Transcript How to start an AGN: the role of host galaxy environment Rachel Gilmour (ESO Chile & IfA, Edinburgh) Philip Best (Edinburgh), Omar Almaini &

How to start an AGN:
the role of host galaxy
environment
Rachel Gilmour (ESO Chile & IfA, Edinburgh)
Philip Best (Edinburgh), Omar Almaini & Meghan Gray (Nottingham)
Why do some galaxies have AGN?
Gas -> black hole = AGN
No AGN Internal: size, morphology, star-formation
Historical: previous activity -- depletion,
feedback
0.01%
External: mergers, close encounters, tidal
field, strangulation, ram-pressure stripping
30%
External effects on galaxies
Morphology: spirals -> S0s
Star-formation rate: high -> low
Q1 – Do the frequency and properties of AGN
depend on the external environment?
Q2 – Can this be explained by the changes in the
type of host galaxies?
Where are AGN found?
Optical
Radio
~0.8
X-ray
Best '02
Johnson '03
Redshift
Ruderman '05
Eckart '05
Miller '03, Wake '05
Kauffmann '04, Coldwell '02
Best '04
~0.1
Reddy '04
Dressler '99
Ledlow & Owen '96
Galaxy density / AGN clustering
My projects
1. AGN in the A901/2 supercluster
• Detailed study
• X-ray detected AGN
• Includes groups, clusters, filaments, field etc.
2. Statistical survey of AGN in > 100 galaxy clusters
• X-ray detected AGN
• Find statistical excess of sources compared to “blank” field
• Split sample by cluster properties and redshift
The A901/2 supercluster (z=0.17)
Optical data (from COMBO-17 team)
People: Meghan Gray, Chris Wolf + COMBO-17
team, Bell and Papovich, Andy Taylor.
• Deep R-band imaging
• 17-band photometric redshifts for
~18000 objects (mR<24)
• 1240 supercluster galaxies found
A901a
• 282 supercluster spectra from 2dF
• Weak lensing map
A901a
A901b
Spitzer data
• MIPS 24-micron sources
X-ray data
• 12 ksec ROSAT images (HRI)
• 90 ksec XMM-Newton image
Filament
A902
SW group
A901/2: Finding the supercluster AGN
• Identify point sources
Sources
- wavelet detection on images from 3 cameras
- remove uncertain and extended sources
150
139
A901a
A901a
A901b
Emission
z=0.5 cluster
A902
SW group
A901/2: Finding the supercluster AGN
• Identify point sources
- wavelet detection on images from 3 cameras
- remove uncertain and extended sources
Sources
150
139
• Match with optical sources
- R-band, using likelihood ratios from 14000 random sources
- also Spitzer 24-micron data to resolve uncertainties
88
A901/2: Finding the supercluster AGN
• Identify point sources
- wavelet detection on images from 3 cameras
- remove uncertain and extended sources
Sources
150
139
• Match with optical sources
- R-band, using likelihood ratios from 14000 random sources
- also Spitzer 24-micron data to resolve uncertainties
88
• Determine supercluster membership
- COMBO-17 photometric redshifts and 2dF spectra
- Manual check for AGN contaminated sources
11
12
A901/2: Finding the supercluster AGN
• Identify point sources
- wavelet detection on images from 3 cameras
- remove uncertain and extended sources
Sources
150
139
• Match with optical sources
- R-band, using likelihood ratios from 14000 random sources
- also Spitzer 24-micron data to resolve uncertainties
88
• Determine supercluster membership
- COMBO-17 photometric redshifts and 2dF spectra
- Manual check for AGN contaminated sources
11
12
• Find out which are AGN
- check for low-mass X-ray binaries using fx/fB
12
- check for star-forming galaxies using Lx, hardness ratios, fx/fR,
star-formation rates from OII lines and OIII/Hβ line ratios
11
A901/2: Finding the non-AGN
Aim: Compare the AGN environments with control samples of galaxies which
have:
• no AGN
• similar magnitudes
• similar colours
• where AGN could be detected
Method:
• 100 samples of 66 galaxies
• equal number of galaxies in
each 0.5 magnitude bin
• exclude cluster centres
• use K-S and Kuipers tests
A901/2: AGN host galaxies
RESULT 1 : All of the AGN lie
in galaxies with mR < 20
RESULT 2 : ~5% of bright
supercluster galaxies contain
X-ray detected AGN (~1%
optically detected)
RESULT 3 : Brighter galaxies
have equal luminosity or
fainter AGN (92%)
A901/2: Separating the Environments
Define by
hand:
• Clusters
(A901a, A901a,
A901b, A902)
• Groups
• Outskirts of
large clusters
and groups
• Filaments
A901/2: Separating
the Environments - 2
1.5'
Two parameter
separation for
environments:
(1.5' = 250 kpc)
Local density:
clusters & field
Local colour:
groups & edges
filaments & clusters
A901/2: Separating the environments:
Does it work for all galaxies?
Blue group
Filament
Cluster
Red group / Edge
Field
A901/2: Environments of AGN
3.3% - AGN match
control in 2D
space
cluster
field
18% -AGN match
control in edge
and group
4% - AGN match
control in 1D
edge
space along
filament
cluster line (30%
in density only)
>98%-Lx
decreases along
the cluster line
direction
group
A901/2: Conclusions
1. ~5% of bright supercluster galaxies contain X-ray detected AGN.
