Upload
raven-lewis
View
23
Download
5
Tags:
Embed Size (px)
DESCRIPTION
Red-Sequence Galaxies with young stars and dust. The cluster A901/902 seen with COMBO-17 Christian Wolf (Oxford) Meghan E. Gray (Nottingham) Klaus Meisenheimer (Heidelberg) A&A, in press. A901a. A901a. A901b. A901b. A902. A902. Testing ground: the A901/902 supercluster. - PowerPoint PPT Presentation
Citation preview
Red-Sequence Galaxies with young stars and dust
The cluster A901/902 seen with COMBO-17
Christian Wolf (Oxford)
Meghan E. Gray (Nottingham)
Klaus Meisenheimer (Heidelberg)
A&A, in press
A901aA901a
A901b
A901b
A902
A902
Testing ground: the A901/902 supercluster
z=0.16: ~5x5 Mpc
COMBO-17 SEDs
• SED classification ~98% complete at R<23– Stars (~2000)
COMBO-17 SEDs
• SED classification ~98% complete at R<23– Stars (~2000)– White Dwarfs (13)
COMBO-17 SEDs
• SED classification ~98% complete at R<23– Stars (~2000)– White Dwarfs (13)
– Galaxies (~6000)
COMBO-17 SEDs
• SED classification ~98% complete at R<23– Stars (~2000)– White Dwarfs (13)
– Galaxies (~6000)– QSOs (~100)
Redshift Accuracy
But first photo-z trials in 2002: 1/4 galaxies wrong!!!
Selecting The Cluster Sample
zphot = 0.170 ± 0.006 795 galaxies within cz = 1900 km/s 1575 = 3.7 x 3.5 x 120 (Mpc/h)3
Field Sample
COMBO-17 field @ 0.05<z<0.25 excluding overdensities385 galaxies from 9750 (Mpc/h)3 with <z>=0.172
Colour-Magnitude Diagram
COMBO-17 evolving red-sequence fit @ 0.2<z<1.2795 galaxies = 462 red-sequence + 333 blue-cloud (field: 62=13+49)
2-D Family: Age x Extinction
What is in the Red Sequence?
• Examine age x extinction diagram • Try splitting red-sequence:
– Dust-free old clump• Cleaner sample of
old red galaxies
– Dusty contaminants• What are these?
• Blue cloud as usual• Regular star-forming
galaxies
Dust-freeold clump
Dusty redcontaminants
Blue cloud
Templates: Old vs. Dusty Red
Dusty red galaxies are- redder at red end- bluer at blue endthan old red galaxies
Old vs. Dusty Near 4000A
Mean Spectra: Old / Dusty
Trends in continuum colour and spectral lines!
Mean Spectra
Ratio Spectrum: Dusty/Old
Population Mix: Cluster / FieldE
nhanced / red
der
2-D Clustering
Old red = cluster coresDusty red ~ blue cloud
(x,y): old red = cluster coresdusty red ~ blue cloud
(y,z): old red ~ dusty redblue cloud = ‘voids’
v ~ 550 km/sv ~ 1400 km/s
Luminosity Distribution
Type-Density Relation
field cluster
A “Third Party”(??)…
• Three types of galaxies:1. Old red, passively evolving2. Intermediate3. Young blue, actively star-forming
• Intermediate properties– Ages: intermediate or “old + young”– Star formation: Little but present– Colour: like red / Dust: like blue galaxies– Luminosities: intermediate– Habitat: medium-density preferred
• Small contribution from edge-on disks
Origin of Intermediate Type
• Transformed infalling blue galaxies:
• Contra:– Luminosity of progenitors– High mean stellar ages
• Age sequence:cores - intermediates -outskirts - field
• Pro:– Spirals redder as well
(Butcher-Oemler effect)
• Minor mergers: established large old cluster
elliptical + infalling small blue galaxy
• Pro:– Properties fine without
invoking special process– High-luminosity and old-age
component required
• Contra:– Very few undisturbed
established old cluster ellipticals in outskirts left
Summary: Data & Galaxy Types
• COMBO-17 surveys dynamically complex supercluster Abell 901/902
• photo-z’s provide ~800 galaxies at MV<-17
• Detailed 17-band SED - age x extinction grid
• More than 1/3 of the red-sequence are not old red galaxies, but dustier intermediate-age ones
• Added complexity in colour-density relation:dusty red galaxies don’t conform with old red or young blue
Summary: Properties of Dusty Red Galaxies
• Peak at mid-density (40%)
• Form interface between blue and old red
• Currently forming stars
• Have plenty of old stars
• Result of– Environmentally triggered transformation of infalling blue
galaxies– Age sequence– Minor merger of infalling blue galaxy into old red cluster
elliptical
Outlook: Spitzer 24 Analysis
• Most EB-V>0.2 red-sequence galaxies are luminous 24 sources
• Bell et al.in prep.
STAGES: Center of A901a
[email protected] HST/ACS