Spectacular Shells in the Host Galaxy of the QSO MC2 1635+119

Spectacular Shells in the Spectacular Shells in the Host Galaxy of the QSO Host Galaxy of the QSO

MC2 1635+119MC2 1635+119

Nicola BennertNicola Bennert

University of California RiversideUniversity of California Riverside

Collaborators: Gabriela Canalizo, Bruno Jungwiert, Alan Stockton, Collaborators: Gabriela Canalizo, Bruno Jungwiert, Alan Stockton, Francois Schweizer, Mark Lacy, Chien PengFrancois Schweizer, Mark Lacy, Chien Peng

The Nature of QSO Host GalaxiesThe Nature of QSO Host Galaxies

Majority of luminous low-redshift QSOs in ellipticalsMajority of luminous low-redshift QSOs in ellipticals

(e.g. Disney et al. 1995; Bahcall et al. 1997; Floyd et al. 2004)(e.g. Disney et al. 1995; Bahcall et al. 1997; Floyd et al. 2004)

M_bulge – M_BH relation (e.g. Magorrian et al. 1998): M_bulge – M_BH relation (e.g. Magorrian et al. 1998):

QSOs with most massive BHs in galaxies with most massive bulgesQSOs with most massive BHs in galaxies with most massive bulges

What mechanisms trigger activity? Galaxy interactions/mergers?What mechanisms trigger activity? Galaxy interactions/mergers?

steep evolution of QSO activity with redshift: steep evolution of QSO activity with redshift:

accretion onto BH more common, triggering mechanism more commonaccretion onto BH more common, triggering mechanism more common

ULIRGs: close connection between mergers and QSO activityULIRGs: close connection between mergers and QSO activity

(e.g. Canalizo & Stockton 2001)(e.g. Canalizo & Stockton 2001)

Most QSOs: begin life as mergers (e.g. Sanders et al. 1988)?Most QSOs: begin life as mergers (e.g. Sanders et al. 1988)?

reside in old ellipticals (e.g. Dunlop et al. 2003)?reside in old ellipticals (e.g. Dunlop et al. 2003)?

The Nature of QSO Host GalaxiesThe Nature of QSO Host Galaxies

Dunlop et al. (2003): 33 AGNs (RQQs, RLQs, RGs, 0.1<z<0.25)Dunlop et al. (2003): 33 AGNs (RQQs, RLQs, RGs, 0.1<z<0.25)

hosts are massive ellipticalshosts are massive ellipticals

„ „indistinguishable from quiescent, evolved, low-redshift ellipticals atindistinguishable from quiescent, evolved, low-redshift ellipticals at

comparable mass“ comparable mass“

Elliptical galaxies formed through mergers given enough time?Elliptical galaxies formed through mergers given enough time?

(e.g. Toomre & Toomre 1972)(e.g. Toomre & Toomre 1972)

QSO activity triggered by merger, activity can outlast the signs of QSO activity triggered by merger, activity can outlast the signs of interactions?interactions?

Keck spectroscopy of 14 QSO host galaxies from Dunlop et al. (2003):Keck spectroscopy of 14 QSO host galaxies from Dunlop et al. (2003):

starburst component in all but one of the hostsstarburst component in all but one of the hosts

major starburst episodes (> 10% of mass) with ages 0.6-2.2 Gyr major starburst episodes (> 10% of mass) with ages 0.6-2.2 Gyr

(Canalizo et al. 2006)(Canalizo et al. 2006)

-> host galaxies not purely ancient stellar populations-> host galaxies not purely ancient stellar populations

Deep HST imagesDeep HST images

Five QSOs from Dunlop et al. (2003): Five QSOs from Dunlop et al. (2003):

~3.2 hours integration time with HST/ACS F606W~3.2 hours integration time with HST/ACS F606W

Are these major starburst episodes connected to merger events?Are these major starburst episodes connected to merger events?

OX 169OX 169PKS 0736+201PKS 0736+201

PG 0923+201PG 0923+201PHL 909PHL 909

Bennert, Canalizo, Jungwiert et al. Bennert, Canalizo, Jungwiert et al.