2. All of the AGN lie in galaxies with mR < 20.
more gas, larger black hole
3. The lack of AGN in fainter galaxies is not due to a LX – mR
correlation.
no correlation or large galaxies are more stable
4. Compared to other similar galaxies, those with AGN lie in group or
edge like environments – moderate density and bluer than average.
suppression in centre, triggering on outskirts,
tracing star-formation, more smaller galaxies
5. AGN in more cluster like environments are fainter.
galaxies with more gas need less disturbance, strangulation reduces available gas
Where are AGN found?
Optical
Radio
~0.8
X-ray
Best '02
Johnson '03
Redshift
Ruderman '05
Eckart '05
Miller '03, Wake '05
Kauffmann '04, Coldwell
'02
A901/2
Best '04
~0.1
Reddy '04
Dressler '99
Ledlow & Owen '96
Galaxy density / AGN clustering
Chandra Clusters: Method
• Find sources in fields of galaxy clusters
• Predict source distribution assuming no cluster AGN
• Compare flux and radial distributions of excess sources
Abell 1689
AGN
HST Credit: NASA / N. Benitez
Chandra Clusters: The sample
Secure redshift and z > 0.1
Exposure > 10 ksec
X-ray detected cluster (after data reduction)
=== 139 good cluster fields ===
Morphology
89 'relaxed'
23 'disturbed'
19 'contaminated'
8 high redshift
(z > 1)
Redshift distribution
Luminosity
0.1 – 70 x 1044 erg/sec
z
+ 8 with z > 1
Chandra Clusters: Prediction
Blank fields – deep surveys (22) and high redshift QSOs (22)
Sensitivity map – background, size, exposure, accuracy + errors
Background
Exposure time
Sensitivity
map
Source size
Good region
Chandra Clusters: Lensing
Lensing changes background sources : flux increases
number density decreases
Net result: lensing causes ~ 10% reduction in the central 0.5 Mpc
N
INPUTS:
• Background AGN redshift distribution (3 used)
Lx
• Cluster model (SIS now, NFW in future)
• Cluster luminosity => mass
Model = Blank fields + Sensitivity map + Lensing
Chandra Clusters: Radial position
Excess of 1 or 2
sources per cluster
Radial trend seen in
physical distance (Mpc)
Lack of AGN in central
regions is not due to the
intra-cluster emission
AGN lie between 0.5 and 1 Mpc
from the cluster centre.
Chandra Clusters: Suppression?
Clusters with low
LX (~1x1044) have
~6 galaxies > L*
(De Propris 2004)
(Excess per
average field =
excess per square
degree x average
field size)
NX(flux)
NOpt(>L*)
=
NX(Cl,flux)
NOpt(Cl,>L*)
AGN appear to be suppressed
in moderate redshift clusters
Chandra Clusters: Evolution
Redshift samples < 1 have
similar luminosity &
morphology distributions
The evolution of AGN in clusters
is faster than in the field
Chandra Clusters: Radial Evolution
High redshift clusters have more
AGN at larger radii
Chandra Clusters: Morphology
Disturbed clusters also
have excess at higher
radius
Disturbed clusters have more
low luminosity sources
Chandra Clusters: Results
AGN lie between 0.5 and 1 Mpc from the cluster centre.
AGN appear to be suppressed in moderate redshift
clusters.
The evolution of AGN in clusters is faster than in the field.
High redshift clusters have more AGN at larger radii.
Disturbed clusters have more low luminosity sources.
Where are AGN found?
Optical
Radio
~0.8
X-ray
Best '02
Johnson '03
Redshift
Ruderman '05
Eckart '05
Miller '03, Wake '05
Kauffmann '04, ColdwellA901/2
'02
Best '04
~0.1
Reddy '04
Dressler '99
Ledlow & Owen '96
Galaxy density / AGN clustering
Results
~5% of bright supercluster
galaxies contain X-ray detected
AGN. All are in galaxies with
mR < 20.
The lack of AGN in fainter
galaxies is not due to a LX – mR
correlation.
Compared to similar galaxies,
those with AGN lie in group or
edge like environments –
moderate density and bluer.
AGN in more cluster like
environments are fainter.
AGN lie between 0.5 and 1 Mpc
from the cluster centre.
AGN appear to be suppressed in
moderate redshift clusters.
The evolution of AGN in clusters
is faster than in the field.
High redshift clusters have more
AGN at larger radii.
Disturbed clusters have more low
luminosity sources.
Results
~5% of bright supercluster
galaxies contain X-ray detected
AGN. All are in galaxies with
mR < 20.
The lack of AGN in fainter
galaxies is not due to a LX – mR
correlation.
Compared to similar galaxies,
those with AGN lie in group or
edge like environments –
moderate density and bluer.
AGN in more cluster like
environments are fainter.
AGN lie between 0.5 and 1 Mpc
from the cluster centre.
AGN appear to be suppressed in
moderate redshift clusters.
The evolution of AGN in clusters
is faster than in the field.
High redshift clusters have more
AGN at larger radii.
Disturbed clusters have more low
luminosity sources.
AGN in more massive clusters
have a larger radial spread.
Chandra Clusters: Cluster size
Expect mass to go as
Lx a M4/3
Expect radius to go as
R a ~Lx
0.3
AGN in more massive clusters
have a larger radial spread