AGN feedbackと銀河進化

京都大学 修士一回生札本佳伸

Contents

• AGN feedbackとはどのようなものか

• AGN feedbackのMotivation

• AGN起源のOutflow観測例

• Remaining Issue

AGN feedbackとは銀河の中心ブラックホールの影響がkpc,Mpcスケールで起こり、星生成を止め、最終的にブラックホール自身に影響することで、銀河の進化を進める過程

大きく分けて”Wind mode””Radio mode”のfeedbackが考えられる

AGNCold Gas

Wind

a few×10kpc a few×Mpc

Jet

Hot Gas

Time

今回はWind modeについて考えたい

Wind mode Radio mode

Wind mode AGN feedbackTime

Cold gasAGN

Wind

a few×10kpc

Quasar mode,Radiative mode とも言われる

1. AGNが何らかの過程で周囲にWindを生む2. 出来たWindが星間物質を加速する(Outflowを生む)

3. 銀河からガスが出て行き、星形成やBlack HoleへのGas accretionが抑制される

超巨大ブラックホールと銀河の共進化AGN host 銀河の星形成史を考える上で重要になる

Outflow

AGN feedbackのMotivation~Negative feedback of AGN~

local color-mass diagram(図: Cattaneo+09より)

REVIEWS

The role of black holes in galaxy formationand evolutionA. Cattaneo1,2, S. M. Faber3, J. Binney4, A. Dekel5, J. Kormendy6, R. Mushotzky7, A. Babul8, P. N. Best9, M. Bruggen10,A. C. Fabian11, C. S. Frenk12, A. Khalatyan13, H. Netzer14, A. Mahdavi15, J. Silk4, M. Steinmetz1 & L. Wisotzki1

Virtually all massive galaxies, including our own, host central black holes ranging in mass from millions to billions of solarmasses. The growth of these black holes releases vast amounts of energy that powers quasars and other weaker activegalactic nuclei. A tiny fraction of this energy, if absorbed by the host galaxy, could halt star formation by heating and ejectingambient gas. A central question in galaxy evolution is the degree to which this process has caused the decline of starformation in large elliptical galaxies, which typically have little cold gas and few young stars, unlike spiral galaxies.

Galaxies come in two basic types: ‘football-shaped’ ellipti-cals and ‘disk-shaped’ spirals (Fig. 1). Spirals containplenty of cold gas, which forms stars, whereas the gas inellipticals is too hot to form stars. Thus, ellipticals lack the

young blue stars that are usually seen in spirals, and are generallyquite red. Spirals also have central bulges structurally resemblingminiature ellipticals. Owing to this similarity, we use the term‘bulges’ for bulges within spirals and for ellipticals indiscriminately.

Each bulge contains a central black hole, whose mass is propor-tional to the bulge stellar mass1–5, MBH < 0.001Mbulge. Black holesand bulges also formed at about the same epoch in the lifetime of theUniverse6,7. These observations imply that the formation of blackholes and the formation of bulges are closely linked. Matter fallingonto a black hole releases a huge amount of energy8, of the order of10% of the rest mass energy, E 5 mc2, mainly in the form of photonsbut also in the form of radio-luminous jets of charged particles9,10.Even a tiny fraction (,1%) of the energy released within each bulgecould heat and blow away its entire gas content, thus explaining thelack of star formation in bulges.

The theorist’s goal is to understand these observations in a cosmo-logical context. In the standard picture11–13, most of the Universe iscomposed of dark matter, whose nature is unknown. Protons, elec-trons and neutrons, which compose gas and stars, make up the rest.They interact with dark matter purely through gravity, which deter-mines the evolution of the Universe on large scales. The Universeemerged from the Big Bang with small inhomogeneities. These even-tually grew into lumps, called haloes, by attracting surrounding mattergravitationally (Fig. 2). The competition between radiative coolingand gravitational heating determines the fate of gas in these haloes14–16.In low-mass haloes, cooling dominates. Galaxies grow through theaccretion of gas that falls to the centre in cold flows17,18, settles intodisks19 (but see refs 20, 21), and forms stars. However, when the halomass grows above a critical value of about 1012 solar masses18, heatingdominates, and the gas no longer accretes onto galaxies. Halo mergersform large haloes that contain tens or even hundreds of galaxies,called groups or clusters, respectively. Galaxy mergers within haloes

