How to start an AGN: the role of host galaxy environment

1
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)
2
Why do some galaxies have AGN?
Gas -gt black hole AGN Internal size,
morphology, star-formation Historical previous
activity -- depletion, feedback External
mergers, close encounters, tidal field,
strangulation, ram-pressure stripping
No AGN
0.01
30
3
External effects on galaxies
Morphology spirals -gt S0s Star-formation
rate high -gt 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?
4
Where are AGN found?
Optical Radio X-ray
Porciani '04
Redshift
Dressler '99
Galaxy density / AGN clustering
5
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 gt 100 galaxy
  clusters
• X-ray detected AGN
• Find statistical excess of sources compared to
  blank field
• Split sample by cluster properties and redshift

6
The A901/2 supercluster (z0.17)
People Meghan Gray, Chris Wolf COMBO-17 team,
Bell and Papovich, Andy Taylor.

• Optical data (from COMBO-17 team)
• Deep R-band imaging
• 17-band photometric redshifts for 18000 objects
  (mRlt24)
• 1240 supercluster galaxies found
• 282 supercluster spectra from 2dF
• Weak lensing map
• Spitzer data
• MIPS 24-micron sources
• X-ray data
• 12 ksec ROSAT images (HRI)
• 90 ksec XMM-Newton image

A901a
A901a
A901b
Filament
A902
SW group
7
A901/2 Finding the supercluster AGN

• Identify point sources Sources
• - wavelet detection on images from 3
  cameras 150
• - remove uncertain and extended sources 139

A901a
A901b
A901a
Emission
z0.5 cluster
SW group
A902
8
A901/2 Finding the supercluster AGN

• Identify point sources Sources
• - wavelet detection on images from 3
  cameras 150
• - remove uncertain and extended sources 139
• Match with optical sources
• - R-band, using likelihood ratios from 14000
  random sources
• - also Spitzer 24-micron data to resolve
  uncertainties 88

9
A901/2 Finding the supercluster AGN

• Identify point sources Sources
• - wavelet detection on images from 3
  cameras 150
• - remove uncertain and extended sources 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 11
• - Manual check for AGN contaminated sources
  12

10
A901/2 Finding the supercluster AGN

• Identify point sources Sources
• - wavelet detection on images from 3
  cameras 150
• - remove uncertain and extended sources 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 11
• - Manual check for AGN contaminated sources
  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/Hß line ratios 11

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

12
A901/2 AGN host galaxies
RESULT 1 All of the AGN lie in galaxies with mR
lt 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)
13
A901/2 Separating the Environments

• Define by hand
• Clusters (A901a, A901a, A901b, A902)
• Groups
• Outskirts of large clusters and groups
• Filaments

14
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
15
A901/2 Separating the environments Does it work
for all galaxies?
Blue group Filament
Cluster Red group / Edge
Field
16
A901/2 Environments of AGN
3.3 - AGN match control in 2D space 18 -AGN
match control in edge and group 4 - AGN match
control in 1D space along cluster line (30 in
density only) gt98-Lx decreases along the cluster
line direction
cluster
field
Cluster line
edge
filament
group
17
A901/2 Conclusions
1. 5 of bright supercluster galaxies contain
X-ray detected AGN. 2. All of the AGN lie in
galaxies with mR lt 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
18
Where are AGN found?
Optical Radio X-ray
Porciani '04
Redshift
Dressler '99
Galaxy density / AGN clustering
19
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

HST Credit NASA / N. Benitez
20
Chandra Clusters The sample
Secure redshift and z gt 0.1 Exposure gt 10
ksec X-ray detected cluster (after data
reduction) 139 good cluster fields
8 with z gt 1
21
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
22
Chandra Clusters Lensing

• Lensing changes background sources flux
  increases
• number density decreases
• Net result lensing causes 10 reduction in the
  central 0.5 Mpc
• INPUTS
• Background AGN redshift distribution (3 used)
• Cluster model (SIS now, NFW in future)
• Cluster luminosity gt mass

N
Lx
Model Blank fields Sensitivity map Lensing
23
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.
24
Chandra Clusters Suppression?
Clusters with low LX (1x1044) have 6 galaxies gt
L (De Propris 2004) (Excess per average field
excess per square degree x average field size)
AGN appear to be suppressed in moderate redshift
clusters
25
Chandra Clusters Evolution
25 gal.
25 galaxies
5 galaxies
25 gal.
25 gal.
Redshift samples lt 1 have similar luminosity
morphology distributions
The evolution of AGN in clusters is faster than
in the field
26
Chandra Clusters Radial Evolution
High redshift clusters have more AGN at larger
radii
27
Chandra Clusters Morphology
Disturbed clusters also have excess at higher
radius
Disturbed clusters have more low luminosity
sources
28
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.
29
Where are AGN found?
Optical Radio X-ray
Porciani '04
Redshift
Dressler '99
Galaxy density / AGN clustering
30
Results
5 of bright supercluster galaxies contain X-ray
detected AGN. All are in galaxies with mR lt 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.
31
Results
5 of bright supercluster galaxies contain X-ray
detected AGN. All are in galaxies with mR lt 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.
32
Chandra Clusters Cluster size
Expect mass to go as Lx ? M4/3 Expect radius
to go as R ? Lx 0.3
AGN in more massive clusters have a larger radial
spread