reynolds 13)
  • ISCO depends on BH spin.
  • spectral blurring can be used to estimate the BH spin. (blurring from gravitation bending, beaming, doppler effect, gravitational redshift …)
  • measure of BH spin
    • Continuum Fitting (Zhang+97). (Stellar BHs)
    • Fe-K Method (Fabian+89) relativistically-broadened profile of the 6.4 keV Fe K$\alpha$ line (Stellar BHs, SMBHs)
    • QPOs. (Stellar BH)
  • BH spin vs. BH mass (Vasudevan+15, Reynolds 14)
  • large fraction of BHs are rapidly spinning. (Berti&Volonteri 08)
  • Bonson&Gallo (2016): BH spin can be easily overestimated.
  • hard-to-soft ratio: optical depth & temperature. (harder by Compton Scattering)

17.03.15

Journal: Narayan+03 Magnetically Arrested Disk: An Energetically Efficient Accretion Flow (Fuguo)

  • How MRI transport angular momentum outward
  • interchange instability
  • In MAD, radial velocity is very small in the accretion disk, and kinetic E is negligible. Large portion of potential E would be converted to other form during the accretion process, in the forms of radiation, kinetic energy, poynting flux.

Journal: Heath+06 Chemical enrichment of the intracluster medium by FR II radio sources (Xiadong)

17.03.13

Lunch:// BH mass growth over cosmic time// (Andrea Schulze @ NAOJ)

  • SFR History over cosmic time (Aird+15)
  • SF is most efficient at $M_{\rm h}\sim 10^{12} \,M_{\odot}$ (Behroozi+13)
  • observation evidence of outflows in quasar mode (Maiolino+12; Cresci+15)
  • AGN cosmic downsizing (Aird+15) —> hierarchic evolution
  • AGN luminosty (observed) degerate between $M_{\rm BH}$ and $\lambda=L_{\rm BH}/L_{\rm Edd}$
    • Type 1 AGN: estimate virial BH mass
    • Type 2&1 AGN: $M_{\star}$ and $L_{x}/M_{\star}$ as surrogate for lambda
  • virial motion in the BLR: $M_{\rm BH} = f \frac{R_{\rm BLR} \Delta v^{2}}{G}$
  • reverberation mapping: measure time lag, $\tau$, between variablility in continuum and broad line —> $R_{\rm BLR} = c \tau$
    • only nearby few samples
    • for larger samples: $R_{\rm BLR} \propto L_{5100}^{0.5}$ —> $M_{\rm BH} \propto L_{5100}^{0.5}\Delta v^{2}$
      • $L_{5100}$ is the luminosity at 5100 angstrom
  • $M_{\rm BH} - \lambda$ relation (Schulze+10)

17.03.09

Colloq: // FAST (Five-hundred-meter Aperture Spherical radio Telescope) // (Di Li @ NAOC)

  • Arecibo technique has a limitation that it works only on narrow-band.

17.03.01

Journal: Roberts+17 Towards self-consistent modelling of the Sgr A* accretion flow (Weixiao)

Journal: Yang&Reynolds How AGN jets heat the ICM (Maochun)

17.02.21

Lunch Talk: New results of nearby Galaxy survey from JCMT (Chris Wilson @ McMaster Univ.)

  • Gas depletion time: $t_{\rm gas} = M_{\rm mol}/SFR$
  • Environmental effects on H2 depletion (Mok+16)
  • Virgo galaxies clearly shows the enhanced H2/HI ratio.
    • preferentially caused by ram-pressure stripping. (other mechanisms: starvation, gravitational harassment …)
  • Despite enhanced H2 surface density in Virgo, gas is being turned into stars at low rate.
    • Possibly affected by high pressure in IGM.
  • JINGLE: The JCMT dust and gas In Nearby Galaxies Legacy Exploration

17.02.16

Seminar:Density Waves in Strongly Radiation Pressure Dominated AGN Accretion Disks(Yan-Fei Jiang @ UC Santa Barbara )