1Astrophysikalisches Institut Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany. 2Observatoire de Lyon, Universite de Lyon 1, 9 avenue Charles Andre, 69561 Saint Genis Lavalcedex, France. 3University of California Observatories/Lick Observatory, University of California, Santa Cruz, California 95064, USA. 4Department of Physics, University of Oxford,Keble Road, Oxford OX1 3RH, UK. 5Racah Institute of Physics, The Hebrew University, Jerusalem 91904, Israel. 6Department of Astronomy, University of Texas, Austin, Texas 78712,USA. 7Goddard Space Flight Center, NASA, Greenbelt, Maryland 20771, USA. 8Department of Physics and Astronomy, University of Victoria, Elliot Building, 3800 Finnerty Road,Victoria, British Columbia V8P 1A1, Canada. 9Institute for Astronomy, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK. 10Jacobs University Bremen, Campus Ring 1, 28759Bremen, Germany. 11Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK. 12Institute for Computational Cosmology, University of Durham,South Road, Durham DH1 3LE, UK. 13Observatoire Astronomique Marseille-Provence, 38 rue Frederic Joliot-Curie, 13388 Marseille cedex 13, France. 14Wise Observatory, University ofTel Aviv, 69978 Tel Aviv, Israel. 15Department of Physics and Astronomy, San Francisco State University, 1600 Holloway Avenue, San Francisco, California 94132, USA.

2.5

2.0

9.5 10 10.5 11 11.5

1.5

u –

rLog(Mgal

/M . )

Figure 1 | The galaxy bimodality. The contours show the galaxy distributionon a stellar mass (Mgal) – colour diagram92. The difference between ultravioletluminosity and red luminosity, quantified by the magnitude difference u 2 r, isa colour indicator; larger values of u 2 r correspond to redder galaxies. Thecolour bar has been inserted to convey this notion visually and has noquantitative meaning. Galaxies are classified into two main types: spirals thatmainly grew through gas accretion (‘S’, shown in blue) and ellipticals thatmainly grew through mergers with other galaxies (‘E’, shown in red). ‘S0’galaxies are an intermediate type, but we assimilate them to ellipticals. Spiralshave central bulges, shown in red, that resemble miniature ellipticals. Allellipticals and bulges within spirals contain a central black hole, shown with ablack dot. Moreover, ellipticals and bulges within spirals have the same black-hole mass to stellar mass ratio, of the order of 0.1%. This is why we call them‘bulges’ indiscriminately. In contrast, there is no connection between masses ofblack holes and masses of disks (the galactic component shown in blue). Spiralsand ellipticals are separated by a colour watershed at u 2 r < 2 and a masswatershed at Mgal < M*< 1010.5M[ (ref. 92). M* is of the order of fbMcrit,where Mcrit < 1012M[ is the critical halo mass for gas accretion and fb < 0.17 isthe cosmic baryon fraction. Spirals form a sequence where the bulge-to-diskratio tends to grow with Mgal (Sc, Sb, Sa). Ellipticals have two subtypes57,93:giant ellipticals with smooth low-density central cores formed in mergers ofgalaxies that have long finished their gas (‘E core’)94 and lower-mass ellipticalswith steep central light cusps formed in mergers of galaxies that still have gas(‘E cusp’)95. Whereas core ellipticals formed all their stars over a short timespan at high redshift42, the formation of the lower-mass cuspy ellipticals fromthe ‘quenching’ and reddening of blue galaxies continues to low redshift96.

