Probing AGN/Galaxy Co-Evolution with Spitzer-Selected AGN

Jennifer Donley, Hubble Symposium

Probing AGN/Galaxy Co-Evolution with Spitzer-Selected AGN

Jennifer DonleyLos Alamos National Laboratory

Collaborators: CANDELS and COSMOS Collaborations, including: Marcella Brusa, Peter Capak, Carrie Cardamone, Angel Castro, Mauricio Cisternas, Francesca Civano,

Chris Conselice, Darren Croton, Stephanie Fiorenza, Nimish Hathi, Olivier Ilbert, Chris Impey, Jeyhan Kartaltepe, Anton Koekemoer, Dale Kocevski, Charles Liu, Ray

Lucas, Vincenzo Mainieri, Mark Mozena, Takamitsu Miyaji, Preethi Nair, David Rosario, Mara Salvato, Dave Sanders, Brooke Simmons, Vernesa Smolcic, Eva

Schinnerer, John Silverman, Jon Trump, Carolin Villforth, Gianni Zamorani


AGN/Galaxy Co-Evolutionn

orm

alize

d s

pace

den

sity

(M

pc-

3)

Wall+ 05 Wall+ 05

AGN Activity Star-formationradioX-ray

X-rayoptical

AGN Evolution

tage = 3.3 Gyr

Velocity Dispersion of Host Bulge (km/s)

Bla

ck H

ole

Mass

(M

sun)

M-σ: Local Inactive Galaxies

Gultekin+ 09d<150Mpc

M-σ Relation: Unexpected correlation between SMBH mass and the stellar velocity dispersion/mass/luminosity of the kpc-scale galaxy spheroid (bulge) for local inactive (and active) galaxies (Ferrarese & Merritt 2000, Gebhardt+ 2000)

Implies a connection across 9 orders of magnitude in scale, which suggests co-evolution of the AGN and galaxy populations.


Implies a connection across 9 orders of magnitude in scale, which suggests co-evolution of the AGN and galaxy populations.

•AGN Feedback: if radiation pressure from an AGN growing at its maximum possible rate (LEdd) all of the gas to the edge of the bulge, balancing the outward radiative force with the inward gravitational force gives:

• (Feedback) + Merger-Driven Fueling: gravitational torques from major galaxy mergers could fuel the AGN near LEdd, simulations invoking merger-driven fueling+ AGN feedback reproduce many properties of the AGN and galaxy populations (e.g. Di Matteo + 05, Hopkins+ 08)

M-SIGMA Relation

predicted (e.g., Fabian+ 99):

observed (Gultekin+09):

Sanders+ 88Alexander+ 12


EVIDENCE FOR MERGERS?

• Merger-driven accretion (and AGN/galaxy co-evolution) may be most important at high AGN luminosities and/or high redshifts (e.g., Kauffman+ 03, Hopkins & Hernquist 06, Hasinger+ 08, Kartaltepe+ 10, Lutz+ 10, Shao+ 10, Rovilos+ 12, Treister+ 12, Urrutia+ 12).

X-ray Selected AGN Samples: •Seyfert-luminosity AGN are often found in disks and do not appear to be merging/interacting more frequently than control samples, either at z<1 or z~2 (e.g. Grogin+ 05, Gabor+ 09, Cisternas+ 10, Schawinski+ 11/12, Kocevski+ 12, Simmons+ 12)

• However... there is evidence for a factor of ~2.5 enhancement of Seyfert-level AGN activity in close pairs (Silverman+ 11, Ellison+ 11), as well as an increased merger fraction in local hard X-ray selected samples (Koss+ 10).

Koce

vsk

i+ 1

2


Defining a Better AGN Sample

Requirements: high-luminosity, high-redshift, host galaxy/merger signatures visible (low-luminosity or obscured by the torus or the host galaxy)

Alexander+ 12

3C273

optical

selection

X-ray Obscuration

Gilli+ 07

X-ray selection

Solution: use the infrared signature from the hot obscuring dust to select the AGN


Spitzer Selected AGN

Main challenge: both AGN and star-forming galaxies can be bright in the infrared

•(reliable) Spitzer selection tends to identify twice as many AGN as X-ray selection (Donley+ 08)

IRAC Power-law/IRAC Colors (Lacy+ 05, Stern+ 06, Alonso-Herrero+ 06, Donley+ 07, 08, 12)

•IR emission from hot AGN-heated dust fills in the dip in the host galaxy’s SED.

•The strength of this feature depends on the relative luminosities of the AGN and its host.

•The red thermal power-law-like continuum is visible in both unobscured and obscured AGN.

Luminous AGN

Star-forming Galaxy

Donley+ 12


IRAC AGN Selection Wedges

Spitzer IRAC Color/Color cuts:

1) Luminous AGN templates occupy a well-defined region in IRAC color-space.