Spectacular shells in MC2 1635+119Spectacular shells in MC2 1635+119

V-mag = 16.5; z=0.146; 1 arcsec ~ 2.5 kpc; radio-quietV-mag = 16.5; z=0.146; 1 arcsec ~ 2.5 kpc; radio-quiet

M_BH = 1-7x10^8 M_sun (e.g. McLure & Dunlop 2001, Dunlop et al. 2003)M_BH = 1-7x10^8 M_sun (e.g. McLure & Dunlop 2001, Dunlop et al. 2003)

Host galaxy: elliptical with r_e = 5.75 kpc (Dunlop et al. 2003)Host galaxy: elliptical with r_e = 5.75 kpc (Dunlop et al. 2003)

~32x32 arcsec ~32x32 arcsec NGC 3923 (z=0.0058)NGC 3923 (z=0.0058)

10 arcmin 10 arcmin MC2 1635+119MC2 1635+119

Like NGC 3923, best example of ellipticals with shells (Malin & Carter 1983)Like NGC 3923, best example of ellipticals with shells (Malin & Carter 1983)


Shells at radii of 5-12 kpc, width of 1-2.5 kpcShells at radii of 5-12 kpc, width of 1-2.5 kpc

Use GALFIT (Peng et al. 2002):Use GALFIT (Peng et al. 2002):

PSF star (star at same position) PSF star (star at same position)

outmask saturated center outmask saturated center

fit to wings onlyfit to wings only

Fit host galaxy (1-3 Sersic profiles)Fit host galaxy (1-3 Sersic profiles)

BackgroundBackground

Outmask surrounding objectsOutmask surrounding objects

Fit bright neighbor galaxy Fit bright neighbor galaxy

~14x14 arcsec ~14x14 arcsec

Interleaved (shells appear on alternate sides of nucleus as Interleaved (shells appear on alternate sides of nucleus as rr increases) increases)

5 shells?5 shells?


De Vaucouleurs profile: similar results to Dunlop et al. (2003) but not good fitDe Vaucouleurs profile: similar results to Dunlop et al. (2003) but not good fit

2 Sersic profiles: 1 close to de Vauc. (R_e ~ 3kpc), 1 close to exp. (R_e ~ 16kpc)2 Sersic profiles: 1 close to de Vauc. (R_e ~ 3kpc), 1 close to exp. (R_e ~ 16kpc)

Canalizo, Bennert, Jungwiert et al. Canalizo, Bennert, Jungwiert et al.

de Vaucouleursde Vaucouleurs exponentialexponential

de Vaucouleurs+exponentialde Vaucouleurs+exponential 2 Sersics2 Sersics

Comparison with numerical simulationsComparison with numerical simulations

Shells known from local giant ellipticalsShells known from local giant ellipticals

(e.g. Schweizer 1980, 1983, Malin & Carter 1983)(e.g. Schweizer 1980, 1983, Malin & Carter 1983)

N-body simulations: minor mergerN-body simulations: minor merger

radial collition of dwarf elliptical/spiral with large ellipticalradial collition of dwarf elliptical/spiral with large elliptical

(e.g. Quinn 1982, 1984; Dupraz & Combes 1986; Hernquist & Quinn 1988, 1989)(e.g. Quinn 1982, 1984; Dupraz & Combes 1986; Hernquist & Quinn 1988, 1989)

t_dyn = dynamical time, center to turning pointt_dyn = dynamical time, center to turning point

Age of shell: t_shell ~ 3 x t_dyn (R_shell)Age of shell: t_shell ~ 3 x t_dyn (R_shell)

Outermost shell: stars captured during first passageOutermost shell: stars captured during first passage

Travel through giant galaxy, turn at R_turn, sweep back through center,Travel through giant galaxy, turn at R_turn, sweep back through center,

Form shell at other side R_shell ~ R_turnForm shell at other side R_shell ~ R_turn

-> have travelled 3 x R_turn since first passage through galaxy-> have travelled 3 x R_turn since first passage through galaxy