Vol 460j9 July 2009jdoi:10.1038/nature08135

213 Macmillan Publishers Limited. All rights reserved©2009

red sequence

blue cloud

green valley

星生成によるガスの消耗AGN feedbackによるガスの放出

Disk(star formation)銀河の合体によりElliptical(red and dead)銀河が出来る

と考えられている

二つしか分布が無いのは、中間のGreen valleyに滞在する時間が短い

合体後短時間で星生成が止まる

Motivation~Negative feedback of AGN (Springel+05より) ~

L82 SPRINGEL, DI MATTEO, & HERNQUIST Vol. 620

Fig. 4.—Color evolution in the vs. plane for gas-rich mergers withu! r Mr

BH accretion. Symbols on the tracks are spaced 0.5 Gyr apart, with the lastpoint corresponding to an age of !5.5 Gyr after the merger-induced starburst.For comparison, triangles show mergers without BHs at the same time, andthe filled circles give the observed mean color of the red part of the bimodalcolor distribution at a given luminosity (Balogh et al. 2004). [See the electronicedition of the Journal for a color version of this figure.]

This result demonstrates an important connection to the ob-served bimodal color distribution of galaxies and to the color-magnitude relationship for early-type galaxies. AGN feedbackappears to be required in order to move galaxies from the bluestar-forming population into the red population of “dead” gal-axies sufficiently rapidly. If the transition is too slow, thereshould be many more galaxies with intermediate colors, whichwould wash out the observed bimodality. Also, the observedtrend with luminosity of the mean color of the red mode ofthe bimodal color distribution, i.e., the color-magnitude rela-tion, is made steeper by the AGN feedback. Interestingly, thistrend can be approximately reproduced by our merger remnantswith BHs, at a time roughly 5.5 Gyr after completion of themergers. As a look-back time, this would correspond to a for-mation redshift of . Without BHs, the galaxies reachz ! 0.7

the required redness only much later, or not at all within aHubble time. While the idealized nature of our individual gal-axy mergers precludes us from drawing definite statistical con-clusions, our results indicate that BH feedback is essential forshaping the bimodal color distribution of galaxies.

4. CONCLUSIONS

We have demonstrated that gas-rich galaxies do not neces-sarily consume all their gas in the starbursts that accompanymajor mergers. Consequently, elliptical galaxies formed in suchevents can sustain star formation for extended periods of manygigayears that makes them relatively blue. However, if themerging galaxies host supermassive BHs at their centers, AGNfeedback provides a mechanism to quench star formation on ashort timescale. This introduces a marked difference in the colorevolution of galaxies: mergers of massive galaxies can produceremnants that redden to in about 1–2 Gyr.u! r ! 2.2–2.3Moreover, the AGN feedback drives a gaseous outflow thatleaves behind a gas-poor remnant. The dead elliptical galaxiesformed in this manner should be a good match to the luminousred stellar populations of many massive elliptical galaxies,which are devoid of star-forming gas and lack young stars.Also, AGN feedback may be an important driver in shapingthe observed bimodal color distribution of galaxies.Because BH growth is a strong function of the size of the

spheroid formed, the effects of AGN feedback sensitively de-pend on the masses of the merging galaxies. In our simulations,BH accretion modifies the properties of large elliptical remnantsstrongly, while those of forming dwarf spheroidal systems arelargely unaffected.

We thank Sandy Faber for interesting discussions. This workwas supported in part by NSF grants ACI 96-19019, AST 00-71019, AST 02-06299, and AST 03-07690, and NASA ATPgrants NAG5-12140, NAG5-13292, and NAG5-13381. Thesimulations were performed at the Center for Parallel Astro-physical Computing at the Harvard-Smithsonian Center forAstrophysics.