2) Star-forming galaxy templates also fall in the selection wedges (Lacy+ 04, Stern+ 05), which were originally defined for use in shallow surveys. The problem gets worse at high-z.

Lacy+ 04 Color Space (Donley+ 12)


SElecting luminous AGN

Lacy+ 2004 Selection Region Stern+ 2005 Selection Region

IRAC-Selected AGN in COSMOS (Donley+ 12)

Box containing power-law AGN

















New IRAC SElection

• The new criteria recover 75% of AGN with QSO-luminosities (log Lx >= 44), yet only ~50% of IRAGN are X-ray detected (at 50-160ks depth).

• Typical redshift of IRAGN: z~ 2 ± 1

Donley+ 12Donley+ 12

IRAGN = intrinsically luminous, often heavily obscured AGN at z~2 ± 1

17% of Lacy AGN28% of Stern AGN


Recap

• The M-σ relationship tells us that galaxies and supermassive black holes are evolutionarily related.

• Major galaxy mergers + AGN feedback provide the most likely explanation for this scenario.

• Studies of X-ray selected AGN (samples dominated by low-luminosity AGN with low to moderate obscuration) find no evidence for increased merger activity in AGN.

• What we need to test this model is a sample of luminous, high-redshift, and heavily obscured AGN.

• Spitzer IRAC selection identifies this sample of AGN!

• Question: Are mergers driving the growth of infrared AGN? If so, their morphologies should be different than those of X-ray AGN.


CANDELS• CANDELS: Cosmic Assembly Near-Infrared Deep

Extragalactic Legacy Survey (Grogin+ 11, Koekemoer+ 11)

Grogin+ 11


Visual Morphologies of AGN in CANDELS/COSMOS

• CANDELS covers ~200 sq. arcmin. of the COSMOS field and contains:

• 43 IRAGN, 16 of which have no X-ray counterpart

• 73 Chandra or XMM-selected AGN that are not IRAGN (these lower-luminosity/lower-redshift AGN will serve as our control sample).

• Each AGN was classified by 21 classifiers:

• Morphology (NOT mutually exclusive): Spheroid, Disk, Irregular/Peculiar, Compact/Pt. Src, Unclassifiable

• Interaction Class (mutually exclusive): Merger, Interaction in segmap, Interaction beyond segmap, Non-interacting Companion, None

• Flags include: Tidal Arms, Double Nuclei, Asymmetric, Pt Source Contamination


Example:

• Consensus Morphology Class: classes chosen by at least half of the classifiers (11+)

• Consensus Interaction Class: most common of the following:• U: undisturbed (no

interaction, no asymmetry, tidal tails, or double nuclei)

• UC: undisturbed companion

• D: disturbed (though not clearly interacting/merging)

• IM: interacting or merging (will later be broken down into IM-undisturbed and IM-disturbed)

Donley+ 13 (in prep)


CANDELS/COSMOS AGN


Morphology Classes

Interaction Classes

Fract

ion

X-ray-only AGN

•low luminosity, range of redshifts, low to moderate obscuration

•very few irregular or asymmetric hosts, most likely to be undisturbed or undergoing interactions that are not disturbing their host galaxy

IR-only AGN

•high luminosity, mostly high redshift, heavily obscured

•tend to have irregular, asymmetric hosts, and are most likely to be either interacting or merging in a way that is disturbing the host or disturbed though not clearly interacting (late phase of merger?)


Morphology Classes

Interaction Classes

Fract

ion


IR+X-ray AGN (excluding BLAGN)

•high luminosity, mostly high redshift, less heavily obscured

•tend to have properties between those of X-ray only and IR-only AGN

•are as likely as IR-only AGN to be interacting/merger and disturbed

CANDELS/COSMOS AGN


Summary

• Galaxy mergers + feedback provide a theoretical explanation for M-σ, but the most studied AGN (X-ray AGN) appear to be dominated by secular processes.

• Infrared selection of obscured AGN identified the population of AGN missed by X-ray surveys that is most likely to be driven by major mergers.

• The CANDELS/COSMOS morphologies of IR and X-ray selected AGN indicates that, as predicted, mergers likely play a dominant role in triggering luminous, high-redshift, and obscured AGN, and may therefore be responsible for driving the M-σ relation.

low-moderate luminosity X-ray AGN

mergers(high luminosity)

low-moderate luminosity X-ray AGN (?)

IR+X-ray (obscured)

IR-only (very

obscured)

IR-only (disturbed)

unobscured IR/X-ray/Optical AGN

Figure

s fr

om

Ale

xander+

12secular

(low luminosity)

Documents

Probing AGN/Galaxy Co-Evolution with Spitzer-Selected AGN