  • XRBs: $P_{r}/P_{g} \sim 15$
  • AGN: $P_r/P_g \sim 10^{3}$ - radiation pressure dominated
  • Radiation pressure dominated flows are very compressible
  • radiation viscosity ; radiation is not scalar but tensor-like (Kaufman&Blaes 16)
  • angular momentum transfer: Reynolds stress (shock-driven accretion; $\delta \rho v_r \delta \phi$ ), Maxwell stress (conventional MRI; $-B_r B_\phi$), Radiation stress
  • Density waves [e.g. excited by self-gravity (Dong+15), or tidal torque (Ju+16) or turbulence (Heinemann+09)] provide Reynolds stress
  • Super Edd Accretion disks in AGNs
    • Growth of SMBH in early universe
    • Tidal disruption events
    • Narrow line Seyfert galaxies
  • Disks driven by spiral shocks may not behave like an alpha disk (Dexter&Agol 11)

17.01.19

Colloq.:Not-so-simple stellar populations in nearby, massive star clusters(Richrd de Grijs @ PKU)

  • simple stellar populations
    • single age
    • single metallicity
    • mass range given by the IMF
    • but for single stars only —> exclude "blue stragglers" & "binary systems"
    • deviate from simple stellar populations should be taken into account
  • In the binary, if one of them is evolved star, how it can be shown in HR diagram?
  • binary fraction is lower in the cluster center, and is larger in the cluster outskirt. (Li+13; N-body simulation by Geller+13)
    • But the cluster get aged, the fraction increase in the cluster center.
  • Possible reasons of broadening in HR diagram
    • binaries
    • secondary population (AGBs provide huge gas via wind, forming stars at the later time)
      • against by Li+16; the wind is too fast for the gas to be captured by gravity that lead to form secondary star.
    • rapid rotation (Royer+07; Bastian&de Mink 09) <- what makes stars rotate so fast?
    • -different He abundance- —> it should lead to be redder, which is not consistent with observation.
  • multiple stellar population should be needed; infalling gas from outside the cluster may provide gas to form stars.

17.01.17

Journal: Li+16AGN Heating iin Simulated Cool-Core Clusters (by Duan)

  • viscosity: shear viscosity & volume viscosity (just by jump like shock)
  • Always overheated within 100kpc in the simulation
  • Heating: Shock is more dominant than turbulence.
  • Heat radial transportation —> by advection.

Journal: Spin-Orbit Misalignment of merging Black Hole Binary (by Bin)

  • Spin-Orbit coupling: de Sitter precession > Spin-Spin: Lense-Thirring precession

17.01.14

Seminar: Polrized Emission of Blazars (Haocheng Zhang @ Univ. of New Mexico)

  • Synchrotron is strongly polarized. (proportion to particle density & magnetic field density)
  • comptron scattering is moderately polarized. (proportion to particle density & seed photon energy density)
  • High enery: electron compton scattering or protron synchrotron.
  • Low energy: electron synchrotron
  • Polarization degree (PD) ~ 10-20 deg.
  • Kink instability with weak magnetic field can produce low level of PD, which is consistent with observation.
  • Circular polarization : Weak compare to the linear polarization, but it is intrinsic from anisotropic particle distribution.

Colloq.: Red but not Dead: Starbursting Brightet Cluster Galaxies (BCGs) (Haojing Yan @ Univ. of Missouri-Columbia)

  • At low-z (z<0.5)
    • "red": dominated by old stellar populations
  • At early in time (z~3 and beyond)
    • "dead": little ongoing star formation
    • fit in the "down-sizing"(passive evolution) formation picture of high mass
  • Cooling Flow (Donahue+15): ICM has a temperature gradient such that materials can be funneled to the center
    • previously known as the "cooling flow" cluster
    • however not all cool core clusters have a star-forming BCG even though the "cooling flow" seems inevitable
  • BPT Diagram(Baldwin, Phillips Terlevich 1981): Distinguish AGN from SF galaxies.
  • W4 BCGs (Red but not Dead Clusters in WISE) - not dominant but still interesting
    • merger is likely being ruled out.
    • AGN is not important cause.
    • Their existing stellar populations have the same properties.
    • Their extraordinarily high SFRs based on mid-IR fluxes(W4) are backed up by the FIR measurements.
    • So where the gas for SF came from?