REFERENCES

Baldry, I. K., Glazebrook, K., Brinkmann, J., Ivezic, Z., Lupton, R. H., Nichol,R. C., & Szalay, A. S. 2004, ApJ, 600, 681

Balogh, M. L., Baldry, I. K., Nichol, R. C., Miller, C., Bower, R., &Glazebrook,K. 2004, ApJ, 615, L101

Barnes, J. E. 1988, ApJ, 331, 699———. 1992, ApJ, 393, 484Bell, E., et al. 2004, ApJ, 608, 752Blanton, M. R., et al. 2003, ApJ, 594, 186Bruzual, G., & Charlot, S. 2003, MNRAS, 344, 1000Ciotti, L., & Ostriker, J. P. 1997, ApJ, 487, L105———. 2001, ApJ, 551, 131Cowie, L. L., Songaila, A., Hu, E. M., & Cohen, J. G. 1996, AJ, 112, 839Di Matteo, T., Springel, V., & Hernquist, L. 2005, Nature, in pressFranx, M., et al. 2003, ApJ, 587, L79Hernquist, L. 1990, ApJ, 356, 359———. 1992, ApJ, 400, 460———. 1993, ApJ, 409, 548Hernquist, L., & Mihos, J. C. 1995, ApJ, 448, 41Im, M., Faber, S. M., Gebhardt, K., Koo, D. C., Phillips, A. C., Schiavon,R. P., Simard, L., & Willmer, C. N. A. 2001, AJ, 122, 750

Kauffmann, G., et al. 2003a, MNRAS, 341, 33———. 2003b, MNRAS, 341, 54Kawata, D., & Gibson, B. K. 2005, MNRAS, in press (astro-ph/0409068)Kazantzidis, S., et al. 2004, ApJL, submitted (astro-ph/0407407)Menanteau, F., Abraham, R. G., & Ellis, R. S. 2001, MNRAS, 322, 1Mihos, J. C., & Hernquist, L. 1994, ApJ, 425, L13———. 1996, ApJ, 464, 641Silk, J., & Rees, M. J. 1998, A&A, 331, L1Springel, V., Di Matteo, T., & Hernquist, L. 2004, MNRAS, submitted (astro-ph/0411108)

Springel, V., & Hernquist, L. 2002, MNRAS, 333, 649———. 2003, MNRAS, 339, 289Springel, V., Yoshida, N., & White, S. D. M. 2001, NewA, 6, 79Strateva, I., et al. 2001, AJ, 122, 1861Toomre, A. 1977, in The Evolution of Galaxies and Stellar Populations, ed.B. M. Tinsley & R. B. Larson (New Haven: Yale Univ. Obs.), 401

Toomre, A., & Toomre, J. 1972, ApJ, 178, 623Tremaine, S., et al. 2002, ApJ, 574, 740Weiner, B. J., et al. 2005, ApJ, in press (astro-ph/0411128)Wyithe, J. S. B., & Loeb, A. 2003, ApJ, 595, 614

No. 2, 2005 BLACK HOLES IN GALAXY MERGERS L81

Fig. 2.—Comparison of the star formation rate history of two colliding gas-rich spiral galaxies of mass with (solid line) and without123.85# 10 M,

(dashed line) central supermassive BHs. The merger triggers a powerful star-burst at time !1.5 Gyr, which is accompanied by a phase of Eddington accretionin the simulation with BHs. The feedback energy from accretion eventuallyblows away the gas surrounding the BHs, nearly terminating star formationin the remnant and stalling further growth of the BHs. [See the electronicedition of the Journal for a color version of this figure.]

Fig. 3.—Comparison of the color evolution of the merger of two collidinggas-rich spiral galaxies of mass ( km s!1) with123.85# 10 M V p 226, vir(solid line) and without (dashed line) central supermassive BHs. The thin dottedline marks a fiducial color evolution when it is assumed that no stars areformed after Gyr. [See the electronic edition of the Journal for a colorT p 2version of this figure.]

expected from the density dependence of the assumed Schmidt-like star formation law (Springel & Hernquist 2003). Thismakes them slightly redder at the same age. However, to re-produce the strong trend with luminosity seen in the mean colorof the blue population of star-forming galaxies (Balogh et al.2004), one needs to assume that larger galaxies are also older.Formally, we obtain a good match to the observed trend ifgalaxies of total mass ! started forming their stars124# 10 M,

about 4 Gyr earlier than galaxies of mass ! . While1110 M,

this trend qualitatively agrees with the proposed notion of “cos-mic downsizing” of star formation (Cowie et al. 1996; Kauff-mann et al. 2003b), it is important to note that our isolatedsystems represent at best a crude model for disk formationbecause several cosmological effects are neglected, most no-tably infall. The results therefore primarily serve to illustratethe color evolution of our galaxies when they do not suffer amerger.