Shells: outward moving density wave composed of stars from accreted materialShells: outward moving density wave composed of stars from accreted material

on primarily radial orbits in potential of ellipticalon primarily radial orbits in potential of elliptical


Assume: Merger of giant elliptical + dwarf elliptical on nearly radial orbitAssume: Merger of giant elliptical + dwarf elliptical on nearly radial orbit

Dwarf is completely disrupted during first passageDwarf is completely disrupted during first passage

No outer shell dissolved so farNo outer shell dissolved so far

No outer shell missed due to low S/NNo outer shell missed due to low S/N

R_shell = 12 kpcR_shell = 12 kpc

t_dyn: depends on surface brightness profile of giant ellipticalt_dyn: depends on surface brightness profile of giant elliptical

Assume: Plummer sphere and de VaucouleursAssume: Plummer sphere and de Vaucouleurs


Plummer; R_e = 7.6 kpc; M=10^11 M_sunPlummer; R_e = 7.6 kpc; M=10^11 M_sun

150x150 kpc150x150 kpc

60x60 kpc60x60 kpc

Giant elliptical Dwarf elliptical dE (unsharp) Giant elliptical Dwarf elliptical dE (unsharp)

Jungwiert, Canalizo, Bennert et al. Jungwiert, Canalizo, Bennert et al.


Plummer sphere and de Vaucouleurs; R_e = 6-27 kpcPlummer sphere and de Vaucouleurs; R_e = 6-27 kpc

-> results of simplest plausible scenario: merging timescale ~100-700 Myr -> results of simplest plausible scenario: merging timescale ~100-700 Myr

Shell structure: highly sensitive to surface-density profileShell structure: highly sensitive to surface-density profile

sensitive to viewing angle; highest contrast if perpendicularsensitive to viewing angle; highest contrast if perpendicular

(Preliminary) Conclusions(Preliminary) Conclusions

Host galaxy: not de Vaucouleurs (modeling & simulations)Host galaxy: not de Vaucouleurs (modeling & simulations)

Younger stellar pop. (1-2 Gyr; see e.g. Kauffmann et al. 2003)Younger stellar pop. (1-2 Gyr; see e.g. Kauffmann et al. 2003)

Clear signs of recent minor merger (10-70 x 10^7 yrs), triggered QSO activity?Clear signs of recent minor merger (10-70 x 10^7 yrs), triggered QSO activity?

Comparable to quasar duty cycles (3-13 x 10^7 yrs; Yu & Tremaine 2002)Comparable to quasar duty cycles (3-13 x 10^7 yrs; Yu & Tremaine 2002)

No extended major starburst with minor mergerNo extended major starburst with minor merger

Outer arc: ~32 kpc radiusOuter arc: ~32 kpc radius

Debris from an older merger?Debris from an older merger?

Very deep HST images: Very deep HST images:

shells that did not show up in previous HST images!shells that did not show up in previous HST images!

First: collection of gas by major mergerFirst: collection of gas by major merger

Then: triggering of AGN by minor merger? Then: triggering of AGN by minor merger?

Shell structure depends on orbit, potential well, viewing angle:Shell structure depends on orbit, potential well, viewing angle:

Only small percentage of mergers detectableOnly small percentage of mergers detectable

-> are very common?-> are very common?

Canalizo, Bennert, Jungwiert et al. Canalizo, Bennert, Jungwiert et al.

OutlookOutlook

Include gas in simulations - so far only stars, but gas important for QSOInclude gas in simulations - so far only stars, but gas important for QSO

Same study for comparison sample of inactive „normal“ ellipticalsSame study for comparison sample of inactive „normal“ ellipticals

Candidates selected from HST archive Candidates selected from HST archive (deep images in broad filter close to F606W)(deep images in broad filter close to F606W)

Determine redshift from spectroscopyDetermine redshift from spectroscopy

Look for signs of interactionsLook for signs of interactions

Get deep Keck spectraGet deep Keck spectra

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Spectacular Shells in the Host Galaxy of the QSO MC2 1635+119