17.01.12

Colloq.: Some Unsolved Problems in Black Hole - Galaxy Coevolution (Luis Ho @ KIAA/PKU)

  • (Wu - Nature 2015) How the seed black hole becomes so massive ??
  • Correlation between black hole mass and bulge mass
    • Lowest mass of BH ?? - not observable
    • Highest mass of BH ??
    • —> Black hole accretion rate vs. Host galaxy star formation rate
      • observation: radiation —> challenging: calculation of BH accretion rate highly depend on the model (disk mode, efficiencies, etc)
  • What triggers AGN??
    • merger?? or stochastic secular evolution of galaxy??
  • AGN FB affects cold gas in the galaxy
    • in order to check the effectiveness of AGN FB, it would be essential to measure the ratio of cold gas and hot gas.
  • Key program: BHOLE (Black hole - Host Lifecycle Evolution)
  • M-sigma M-Mbulge: small scatter only ETGs or classical bulge.
    • Pseudo-bulge & LTGs: significantly large scatter
  • Reverberation Mapping of AGNs
    • cannot measure spatially, so try to resolve temporally !!
    • $M_{BH}(RM) = f \frac{R(\Delta V)^2}{G}$ (R=BLR size, $\Delta$ V=virial velocity, f=virial factor)
  • Radius-Luminosity Relation $R\propto L^{0.5}$ (Bentz+13)
  • 25% of ETGs has CO-emission : Gas is important even in the ETGs
    • ALMA observation would be critical.
    • Barth+16 M87 - $M_{BH} = 6.64 \times 10^{8} M_{\odot}$ by using CO-emission
  • GALFIT program

17.01.11

Journal: King+16 Discrete knot ejection from the jet in a nearby low-luminosity AGN, M81 (By Peiyao)

Journal: Yang&Reynolds 16 Interplay among cooling, AGN feedback, and anisotropic conduction in cool cores of galaxy clusters. (By Fuguo)

  • heat-flux-driven buoyancy instability (HBI)
  • thermal conduction depends highly on the temperature of clusters.
    • conductive heating - group: negligible; cluster (high mass): may important
  • conductive heating prevent gas from accreting onto the black hole, so reduces the AGN power.

17.01.05

Colloq:Is the IMF universal in galaxies? A MANGA view (Shude Mao @ Tsinghua Univ.)

  • $\xi(m)=\frac{dn}{dm} \sim m \frac{dn}{d\log m}$
  • Salpeter(1955) initial mass function (IMF):
    • $\xi(m) = A m^{-x}$, $x=-2.35$
  • Other: Kroupa($x=-1.3$), Bottom-heavy, Bottom-light, Chabrier
vanDokkum+10.png
  • Low mass stars and stellar remnants contribute little to galaxy's light, but a lot to mass.
  • IMF is critical to understand mass budget of galaxy evolution.
  • Universal stellar IMF: Chabrier 03
  • IFU survey: SAURON, ATLAS 3D, diskMass, CALIFA, CHILI, SAMI, MaNGA
  • IMF + Isochrones + Stellar spectra —> Simple Stellar Populations (+ Dust & SF and chemical evolution) —> Composed Stellar Population
  • fitting software (Starlight/PPXF)
  • ultimately calculate $M_{\star}/L$
  • plot of $(M_{\star}/L)_{\rm salp} vs. (M_{\star}/L)_{\rm stars}$: Cappellari+13
Capellari+13.png
  • $M_{\star}-M_{\rm gas}$ relation from ALFALFA Huang+12
  • conventionally $M_{\star}/L$ is assumed to be constant, but in fact, it should varies with radius of galaxy.
  • M dwarf stars shows significantly enhanced NaI absorption line because they have small radius and subsequently have high pressure gradient (van Dokkum & Conroy 10; Conroy & van Dokkum 12).
  • What causes the variation of IMF??
    Contradict conclusions of the correlation between IMF and galaxy properties
    • IMF is strongly correlated with Metallicity (Martin-Navarro+15).
    • IMF is strongly correlated with $\alpha$ particle enhancement (Mg/Fe) (Conroy&van Dokkum 12)
  • Bulge and disk IMFs different??
  • What happens to the IMF when galaxies merge? - Dry merger? or Wet mergers w/ gas
  • stellar mass function of redshift??

17.01.04

Journal: Zhu+15 Dust transportation in MRI turbulent disk (By Defu)