3.2. Star Formation and Color Evolution in Mergers

In Figure 2, we compare the star formation rates in collisionsbetween two large gas-rich spirals, with and without BHs. Thecollision causes a nuclear inflow of gas, triggering a strongstarburst and fueling BH accretion in the simulation withAGNs. The feedback resulting from accretion first only dampsthe starburst, but once the BH has accreted at its Eddingtonrate for several Salpeter times, it begins to drive a powerfulquasar outflow. This wind can remove much of the gas fromthe inner regions of the merging galaxies, thereby nearly ter-minating star formation on a short timescale. As a result, thereis almost no residual star formation in the remnant with BHs,as opposed to the ordinary simulation where the remnant keepsforming stars at a nonnegligible rate of a few solar masses peryear for several gigayears, slowly reducing its star formationrate with a gas consumption timescale of order 2.6 Gyr.In Figure 3, we compare the temporal evolution of the

color in these two merger simulations. After a brief ex-u! rcursion into the extreme blue during the bursts, both remnants

begin to redden. However, this happens substantially fasterwhen AGN feedback is included. In fact, in our simulation setwe find that for galaxies more massive than ! the123# 10 M,

color evolution of the remnants is consistent with one whereno stars are formed at all after the burst—they will hencequickly evolve into extremely red, massive elliptical galaxies.However, the magnitude of this “termination effect” depends

on the masses of the galaxies involved. Because the BHs insmall galaxies grow only relatively little in mass, consistentwith the relation, AGN feedback is much less efficientM -jB

in smaller galaxies. Consequently, the change in the remnantevolution is progressively weaker for less massive galaxies. Inthe smallest galaxies we considered, of virial velocity V pvirkm s!1, the color evolution is nearly unchanged between80

simulations with and without BHs. In mergers of these systems,the small spheroids that form are relatively gas-rich and exhibitongoing star formation. Such galaxies appear to exist (e.g.,Menanteau et al. 2001; Im et al. 2001). For example, usingdata from the DEEP survey, Im et al. (2001) show that manymorphologically selected early-type galaxies at have bluez " 1colors and that they are likely to be low-mass, star-formingspheroids.

3.3. Relation to the Bimodal Color Distribution

In Figure 4, we show evolutionary tracks of the color evo-lution of the merger simulations for different progenitormasses,again in the versus plane. The last points on the tracksu! r Mr

correspond to an age of !5.5 Gyr after the merger-inducedstarbursts. At this fiducial time, we compare to the mean colorof the red part of the bimodal color distribution in the localuniverse, as determined by Balogh et al. (2004) for the SDSS.The large spacings of the markers on the track of the massive

disk galaxies during the transition from blue to red illustratehow rapidly the color transformation proceeds. Already !1 Gyrafter the merger, the color has reddened to about ,u! r ! 2.0and after a further gigayear, it reaches about . Inu! r ! 2.2contrast, without BHs the remnant takes 5.5 Gyr to reach

and has difficulty reaching the observed rednessu! r ! 2.1even after a Hubble time.

Time (Gyr)

SFR(M_sun

/yr)

R_magu-r

merger w AGNw/o AGN

5.5Gyr

Observedred sequence

・二つのdisk銀河のMajor merger・AGN luminosityの5%のエネルギーが周囲のガスに渡される・Starburst windもいれる・中心にAGNを持つときと持たないときを比較

REVIEWS

The role of black holes in galaxy formationand evolutionA. Cattaneo1,2, S. M. Faber3, J. Binney4, A. Dekel5, J. Kormendy6, R. Mushotzky7, A. Babul8, P. N. Best9, M. Bruggen10,A. C. Fabian11, C. S. Frenk12, A. Khalatyan13, H. Netzer14, A. Mahdavi15, J. Silk4, M. Steinmetz1 & L. Wisotzki1

Virtually all massive galaxies, including our own, host central black holes ranging in mass from millions to billions of solarmasses. The growth of these black holes releases vast amounts of energy that powers quasars and other weaker activegalactic nuclei. A tiny fraction of this energy, if absorbed by the host galaxy, could halt star formation by heating and ejectingambient gas. A central question in galaxy evolution is the degree to which this process has caused the decline of starformation in large elliptical galaxies, which typically have little cold gas and few young stars, unlike spiral galaxies.

Galaxies come in two basic types: ‘football-shaped’ ellipti-cals and ‘disk-shaped’ spirals (Fig. 1). Spirals containplenty of cold gas, which forms stars, whereas the gas inellipticals is too hot to form stars. Thus, ellipticals lack the

young blue stars that are usually seen in spirals, and are generallyquite red. Spirals also have central bulges structurally resemblingminiature ellipticals. Owing to this similarity, we use the term‘bulges’ for bulges within spirals and for ellipticals indiscriminately.

Each bulge contains a central black hole, whose mass is propor-tional to the bulge stellar mass1–5, MBH < 0.001Mbulge. Black holesand bulges also formed at about the same epoch in the lifetime of theUniverse6,7. These observations imply that the formation of blackholes and the formation of bulges are closely linked. Matter fallingonto a black hole releases a huge amount of energy8, of the order of10% of the rest mass energy, E 5 mc2, mainly in the form of photonsbut also in the form of radio-luminous jets of charged particles9,10.Even a tiny fraction (,1%) of the energy released within each bulgecould heat and blow away its entire gas content, thus explaining thelack of star formation in bulges.

The theorist’s goal is to understand these observations in a cosmo-logical context. In the standard picture11–13, most of the Universe iscomposed of dark matter, whose nature is unknown. Protons, elec-trons and neutrons, which compose gas and stars, make up the rest.They interact with dark matter purely through gravity, which deter-mines the evolution of the Universe on large scales. The Universeemerged from the Big Bang with small inhomogeneities. These even-tually grew into lumps, called haloes, by attracting surrounding mattergravitationally (Fig. 2). The competition between radiative coolingand gravitational heating determines the fate of gas in these haloes14–16.In low-mass haloes, cooling dominates. Galaxies grow through theaccretion of gas that falls to the centre in cold flows17,18, settles intodisks19 (but see refs 20, 21), and forms stars. However, when the halomass grows above a critical value of about 1012 solar masses18, heatingdominates, and the gas no longer accretes onto galaxies. Halo mergersform large haloes that contain tens or even hundreds of galaxies,called groups or clusters, respectively. Galaxy mergers within haloes

1Astrophysikalisches Institut Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany. 2Observatoire de Lyon, Universite de Lyon 1, 9 avenue Charles Andre, 69561 Saint Genis Lavalcedex, France. 3University of California Observatories/Lick Observatory, University of California, Santa Cruz, California 95064, USA. 4Department of Physics, University of Oxford,Keble Road, Oxford OX1 3RH, UK. 5Racah Institute of Physics, The Hebrew University, Jerusalem 91904, Israel. 6Department of Astronomy, University of Texas, Austin, Texas 78712,USA. 7Goddard Space Flight Center, NASA, Greenbelt, Maryland 20771, USA. 8Department of Physics and Astronomy, University of Victoria, Elliot Building, 3800 Finnerty Road,Victoria, British Columbia V8P 1A1, Canada. 9Institute for Astronomy, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK. 10Jacobs University Bremen, Campus Ring 1, 28759Bremen, Germany. 11Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK. 12Institute for Computational Cosmology, University of Durham,South Road, Durham DH1 3LE, UK. 13Observatoire Astronomique Marseille-Provence, 38 rue Frederic Joliot-Curie, 13388 Marseille cedex 13, France. 14Wise Observatory, University ofTel Aviv, 69978 Tel Aviv, Israel. 15Department of Physics and Astronomy, San Francisco State University, 1600 Holloway Avenue, San Francisco, California 94132, USA.

2.5

2.0

9.5 10 10.5 11 11.5

1.5

u –

r

Log(Mgal /M . )

Figure 1 | The galaxy bimodality. The contours show the galaxy distributionon a stellar mass (Mgal) – colour diagram92. The difference between ultravioletluminosity and red luminosity, quantified by the magnitude difference u 2 r, isa colour indicator; larger values of u 2 r correspond to redder galaxies. Thecolour bar has been inserted to convey this notion visually and has noquantitative meaning. Galaxies are classified into two main types: spirals thatmainly grew through gas accretion (‘S’, shown in blue) and ellipticals thatmainly grew through mergers with other galaxies (‘E’, shown in red). ‘S0’galaxies are an intermediate type, but we assimilate them to ellipticals. Spiralshave central bulges, shown in red, that resemble miniature ellipticals. Allellipticals and bulges within spirals contain a central black hole, shown with ablack dot. Moreover, ellipticals and bulges within spirals have the same black-hole mass to stellar mass ratio, of the order of 0.1%. This is why we call them‘bulges’ indiscriminately. In contrast, there is no connection between masses ofblack holes and masses of disks (the galactic component shown in blue). Spiralsand ellipticals are separated by a colour watershed at u 2 r < 2 and a masswatershed at Mgal < M*< 1010.5M[ (ref. 92). M* is of the order of fbMcrit,where Mcrit < 1012M[ is the critical halo mass for gas accretion and fb < 0.17 isthe cosmic baryon fraction. Spirals form a sequence where the bulge-to-diskratio tends to grow with Mgal (Sc, Sb, Sa). Ellipticals have two subtypes57,93:giant ellipticals with smooth low-density central cores formed in mergers ofgalaxies that have long finished their gas (‘E core’)94 and lower-mass ellipticalswith steep central light cusps formed in mergers of galaxies that still have gas(‘E cusp’)95. Whereas core ellipticals formed all their stars over a short timespan at high redshift42, the formation of the lower-mass cuspy ellipticals fromthe ‘quenching’ and reddening of blue galaxies continues to low redshift96.

Vol 460j9 July 2009jdoi:10.1038/nature08135

213 Macmillan Publishers Limited. All rights reserved©2009

w/o AGN

Red sequenceより青い銀河が増えるとRed sequenceが

消えてしまう

AGN feedbackの観測的証拠~quenching star formation Cano-Diaz+12より~

z=2.4のquasarを面分光観測Hαのfluxと[OⅢ]の速度場を同時に観測した

Outflowの見えるところではHα線が弱くAGN feedbackによって星生成が止まっ

ているものと考えられる

HαのFlux[OⅢ]の速度場

Outflow 星生成の停止

10kpc

この観測では、星生成由来と思われるHαの場所とOutflowの場所を比べてOutflowの起源を星形成で

なくAGNであるとしている

速度 flux

Observation of AGN Outflow~energy calculation Maiolino+12より~

Outflow成分[CⅡ]158um z=6.4の

quasarの観測

星生成の成分

炭素のアバンダンスを仮定　　　ガス質量一様球対称のoutflowを仮定　　　outflow velocity, outflow volume

outflowのエネルギーのlower limitは1.9×10^45erg/s

Star Burst由来のoutflowでは説明が苦しい

のでAGN由来が有力

一方で、[CⅡ]が全て星生成だとすると Starburst windが出せるエネルギーは

2×10^45erg/s

Remaining Issue1.Outflowのエネルギー源は本当にAGNか？・Starburst wind or AGN feedback?　　outflowを分解して、星生成の成分とOutflowの成分のgeometryを見る　　　星生成している場所とoutflowの場所を比べる　　　outflowのエネルギー計算の精度を上げる 星生成の

成分

Outflowの成分

2.AGN からのoutflowはどんなガスが見える？・よくわからない3.AGN feedbackは本当に銀河進化上大切？・銀河進化過程とAGN feedbackの関係を見る

銀河の金属量とAGN光度の比較形態進化との比較